,transcriber's ,note ,when italics were used in the original book1 the corresponding text has been surrounded by underscores ,mixed fractions have been displayed with a hyphen between whole number and fraction for clarity4 ,superscripted characters are preceded by and when more than one character is superscripted1 they are surrounded by 4 ,subscripted characters are preceded by an underscore and surrounded by 4 ,some corrections have been made to the printed text4 ,these are listed in a second transcriber's note at the end of the text4 ,,on ,,molecular ,,and ,,microscopic ,,science ,,volume ,,the ,,first ,by the same ,author4 ,,on the ,,connection of the ,,physical ,,sciences4 #ith ,edition4 ,portrait4 ,post #hvo4 #is4 ,,physical ,,geography4 ,new ,edition1 thoroughly revised4 ,portrait4 ,post #hvo4 ,in the press4 ,illustration3 ,fig4 #hi1 p4 #bj4 ,,eucyrtidium ,,cranoides4 ,frontispiece to ,vol4 ,i4 ,,on ,,molecular ,,and ,,microscopic ,,science ,,by ,,mary ,,somerville ,,author ,,of #8,,the ,,mechanism ,,of ,,the ,,heavens' #8,,physical ,,geography' #8,,connection ,,of ,,the ,,physical ,,sciences' ,,etc4 ,deus magnus in magnis1 maximus in minimis--,st4 ,augustine ,,in ,,two ,,volumes--,,vol4 ,i4 ,,with ,,illustrations ,,london ,,john ,,murray1 ,,albemarle ,,street #ahfi ,the right of translation is reserved ,,london3 ,,printed ,,by ,,spottiswoode ,,and ,,co41 ,,new-,,street ,,square ,,and ,,parliament ,,street ,,preface4 ,,microscopic ,,investigation of organic and inorganic matter is so peculiarly characteristic of the actual state of science1 that the ,author has ventured to give a sketch of some of the most prominent discoveries in the life and structure of the lower vegetable and marine animals in addition to a few of those regarding inert matter4 ,the ,author feels bound to return her best thanks to kind friends--,sir ,john ,herschel1 ,mr4 ,huggins1 ,mr4 ,gwyn ,jeffrey1 ,prof4 ,tyndall1 and ,mr4 ,t4 ,moore of ,chelsea1 who have aided in revising some of the sheets for press1 and have thus counteracted the disadvantage under which she labours1 of a residence abroad1 and at a distance from libraries of reference4 ,,contents ,,of ,,the ,,first ,,volume4 ,,part ,i4 ,,atoms ,,and ,,molecules ,,of ,,matter4 ,,sect4 ,,page ,i4 ,,elementary ,,constitution ,,of ,,matter #a ,,ii4 ,,on ,,force1 ,,and ,,the ,,relations ,,between ,,force ,,and #bc ,,matter ,,iii4 ,,atomic ,,theory1 ,,analysis ,,and ,,synthesis ,,of ,,matter1 #ic ,,utility ,,of ,,waste ,,substances--,,coal-,,tar ,,colours1 ,,etc4 ,,iv4 ,,the ,,solar ,,spectrum1 ,,spectrum ,,analysis1 ,,spectra ,,of #abi ,,gases ,,and ,,volatilized ,,matter1 ,,inversion ,,of ,,coloured ,,lines1 ,,constitution ,,of ,,sun ,,and ,,stars ,,part ,,ii4 ,,vegetable ,,organisms4 ,i4 ,,microscopic ,,structure ,,of ,,the ,,vegetable ,,world #afg ,,ii4 ,,alg #agi ,,iii4 ,,fungi #bfj ,,iv4 ,,lichens #bih ,v4 ,,charace #cab ,,vi4 ,,hepatic1 ,,or ,,liverworts #caf ,,vii4 ,,musci1 ,,or ,,mosses #cbc ,,viii4 ,,filices1 ,,or ,,ferns #cce ,,ix4 ,,equisetace1 ,,or ,,horsetails #cfg ,x4 ,,marsileace1 ,,or ,,rhizosperm #cga ,,xi4 ,,lycopodiace1 ,,or ,,club ,,mosses #cgc ,,xii4 ,,general ,,structure ,,of ,,flowering ,,plants #cgh ,,xiii4 ,,monocotyledonous1 ,,or ,,endogenous ,,plants #chc ,,xiv4 ,,dicotyledonous1 ,,or ,,exogenous ,,plants #djd ,,illustrations ,,to ,,the ,,first ,,volume4 7,the ,author is indebted to the works of ,dr4 ,carpenter1 ,rev4 ,m4 ,j4 ,berkeley1 ,mr4 ,gosse1 and ,mr4 ,darwin1 for the larger part of these ,illustrations47 ,,fig4 ,,page #hi4 ,eucyrtidium cranoides frontispiece #a4 ,form of stratified discharge in a vacuum tube #gi #b4 ,form of stratified discharge in a vacuum tube1 as #ha affected by an electro-magnet #c4 ,development of ,ulva #aga #d4 ,vertical section of the cuticle of ,iris germanica #agc #e4 ,longitudinal section of stem of ,italian reed #agf #f4 ,palmogla macrococca #ahb #g4 ,protococcus pluvialis #ahd #h4 ,volvox globator #ahi #i4 ,various species of ,staurastrum #aib #aj4 ,economy of ,closterium ,lunula #aic #aa4 ,diatoma vulgare and ,grammatophora serpentina #aig #ab4 ,biddulphia pulchella #aih #ac4 ,pleurosigma angulatum #aii #ad4 ,actinocyclus undulatus #bjj #ae4 ,meridion circulare #bja #af4 ,bacillaria paradoxa #bjc #ag4 ,cell multiplication in ,conferva glomerata #bjg #ah4 ,zoospores #bjh #ai4 ,threads of ,rivularia nitida #bae #bj4 ,trichodesmium erythrum #baf #ba4 ,conjugation of ,zygnema quininum #bag #bb4 ,ulva latissima #bbe #bc4 ,polyides rotundus and ,furcellaria fastigiata #bbi #bd4 ,vertical sections of conceptacles of ,gracilaria #bcj armata1 ,grinnelia americana1 and ,corallina officinalis #be4 ,callithamnion corymbosum #bcb #bf4 ,rhabdonia ,coulteri1 ,sphrococcus coronopifolius1 #bcf ,wrangelia penicillata1 and ,cruoria pellita #bg4 ,dictyurus purpurascens #bdb #bh4 ,polyzonia cuneifolia #bdc #bi4 ,fruit of various species of ,ectocarpus #bde #cj4 ,dictyota dichotoma #bdg #ca4 ,vertical section of receptacle of ,fucus #bed platycarpus #cb4 ,various species of ,puccinii #bgf #cc4 ,puccinia ,graminis #bhj #cd4 ,various species of ,mucedines #bhf #ce4 ,torula ,cerevisi1 showing successive stages of #bhg cell-multiplication #cf4 ,various species of ,sphriacei #bid #cg4 ,various species of ,lichens #bii #ch4 ,sporopodium ,leprieurii1 ,coccocarpia smaragdina1 #cjj and ,lecanora affinis #ci4 ,paulia perforata1 ,calicium tympanellum1 and #cja ,graphis ,leprevostei #dj4 ,nitella flexilis #cjb #da4 ,antheridia of ,chara fragilis #cad #db4 ,further development of antheridia of ,chara #cae fragilis #dc4 ,marchantia polymorpha #cag #dd4 ,anatomy of frond of ,marchantia polymorpha #cah #de4 ,archegonia of ,marchantia polymorpha #cai #df4 ,elater and spores of ,marchantia #cai #dg4 ,funaria hygrometrica #cbd #dh4 ,polytrichum commune1 group of antheridia #cbe #di4 ,polytrichum commune1 development of spermatozoids #cbe #ej4 ,microscopic structure of leaves of mosses #ccj #ea4 ,development of spores of ,pteris serrulata #ccf #eb4 ,antheridium and spermatozoids of ,pteris serrulata #cch #ec4 ,archegonium of ,pteris serrulata #cch #ed4 ,section of footstalk of fern frond #cda #ee4 ,pinnule of ,polypodium bearing sori #cdb #ef4 ,sporangia of ,polypodiaceous ferns #cdc #eg4 ,pinnule of ,lastrea ,filix-mas with sori #cdf #eh4 ,sorus and indusium of ,polystichum or ,aspidium #cdg #ei4 ,pinna of ,polystichum ,lonchitis #cdh #fj4 ,sorus and cup-shaped indusium of ,deparia prolifera #cej #fa4 ,scolopendrium vulgare #cea #fb4 ,athyrium ,filix-fmina #cec #fc4 ,asplenium ,ruta-muraria #cec #fd4 ,ceterach officinarum #cee #fe4 ,blechnum ,spicant #ceg #ff4 ,pteris aquilina #ceg #fg4 ,adiantum ,capillus-,veneris #cei #fh4 ,trichomanes radicans #cfa #fi4 ,hymenophyllum tunbridgense #cfb #gj4 ,equisetum giganteum #cfh #ga4 ,pilularia minuta #cga #gb4 ,orchis mascula1 side view of flower #chi #gc4 ,orchis mascula1 front view of flower #cij #gd4 ,orchis mascula1 pollinium #cia #ge4 ,orchis mascula1 pollen grains #cia #gf4 ,orchis mascula1 pollinia #cib #gg4 ,orchis pyramidalis1 front view of flower #cic #gh4 ,orchis pyramidalis1 side view of flower #cid #gi4 ,orchis pyramidalis1 disc with one pollinium #cie #hj4 ,orchis pyramidalis1 pollinia1 attached to disc #cie #ha4 ,orchis pyramidalis1 pollinia1 with disc contracted #cie #hb4 ,orchis pyramidalis1 pollinia1 withdrawn #cie #hc4 ,epipactis palustris1 side views of flower #cig #hd4 ,epipactis palustris1 side view and dissection of #cih flower #he4 ,listera ovata1 side view of flower #cii ,errata4 ,page #c1 line #e from bottom1 insert the before earth #ei1 line #ai1 dele the #ei1 line #ba1 dele the #ei1 lines #bj and #bb1 for part read parts #ajj1 ,in the ,table of ,atomic ,weights1 read ,copper #cb2 ,zinc #cbe2 ,rubidium #hf2 ,csium #acc #aja1 lines #aj and #cc1 for #cb read #cbe #ajd1 line #ab from bottom1 for #bi read #cb ,,molecular ,,and ,,microscopic ,,science4 ,,part ,i4 ,,atoms ,,and ,,molecules ,,of ,,matter4 ,,section ,i4 ,,elementary ,,constitution ,,of ,,matter4 ,,the ,,investigations which have revealed the most refined and wonderful relations between light1 heat1 electricity1 and highly elastic media2 the relation of these powers to the particles of solid and liquid matter1 new methods of analysis1 and the microscopic examination of that marvellous creation1 animal and vegetable1 which is invisible to the unaided eye of man1 have brought a new accession to the indefinitely small within the limits of modern science4 ,wherever the astronomer has penetrated into the depths of space1 luminous points are visible2 and since light merely consists in the undulations of the ethereal medium1 matter must exist in every part of the universe of which man is cognizant1 for although the luminiferous ether is so attenuated that its very existence is almost an hypothesis1 its atoms are not more inconceivably small than those of highly elastic ponderable matter on earth4 ,atoms are the ultimate constituents of homogeneous simple substances2 molecules1 or groups of heterogeneous atoms united in definite proportions1 constitute such as are compound4 ,high pressure steam is invisible as it issues from the boiler1 yet each of its molecules contains two atoms of hydrogen and one of oxygen4 ,the perfume of a flower is a compound invisible substance formed of molecules4 ,we know nothing of the forms either of atoms or of those groups of atoms which we call molecules2 but we cannot suppose them otherwise than as excessively hard1 since conceive them how we will1 we are sure that an atom1 whatever be its form or nature1 is ever the same4 ,it never wears1 it never changes1 though it may have formed part of thousands of bodies and entered into thousands of combinations1 organic and inorganic2 when set free by their dissolution1 it is ready to enter into a new series2 it is indestructible even by fire1 the same now as when created4 ,nor has the quantity of matter in our terrestrial abode ever been increased or diminished2 liable to perpetual change of place and combination1 the amount remains the same3 the bed of the seas may be changed to dry land1 and the ocean may again cover the lofty mountains1 but the absolute quantity of matter changes not4 ,all substances1 whether solid1 liquid1 or ariform1 are supposed to consist of hard separate atoms or particles1 and in conformity with that supposition to be surrounded by the ethereal medium1 otherwise they could not transmit light and heat1 which are merely vibrations of that medium4 ,even the hardest and most compact substances are capable of compression1 and have been compressed to an enormous degree by the hydraulic press2 but it probably transcends mechanical force to bring their atoms into contact3 in fact1 no known substance is impervious to both light and heat1 however thin4 ,by far the greater number of terrestrial substances consist of heterogeneous atoms chemically combined into atomic systems or molecules2 but there are sixty-four which have never yielded to chemical analysis1 and are therefore believed to be respectively formed of only one kind of atoms4 ,thirty-five of these are metals found either pure or as ores1 and sixteen are metals existing naturally in chemical combination with alkalies1 alkaline earths1 or earthy bases1 that is as salts1 from which they have been obtained by the analytical power of electricity or other means4 ,the thirteen remaining simple substances are non-metallic3 some are ariform1 some solid1 one liquid4 ,the alkaline metals are sodium1 potassium1 lithium1 csium1 rubidium1 and thallium4 ,they are distinguished by their energetic affinities for1 and the simplicity of their compounds with1 non-metallic elements4 ,they are never met with native1 and are amongst the most difficult metals to reduce from their ores1 and their spectra are remarkable for simplicity4 ,sodium and potassium--which have been such important agents in spectrum science--were reduced from their alkalies of soda and potash by ,sir ,humphry ,davy by means of the voltaic battery1 a discovery which led the way to the reduction of many of the others4 ,lithium is a white metal which burns brilliantly in air and oxygen2 it swims in naphtha1 and is the lightest solid body known4 ,csium is the most energetic of all metals in its chemical affinities4 ,the metals of the alkaline earths are barium1 strontium1 calcium1 and magnesium4 ,they possess1 like the preceding1 energetic affinities for the non-metallic elements1 and are reduced with difficulty from their ores4 ,barium is obtained from earth baryta3 it is powerfully alkaline1 and its salts are colourless and poisonous4 ,calcium is obtained from limestone1 chalk1 marble1 and gypsum1 which are amongst the most abundant constituents in the crust of the earth2 it is a bright ductile metal of a bronze colour4 ,magnesium1 which is a brilliant silver-white hard brittle metal1 is obtained from magnesium limestone or dolomite4 ,although the ores of calcium and magnesium cover vast areas of the globe1 the metals form a very small comparative proportion of them4 ,the metals derived from non-alkaline earths are glucinum1 yttrium1 thorinum1 zirconium1 and aluminium1 which is the only one of any interest3 it is now becoming a very useful metal4 ,it combines readily with oxygen to form clay4 ,the ruby1 sapphire1 and oriental topaz are merely coloured varieties of corundum1 which is nothing but crystallised clay4 ,rubidium1 csium1 and thallium were discovered by spectrum analysis4 ,the avidity of some of these metals for oxygen is quite remarkable3 potassium and rubidium inflame when they touch ice or cold water2 they decompose the water and combine with its oxygen4 ,calcium becomes luminous in warm water1 and burns with intense light when heated to redness2 but a magnesium wire burns with such intense brilliancy that it has been employed for photography1 and will probably become useful for household purposes1 as two ounces and a half of magnesium wire when burnt give a light equal to that of twenty pounds' weight of stearine candles4 ,the metals whose oxides are not reducible by heat without the aid of some form of carbon include nearly all the useful metals4 ,they are all polyatomic1 that is1 they combine with other elements in the number of atoms varying from two to eight1 and are divided into seven groups in regard to this property4 ,for instance1 zinc1 copper1 and cadmium are diatomic4 ,zinc is invaluable as a source of electric light and heat in the voltaic battery1 and its vapour burns brilliantly4 ,copper is one of the most useful of metals1 while cadmium is of no value at all4 ,nickel1 cobalt1 and uranium form the triatomic group2 they are remarkable for their complex spectra4 ,nickel is usually an ingredient in meteorites2 cobalt is employed in pigments and in sympathetic inks2 and the oxide of uranium is used to stain glass1 and gives it some very peculiar properties1 as will be shown4 ,the precious metals have a feeble affinity for oxygen at any temperature1 and their oxides are decomposed by heat alone1 and sometimes even by the undulations of light4 ,metals are excellent conductors of heat1 but they vary exceedingly in that respect2 both theory and experiment prove that the best conductors are invariably the worst radiators4 ,in fact those atoms which transfer the greatest amount of motion to the ethereal medium1 that is1 which radiate most powerfully1 are the least competent to communicate motion to each other1 that is1 to conduct with facility4 ,silver and copper are the best conductors of heat1 but the worst radiators4 ,these two metals are the best conductors of electricity1 but it is influenced by temperature2 for ,,mm4 ,matthiessen and ,von ,bose's experiments have proved that all pure metals in a solid state vary in conducting power to the same extent between zero and #ajj ,cent41 and that the alkaline metals conduct electricity better when heated than when cold4 ,all metals are capable of being vaporized1 but at very different degrees of temperature4 ,platinum requires the heat of the oxy-hydrogen blowpipe1 which by estimation amounts to #hhja ,cent4 ,this property makes it valuable for terminal points to the conducting wires of the voltaic battery and magneto-electric induction machine where great heat can be employed without fusing the platinum terminals4 ,copper is always employed for the conducting wire on account of its superior conductive power4 ,the coil of wire in the magneto-electric machine1 which is often miles long1 is insulated by a coating generally of green silk thread4 ,but in experiments of extreme delicacy where magnetism might vitiate the results1 perfectly pure copper wire which is diamagnetic is used for the conducting wires in the thermo-electric pile of the goniometer1 and the wires are coated with white silk thread1 since it was discovered that the green dye contains some magnetic metal4 ,the mass of the metals however constitutes comparatively but a small part of the terrestrial globe1 which is formed of chemical combinations of only thirteen simple elementary substances1--a wonderful manifestation of creative power that could form a world of such variety and beauty by means of atoms so little diversified2 still more wonderful is it that four simple elements alone constitute the basis of nearly the whole organic fabric4 ,the air we breathe1 water1 the bodies of men and living creatures1 and the vegetation that adorns the earth1 are chiefly combinations of three invisible gases1 oxygen1 hydrogen and nitrogen1 with carbon1 the purest amorphous form of coal4 ,oxygen gas forms three-fourths of the superficial crust of the terrestrial globe1 its productions and its inhabitants4 ,at least a third part of the solid crust of the earth is oxygen in combination2 it constitutes eight parts out of nine in water1 and water covers three-fourths of the surface of the globe2 it forms more than twenty parts out of a hundred of atmospheric air1 and in the organic kingdom it is an essential constituent4 ,except in the atmosphere1 oxygen is never uncombined1 but may be obtained by distilling chlorate of potash1 by the decomposition of water by voltaic electricity1 and by other means4 ,when pure it is a colourless1 tasteless1 inodorous1 invisible gas2 it is incombustible at ordinary temperatures1 yet absolutely essential to combustion2 no animal can live long in it1 and none can exist without it4 ,in the atmosphere oxygen is highly magnetic2 its magnetism increases with cold and decreases with heat2 hence its intensity varies with night and day1 winter and summer1 but its magnetic property vanishes when it enters into composition4 ,oxygen is perfectly quiescent and passive as a gas in the atmosphere1 and as a constituent of water and solid bodies1 yet that inactivity conceals the most intense energy1 which only requires to be called into action4 ,thus combustion of extreme intensity takes place when ignited sulphur is put into a vessel containing oxygen gas2 the metal potassium is instantly inflamed by it on touching water2 some of its combinations with chlorine are highly explosive1 and phosphorus burns in it with dazzling splendour4 ,thus a stupendous amount of energy is latent in oxygen under the most tranquil appearance4 ,m4 ,schnbein of ,basle discovered that oxygen exists in another state1 which has neither the extreme quiescence on the one hand1 nor the intense violence on the other1 of its ordinary form2 and to express that intermediate condition1 in which its activity is less in amount and different in quality1 it has been called by another name1 viz4 ozone1 from the following peculiarity4 ,it had long been observed that there is a peculiar smell when an electric machine is in activity1 and when objects are struck by lightning2 that smell ,professor ,schnbein ascertained to arise from the change of oxygen into ozone1 and actually produced ozone by passing electric sparks through that gas4 ,ozone differs from oxygen in having a strong smell and powerful bleaching property2 it purifies tainted air1 changes vegetable colours1 and stains starch prepared by iodide of potassium blue1 which thus becomes a test of its presence2 yet it certainly is oxygen in an allotropic or changed state1 for it readily oxidizes or rusts silver and other metals1 and when ozonized gas is sent through a red-hot tube1 it comes out pure oxygen4 ,according to the experiments of ,messrs4 ,tait and ,andrews1 oxygen gas loses six eighths of its volume1 and becomes four times more dense by the change2 it contracts more readily with obscure electricity than with the spark4 ,the experiments of ,professor ,tyndall on the absorption of radiant heat by gases give reason to believe that ozone is produced by the packing of the atoms of elementary oxygen into oscillating groups1 and that heating dissolves the bond of union and restores the ozone to the form of oxygen4 ,ozone chiefly exists in air that has passed over a great expanse of sea1 and the quantity is increased during the aurora1 which alone might lead to a surmise of that phenomenon being electric4 ,the change of oxygen into ozone is not the only instance of ,allotropism1--that is to say1 the existence of the same substance in two states differing from each other in every respect1--for ozone itself is allotropic4 ,professor ,schnbein has discovered that there are two kinds of ozone standing to one another in the relation of positively and negatively active oxygen2 namely ozone and antozone1 which neutralize each other into common oxygen when brought into contact4 ,in this respect they are analogous to electricity1 and1 like electricity too1 one kind cannot be produced without a simultaneous development of the other4 ,when a metal1 such as silver for example1 is oxidized or rusts1 it gives polarity to the atoms of oxygen in the atmosphere and divides them into the opposite states of ozone and antozone2 the ozone combines with the silver and rusts or oxidizes it1 at the same time that the antozone is dissolved in the moisture or aqueous vapour in the air and forms peroxide of hydrogen4 ,the oxidized or rusted silver1 as well as every other oxidized substance1 is an ozonide1 while the peroxide of hydrogen is an antozonide4 ,since both kinds of ozone are produced during the decomposition of water by electricity1 and as sea air is always found to contain more or less free ozone1 the ocean is probably an antozonide1 for all the antozone formed by electricity during thunderstorms must be either dissolved in the sea-water1 or carried into it in the form of peroxide of hydrogen by the rain4 ,ozone must be exceedingly abundant in the zone of calms and light breezes near the equator known as the variables1 which is subject to heavy rains and violent thunderstorms1 and also in the regions of the monsoons4 ,on land one of the benefits arising from these formidable phenomena is the production of ozone1 which oxidizes decomposing organic matter and hastens its decay1 while the antozone1 which is dissolved in the atmospheric vapour1 forms the peroxide of hydrogen and frees the air from the antagonist principle4 ,the peroxide of hydrogen thus produced is a transparent colourless inodorous liquid with a metallic taste1 and contains one equivalent of hydrogen and two of oxygen4 ,it retains its liquid state under a great degree of cold1 and mixes with water in any proportion4 ,it has a strong bleaching property1 instantly destroying vegetable colour4 ,if exposed suddenly to a temperature of boiling water it is decomposed with violent explosion1 and readily gives off oxygen at #ei ,fahr4 ,the mere touch of an oxidized metal1 as the oxide of silver1 completely and instantaneously decomposes it1 and oxygen gas is evolved by the union of the ozone and antozone so rapidly as to produce a kind of explosion attended by an intense evolution of heat4 ,during the combustion of phosphorus in the atmosphere both kinds of ozone appear1 and ,professor ,schnbein considers the slow combustion of that substance1 which unites with the ozone and sets the antozone free1 as the type of all the slow oxidations which organic and inorganic bodies undergo in moist atmospheric air2 that true oxidation is always preceded by the appearance of the peroxide of hydrogen1 and that this compound acts an important part in slow oxidations1 and is deeply concerned in animal respiration1 and in many other chemical actions going on in nature4 ,in confirmation of these views1 it is certain that ozone is a powerful minister in the work of decay4 ,if wood be made explosive like gun-cotton by a similar process1 it becomes pulverulent after a time1 and burns without exploding1 though it still retains its shape4 ,in the natural state of the wood the oxygen is passive and quiescent1 for oxygen is a constituent of wood2 in its second state it is explosive1 and after a time that is succeeded by the semi-active state of ozone1 which by a slow imperceptible combustion causes the wood to decay4 ,mr4 ,faraday observes that the force which would have been explosive had it been concentrated into one effort1 expends itself in a long continued progressive change4 #8,the majestic phenomena of combustion bespeak our admiration and rivet our attention because of their imposing grandeur2 yet these are but spasmodic efforts in the grand economy of the material world1 occurrences of now and then4 ,the slower but continuous progress of the elements to their appointed resting-place1 the silent1 tranquil1 ever progressing metamorphic changes involved in the phenomena of decomposition and decay1 these we count for nothing and pass unheeded by4 ,yet with all their majesty1 with all their brilliancy1 all their development of tremendous energy1 what are the phenomena of combustion in the grand scheme of the universe compared with these8 ,when the loud crash of the thunder or the lightning's flash awakens us from our thoughtless abstractions or our reveries1 our feelings become impressed with the grandeur of ,omnipotence and the might of the elements he wields1 yet the whole fury of the thunderstorm--what is that in comparison with the electric energies which silently and continually exert themselves in every chemical change8 ,why1 the electric force in a single drop of water1 and disturbed when that water is decomposed1 is of itself greater than in the electricity of a whole thunderstorm4 ,those of us who limit our appreciation of the powers of oxygen to the energies displayed by this element in its feebly active state1 form but a very inadequate idea of the aggregate results accomplished by it in the economy of the world4' ,oxygen is the only known gas that is allotropic1 and is the only known substance that is doubly allotropic1 that is existing in three different states similar to oxygen1 ozone1 and antozone4 ,hydrogen when pure is an invisible gas without smell or taste2 it is a constituent of various acids and alkalies1 but is itself neither acid nor alkaline4 ,it is highly inflammable1 burning with a pale light1 and1 as already mentioned1 a combined jet of oxygen and hydrogen produces heat of #hhja1 which is so intense that nothing can withstand it4 ,it is the lightest substance known4 ,a balloon having the form of a globe ten feet in diameter1 would hold #cb-a_/b pounds weight of common air1 while two pounds weight of hydrogen gas would fill it4 ,associated with this small quantity of ponderable matter1 hydrogen has an enormous power of combination1 but its activity is only called forth by some exterior and exciting cause4 ,a mixture of two measures of hydrogen and one of oxygen gas would remain inert for ever1 but the instant an electric spark is sent through it1 a bright flash and an explosion takes place1 and the result is water3 thus a tremendous force lies quiescent in that bland element4 ,hydrogen gas is introduced into the atmosphere by imperfect combustion1 but it is instantly diffused and becomes harmless1 for ariform fluids are capable of rapid and perfect diffusion through one another1 each having a capacity peculiar to itself1 which under the same circumstances is greater as its density is less2 therefore hydrogen the lightest of gases not only rises in the air on account of its levity1 but is more quickly and completely diffused than oxygen which is the support of life4 ,though hydrogen is inferior in density to every other gas1 it surpasses them all in conducting electricity1 just as silver and copper conduct electricity better than platinum1 though far less dense4 ,the great refrigerating power of hydrogen is owing to its extreme mobility and consequent rapid convection of heat1 in which it surpasses all other gases4 ,it is as permeable to radiant heat as atmospheric air1 has a very high refractive power1 a specific heat of #cbicf1 and may be substituted in many chemical formul for a metal1 without altering their character3 hence it is sometimes called a metalloid4 ,the quantity of nitrogen gas or azote that exists in nature is enormous4 ,it constitutes four-fifths of the atmosphere1 whence it may be had in a pure state1 as well as by chemical means4 ,like oxygen1 this gas is permanently elastic1 without smell1 taste1 or colour2 it is neither acid nor alkaline1 it does not change vegetable colours1 it neither burns nor supports combustion1 and is incapable when breathed of supporting animal life4 ,it abounds in organic bodies1 in all parts of the animal texture1 in the blood1 muscles1 nerves1 even in the brain2 and is either a highly nutritious or poisonous principle in the vegetable kingdom4 ,nitrogen gas is altogether passive2 it has no affinity for the metals1 and cannot be liberated from any of its compounds even by electricity4 ,excepting boron and titanium1 it will not combine directly or spontaneously with any simple element1 even under the highest temperature1 but its indirect combinations are numerous and violent3 those with hydrogen are either noxious or poisonous1 those with oxygen are all deadly poisonous4 ,had nitrogen combined spontaneously with either of these gases1 especially with oxygen1 life would have been impossible as the organized creation is constituted2 its inertness renders its mixture with oxygen in atmospheric air innocuous4 ,however1 combinations of nitrogen and hydrogen1 forming nitrate of ammonia1 have been discovered in the atmosphere by ,professor ,schnbein1 the union of evaporation1 heat and air being the cause2 and as evaporation is continually going on1 he concludes that nitrate of ammonia1 nitrates and other salts are generated in the moist air1 and are speedily washed down in our rainy climates into the springs and rivers4 ,he considers the formation of nitrates out of water as highly important for vegetation1 because each plant becomes a generator of a portion at least of its azotized food1 while the rain furnishes the ground on which it stands with a supply of the same4 ,in the atmosphere1 nitrogen has all the mechanical properties of common air1 but with a greater refractive power1 and its specific gravity is nearly the same with that of oxygen4 ,since the atmospheric gases are the most permeable to radiant heat1 the earth is in the most favourable circumstances for being warmed by the solar rays1 and thus the properties of the elementary gases are admirably adapted for our comfort1 nourishment1 safety1 and pleasure4 ,carbon1 which combined with the three elementary gases forms the basis of the organic creation1 is widely distributed throughout the globe1 in enormous coal formations1 the vegetation of former ages4 ,diamond is its purest crystalline form2 and charcoal1 which is wood whence the volatile matters have been driven off by heat1 is its purest amorphous state4 ,to this simple substance and to hydrogen1 we are indebted for terrestrial light and heat1 whether our fuel be coal or wood1 our light a candle or a lamp4 ,the products of combustion are carbonic acid gas1 whether pure or mixed with smoke1 for ashes are the incombustible earthy matter mixed with coal or wood1 and smoke is unconsumed carbon arising from the bad construction of our chimneys2 so that the waste is enormous in a great city like ,london where coal is the only fuel4 ,light is given out by incandescent solid particles1 which become luminous sooner than gas1 for all gases have a feeble illuminating power1 and heat results from the chemical combination of the carbon with oxygen1 a process in which the chemical force merges into its correlative heat4 ,mr4 ,faraday observes1 that had the result of the combination of carbon and oxygen been a gas only1 we should have had very little light1 and had it been a permanent solid1 the world would have been buried in its own ashes4 ,diamond and pure carbon leave no residuum when consumed2 they combine with the oxygen of our atmosphere into carbonic acid gas1 which is invisible1 poisonous1 and so heavy1 that it may be poured from one vessel to another like water1 thereby showing how much carbon it contains in an invisible state4 ,the quantity of carbonic acid gas thrown into the atmosphere in this invisible yet ponderous state is immense1 since six tons weight of atmospheric air rushes hourly through an average size blast furnace1 carrying with it more than half a ton of carbon in the form of that gas1 whose constitution and properties are always the same1 whether it arises from combustion1 fermentation1 or respiration1 which latter may be regarded as a slow combustion1 consuming us to the bones if not supplied with carbon by means of food4 ,it has been computed that two thousand million pounds weight of oxygen gas is daily converted into carbonic acid gas by these operations1 and given into the atmosphere1 which would soon be contaminated by its poison and suffocating quality1 were it not for vegetables which decompose it1 assimilate the carbon and set the oxygen free to mingle with the air and make it again fit for respiration4 ,carbon has a greater power of combination than any other simple substance except hydrogen4 ,mr4 ,faraday compressed carbonic acid gas into a liquid by the pressure of its own elasticity when disengaged from combination in close vessels1 a force equal to the weight of thirty-five times that of our atmosphere2 and the liquid was reduced to a solid by ,m4 ,thilorier by rapid evaporation1 during which the heat was given out so quickly by one part of the liquid1 that the remainder was condensed into a substance like snow1 which could be touched with impunity1 but when mixed with sulphuric ether its temperature was reduced to #aff below zero of ,fahrenheit's thermometer4 ,carbon appears naturally under a great variety of forms1 and exhibits one of the most striking instances of allotropism1 the same substance showing the greatest contrast in appearance and physical properties4 ,the diamond1 the most resplendent1 transparent1 and hardest of gems1 is identical with carbon1 which is black1 dull1 opaque1 and brittle4 ,both are combustible2 carbon is easily ignited1 but it requires a heat of #ahfj to consume the diamond4 ,however numerous the crystalline forms assumed by substances either naturally or artificially may be1 they are all capable of being grouped into geometrical systems2 each system possessing its own allied and derivative forms capable of mutual variations among themselves1 but the forms of one system never assuming those of the other4 ,with that law1 however1 carbon and a few other substances are completely at variance4 ,the diamond crystallizes in octohedrons1 while graphite1 which is also carbon1 crystallizes in six-sided plates1--two forms that belong to different systems quite irreconcilable with one another3 and thus carbon possesses the property of being dimorphous4 ,sulphur is a simple inflammable mineral abounding in volcanic countries1 either in a crystalline or amorphous state1 and forming a constituent in organic substances1 animal and vegetable4 ,it is readily dissolved by bisulphide of carbon1 by benzine1 and by a moderate heat2 and copper filings exposed to its vapour spontaneously take fire1 the chemical force of combination merging into light and heat4 ,sulphuretted hydrogen gas1 a combination of sulphur and hydrogen1 forms naturally during the putrefaction of organic matter1 and ,mr4 ,faraday observes with regard to the affinities of sulphur1 #8so numerous are its relations1 so extensive its range of combinations1 that we must consider it to be the very foundation on which chemical manufacture is built up4' ,though a simple substance1 sulphur exhibits the two remarkable phenomena of dimorphism and the allotropic property4 ,when reduced by heat to vapour and cooled slowly1 it crystallizes in rhombic octohedrons2 when merely melted and allowed to cool slowly1 it takes the form of oblique rhombic prisms4 ,here the same atoms when in vapour and in a liquid state are acted upon by different forces2 but however that may be1 sulphur is another singular exception to the law of the immutability of the crystalline systems4 ,sulphur becomes allotropic by the continued application of heat2 that is to say1 it entirely changes its appearance and character1 though it remains chemically the same4 ,naturally it is yellow and brittle1 but when fused1 it is a colourless pellucid fluid which by continued heat is changed into a black tenacious substance that becomes like ,india rubber or gutta percha when thrown into water4 ,in this allotropic state it is endowed with properties more powerful1 energetic1 and exalted2 its tendencies to act chemically being increased like those of ozone4 ,that this black tenacious substance is chemically the same with common sulphur there can be no doubt1 for when it is exposed to greater heat1 it again becomes a colourless pellucid fluid1 which thrown into water resumes the form of brittle yellow sulphur4 ,these new arrangements among atoms of the same kind show that the immutability of matter is not without exceptions4 ,the animal kingdom is the great reservoir of phosphorus1 a simple substance that is never found uncombined4 ,it is sparingly met with in the vegetable kingdom1 and still less in the mineral1 but may be procured abundantly from calcined bones4 ,when pure it is colourless1 transparent1 solid1 extremely poisonous1 and so inflammable that it must be kept in water4 ,in air it is in continual combustion with oxygen1 during which ozone is produced4 ,when burnt in a current of air phosphorus leaves a residuum consisting of two substances1 of which one is an acid1 the other is red allotropic phosphorus1 which has been extensively used in the manufacture of lucifer matches1 because its fumes are not deleterious1 and because it inflames less easily than common phosphorus1 to which it is reduced by heat or friction1 which generates heat4 ,silicon is a simple substance1 never found alone1 but when forty-eight parts of it are combined with fifty-two parts of oxygen gas it forms rock crystal1 the purest form of silica or quartz4 ,silica is so abundant that it may be said to constitute the basis of the mineral world4 ,the sand on the sea-shore1 which is the debris of quartz rocks1 shows how universally it prevails4 ,it is even abundant in the vegetable kingdom1 giving strength to the stalks and leaves of the grasses1 and may be felt in the harshness of the beards of wheat and barley4 ,silicon exists in three different states--the amorphous1 which has no form2 the graphic1 which takes the form of small hexagonal plates2 and that of octohedral silicon3 hence this substance is dimorphous4 ,a singular analogy obtains between silicon and carbon3 the amorphous form of silicon corresponds to charcoal1 the graphic form of silicon corresponds to the graphic form of carbon1 and the octohedral form of silicon to the diamond2 yet the chemical relations between the two substances are very small4 ,silica has hitherto been considered to be insoluble in pure water2 at least ,m4 ,bischoff states that only one part of silica dissolves in #gfi1bcj parts of water2 but by a method hereafter to be explained1 ,professor ,graham has actually obtained a limpid solution of silica in pure water4 ,boron is a constituent of boracic acid1 a natural production in ,thibet and ,monte ,corbalo in ,tuscany4 ,it is a greenish-brown solid1 insoluble in water1 but when heated to about #fjj it burns in open air with a vivid flame4 ,fluorine is a constituent of a very beautiful mineral1 well known as fluor spar1 which is found in cubic crystals of a green1 yellow1 or purple colour4 ,hydrofluoric acid obtained chemically from the mineral is highly volatile and extremely corrosive4 ,three of the non-metallic simple substances1 chlorine1 bromine1 and iodine1 are connected by the most remarkable analogies4 ,they are marine productions1 for chlorine is obtained from common sea-salt and in greater purity from rock-salt1 both of which are compounds of chlorine and the metal sodium4 ,when sea-water is evaporated1 salt and a substance called bittern remain1 which contains a salt whence bromine is separated4 ,again1 when kelp1 the ashes of burnt seaweeds1 is purified from the carbonate of soda and the chloride of potassium1 a salt is left which is the iodide of potassium1 whence iodine is obtained4 ,iodine is also found in sponges1 oysters1 and other low sea animals1 as well as in certain mineral springs1 and sometimes in combination with silver4 ,these three elemental bodies have little affinity for one another1 but they combine powerfully with other substances4 ,chlorine is a yellowish-green gas1 twice as heavy as atmospheric air1 with a noxious suffocating smell and astringent taste4 ,it has a powerful bleaching property1 and when combined with water1 which absorbs twice its volume of the gas1 it is used for bleaching linen1 in calico-printing1 and other arts4 ,the clear solution of chloride of lime is still more in use for the same purpose1 as well as for an antidote against contagion and unwholesome smells4 ,carbon does not burn in chlorine gas1 yet it is capable of supporting combustion1 for oil of turpentine1 phosphorus1 thin leaves of tin and copper1 and powdered antimony1 take fire spontaneously in it4 ,this gas shows its power by the development of intense heat1 but not by brilliant light1 because the results of its combustion are mostly vapours1 or such gases as have a feeble illuminating power2 so chlorine differs materially from oxygen in the phenomena of combustion4 ,mr4 ,faraday observes1 however1 that the bleaching powder is analogous to ozone in being an intermediate state1 for chlorine is pernicious and violently destructive as a gas1 perfectly innocuous and quiescent in common salt and in its other natural combinations1 while in the bleaching substances its energy is subdued by art1 so as to make it an important agent in various manufactures4 ,providentially1 chlorine is never found free2 but in a combined state it exists in enormous quantities in the salt of the ocean1 in salt lakes1 brine springs1 and in extensive deposits of rock-salt1 as well as in organic liquids4 ,it has a strong affinity for hydrogen1 and forms muriatic acid4 ,a mixture of these two gases remains inactive in the dark1 but explodes in sunshine4 ,by chemical means chlorine is made to combine with oxygen so as to produce four substances1 two of which are gases of such unstable equilibrium and weak affinity that the slightest cause makes them detonate violently2 the other two are more stable1 though they contain a greater quantity of oxygen4 ,the only combination of chlorine with nitrogen is the most powerful and dangerous explosive compound known4 ,chlorine combines naturally with sulphur1 and with the metals so as to form ores4 ,common salt affords a remarkable instance of change of volume by chemical combination4 ,twenty-four parts in bulk of salt contain #bjg parts of sodium and #bcc parts of liquid chlorine2 hence by chemical combination a bulk of #dd is compressed into a bulk of #bd1 yet that great compression is consistent with perfect transparency1 crystallized salt being perfectly transparent to light1 and more so as regards radiant heat than any other substance4 ,thus chemical affinity does what no mechanical power could accomplish4 ,at an ordinary temperature and barometric pressure1 bromine is an orange red1 extremely volatile fluid1 which congeals and becomes brittle at a temperature a little below the zero of ,fahrenheit's thermometer1 and if combined with water at that degree of cold it crystallizes in octohedral crystals which are permanent even at #ej ,fahr4 ,bromine is very poisonous1 corrodes the skin1 has a disagreeable taste1 and a smell similar to that of chlorine1 but more pungent and hurtful4 ,it possesses a powerful bleaching property1 does not conduct electricity1 and like chlorine a taper will not burn in its gas1 though it spontaneously sets fire to phosphorus1 and some of the metals4 ,reasoning from analogy ,professor ,schnbein believes that chlorine and bromine are not simple substances2 he considers them to be ozonides analogous to the peroxides of manganese1 lead1 c4 ,he believes chlorine to be the peroxide of murium1 and bromine to be the peroxide of bromium4 ,professor ,tyndall's experiments on the absorption and radiation of gases show that the action of these two substances is very different from that of the simple gases4 ,iodine is a dark purple solid1 crystallized in scales or elongated octohedral plates4 ,it slowly evaporates at ordinary temperatures1 and at that of #cej ,fahr4 it is volatilized into a beautiful violet coloured gas which changes starch into a bright blue1 and for that reason a little starch will detect the millionth of a grain of iodine in composition4 ,iodine is slightly soluble in water1 has a hot acrid taste1 and although used in medicine it is poisonous when taken in large doses4 ,its bleaching properties are inferior to those of its congeners1 but its chemical combinations are the same4 ,with hydrogen it forms a highly explosive compound1 which detonates with the slightest pressure4 ,these three simple substances are analogous in almost every respect4 ,they all possess a bleaching property1 many of their compounds are exceedingly explosive1 combustible substances do not burn in their gases1 while their gases set fire spontaneously to substances generally reckoned incombustible4 ,hence1 though not combustible1 they support combustion1 but in a very different manner from oxygen4 ,chlorine and the gases of bromine and iodine diluted with common air1 do not transmit blue and violet light2 that is to say1 the spectrum of a sunbeam transmitted through them is deprived of its most refrangible coloured rays1 and that which remains is crossed by more than a hundred equidistant dark lines2 their spectral properties however will be given hereafter4 ,they resemble oxygen in one respect--that when a current of electricity is passed continuously through a glass tube filled with any of these three gases1 much attenuated1 they slowly combine with the platinum wire of the negative pole of the battery inserted in the tube4 ,the electricity by degrees passes in diminished quantity1 and at last ceases altogether1 showing that matter1 however attenuated1 is requisite to conduct it4 ,according to the experiments of ,m4 ,dumas1 the volatility of a compound is in the inverse ratio of the condensation of the substances composing it1 and simple bodies come under the same law4 ,for example1 chlorine is more volatile than bromine1 and bromine is more volatile than iodine2 hence according to that law1 chlorine is the least dense of the three1 bromine is intermediate1 and iodine is the most dense1 which is actually the case3 for chlorine is a gas1 bromine a liquid1 and iodine a solid at ordinary temperatures1 which proves that there is a sequence in the intensity of the cohesive forces in this triad4 ,,section ,,ii4 ,,on ,,force1 ,,and ,,the ,,relations ,,between ,,force ,,and ,,matter4 ,,force is only known to us as a manifestation of divine power which can neither be created nor destroyed4 ,the store of force or energy in nature is ever changing its form of action1 its amount never4 ,it may be dispersed in various directions1 and subdivided so as to become evanescent to our perceptions2 it may be balanced so as to be in abeyance1 or it may become potential as in static electricity2 but the instant the impediment is removed the power is manifested by motion4 ,whatever form force may assume it has invariably a compensation or equivalent1 whether in the heavens or on the earth4 ,the total sum of the living forces1 vis viva1 or actual energy of the planets is the same every time they return to the same relative positions with regard to one another1 to their orbits and to space1 whatever may have been their velocities or mutual disturbances4 ,in the ocean1 the energy by which #be1jjj cubic miles of water flow over a quarter of the globe in six hours1 is exactly equal to the force or energy that makes it ebb during the succeeding six hours4 ,a body acquires heat in the exact proportion that the adjacent substances become cold2 and when heat is absorbed by a body1 it becomes an expansive energy at the expense of those around it1 which contract4 ,chemical action many miles distant from the electro-magnet1 as in telegraphs1 is perfectly equivalent to the dominant chemical action in the battery4 ,the two electricities1 positive and negative1 are developed in equal proportions1 which may be combined so as to produce many changes in their respective relations1 yet the sum of the energy of the one kind can never be made in the smallest degree either to exceed or to come short of the sum of the other4 ,the mechanical energy of machinery or working power is exhausted by the very act of working1 and cannot be restored except by the action of other forces4 ,in clockwork1 the weight must sink to move the wheel1 and when the weight is down1 the store of energy is gone1 and can only be restored by raising the weight through the expenditure of energy in the human arm1 and the expenditure of human energy must be restored by food and rest4 ,the heat given off from the bodies of men and animals is restored by the combustion of the oxygen inhaled during respiration and the carbon of the food1 and the light and heat given out by the combustion of fuel1 whether in the form of coal or wood1 is compensated by the light and heat of the sun stored up in living vegetables4 ,it is this equivalent for force or energy which prevails in every department of nature that constitutes the universal and invariable law of the ,conservation of ,energy1 #8a principle in physics as large and sure as that of the indestructibility of matter or the invariability of gravity4 ,no hypothesis should be admitted nor any assertion of a fact credited1 that denies this principle4 ,no view should be inconsistent or incompatible with it4 ,many of our hypotheses in the present state of science may not comprehend it1 and may be unable to suggest its consequences1 but none should oppose or contradict it4'#a ,thus1 #8there is a definite store of energy in the universe1 and every natural change or technical work is produced by a part only of this store1 the store itself being eternal and unchangeable4'#b ,cohesion is a force which acting at inappreciably small distances unites atoms and molecules of the same kind into solids1 liquids1 and ariform fluids1 exactly according to the law of the conservation of energy2 for it requires the very same amount of force to dissolve their union as to form it4 ,cohesion varies with temperature both in simple and compound bodies1 for metals can be fused and vaporized by artificial heat1 and ice becomes water and aqueous vapour as the seasons change from winter to summer4 ,in solids the force of cohesion is so strong1 that their atoms and molecules always retain their respective places2 that power is so weak in liquids1 that their atoms and molecules are capable of motion among themselves1 and in gases and the ethereal medium the atoms are free and have no cohesion whatever4 ,the resistance offered by substances to compression is an equal and contrary force4 ,the reciprocal attraction between solids and liquids in capillary tubes is a case of cohesion4 ,if a glass tube of extremely fine bore be plunged into a glass of water or alcohol1 the liquid will immediately rise in the tube above the level of that in the cup1 and the surface of the little suspended column will be a hollow hemisphere4 ,if on the contrary mercury be the liquid1 it will not rise so high in the glass tube1 and the surface of the little column will be a convex hemisphere4 ,there is a reciprocal attraction between the glass tube and the liquid1 and another between the particles of the liquid itself2 and the effect is produced by the difference between the two4 ,in the first case the attraction of the glass is greater than that of the liquid1 and in the second it is less2 hence the water rises higher in the tube than the mercury1 and its surface is concave1 while that of the mercury is convex4 ,the elevation or depression of the same liquid in different tubes of the same matter is in the inverse ratio of their internal diameters1 and altogether independent of their thickness2 whence it follows that molecular action is insensible at sensible distances1 for when tubes of the same bore are wetted throughout their whole extent with water1 mercury will rise to the same height in all of them whatever be their thickness or density1 the film of water being sufficient to intercept the molecular action1 and to supply the place of a tube by its own capillary attraction4 ,the action of this force is daily seen in the absorption of water by sponges1 sugar1 salt and other porous bodies1 and it is a most important agent in the circulation of fluids in animals and vegetables4 ,every atom of matter is subject to the force of gravitation1 but each substance has its own peculiar weight of specific gravity1 that is to say1 the same bulk of different substances contains different quantities of matter4 ,since nothing is known of absolute weight it is necessary to have some standard of comparison1 and for that purpose pure water at the temperature #ci ,fahr4 7that of its maximum density7 is chosen for solids and liquids2 while for gases and vapours atmospheric air at the temperature of sixty degrees of ,fahrenheit's thermometer1 and a barometric pressure of thirty inches1 is assumed as the unit of specific gravity4 ,the foot-pound1 which is the unit of mechanical force as established by ,mr4 ,joule1 is the force that would raise one pound of matter to the height of one foot2 or it is the impetus or force generated by a body of one pound weight falling by its gravitation through the height of one foot4 ,now impetus or vis viva is equal to the mass of a body multiplied by the square of the velocity with which it is moving3 it is the true measure of work or mechanical labour4 ,for if a weight be raised ten feet1 it will require four times the labour to raise an equal weight to forty feet4 ,if both these weights be allowed to fall freely by their gravitation1 at the end of their descent1 their velocities will be as one to two1 that is as the square roots of their heights1 but the effect produced will be as their masses multiplied by one and four2 but these are the squares of their velocities4 ,hence impetus or vis viva is equal to the mass multiplied by the square of the velocity4 ,thus impetus is the true measure of the labour employed to raise the weights1 and of the effect of their descent1 and is entirely independent of time4 ,it is well known that iron becomes red-hot by percussion or impetus4 ,the atoms of the iron are thrown into vibration1 and these minute motions communicated to the nerves produce the sensation of heat4 ,now the mechanical labour required to raise the hammer to any number of feet is equal to the weight of the hammer multiplied by that number of feet2 but the impetus or mechanical effect of the fall of the hammer is equal to its mass multiplied by the square of the velocity1 that is to the vis viva3 hence the quantity of heat generated is proportional to the vis viva4 ,the circumstances being the same1 if the mass be doubled the amount of heat is doubled2 and if the velocity be doubled the amount of heat is quadrupled4 ,if the weight and the perpendicular height through which a body has fallen be known1 the quantity of heat generated may be determined4 ,the same amount of heat is generated by the same amount of force1 whatever that force may be1 whether impetus1 friction1 or any other4 ,dr4 ,thomson has put in a strong point of view the quantity of heat that might be generated by percussion or impetus4 ,he computed that if by any sudden shock the earth were arrested in its orbit1 the heat generated by the impulse would be equal to #aa1bjj degrees of the centigrade thermometer1 even if the capacity of our planet for heat were as low as that of water2 it would therefore be mostly reduced to vapour1 and should the earth then fall to the sun as it certainly would do1 the quantity of heat developed by striking on the sun would be #djj times greater4 ,it is even supposed that the light and heat of the sun are owing to showers of bodies falling on the surface with impetus proportionate to his attraction1 for had he been in combustion he would have been burnt out ages ago4 ,the masses of meteoric iron and stone that occasionally fall on the earth show that matter may be wandering in space2 the vast zone of smaller bodies that in their annual revolutions round the sun come within the earth's attraction in ,august and ,november1 when thousands of them take fire and are consumed on entering our atmosphere1 show that a great amount of matter of small dimensions exists within our own system4 ,much may be beyond it which drawn by the sun's attraction may fall on his surface4 ,when a body is heated1 it absorbs one part of the heat2 the other part raises its temperature4 ,the part absorbed increases the bulk or volume of the body1 the expansion being the exact measure1 or mechanical equivalent of the heat absorbed4 ,in fact the coefficient of expansion is the fractional part of the expansion in length1 surface1 or volume of the body when its temperature is raised one degree4 ,when the body is cooled1 its volume is diminished1 and then the contraction is an exact measure1 or mechanical equivalent of the heat given out1 and thus expansion and contraction are correlatives with and represent heat and cold4 ,specific heat is the quantity of heat required to raise a given bulk or a given weight of a body a given number of degrees4 ,in the one case it is distinguished as the specific heat for a constant volume1 in the other for a constant weight4 ,although the specific heat of a substance remains the same1 its sensible and absorbed heat may vary reciprocally to a great extent4 ,as there can be no direct measurement of heat independent of matter1 its mutations and action on matter are the sole means we have of forming our judgment concerning its agency in the material world4 ,mr4 ,joule has proved that the quantity of heat requisite to raise the temperature of a pound of water one degree of the centigrade thermometer is equivalent to the mechanical work or force that would raise the same mass of water to the height of #a1chi feet4 ,this is the unit1 or mechanical equivalent of heat4 ,in fact1 for every unit of force expended in percussion1 friction1 or raising a weight1 a definite quantity of heat is generated2 and conversely1 when work is performed by the consumption of heat1 for each unit of force gained1 a unit of heat disappears4 ,for since heat is a dynamical force of mechanical effect1 there must be an equivalence between mechanical work and heat as between cause and effect4 ,that equivalence is a law of nature4 ,the mechanical force exerted by the steam engine is exactly in proportion to the consumption of heat1 neither more nor less2 for if we could produce a greater quantity than its equivalent we should have perpetual motion1 which is impossible4 ,when steam is employed to perform any work1 the temperature of the steam is lowered2 the heat that disappears is transformed into the force that performs the work1 and is exactly proportional to the work done1 and vice vers4 ,the heat which is the motive force in the steam engine is due to the chemical combination of the carbon of the fuel with the oxygen of the atmosphere4 ,a pound weight of coal when consumed in one of our best steam engines produces an effect equal to raising a weight of a million of pounds a foot high1 yet marvellous as that is1 the investigations of recent years have demonstrated the fact1 that the mechanical energy resident in a pound of coal and liberated by its combustion is capable of raising to the same height ten times that weight4#c ,the quantity of coal existing in the whole globe is believed to be inexhaustible1 hence the energy in abeyance is incalculable4 ,the chemical energy continually and actually exerted in the great laboratory of nature is greater than that which maintains the planets in their orbits4 ,the act of the combination of the atoms of carbon and oxygen in combustion is #8now regarded exactly as we regard the clashing of a falling weight against the earth1 and the heat produced in both cases is referable to the same cause2'#d so chemical combination in combustion is only a particular case of falling bodies4 ,drummond's light1 the most brilliant of artificial illuminations1 is produced by a simultaneous shower of the atoms of oxygen and hydrogen gas upon lime2 and platinum1 the least fusible of metals1 is vaporized by a similar shower from the oxy-hydrogen blowpipe1 and thus impetus generates both light and heat1 for although the atoms are too small to admit of an estimation of their individual vis viva1 there can be no doubt that like causes produce like effects4 ,in what manner or under what form magnetism and electricity exist when quiescent in matter we know not1 but the compass needles show that numerous lines of magnetic force1 subject to periodic and secular variations1 perpetually traverse the earth and the ocean2 and that waves of magnetic force occasionally sweep rapidly over great tracts of the globe4 ,these phenomena would seem to stand in some periodic connection with the solar spots4 ,professor ,lamont of ,munich has discovered that a permanent and regular current of electricity is propagated parallel to the equator all over the earth1 and another similar to it in the atmosphere4 ,besides these1 there are currents of electricity in the surface of the earth1 sometimes in one direction and sometimes in another1 which decrease with the depth2 and ,m4 ,lamont conceives that this electric system is the cause of terrestrial magnetism4 ,electricity of intense power and inappreciable quantity certainly exists in abeyance in the atmosphere and in all terrestrial matter till the equilibrium between the antagonist forces be disturbed1 and then it bursts forth with terrific violence in the lightning flash and stunning crash of thunder4 ,since it requires electricity equivalent to that in activity during a thunderstorm to form one drop of water1 what must that power have been which the ,omnipotent wielded when he created that deep over the face of which #8darkness brooded4' ,electricity1 though the most formidable power in nature1 is made available to man by the voltaic battery1 and by the electro-magnetic induction apparatus1 in the battery of which it is generated by the chemical action of dilute sulphuric acid on zinc4 ,the positive and negative electricities thus produced pass in opposite directions through the two conducting wires of the machine by a continuous transmission of force or vibration from atom to atom1 a circulation that is accompanied by a continual development of heat in overcoming the resistance it meets with in the wires4 ,the electricity decreases as the heat increases1 and vice vers2 the action is reciprocal4 ,thus electricity is merely a transmission of force4 ,mr4 ,joule has proved that the quantity of heat produced in a unit of time is proportional to the strength of the current1 whatever may be its direction1 and that its power to overcome resistance is as the square of the force of the current4 ,the force is exactly in proportion to the chemical action which produces it1 and that is measured by the quantity of zinc consumed in the battery4 ,thus chemical action produces electricity1 and conversely electricity is a powerful agent in the chemical composition and decomposition of matter4 ,the light and heat of the electric spark are intense though instantaneous2 but a powerful induction apparatus like ,ruhmkorff's gives so rapid a succession of sparks that the light and heat are sensibly continuous and of great intensity4 ,the light and heat1 powerful as lightning itself1 are produced by the combined currents of two batteries1 each consisting of fifty ,bunsen elements of moderate size4 ,this formidable united current passes through a circuit of thick copper wire coated with silk thread1 with an intensity of perpetually renewed heat that no substance can resist4 ,when the copper conducting wires are fitted with charcoal terminals and brought near to one another1 the dazzling lights emanating from each pole combine in one blaze of insupportable brilliancy4 ,the most refractory substances1 silica1 alumina1 iron and platinum1 when placed between the poles1 immediately melt like wax1 and volatilize4 ,charcoal is so good a conductor of electricity that when the terminals are in contact they complete the circuit1 and neither light nor heat appear4 ,air and glass are non-conductors1 yet the spark has passed through several inches of air and perforated a mass of glass two inches thick4 ,a long electric spark combines or decomposes a greater quantity of gas or vapour than a short one1 and for a given induction apparatus and induction current1 ,m4 ,perrot has shown that there exists a length of spark corresponding to a maximum chemical action4 ,professor ,seebeck of ,berlin discovered that electric currents are produced by the partial application of heat to a circuit formed of two solid conducting substances as antimony and bismuth soldered together1--another proof of the correlation of heat and electricity4 ,there cannot be a doubt that the atoms of a conducting wire are in motion1 and that they successively take definite and momentary positions during the passage of an electric current1 after which they return successively to their normal state4 ,when electricity is invariably sent from the same pole of an inductive apparatus through the wire of a telegraph1 in a very short time the wire is torn or divided into small sections1 which destroy its continuity2 but when the electricity is sent from each pole alternately1 the conducting wire is not injured4 ,as each atom of the wire has its own electricity1 this seems to indicate that during the successive transits of the same kind of electricity1 the pole of each individual atom is attracted more and more in the same direction1 till at last they no longer return to their normal state1 the cohesive force is overcome1 and a rupture takes place1 the more readily if there be any imperfection in the wire4 ,since the electricity from the other pole of the machine would have the same effect1 but in the contrary direction1 an alternate motion in the atoms must maintain the continuity of the wire4 ,a closed current of electricity or magnetism is accompanied by a simultaneous current of the opposite force in the tangential direction equal in quality and intensity4 ,thus the electric and magnetic currents1 which are merely transmissions of energy1 differ by moving at right angles to one another2 their effects are alike1 yet they are not identical4 ,the amount of the chemical action of light has been determined by ,professor ,roscoe to be directly proportional to the intensity of the light2 and when the light is constant the amount of action is exactly proportional to the time of exposure4 ,it appears that equal volumes of chlorine and hydrogen explode in sunshine1 but combine slowly in shade2 and as the combined gases are absorbed by water as soon as combined1 the gradual diminution of the volume of the mixed gases during the time of absorption is a measure of the amount of action exerted by the light4 ,professor ,wm4 ,thomson has computed1 by the aid of ,poullet's data of solar radiations and ,mr4 ,joule's mechanical equivalent of heat1 that the mechanical value of the whole energy1 active and potential1 of the disturbances kept up on the ethereal medium by the vibrations of the solar light in a cubic mile of our atmosphere1 is equal to #ab1jej times the unit of mechanical force3 that is to say1 twelve thousand and fifty times the force that would raise a pound weight of matter to the height of one foot4 ,the sensible height of the atmosphere is about forty miles1 whence some idea may be formed of the vast amount of force exerted by the sun's light within the limits of the terrestrial atmosphere4 ,the green mantle which clothes the earth proves under a beautiful form the influence of light on the organic world4 ,it has been proved that at any given fixed temperature the amount of light and heat absorbed and that which is emitted remains constant for all bodies4 ,the greater the amount absorbed1 the greater the amount radiated4 ,the molecules or atoms of the bodies in consequence of the law of resonance emit those ethereal undulatory motions which have been previously impressed upon them1 as a musical instrument resounds in answer to the note impressed upon it4 ,the whole is referable to molecular or atomic motion1 for in absorption the vibrations of the ether are communicated to the atoms1 and in radiation1 the vibrations are returned again to the ether4 ,this principle is known as the law of exchange4#e ,matter has a decomposing and an elective power with regard to both radiant light and heat2 most coloured bodies1 such as flowers1 green leaves1 dyed cloth1 c41 though seen by reflection1 owe their colour to absorption4 ,the light by which they are seen is reflected1 but it is not in reflection that the selection of the rays is made which causes the objects to appear coloured4 ,when light falls upon red cloth1 a small portion is reflected at the outer surfaces of the fibres1 and this portion1 if it could be observed alone1 would be found to be colourless4 ,the greater portion of the light penetrates into the fibres1 when it immediately begins to suffer absorption on the part of the colouring matter4 ,on arriving at the second surface of the fibre1 a portion is reflected and a portion passes on1 to be afterwards reflected from1 or absorbed by1 fibres lying more deeply4 ,at each reflection the various kinds of light are reflected in as nearly as possible the same proportion1 but in passing across the fibres while going and returning they suffer very unequal absorption on the part of the colouring matter2 so that in the aggregation of the light perceived the different components of white light are present in proportions widely different from those they bear to each other in white light itself1 and the result is a vivid colouring4 ,in certain substances however1 as gold and copper1 the different components of white light are reflected with different degrees of intensity1 and the light becomes coloured by these reflections4 ,gold is yellow by reflection2 red cloth is red by absorption4 ,in the same sense1 physically speaking1 in which the red cloth is red1 gold is not yellow but blue or green2 such is in fact the colour of gold by transmission through gold leaf1 and therefore gold is greenish blue by absorption4 ,in this case we see that while the substance copiously reflects and intensely absorbs rays of all kinds1 it more copiously reflects the less refrangible rays with respect to which it is more intensely opaque4 ,in general absorption and radiation are independent of colour4 ,there is a vast diversity in the property which substances possess with regard to the transmission of radiant light and heat2 glass1 for instance1 transmits light abundantly1 but is impervious to heat from non-luminous sources2 while other substances1 which are altogether opaque to light1 transmit heat copiously1 as the bisulphide of carbon1 which of all liquids is the most diathermic1 while water in all its forms is almost impervious to heat4 ,sir ,william ,herschel discovered that invisible rays of high heating power exist beyond the red end of the solar spectrum1 and ,mr4 ,tyndall has shown that the reason of a substance being impervious to the light of the most brilliant flame and at the same time pervious to these extra red rays is1 that the intercepted rays of light are those whose periods of recurrence coincide with the periods of oscillation possible to the atoms of the substance in question4 ,the elastic forces which separate these atoms are such as to compel them to vibrate in definite periods1 and when their periods synchronize with those of the ethereal waves1 the latter are absorbed4 ,thus transparency in liquids as well as in gases is synonymous with discord1 while opacity is synonymous with accord between the periods of the waves of ether and those of the body on which they impinge4 ,all ordinary transparent and colourless substances owe their transparency to the discord which exists between the oscillating periods of their molecules and those of the waves of the whole visible spectrum4 ,the general discord of the vibrating periods of the molecules of compound bodies with the light-giving waves of the spectrum may be inferred from the prevalence of the property of transparency in compounds1 while their greater harmony with the extra red periods is to be inferred from their opacity to the extra red rays4 ,water illustrates this transparency and opacity in the most striking manner4 ,it is highly transparent to the luminous rays1 which demonstrates the incapacity of its molecules to oscillate in periods which excite vision4 ,it is as highly opaque to the extra red oscillations1 which proves the synchronism of its periods with more of the longer waves4 ,if1 then1 to the radiation from any source water shows itself to be eminently or perfectly opaque1 it is a proof that the molecules whence the radiation emanates must oscillate in extra red periods4 ,it has been already mentioned that many substances which transmit radiant heat freely radiate badly1 and vice vers4 ,rock-salt is extremely permeable to radiant heat but radiates feebly2 the reason according to ,mr4 ,tyndall is1 that the motion of the molecules of the salt1 instead of being expended on the ether between them and then communicated to the ether external to the mass1 is transmitted freely from molecule to molecule4 ,alum is exactly the reverse4 ,mr4 ,balfour ,stewart proved that alum is an excellent radiator1 and ,mr4 ,tyndall proved it to be a very bad conductor1 imparting freely and with ease the motion of its molecules to the external ether1 and #8for that very reason it finds difficulty in transferring the motion from molecule to molecule4 ,the molecules are so constituted that when one of them approaches its neighbour1 a swell is produced in the intervening ether2 this motion is immediately communicated to the ether outside1 and is thus lost for the purposes of conduction4'#f ,melloni had investigated the laws of the radiation and absorption of radiant heat in solid and liquid matter2 but its radiation and absorption by gases and vapours was unknown previous to the experiments of ,mr4 ,tyndall4 ,the apparatus employed was a horizontal brass tube four feet long1 between two and three inches in diameter1 polished inside1 and closed air-tight at each end by a plate of rock-salt1 which transmits more heat than any other substance4 ,the air could be pumped out of the tube by one pipe1 and the gas or vapour for the experiment introduced by another4 ,close to one end of the brass tube there was a thermo-electric pile connected with its goniometer4 ,on each side of this arrangement there was a vessel of water kept at the boiling point4 ,these two vessels were so placed that when the rays of heat from one of them passed through the exhausted tube1 and fell upon one face of the thermo-electric pile1 their effect was so neutralized or balanced by the rays of heat falling on the opposite face of the pile from the other1 thus the needle of the goniometer was steadily maintained at zero1 and its deflection instantly showed the absorbent effect produced by any gas or vapour that was admitted into the exhausted tube4 ,since aqueous vapour has a very exalted absorbent power1 a gas or vapour was rendered perfectly dry before its absorbent capacity was determined4 ,for that purpose the pipe that introduced it into the brass experimental tube was so constructed that the gas had first to pass over fragments of pumice-stone wet with strong sulphuric acid1 which absorbed its moisture and dried it4 ,common atmospheric air1 however1 was not only dried in this manner1 but it was deprived of its carbonic acid by passing over caustic potash1 and many other precautions were taken to prevent the possibility of error4 ,under the ordinary pressure of the atmosphere1 when the experimental tube was exhausted1 the needle of the goniometer stood at zero1 but as soon as pure dry atmospheric air was introduced into the tube its absorption caused the needle to move from zero to #a4 ,the tube was again exhausted2 the needle stood at zero1 but was deflected from zero to #a as soon as the tube was filled with oxygen4 ,a similar experiment was made with nitrogen and hydrogen with the same result4 ,thus1 dry air and the elementary gases1 oxygen1 nitrogen1 and hydrogen1 have the same absorptive power1 and consequently they all deflected the needle of the goniometer one degree4 ,the whole amount of radiant heat that passed through the exhausted tube produced a deflection of #ga #e2 hence taking as unit of heat the amount that would deflect the needle one degree1 the number of units expressed by #ga #e is #cjh1 consequently the absorption of each of these four gases amounts to #ajj_/cjh or #jc per cent4 ,the most delicate tests could not show any difference between the three first1 but ,professor ,tyndall had reason to believe that hydrogen has the lowest absorptive power of all gases and vapours1 though he was unable to express the amount4 ,the absorptive power of all four is very much less than that of every other gas or vapour1 and invariably deflects the needle to #a1 which thus becomes the unit of comparison4 ,olefiant gas1 the most luminous of the constituents of coal gas1 possesses the highest absorptive power of the permanent gases4 ,when sent into the exhausted tube it deflected the needle of the goniometer from #j to #gj #c1 which is equivalent to #bij units4 ,the whole heat that passed through the exhausted tube before the gas was admitted produced a deflection of #ge or #cfj units1 consequently more than #g_/ajths or #ha per cent4 of the whole heat was cut off by the olefiant gas4 ,such opacity to heat in so transparent a gas is quite marvellous4 ,a current of it was sent into the open air between the thermo-electric pile and one of the sources of heat1 and although it was perfectly invisible1 it instantly deflected the needle of the goniometer from #j to #da4 ,in order to ascertain the relation between the density of the gas and the quantity of heat extinguished or absorbed1 an ordinary mercurial gauge was attached to the air-pump4 ,the experimental tube was exhausted1 and the needle of the goniometer stood at zero4 ,then1 from a graduated glass vessel1 measures of olefiant gas1 each amounting to the #a_/ejth of a cubic inch1 were successively sent through the drying pipe into the exhausted tube4 ,the amount of the heat absorbed and the depression of the mercurial column corresponding to each measure of gas as it was introduced1 was registered from one to fifteen measures4 ,this experiment showed that for very small quantities of gas1 the absorption is exactly proportional to the density or tension4 ,one measure of the gas only produced a depression of the mercurial column amounting to the #a_/cfgth part of an inch1 or about the #a_/aeth of a millimetre4 ,in many of the vapours of volatile liquids1 the preceding law only prevails to a certain amount of pressure differing in each case1 beyond which increase of tension produces diminished effects4 ,in sulphuric ether the change begins at the eleventh term4 ,in bisulphide of carbon the law changes after the sixth measure1 c4 ,in order to adapt the apparatus for experiments on coloured gases1 a glass experimental tube #b ft4 #i in4 long1 and #b ft4 #d in4 in diameter1 was substituted for the brass tube1 and1 instead of boiling water1 sources of radiant heat having a constant temperature of #bgj ,cent4 were adopted4 ,the following table shows the absorption of a number of gases at a common pressure or tension of one atmosphere4 ,dry air #a ,oxygen #a ,nitrogen #a ,hydrogen #a ,chlorine #ci ,hydrochloric acid #fb ,carbonic oxide #ij ,carbonic acid #ij ,nitrous oxide #cee ,sulphuretted hydrogen #cij ,marsh gas #djc ,sulphurous acid #gaj ,olefiant gas #igj ,ammonia #aaie ,the absorptive power of ammonia is so great1 that although as transparent in the glass tube as if it had been a vacuum1 a length of three feet of it would be perfectly impervious or black to the heat here employed1 yet even this does not express the energy which it exhibits under one inch of pressure4 ,when the relative absorptive actions of gases and vapours is compared1 it must be under the same amount of pressure4 ,hence1 for one inch of tension1 the absorptive action of ,dry air #a ,oxygen #a ,nitrogen #a ,hydrogen #a ,chlorine #fj ,bromine #afj ,hydrochloric acid #ajje ,carbonic oxide #gej ,nitric oxide #aeij ,nitrous oxide #ahfj ,sulphide of hydrogen #bajj ,ammonia #gbfj ,olefiant gas #giej ,sulphurous acid #hhjj ,thus1 for a tension of an inch of mercury1 the absorption of ammonia exceeds that of air more than #gjjj times2 the action of olefiant gas is #giej times1 and that of sulphurous acid #hhjj times1 greater than the absorption of air4 ,the effect produced by #a_/cjth of an inch of tension of air and the elementary gases is equivalent to that produced by one inch in the others1 so the unit representing the absorption of these four gases is only the #a_/cjth part of the unit in the preceding table4 ,it appears from the preceding tables of comparative absorption that chlorine1 a highly-coloured gas with a specific gravity of #bde1 has an absorptive power expressed by #ci under the pressure of one atmosphere1 while1 at the same tension1 hydrochloric acid1 a chemical compound of chlorine and hydrogen which is perfectly transparent1 with a specific gravity of only #abf1 has an absorptive action amounting to #fb1 whence it appears that the chemical change which renders chlorine more transparent to light1 makes it more opaque to obscure heat4 ,again1 bromine1 which is far less permeable to light than chlorine1 and has a specific gravity of #eed1 has an absorptive power of #afj under a tension of one inch2 while hydrobromic acid1 which is perfectly transparent to light1 has an absorptive action for obscure heat amounting to #ajje4 ,this is a striking instance of transparency to light and opacity to heat being produced by the very same chemical art4 ,the enormous difference between the absorptive power of compound and simple gases and vapours is ascribed to their atomic structure2 in fact the radiant and absorptive powers augment as the number of atoms in the compound molecule augments4 ,the three elementary gases are formed of simple atoms1 the compound gases and vapours consist of different kinds of atoms chemically united into groups4 ,both are free to receive the vibratory motions of the ether which constitute heat2 but single atoms must produce a less effect than when a number of them are united into a molecule4 ,the atoms are loaded by their chemical union1 which offers a greater surface of resistance to the vibrations of heat1 and renders the motion of the molecule more sluggish and more fit to accept the slowly recurrent waves of the obscure heat that strike upon it4 ,thus when atoms of hydrogen and nitrogen are mixed in the proportion of three to one1 the absorption of the mixture is represented by unity2 but when they are chemically united in ammonia1 the absorption is #aaij times as great4 ,atoms of hydrogen and oxygen mixed in the proportion of two to one absorb very feebly2 when chemically united into a molecule of aqueous vapour the absorptive power is enormous4 ,the absorptive power of nitrous oxide1 a chemical compound of oxygen and nitrogen1 exceeds that of dry air #bej times2 a convincing proof that the atmosphere is a mixture and not a compound gas4 ,olefiant gas at five inches of tension absorbs #ajjj times that of its constituent hydrogen4 ,in fact all the compound gases and vapours far surpass the simple elementary gases and dry atmospheric air in their capacity for absorption4 ,chlorine and bromine1 which have so many singular properties in common1 have this peculiarity also1 that though simple substances respectively formed of homogeneous atoms1 their absorptive powers are similar to those of compound substances1 for the absorptive power of chlorine is #fj times that of the elementary gases1 and that of bromine #afj times4 ,this high absorptive power is ascribed by ,professor ,tyndall to their atoms being united into groups which act powerfully as oscillating systems1 instead of the feeble action of single atoms4 ,ozone is an analogous instance of the presumed union of homologous atoms into oscillating groups4 ,by comparing the absorptive effect of ozonized oxygen obtained from the electric decomposition of water with that of the same oxygen deprived of its ozone by passing it over a very strong solution of iodide of potassium1 ,professor ,tyndall found that ozonized oxygen possesses an absorption force #acf times greater than that of pure oxygen4 ,the quantity of ozone producing this astonishing effect was too small even to admit of estimation1 far less of measurement4 ,this result induced ,professor ,tyndall to believe that ozone is produced by the packing of the atoms of elementary oxygen into oscillatory groups2 and that heating dissolves the bond of union and allows the atoms to swing singly1 thus disqualifying them from either intercepting or generating the motion which as systems they were competent to intercept and generate4 ,the indefinitely small and invisible constituents of perfumes of plants and flowers are proved to be compound bodies by their absorptive and radiating properties4 ,the dried leaves of a flower or aromatic plant such as thyme were stuffed into a glass tube #ah inches long and a quarter of an inch in diameter4 ,it was then inserted between the drying pipe of the machine and the experimental glass tube1 which was exhausted1 and the needle of the goniometer stood at zero4 ,then when the air admitted into the drying pipe passed over the thyme and carried its aroma into the experimental tube1 the needle was deflected1 and from thence the absorption of the thyme was computed to be #cc times greater than that of the air which carried it4 ,by the same process it was found that the absorption of peppermint was #cd times1 spearmint #ch times1 lavender #cb times1 and wormwood #da times greater than that of the dry air1 which was unity as usual4 ,when small equal squares of bibulous paper rolled into cylinders and moistened with an aromatic oil1 were substituted for the dried herbs1 the absorption corresponding to the deflection of the needle was for dry air1 equal to #a1-- ,patchouli #cj ,sandal wood #cb ,geranium #cc ,oil of cloves #cce ,otto of roses #cfe ,bergamot #dd ,lavender #fj ,lemon #fg ,orange #fg ,thyme #fh ,rosemary #gd ,oil of laurel #hj ,chamomile flowers #hg ,spikenard #cee ,anise seed #cgb ,the absorption of thyme and lavender shows how much aroma is lost when plants are dried4 ,so great is the absorption of heat1 that the perfume of a flower-bed may be more efficacious than the entire oxygen and nitrogen of the atmosphere above it4 ,the enormous absorption and consequently radiating power of the perfumes of plants and flowers is a proof that their constituent parts are molecules and not simple atoms1 incredible as it may seem4 ,the absolute weight of the substances producing these wonderful effects is unknown1 but there must be great differences3 some perfumes are carried to vast distances1 others are less volatile1 and that of mignonette was remarked by ,dr4 ,wollaston to be absolutely so heavy that it was quite as powerful below a balcony containing a box of that plant1 as in the balcony itself4 ,the perfumes during the experiments adhered to all parts of the apparatus so pertinaciously1 that after a continued stream of dry air had been pumped through the tube till the exhaustion seemed to be complete and the needle stood at zero1 after a few minutes' repose1 the residue of the perfume came out so powerfully from the crannies of the apparatus as almost to restore the original deflection4 #8,the quantities of those residues must be left to the imagination to conceive4 ,if they were multiplied by billions they probably would not obtain the density of the air4' ,the absorptive power of the odour of musk was #gb or #gd times that of the air that conveyed it into the experimental tube2 the quantity that produced it was quite inappreciable1 yet the perfume was so persistent that the pieces of the apparatus through which it had passed had to be boiled in a solution of soda before they were fit for other experiments4 ,the absorption of many gases and vapours having been determined1 their radiation was measured by a very simple arrangement4 ,the thermo-electric pile was raised on a stand with a screen of polished tin in front of it4 ,a heated copper ball in a perforated ring on a low stand was placed behind the screen2 all direct radiation from the ball was thus cut off1 but the heated air rising in a column above the screen radiated its heat on the pile and deflected the needle of the goniometer #fj when the ball was red-hot2 but the radiation of the hot air was neutralized by another source of radiant heat on the opposite side of the pile which kept the needle steadily at zero4 ,then a purified gas or vapour conveyed by a pipe into the perforated ring which held the ball rose mixed with the heated air above the screen1 but the radiation of the gas or vapour alone was shown by the deflection of the needle1 because that of the air was compensated4 ,with this apparatus ,professor ,tyndall proved that the amount of the absorption of each gas and vapour is exactly equal to the amount of its radiation4 ,he has shown that this result is a necessary consequence of the dynamical nature of heat4 ,for as no atom or molecule is capable of existing in vibrating ether without accepting a portion of the motion1 the very same quality whatever it may be that enables it to do so1 must enable it to impart its motion to still ether when plunged into it4 #8,hence from the existence of absorption we may on theoretic grounds infallibly infer a capacity for radiation2 from the existence of radiation we may with equal certainty infer a capacity for absorption1 and each of them must be regarded as the measure of the other4' ,this reasoning1 founded simply on the mechanical relations of the ether and the atoms immersed in it1 is completely verified by experiment4 ,hitherto the absorption and radiation of heat by the same thickness of different gases and vapours have been compared with each other1 but in a recent series of experiments ,mr4 ,tyndall has compared the action of different thicknesses of the same gas or vapour on radiant heat4 ,the experiments extend from a thickness of #jja of an inch to that of #did inches4 ,the instrument employed for ascertaining the action of the smaller thickness was a horizontal hollow cylinder closed at one end by a plate of rock-salt4 ,a second cylinder was fitted into this with its end also closed by a plate of rock-salt4 ,this cylinder moved within the other like a piston1 so that the two plates of rock-salt could be brought into flat contact with one another1 or could be separated to any required distance1 and the distance between the plates was measured by a vernier4 ,at one end of the cylinder there was a source of constant heat1 and the differential goniometer already described at the other4 ,with this apparatus ,mr4 ,tyndall found that olefiant gas maintains its great superiority over the other gases in absorptive power at all thicknesses4 ,a layer of that gas not more than #jja of an inch thick intercepted about one per cent4 of the total radiation4 ,this great absorption corresponded to a deflection of #aa of the needle of the goniometer1 and such was the delicacy of the apparatus that it would be possible to measure the action of a layer of this gas of less thickness than a sheet of writing paper4 ,a layer of olefiant gas two inches thick intercepts nearly #cj per cent4 of the entire radiation4 ,a shell of olefiant gas two inches thick surrounding our globe would offer no appreciable hindrance to the solar rays in coming to the earth1 but it would intercept1 and in great part return1 #cj per cent4 of the terrestrial radiation2 under such a canopy the surface of the earth would probably be raised to a stifling temperature4 ,the apparatus for measuring the action of the greater thicknesses of gas was a hollow brass cylinder #did inches long1 closed at both ends by plates of rock-salt1 and divided internally into two compartments or chambers by a third plate of rock-salt movable in the interior2 the source of heat being at one end and the differential goniometer at the other4 ,carbonic oxide and carbonic acid are pervious to a vast majority of the rays of radiant heat4 ,when the cylinder was filled with carbonic oxide gas and so divided1 by moving the internal plate of rock-salt1 that a stratum of the gas #h inches long was next to the source of heat1 and that #dad inches long farthest from it1 the #h inches of gas intercepted #f per cent4 of the whole radiation4 ,but when the plate of rock-salt was moved till the column #dad inches long was next to the source of heat1 and that of #h inches farthest from that source1 or behind the long one1 the absorption of the #h inches was sensibly zero4 ,in like manner eight inches of carbonic acid gas when in front of a column of #dad inches of the same gas absorbed #f-a_/d per cent4 of the whole radiation1 while placed behind that column the effect was nearly zero4 ,the reason is that when the #h inch stratum is in front1 it stops the main portion of the rays which give it its thermal colours1#g while placed behind these same rays have been almost wholly withdrawn1 and to the remaining #id per cent4 of the radiation the gases are sensibly permeable4 ,it is inferred from an extension of this reasoning that the sum of the absorptions of the two chambers taken separately must always be greater than the absorption effected by a single column of the gas of a length equal to the sum of the two chambers2 this conclusion is illustrated in a striking manner by the experiments4 ,it is also found that when the mean of the sums of the absorptions is divided by the absorption of the sum1 the quotient is sensibly the same for all gases4 ,it may farther be inferred that the sum of the absorptions must diminish and approximate to the absorption of the sum as the two chambers become more unequal in length1 and that the sum of the absorptions of the two chambers is a maximum when the medial plate of rock-salt divides the long tube into two equal parts4 ,when air enters an exhausted tube it is heated dynamically by the collision of its particles on the sides of the tube as it rushes in to fill the vacuum2 and when the tube is exhausted again by the air pump1 chilling is produced by the application of a portion of the heat of the air to generate vis viva4 ,this dynamic principle occurred in some of the experiments1 and was dexterously adopted and applied to the solution of a striking and unprecedented problem3 #8,to determine the radiation and absorption of gases and vapours without any source of heat external to the gaseous body itself4' ,the two external sources of heat being therefore dispensed with in the absorptive apparatus1 the thermo-electric pile was presented to the cold glass tube which was exhausted1 and the needle of the goniometer stood at zero4 ,nitrous acid on entering the exhausted tube became heated and radiated its heat upon the adjacent face of the pile which deflected the needle of the goniometer through #bh in the direction that indicates absorption4 ,as the heat of the gas became gradually exhausted1 the needle returned slowly to zero4 ,the pump was now worked1 the rarefied gas in the tube was chilled1 and the adjacent face of the pile gradually poured its heat on the chilled tube till the temperature of the pile was so much lowered1 that the needle was deflected #bj on the negative side of zero1 that is on the side denoting radiation4 ,when olefiant gas entered the exhausted tube1 the needle showed an absorption of #fg1 and when the gas was pumped out again1 the needle showed a radiation amounting to #da4 ,when the gas was then pumped out1 very dry atmospheric air was introduced into the tube1--the needle pointed to #ei indicating absorption2 and when it was pumped out again the needle swung to nearly #dj on the other side of zero1 indicating radiation4 ,remembering that the radiation and absorption of dry air only produce a deflection of #a1 it is evident that the preceding great deflection of the needle is entirely owing to the action of the small residue of olefiant gas that remained in the exhausted tube4 ,in order to ascertain how much the quantity of a gas or vapour might be reduced before its action became insensible1 the vapour of boracic ether1 which has the greatest absorptive energy1 was chosen4 ,the mercurial gauge for measuring the pressure or tension of the vapour already mentioned remained attached to the apparatus4 ,when one-tenth of an inch of the vapour of boracic ether was admitted into the exhausted tube1 the barometer stood at #cj inches3 hence the tension of the vapour within the tube was the #a_/cjjth part of an atmosphere4 ,dynamically heated by dry air the radiation of the vapour produced a deflection of #ef4 ,again the tube was exhausted to #jb of an inch and the quantity of vapour was thereby reduced to #a_/aejth of its first amount2 the needle was allowed to come to zero1 and the residue of the vapour produced a deflection of #db4 ,the pump was again worked till a vacuum of #jb of an inch was obtained1 this residue containing of course the #a_/aejth of the quantity of ether present in the tube2 and on dynamically heating the residue1 its radiation produced a deflection of #bj4 ,thus it is evident that the tension of the ether in these experiments was continually diminished by the #jb of an inch1 consequently its quantity was continually diminished by its #a_/aejth part1 accompanied by a corresponding decrease in the deflections of the needle4 ,the final result of this process showed that the radiation of an amount of vapour in the tube possessing a tension of less than the thousand millionth of an atmosphere is perfectly measurable4 ,the temperature imparted to this infinitesimal quantity of matter did not exceed #jge of a centesimal degree4 ,the molecules which constituted this intensely attenuated vapour1 though inconceivable1 had as true an existence as the suns which constitute the star-dust of the nebul4 #8,a platinum wire raised to whiteness in a vacuum by an electric current1 becomes comparatively cold in a second after the current has been interrupted2 yet that wire1 while ignited1 was the repository of an immense amount of mechanical force4 ,what has become of this8 ,it has been conveyed away by a substance so attenuated that its very existence must for ever remain an hypothesis4 ,but here is matter that we can weigh1 measure1 taste1 and smell2 that we can reduce to a tenuity which1 though expressible by numbers1 defeats the imagination to conceive of it4 ,still we see it competent to arrest and originate quantities of force which on comparison with its own mass are almost infinite1 a small fraction of this force causing the double needle of the galvanometer to swing through considerable arcs4 ,when we find ponderable matter producing these effects1 we have less difficulty in investing the luminiferous ether with those mechanical properties which have long excited the interest and wonder of all who have reflected upon the circumstances involved in the undulatory theory of light4' ,the dynamical principle was next applied to determine the radiation of a gas through itself2 or through any other gas having the same period of vibration4 ,for that purpose ,mr4 ,tyndall made use of the hollow cylinder #did inches long already mentioned1 closed at both ends by plates of rock-salt1 and divided internally into two chambers by a movable plate of the same substance4 ,all sources of heat being dispensed with1 the chamber next the voltaic pile contained the gas which was to act as an absorber1 and the more remote as a radiator4 ,heat is evolved in air when its motion is arrested2 on entering an exhausted tube1 the more rapid the motion the greater the heat4 ,both chambers of the cylinder were at first filled with the vapour to be examined1 the usual pressure being the #a_/fj part of an atmosphere4 ,but the vapour entered so slowly1 and the quantity was so small that the radiation due to the warming of the vapour by its own collision was insensible4 ,the needle of the goniometer being at zero1 dry air was allowed to enter the chamber most distant from the pile2 this air became heated dynamically by the collision of its particles against the sides of the tube1 communicated its heat to the vapour1 and the vapour immediately discharged the heat thus communicated to it against the pile4 ,this case not only resembles1 but is actually of the same mechanical character as1 that in which a vibrating tuning fork is brought into contact with a surface of some extent4 ,the fork1 which before was inaudible1 becomes at once a copious source of sound4 ,what the sounding board is to the fork1 the compound molecule is to the elementary atom4 ,the tuning fork vibrating alone is in the condition of the atom radiating alone2 the sound of the one and the heat of the other being insensible4 ,but in association with sulphuric or acetic ether vapour the elementary atom is in the condition of the tuning fork applied to its sounding board1 communicating motion to the luminiferous ether through the molecules1 as the fork through the board communicates its motion to the air4 ,mr4 ,tyndall's experiments show the great opacity of a gas to radiations from the same gas1 and may likewise show the remarkable influence of attenuation in the case of vapour4 ,the individual molecules of a vapour may be powerful absorbers and radiators1 but in their strata they constitute an open sieve through which a great quantity of radiant heat may pass4 ,in such thin strata1 therefore1 the vapours as used in the experiments were generally found far less energetic than the gases1 while in thick strata the same vapours showed an energy greatly superior to the same gases1 but the gases were always employed at a pressure of one atmosphere4 ,lastly ,mr4 ,tyndall examined the diathermancy of the liquids from which his vapours were derived1 and the result leaves not a doubt that both absorption and radiation are phenomena irrespective of aggregation4 ,if any vapour is a strong absorber and radiator1 the liquid from whence it comes is also a strong absorber and radiator4 ,perfectly dry pure air is as pervious to light and heat as a vacuum itself2 consequently1 if the atmosphere was quite pure and dry1 the rays of the sun would fall on the earth with unmitigated force during the day1 and would be radiated back again and dissipated in space during the night to the destruction of vegetation4 ,but the earth is protected from these extremes by the absorptive power of aqueous vapour1 which is always present more or less in the atmosphere2 even when the air is so transparent that distant objects seem to be near1 it is loaded with vapour in an elastic invisible state1 which a change of temperature may condense into cloud or precipitate in rain4 ,the absorptive power of aqueous vapour was determined by placing tubes containing fragments of glass moistened with water between the drying apparatus and the experimental glass tube of the instrument1 so that perfectly pure dry air in passing over the wet fragments of glass carried a portion of aqueous vapour with it into the exhausted experimental tube1 and the deflection of the needle of the goniometer showed that the absorptive power of the aqueous vapour exceeded that of the dry air #hj times4 ,now since in the atmosphere there is one molecule of aqueous vapour with an absorptive power of #hj for every #bjj atoms of oxygen and nitrogen whose absorptive power is #a like that of one of its constituent atoms1 it follows by comparison that the absorptive power of the molecule is #af1jjj times greater than that of an atom of either oxygen or nitrogen4 ,from this enormous opacity to obscure heat #8it is certain that more than ten per cent4 of the terrestrial radiation from the soil of ,england is stopped within ten feet of the surface of the soil2 remove for a single summer night the aqueous vapour from the air which overspreads the country1 and you would assuredly destroy every plant capable of being destroyed by a freezing temperature4' ,the quantity of vapour in each place varies with the latitude1 the season1 and other circumstances2 but whenever the amount of heat radiated from the earth surpasses the absorption1 the remainder passes through the vapour into space1 and for the same reason the residue of that coming from the sun passes through the vapour and comes to the earth1 so that whatever may be the local differences it has been decidedly proved with regard to the whole globe1 that the quantity of heat annually received from the sun is annually radiated into space2 the latter is a force lost to the earth1 nevertheless it does not interfere with the law of the conservation of force which extends to the universe4 ,by observations made during ten scientific ascents in a balloon to very great altitudes1 ,mr4 ,glaisher has proved1 that the theory of the uniform decrease of temperature with increase of elevation is no longer tenable4 ,since the absorptive force of aqueous vapour is #af1jjj times that of dry air1 the whole of the heat radiated by the full moon is intercepted by our atmosphere4 ,it raises the temperature of the higher regions1 dissolves the vapour1 dissipates the clouds1 prevents the formation of more1 and allows the heat radiated from the earth to pass freely into space3 thus confirming the common1 and almost universal1 belief that the full moon dispels the clouds4 ,the absorptive power of aqueous vapour is so enormous that even the planet ,mercury may be habitable should his atmosphere contain a sufficient quantity of it to mitigate the heat of the sun4 ,no doubt all the heat from the stars must be absorbed by the atmosphere1 but their photographs show that it is pervious to the chemical rays4 ,those from ,sirius1 the nearest and brightest of the stars1 travelling through #ahj millions of millions of miles and decreasing in quantity inversely as the square of the distance1 still have sufficient energy to give a perfect photographic impression of its spectrum2 but ,sirius is sixty times larger than the sun1 and is many times more luminous4 ,a photograph of the spectrum of ,capella has been taken1 though three times more distant than ,sirius4 ,photographs of double stars of the sixth and seventh magnitude show that actinic rays from immeasurable distances in space have power sufficient to decompose matter in unstable equilibrium on the surface of the earth4 ,the chemical power of the moon's light only surpasses that of ,jupiter in the ratio of #f to #d or #e1 and ,jupiter's light has twelve times more actinic energy than that of ,saturn4 ,for such comparisons a standard of photographic intensity is requisite4 ,a paper coated with chloride of silver can be prepared which has a constant degree of sensitiveness1 and ,dr4 ,roscoe has proved that a constant dark tint is produced on this standard paper by a constant quantity of light1 the tint being the same1 whether light of the intensity represented by #a acts for the time represented by #ej1 or light represented by #ej acts for the time represented by #a2 or in other words the amount of the chemical action of light is directly proportional to the intensity of the light1 and when the light is constant1 the amount of action is exactly proportional to the time of exposure4 ,the ratio of the chemical action of the rays of light falling directly from the sun to the chemical action of the light diffused over the whole sky can be determined by means of an instrument1 in which the shadow of a little ball is made to fall on a sensitive paper so as to intercept the direct rays of the sun1 and allow it to be impressed by an action of the light diffused over sky alone2 this compared with a similar paper1 on which both the direct and indirect light has fallen1 gives the ratio required4 ,from this it appears1 that the relative amount of chemically active light which comes directly from the sun1 is very much less than the amount of his direct visible light4 ,for while ,professor ,roscoe was making experiments at ,manchester on the maximum effect of the chemical action of light1 he found when the sun had an altitude of #bj1 that of #ajj chemical rays which fell on a piece of standard paper1 only about #h came from the direct light of the sun2 while on the contrary1 of #ajj rays of visible light1 #ff came directly from the sun1 and only #dj from the light diffused over the whole sky1 so that the diffused light is richer in chemical rays than the direct solar beam1 #8a startling result1' but borne out by observations not only made at ,manchester and in its vicinity1 but at ,kew1 ,heidelberg1 and at ,par on the ,amazon nearly under the equator4 ,on account of the increasing rarity of the atmosphere1 the greater the height above the level of the sea1 the less the amount of diffused light and consequently of actinic power4 ,hence photographers have to expose their plates for a much longer time to the light on the snowy peaks of the ,alps and other great heights than in ,england or at the level of the sea4 ,during ,mr4 ,glaisher's tenth balloon ascent simultaneous observations were made at ,greenwich ,observatory and in the balloon1 when at more than three miles above the surface of the earth1 the standard paper exposed to the full rays of the sun was not as much coloured in half an hour as the corresponding paper at ,greenwich in one minute4 ,by a series of observations at ,heidelberg1 ,kew1 and ,manchester1 it has been proved that the very small relative chemical action of the sun's direct light decreases rapidly with his altitude1 and at these three places of observation1 it has frequently happened when the sun's altitude was very low1 as at #ab1 that his direct light made no impression on a sensitive paper4 #8,the sun's light had been robbed of its chemical power in passing through the air4' ,this singular result is ascribed by ,professor ,roscoe to what he calls the opalescence of the atmosphere4 ,opalescent glass1 slightly milky liquids1 pure water with particles of sulphur floating in it1 are impervious to the chemical rays1 whence ,professor ,roscoe infers that the atmosphere1 more especially its lower regions1 possesses that property in consequence of multitudes of solid particles floating in it4 ,what they are is unknown1 but infinitesimal particles of soda seem to be everywhere1 and no doubt particles of other substances mixed with them may be often seen as motes dancing in the sunbeams4 ,besides1 it is clearly proved that myriads of the eggs and germs of organized beings1 though invisible to the naked eye1 are continually floating in the air1 and that they are more abundant in the lower than in the higher strata of the atmosphere4 ,since opalescent matter reflects the blue rays of light and transmits the red1 ,professor ,roscoe ascribes the blue colour of the sky and the bright tints at sunrise and sunset to the opalescent property of the air4 ,the atmosphere is permeable to every kind of chemical rays1 which is far from being the case with bodies on earth1 some of which though transparent to all the visible rays1 vary greatly in their transparency to the chemical rays4 ,the atoms and molecules of matter not only have the power of turning the rays of the solar beam out of their rectilinear path1 but of changing their refrangibility4 ,the myriads of ethereal waves or rays of light that constitute the seven colours of the solar spectrum1 decrease in refrangibility and increase in rapidity of vibration and length of wave from the extreme violet to the end of the red2 each ray having its own rate of vibration1 its own length of wave1 and its own colour4 ,from the middle of the yellow1 which is the luminous part of the spectrum1 the chemical spectrum extends invisibly1 but with increasing refrangibility and increasing velocity of vibration1 to a point far beyond the violet4 ,on the contrary1 the heat spectrum1 which may also be said to begin in the yellow light1 extends invisibly but with decreasing refrangibility1 and decreasing velocity of vibration to some distance beyond the visible red4 ,the rays of heat are absorbed by the humours of the eye1 but were they to reach the retina we should see that they differ from one another as much as those of the luminous spectrum2 the chemical spectrum from its greater length is still more diversified4 ,the whole of the solar spectrum1 visible and invisible1 is crossed at right angles to its length by innumerable dark rayless lines1 differing in breadth and intensity4 ,sir ,john ,herschel discovered vacant spaces in the extra-luminous part of the heat spectrum1 and more recently ,m4 ,edouard ,becquerel1 by throwing the solar spectrum upon a daguerreotype plate1 discovered that the chemical spectrum given by a glass prism1 from its beginning in the yellow to its extreme point beyond the violet1 is crossed by rayless lines1 and that the lines in the part passing through the visible spectrum coincide exactly with the rayless lines in the luminous part4 ,this coincidence was confirmed by the independent researches of ,dr4 ,draper at ,new ,york4 ,by means of the rayless spaces or black lines in the visible spectrum1 ,m4 ,kirchhoff has proved that thirteen terrestrial substances are constituents of the sun's atmosphere4 ,the length of the undulations of the ether which produce the impression of the extreme violet rays of the solar spectrum on our eyes1 is the seventeen millionth part of an inch2 the length of the ethereal undulation that produces the sensation of the extreme red is the twenty-six millionth part of an inch2 the ethereal undulations beyond these limits are invisible to human eyes4 ,nevertheless certain substances have the power of increasing the length of the vibrations1 and reducing the rays of the spectrum to a lower grade in the scale of refrangibility1 so that the invisible rays of the chemical spectrum have thus been brought within the limit of human vision4 ,for example1 the chemical rays shine as visible light when they fall on glass tinged with the oxide of uranium4 ,when these dark rays fall upon the glass1 they put the whole of its molecules into vibrations1 the same with their own1 while at the same time they give a more rapid vibration to a certain number of the same molecules4 ,the whole of the molecules restore their vibrations to the surrounding ether4 ,those having the same velocity with the chemical rays make no sensible impression on our eyes2 but the more rapid vibrations come within the limits of the visible spectrum2 they have consequently a lower refrangibility1 and shine as visible light4 ,it is called degraded light on account of its lower position in the prismatic scale1 but more frequently fluorescent light1 because fluor spar was the first solid known to possess the property4 ,a number of substances are fluorescent1 both solid and liquid1 organic and inorganic4 ,if in a dark room a non-fluorescent body be illuminated by a sunbeam passing through glass stained deep blue by cobalt1 it will reflect blue light2 but it will appear to be perfectly black if it be viewed through glass tinged yellow by silver2 while a piece of canary glass1 which is highly fluorescent1 will shine with a vivid light under the same circumstances4 ,all the molecules of the canary glass give back to the ether the undulations that have been impressed on them by the blue light2 while a certain number of them possess the power of receiving and giving back more rapid vibrations to the ether4 ,the yellow glass held before the eye is impervious to the undulations of the blue rays1 but transmits those of the fluorescent light1 which emanate from the smaller number of molecules1 and which thus become in reality new centres of light1 different from the sun's light1 though dependent upon it3 the one terrestrial1 the other celestial4 ,since the vibrations of the fluorescent light are more rapid than those of the blue light their colour is lower in the prismatic scale4 ,the vibrations of the molecules in a fluorescent substance are analogous to those of a musical cord1 which give the fundamental note or pitch and its harmonics1 for the whole of the musical cord while vibrating the fundamental note divides itself spontaneously into parts having more rapid vibrations1 which give the harmonics4 ,professor ,stokes of ,cambridge1 who made this beautiful experiment1 computed that the vibrations which produced the fluorescent light were a major or minor third below the pitch or vibrations of the blue light4 ,one of the first discoveries of fluorescence was made by ,sir ,john ,herschel--certainly the first who observed the property in a liquid4 ,he found that the blue light which emanates from all parts of a solution of the sulphate of quinine1 especially from its surface1 is fluorescent1 and that the light transmitted through the liquid1 though sensibly like the incident white light1 is no longer capable of producing fluorescence2 it has been deprived of its chemical rays by absorption4 ,the chemical rays having been rendered visible by an increase in the length of the periods of vibration1 unsuccessful attempts have been made to change the periods of the rays of heat beyond the red end of the spectrum so as to bring them within the limits of vision4 ,the idea of effecting such a change by employing a substance opaque to light1 but pervious to heat1 is due to ,dr4 ,akin2 but it has since been accomplished by ,dr4 ,tyndall1 who1 in the course of his experiments on radiant heat1 found that a solution of iodine in the bisulphide of carbon excludes the most dazzling light1 but transmits the rays of heat freely4 ,he employed a mirror1 lined in front with silver1 to concentrate the rays emitted from the charcoal points of the electric lamp1 and interposed a vessel containing the solution in question1 so that the rays of heat alone were brought to a focus almost undiminished4 ,when the solar spectrum was examined1 the point of maximum heat was found to be as far beyond the extreme red on one side as the green rays on the other4 ,in the spectrum of the electrical light the point of maximum heat was also found to lie beyond the extreme red1 but the augmentation of intensity was so sudden and enormous as far to exceed the maximum heat of the sun previously determined by ,professor ,mller4 ,aqueous vapour powerfully absorbs radiant heat2 so a solar spectrum beyond the earth's atmosphere might probably exhibit as great intensity as the electrical light4 ,with the apparatus described oxidizable substances burst into the flame of common combustion when put into the focus2 but when the chemical action of the oxygen of the atmosphere was excluded by igniting substances in vacuo by the invisible rays of heat1 their periods of vibration were so changed as to bring them within the limits of vision4 ,when the electric light is very powerful1 a plate of platinized platinum in vacuo is raised to white heat at the focus of invisible rays2 and when the incandescent platinum is looked at through a prism1 its light yields a complete and brilliant spectrum4 #8,in all these cases we have a perfectly invisible image of the charcoal points formed by the mirror2 and no experiment illustrates the change of heat into light' more strongly than the following3--,when the plate of platinum or one of charcoal is placed in the focus1 the invisible image raises it to incandescence1 and thus prints itself visibly on the plate4 ,on drawing the coal points of the lamp apart1 or causing them to approach each other1 the thermograph follows their motion4 ,by cutting the plate of carbon along the boundary of the thermograph1 a second pair of coal points may be formed of the same shape as the original ones1 but turned upside down2 and thus by the rays of the one pair of coal points which are incompetent to excite vision1 we may cause a second pair to emit all the rays of the spectrum4 ,fluorescence and calorescence act in contrary directions4 ,fluorescence causes the molecules of a fluorescent substance to oscillate in slower periods than the incident light1 while calorescence causes the molecules of a substance to oscillate in longer periods than the incident light4 ,the refrangibility of the rays is lowered in the first case1 and raised in the second4 ,substances differ as much in their transmission of the chemical rays as those of light and heat4 ,glass is impervious to the most highly refrangible chemical rays1 while rock crystal transmits them with the greatest facility2 and on that account the absolute length of the spectrum was not known till the light was refracted by prisms of rock crystal4 ,besides1 the number1 position1 and intensity of the chemical rays vary with the source of light4 ,some flames have scarcely any chemical rays2 that of the oxy-hydrogen blowpipe1 though intensely hot1 has very few1 and even the solar light is inferior in that respect to electricity4 ,the electric spark from the prime conductor of a common electrifying machine1 or the discharge of a ,leyden jar1 emits rays of very high refrangibility1 far surpassing those which emanate from the sun4 ,for1 when the electric light from a highly charged ,leyden jar was refracted by two quartz prisms and thrown by ,professor ,stokes on a plate of uranium glass1 the chemical spectrum was highly luminous1 and six or eight times as long as the visible spectrum4 ,an equally extensive spectrum was obtained from the voltaic arc taken between copper points2 it consisted entirely of bright lines4 ,the long spectrum also appeared on the uranium glass when the spark refracted by quartz prisms was obtained from the secondary terminals of an induction coil in connection with the coatings of a ,leyden jar4 ,it consisted of bright lines1 but was not so luminous as that from a powerful voltaic battery4 ,on changing the metals of the points between which the sparks passed1 the bright lines were changed1 which showed that they were due to the particular metals4 ,the heat of the electric spark volatilizes the metals which form the points of the conducting wires2 and all volatilized metals give characteristic spectra1 both visible and chemical4 ,the visible part differs from that of the solar spectrum in being crossed by bright lines instead of dark ones2 but the number1 intensity1 and position of both the visible and invisible lines change with each metal4 ,the changes in the invisible part under consideration may be readily observed by throwing the spectra either on a fluorescent or collodion plate4 ,for example3 in the spectrum from the spark between thallium points thrown on the latter1 ,dr4 ,miller found that there were two strong groups of lines in the least refrangible part of the spectrum2 at a little distance from these there were three groups1 the two first less intense than the third2 several rows of feeble dots followed1 and the chemical spectrum terminated rather abruptly with four nearly equidistant groups4 ,this spectrum bears a resemblance to those of zinc and cadmium1 less strongly to that of lead4 ,dr4 ,miller found that the photographic spectra of iron1 cobalt1 and nickel1 also have a strong analogy1 but that the metals arsenic1 antimony1 and tin showed as great a difference in the invisible as in the visible part of their spectrum4 ,the fluorescent spectra of seventeen metals were examined by ,professor ,stokes of ,cambridge2 several of them showed luminous lines of extraordinary strength1 especially zinc1 cadmium1 magnesium1 aluminium1 and lead1 which in a spectrum not generally remarkable contains one line surpassing perhaps all other metals in brilliancy4 ,some other metals exhibit in certain parts of their spectra lines that are both bright and numerous2 on the whole some parts of the spectra are strong and tolerably continuous1 while in others they are weak4 ,this grouping of the lines is most remarkable in copper1 nickel1 cobalt1 iron1 and tin4 ,of all the metals examined1 magnesium gave the shortest spectrum1 ending in a very bright line1 beyond which however excessively faint light extended to a distance equal to that of the long spectra4 ,aluminium1 on the other hand exceeded all the other metals in richness of the rays of the very highest refrangibility4 ,all the strong lines mentioned lie in that part of the spectra4 ,in the course of these experiments ,professor ,stokes observed that even quartz of a certain thickness is not transparent to invisible lines of the highest refrangibility1 for the highest aluminium line1 which is double1 could only be seen by rays passing through the edge of the prism4 ,this leads to another branch of the subject1 namely1 the absorption of the invisible rays by solids1 liquids and gases4 ,mr4 ,wm4 ,allen ,miller has shown from his own experiments that bodies pervious to the chemical rays in the solid form1 are so also in the liquid and gaseous form2 that colourless transparent solids which absorb the photographic rays1 absorb them more or less also in their liquid and gaseous states4 ,he has moreover found that the following substances have the same maximum transparency3--rock crystal1 ice1 and fluor spar among solids1 water among liquids1 the three elementary gases and carbonic acid among gaseous substances4 ,the most opaque to the invisible rays are1 nitrate of potash1 bisulphide of carbon1 and sulphuretted hydrogen4 ,it appears that a thin plate of mica is intensely opaque to all the invisible rays except a small portion of them of the lowest refrangibility4 ,the absorptive property however is partial3 an absorptive substance either cuts off a portion of the light of a fluorescent spectrum or stripes it with dark lines3 each substance absorbs rays peculiar to itself4 ,those employed by ,professor ,stokes were the alkaloids and glucosides1 and he assumed the spectrum of tin for their examination because it has a long interval of continuity4 ,the fluorescent property of yellow uranite was discovered by ,professor ,stokes some years ago1 and now he has added another fluorescent mineral in adularia or moonstone2 from its natural faces and planes of cleavage alike a beautiful blue fluorescence emanated under the induction spark4 ,as the same was observed in colourless felspars generally1 ,professor ,stokes concluded that fluorescence is an inherent property in the silicate of alumina and potash constituting the crystal of moonstone4 ,the blue fluorescence extended to a very sensible though small depth within the substance4 ,a particular variety of fluor spar found at ,alston ,moor in ,cumberland1 which is very pale by transmitted light1 shows a strong blue fluorescence1 and is eminently phosphorescent on exposure to the electric spark4 ,it is the same kind of crystal in which ,sir ,david ,brewster originally discovered the property of fluorescence4 ,on presenting such a crystal to the spark passing between aluminium terminals1 besides the usual blue fluorescence1 there was another of a reddish colour extending not near so far into the crystal1 produced by the rays belonging to the strong lines of aluminium of extreme refrangibility4 ,the cube of fluor spar which showed these effects was externally colourless to the depth of #a_/bj of an inch2 then came one or two strata parallel to the faces of the cube showing the ruddy fluorescence1 while the blue fluorescence extended to a much greater depth and had a stratified appearance4 ,this crystal was eminently phosphorescent1 its blue phosphorescence being arranged in strata parallel to the face of the cube like the blue fluorescence1 but it was not perceptible beyond a very moderate distance below the surface at which the exciting cause entered1 that cause being the photographic rays of extremely high refrangibility of the electric spark--taken1 as in all these experiments1 between the secondary terminals of an induction coil in connection with the coatings of a ,leyden jar1 and refracted by quartz prisms4 ,mr4 ,stokes has employed fluorescence as a means of tracing substances in impure chemical solutions4 ,when a pure fluorescent substance is examined in a pure spectrum it is found that on passing from the extreme red to the violet and beyond1 the fluorescence commences at a certain point of the spectrum1 varying from one substance to another1 and continues from thence onwards more or less strongly in one part or another according to the particular substance4 ,the colour of the fluorescent light is found to be nearly constant throughout the spectrum4 #8,hence when in a solution examined in a pure spectrum we notice the fluorescence taking as it were a fresh start with a different colour1 we may be pretty sure that we have to deal with a mixture of two fluorescent substances4' ,experience as well as theory shows that rapid absorption is accompanied by copious fluorescence4 ,but experience has hitherto also shown what could not have been predicted1 and may not be universally true1 that conversely absorption is accompanied in the case of a fluorescent substance by fluorescence4 ,the phosphorescent light of insects1 fish1 and plants is owing to chemical action1 which produces many luminous phenomena2 but a great number of inorganic and organic substances shine in the dark with a phosphorescence which is nearly allied to fluorescence4 ,it is produced by exposure to the sun1 by heat1 electricity1 insulation1 cleavage1 friction1 and motion4 ,for if a bottle containing nitrate of uranium be shaken1 it shines spontaneously with a vivid light2 even the hand shows phosphorescence in the dark after being exposed to the sun4 ,the essential difference between fluorescence and phosphorescence consists in the time during which the light lasts4 ,fluorescence ceases almost immediately after the exciting cause is withdrawn1 while a phosphorescent body whether excited by heat1 solar light1 or electricity1 lasts a much longer time2 besides1 the fluorescent rays are generally of lower refrangibility4 ,light and heat are temporarily absorbed and given out again by every body on the surface of the earth1 more or less1 that are exposed to the sun's light4 ,the nights would be much darker even when illuminated by the stars were it not for earth light1 for the molecules restore to the ether1 in the form of phosphorescence1 the undulations they have received from the sun's light during the day4 ,the snow and ice blink of the sailors is a striking instance2 generally1 however1 it is of much shorter duration4 ,the phosphorescent property is nearly allied to electricity1 for bodies that are bad conductors are apt to become phosphorescent1 while good conductors of electricity rarely if ever show it4 ,ozone must be phosphorescent1 for oxygen exhibits persistent light when electric discharges are sent through it1 and ,mr4 ,faraday saw a flash of lightning leave a luminous trace on a cloud which lasted for a short time4 ,in the solar spectrum the chemical or actinic rays produce phosphorescence1 which the red rays have the power to extinguish4 ,m4 ,nipce de ,st-,victor found that solar light impresses its vibrations so strongly on substances exposed for a short time to its influence that they not only shine in the dark1 but that the phosphorescent light they radiate has chemical energy enough to decompose substances in unstable equilibrium1 and leave daguerreotype impressions of great delicacy and beauty4 ,the polarization of light and heat affords a remarkable instance of the elective power of matter4 ,light and heat are said to be polarized1 which1 having been once reflected1 are rendered incapable of being again reflected at certain angles4 ,for example1 a ray incident on a plate of flint glass at an angle of #eg is rendered totally incapable of being reflected at that same angle from another plate of flint glass in a plane at right angles to the first4 ,at the incidence of #eg the whole of the ray is polarized3 it is the maximum of polarization for flint glass1 but there is a partial polarization for every other angle2 the portion of the ray polarized increases gradually up to the maximum1 as the incidence approaches to #eg4 ,all reflecting surfaces are capable of polarizing light and heat1 but the angle of incidence at which the ray is totally polarized is different in each substance4 ,thus1 the angle of incidence for the maximum polarization of crown glass is #ef #ee1 and no ray can be totally polarized by reflection from the surface of water unless the angle of incidence is #ec #aa4 ,as each substance has its own maximum polarizing angle1 the effect is evidently owing to the action of the molecules of matter1 and not to any peculiarity in the light or heat4#h ,light and heat are also polarized by refraction1 for certain substances1 especially irregularly crystallised minerals like ,iceland spar1 possess the property of dividing a ray of light or heat passing through them in certain directions into two pencils1 namely1 the ordinary and extraordinary rays4 ,the first of these is refracted according to the same law as in glass or water1 never quitting the plane perpendicular to the refracting surface1 while the second does quit that plane1 being refracted according to a different and more complicated law4 ,hence1 if a crystal of ,iceland spar be held to the eye1 two images of the same object will generally be seen of equal brightness4 ,but when they are viewed through a plate of tourmaline it will be found that while the spar remains in the same position the images vary in relative brightness as the tourmaline is made to revolve in the same plane2 one increases in intensity till it arrives at a maximum1 at the same time that the other diminishes till it vanishes1 and so on alternately at each quarter revolution of the tourmaline1 proving both rays to be polarized4 ,for in one position the tourmaline transmits the ordinary ray and reflects the extraordinary1 and after revolving #ij1 the extraordinary ray is transmitted and the ordinary ray is reflected4 ,the undulations of the ethereal medium which produce the sensation of common light1 are performed in every plane at right angles to the direction in which the ray is moving1 but the case is very different after the ray has been polarized by passing through a substance like ,iceland spar1 for the light then proceeds in two parallel pencils whose undulations are still indeed transverse to the direction of the rays1 but they are accomplished in planes at right angles to one another4 ,the ray of common light is like a round rod1 whereas the parallel polarized rays resemble two long flat rulers1 one of which lies on its broad surface1 and the other on its edge4 ,by a simple mechanical law1 each vibratory motion of the common light is resolved into vibratory motions at right angles to one another4 ,the polarization of light and heat by refraction is not owing to the chemical composition1 but to a want of homogeneity in the molecular structure of the substances through which they pass2 for regular crystals and substances which are throughout of the same temperature1 density1 and structure1 are incapable of double refraction4 ,the effect of molecular structure is strikingly exhibited by the circular polarisation in the dimorphic crystals of quartz4 ,in one form the plane of polarization revolves from right to left1 and in the other that plane revolves from left to right1 although the crystals themselves differ apparently by a very slight and often almost imperceptible variety of forms4 ,thus polarization forms the most admirable connection between light1 heat1 and crystalline structure2 showing peculiar arrangements of the molecules in regions otherwise unapproachable1 and too refined for our perceptions4 ,besides1 the gorgeously coloured images displayed by depolarization are splendid examples of the power of matter in decomposing light4 ,the perfect correspondence of the properties of the symmetrical1 elastic1 and optical axes of crystals with light and heat is another instance of the connection between the latter and crystalline form4 ,the axis of symmetry is that direction or imaginary line within a crystal1 round which all the parts or particles are symmetrically arranged4 ,a medium is said to be elastic which returns to its original form with a resilient force after being relieved from compression1 and the axis of elasticity of a crystal is that direction in which it is most elastic4 ,the optic axis is that line or direction through which light passes in one beam according to the law of ordinary refraction4 ,crystals may have one1 two or more optical axes according to their form4 ,doubly refracting crystals such as ,iceland spar have only one principal optic axis in which the whole beam passes according to the ordinary law2 in every other direction the beam of light is divided into two polarized rays1 one of which called the ordinary ray passes according to the ordinary law1 while the other1 known as the extraordinary ray1 traverses the crystal in a different direction1 with more rapidity and according to a different and more complicated law4 ,the velocity of this extraordinary ray is a maximum when at right angles to the principal optical axis1 and a minimum when parallel to it4 ,in perfectly regular crystals like the cube or die1 the octohedron1 c41 there are three axes of symmetry and of equal elasticity at right angles to one another4 ,in these regular crystals all the axes are optical1 so that they have no double refraction4 ,right square prisms have two equal rectangular axes of symmetry1 two axes of equal elasticity1 and one optical axis4 ,all crystals of the pyramidal and rhomboidal systems have one axis of symmetry1 two axes of elasticity1 one optical axis2 and form coloured circular rings traversed by a black cross when viewed by depolarized light4 ,lastly oblique prismatic crystals which have three unequal axes of symmetry have three axes of unequal elasticity1 two optical axes2 and by depolarization give coloured lamnescata1 that is coloured figures having the form of the figure #h which are traversed by a black cross in two opposite quadrants1 and when the crystal is made to revolve1 the same figure1 but in the complementary colours and traversed by a white cross1 appears in the other two quadrants4 ,the right and left-handed circular polarization of quartz1 according as certain facettes of the crystal are turned to the right or left1 and the property of double refraction being exclusively possessed by crystals of the rhomboidal form1 are striking instances of the connection between the geometrical arrangement of the molecules of matter and the optical and thermal forces1 for the polarization of heat and all its consequences are in every respect analogous to those of light1 and similar phenomena would be seen were heat visible4 ,heat changes the position of the optical axes of crystals4 ,when applied to a crystal of sulphate of lime1 the two optical axes gradually approach to each other and at last coincide2 if the heat be continued and increased1 the axes open again1 but in a direction at right angles to their former position4 ,thus the force of heat throws every molecule in the body into correlative motion4 ,the angles of all crystals that are not of the octohedral group are changed by heat and vary with the intensity2 the difference between the length of the greatest and least optic axes in such crystals diminishes as the temperature is raised1 increases when it is lowered1 and is constant at a given heat4 ,in ,iceland spar heat indirectly affects the doubly refracting power1 for the expansion of the crystal in the direction of its axis is accompanied by contraction at right angles to it1 which brings the crystal nearer to the cubical form1 and consequently diminishes its doubly refracting power4 ,according to the researches of ,m4 ,angstrm1 in crystals with different axes of elasticity the velocity of the molecular vibrations is different in different directions when they are heated4 ,in rock crystal and tourmaline the heat radiates from a surface cut parallel to the axis of the crystal2 in felspar the radiating surface is at right angles to the symmetrical axis4 ,the optical axes of crystals are also affected by pressure4 ,doubly refracting crystals with one principal axis acquire two when the pressure is perpendicular to it4 ,the new principal axis coincides with the line of pressure or is at right angles to it according as the crystal is positive or negative1 that is1 according as the extraordinary ray is refracted to or from the optic axis of the crystal4 ,the colours produced by polarization are affected by compression and dilatation according as the crystal is positive or negative4 ,sir ,david ,brewster is of opinion that all the properties of double refraction and the gorgeous phenomena of polarization1 whether by crystals or produced in various substances permanently or transiently by heat1 cold1 rapid cooling1 compression1 dilatation1 and induration1 are wholly the result of the forces by which the atoms are held together2 but these phenomena may rather be said to depend upon a reciprocal action between an irregular molecular structure and the agency of light and heat3 which indeed seems to be confirmed by the transit of these two forces through right and left-handed quartz1 for there is no reason to believe that there is any difference in the form of the particles in these two crystalline substances4 ,the experiments of ,m4 ,becquerel show that electricity is a power which makes the atoms of matter aggregate in crystalline forms2 for he has succeeded in forming crystals of gold1 silver1 cobalt1 nickel1 platinum1 and a variety of the gems undistinguishable from those in nature1 by exposing saturated solutions of these substances for a very long time to feeble voltaic electricity2 and crystals of earthy matter have been obtained in the same manner4 ,the electric and magnetic state of mineral veins in mines which contain a vast variety of crystals1 metallic and non-metallic1 strongly favours this view of the origin of crystalline form4 ,m4 ,regnault has proved that the ratio between the specific heat and the weight of the atoms of matter is intimately connected with the mode of their aggregation2 and indeed if it be considered that the atoms have not only specific heat and weight1 but specific affinity1 electricity1 magnetism1 consequently polarity1 and probably specific forms1 these peculiar forces must necessarily influence the structure of crystals according as they combine with or oppose the natural or artificial forces acting upon them1 or upon their dissimilar faces1 and this may be the cause of the great variety of forms that matter appears under4 ,carbonate of lime alone assumes more than #a1bjj different modifications of its primitive type1 but whatever be the variety of forms which any one substance may take1 they are found to be all compatible with and derivative from a common type4 ,the circumstances which have caused dimorphous crystals to deviate from the general law have not yet been explained4 ,it is very singular that when chlorate of soda is dissolved in water the solution does not possess the property of circular polarization1 but when evaporated and allowed to crystallise1 some of the crystals turn light to the right1 and others to the left4 ,now if all the crystals that have the same property be picked out and dissolved in water a second time1 the liquid will still have no circular polarization1 but when allowed to crystallise1 some of the crystals make light revolve through them to the right and others to the left as before4 ,from this it is supposed that the atoms of liquids1 which are free to move in every direction1 already possess part of the characters which the change to solidity renders evident and permanent4 ,although the relations between the force of magnetism and the atoms of matter do not exhibit such brilliant phenomena as light does1 they are nevertheless most interesting and wonderful4 ,mr4 ,faraday discovered that all substances1 whether solid1 liquid1 or ariform1 are either magnetic like iron1 or diamagnetic like bismuth1 the latter being by far the most numerous4 ,thus if a bar of iron be freely suspended between the poles of an extremely powerful magnet or electro-magnet1 it will be attracted by both poles and will rest or sit axially1 that is1 with its length between the poles or in the line of magnetic force2 whereas an equal and similar bar of bismuth so suspended will be repelled by both poles and will rest or sit equatorially1 that is with its length perpendicular to the line of magnetic force4 ,magnetism and diamagnetism are both dual forces1 but they are in complete antithesis to one another1 which is strikingly illustrated by their action on crystalline matter4 ,a sphere of amorphous substance freely suspended under magnetic influence is indifferent1 that is to say it has no tendency to set one way more than another2 but a sphere cut out of a crystal whether magnetic or diamagnetic1 is more powerfully attracted or repelled in one direction than in any other1 which shows a connection between the magnetic forces and crystalline structure4 ,crystals of carbonate of iron and carbonate of lime are isomorphous1 that is1 they have exactly the same crystalline form1 but the carbonate of iron being highly magnetic is most powerfully attracted in the direction of its greatest optical axis which therefore sets axially1 that is1 in the line of magnetic force2 while the principal optic axis of the carbonate of lime1 which is diamagnetic1 is most powerfully repelled and therefore sets equatorially4 ,in both cases the antithetic forces follow the same law of decrease in intensity from the greatest optical axis to the least4 ,a bar of soft iron sets with its longest dimensions axially1 but a bar of highly compressed iron-dust1 whose shortest dimensions coincide with the line of pressure1 sets equatorially1 because it is most powerfully attracted in the line of greatest density4 ,a bar of bismuth sets equatorially1 but a bar of highly compressed bismuth dust1 whose shortest dimensions coincide with the line of pressure1 sets with its length axially1 because it is most strongly repelled in the direction of its greatest density4 ,hence the action of magnets upon matter is most powerful in the line of maximum density1 the force being attractive or repulsive according to the kind of magnetism possessed by the atoms4 ,it follows therefore that the density is greatest in the line of the principal optical axis1 and gradually decreases to the least optical axis1 where it is a minimum4 ,the position which crystals take with regard to the magnetic force depends also upon their natural joints of cleavages1 and upon their power of transmitting electricity4 ,the diamagnetic force is inversely as the conducting power of bodies1 and the conducting power of crystals is a maximum in the planes of their principal natural joints4 ,hence the action of the diamagnetic power is least in the natural joints1 and conversely the magnetic force is greatest4 ,in fact1 the magnetic phenomena of crystals depends upon unequal conductibility in different directions1 and their set is determined by the difference between the forces of attraction and repulsion of the poles1 for one pole of the magne-crystallic axis is attracted and the other repelled4 ,it is unnecessary to give more examples to show the action of the magnetic forces upon the atomic structure of crystals4#i ,magnetism changes the relations and distances between the ultimate atoms of matter1 a circumstance which probably depends upon their polarity4 ,it changes steel permanently1 iron temporarily1 and it elongates a bar of iron1 which loses in breadth what it gains in length2 and as heat is developed in one direction and absorbed in the other1 the temperature of the bar remains the same4 ,heat being an expansive force1 diminishes the magnetism of iron and nickel in proportion as it increases the distance between their atoms1 till at length they lose their cohesive force altogether4 ,but there seems to be a temperature at which the magnetic force is a maximum1 above and below which temperature it diminishes4 ,thus the magnetism of cobalt increases with the temperature up to a certain point2 it then decreases as the temperature increases1 and it loses its magnetism altogether when the heat amounts to #aiif4 ,sir ,humphry ,davy and ,m4 ,arago noticed that the voltaic arc takes a rotatory motion on the approach of a magnet2 and the effect of magnetism on the stratified appearance of the electric light in highly rarefied air shows how powerful its action is4 ,in the year #aheh1 ,mr4 ,gassiot published a series of observations on stratified light2 subsequently various publications appeared on the subject both by ,mr4 ,gassiot and by ,professor ,plcker1 who made a series of very interesting observations on the nature of the stratifications1 but more especially on the effects produced when they are under the influences of magnetism4 ,since that time1 ,mr4 ,gassiot has published several papers on the subject1 and still continues his experiments on the stratifications of electric light1 which give a visible proof of the connection between electricity and magnetism4 ,he first showed that the stratified character of the electric discharge through highly attenuated media is remarkably developed in the ,torricellian vacuum2 latterly he has made his experiments by passing electricity through closed glass tubes of various lengths and internal diameters1 filled with highly attenuated gases and vapours4#aj ,two among the many brilliant experiments of this gentleman may be selected as illustrations of the property of electric light4 ,one of these closed glass tubes containing a highly attenuated gas was #ch inches long with an internal diameter of about an inch1 and had the extremities of two platinum wires fused into the same side #cb inches apart4 ,when these wires were put in connection with the wires of an induction battery and brought into contact1 and the electricity passed through the tube1 the luminous appearances at the extremities or poles of the platinum wires were very different1 but simultaneous4 ,a glow surrounded the negative pole1 and in close approximation to the glow1 a well defined black space appeared1 while from the positive pole there issued in rapid succession a series of alternate dark and brilliantly luminous curved strata1 which formed a column of stratified light1 the concavities of the strata being turned to the positive pole4 ,the stratifications do not extend to the black band round the negative wire or ball1 which is quite different to the dark intervening space between the stratified discharge and the luminous negative glow4 ,on making and breaking the electric circuit1 the stratified discharge emanates from each pole alternately1 the concavities of the strata turning alternately in different directions2 in fact the whole phenomena are reversed1 but not changed4 #8,the stratified discharge arises from the impulses of a force acting on highly attenuated but resisting media1' a new proof of the wonderful power inherent in highly attenuated gases2 the number of stratifications given out at each discharge1 depending upon the intensity of the electricity and rarity of the gas4 ,illustration3 ,fig4 #a4 ,fig4 #a represents the form which the stratified discharge assumes in a vacuum tube one inch diameter and #ch inches in length1 and - representing platinum wires attached to the terminals of a ,ruhmkorff's induction coil4 ,when the tube1 with its stratifications just described1 was laid horizontally on the pole of a magnet1 the stratified column showed a tendency to rotate as a whole round it4 ,according to the theory of ,ampre1 the polarity of a magnet is owing to a superficial current of electricity perpetually circulating in a direction perpendicular to its axis2 and he also showed that currents of electricity flowing in the same direction attract one another1 while currents flowing in opposite directions repel each other4 ,hence1 since the currents of electricity in the magnet and tube were flowing in the same direction on one side of the magnet1 and in opposite directions on the other side1 the stratified column was attracted at one end and repelled at the other1 so as to take the form sideways ,s1 in consequence of its tendency to rotate as a whole round the pole of the magnet4 ,when narrow bands of tin foil wrapped round the glass tube near the platinum wires were put in communication with the poles of the induction battery1 brilliant stratifications filled the whole tube between the tin coatings every time the electric circuit was broken or renewed2 and when the tube was placed horizontally on the pole of a magnet1 the stratifications no longer showed a tendency to rotate as a whole1 they were divided into two parts tending to rotate in opposite directions2 when the tube was placed between the poles of a powerful electro-magnet1 one half of the stratifications were repelled and the other half attracted4 ,when the tube was placed on the north pole1 the divided stratifications arranged themselves on each side of the tube1 changing their respective positions when placed on the south pole1 but in every case each half was concave in opposite directions4 ,fig4 #b 7p4 #ha7 represents the form which the induced stratified discharges assume when the vacuum tube is placed on or between the poles of a powerful electro-magnet--the tin foil coatings ,c ,c- being attached by wires to the terminals of an induction coil4 ,illustration3 ,fig4 #b4 ,if a vacuum tube with or without wires or tin coatings be laid upon the induction coil of a battery1 or upon the prime conductor of an electrifying machine1 stratifications are produced by induction which are divided by a magnet4 ,thus there are two distinct forms of the stratified discharge1 one direct1 the other induced4 ,when ,professor ,plcker of ,bonn sent an induced current of electricity from ,ruhmkorff's coil through a vacuum tube having a platinum wire fused into each extremity1 and extending a little way into the interior of the tube1 electric light radiated from every point of the negative wire1 and when exposed to the action of an electro-magnet the whole tube was filled with a luminous atmosphere4 ,but when all the negative platinum wire except its extreme point was insulated by a coating of glass1 the rays of electric light which radiated from the point were united into one single and perfectly regular magnetic curve1 upon the approach of an electro-magnet2 when the negative platinum wire was partially insulated by glass coating1 electric light emanated from every exposed part1 and assumed the form of magnetic curves under electro-magnetic action4 ,whence ,professor ,plcker concluded that the luminous atmosphere in the first experiment was the locus of an infinite number of magnetic curves1 and consequently that magnetic light emanates from the negative or warmth pole1 and electric light from the positive or light pole4 ,these magnetic curves of light are precisely similar to those assumed by iron filings from magnetic action4 ,the most remarkable of these experiments is the absolute extinction of a powerful electric discharge by magnetic action4 ,mr4 ,gassiot sent a discharge from a voltaic water battery1 containing #c1ebj insulated cells1 into a tube filled with attenuated carbonic acid gas4 ,the discharge was so strong that it was capable of passing through more than six inches of the gas1 yet1 on the approach of a very powerful electro-magnet1 the stratifications were arrested as soon as they appeared1 as if blown out1 and finally extinguished4 ,a stratified discharge1 in vacuo1 from #djj insulated cells of a nitric acid battery1 was extinguished by the large electro-magnet of the ,royal ,institution2 the luminous strata rushed from the positive pole of the battery1 but under the magnetic force they retreated2 cloud followed after cloud with deliberate motion1 appearing as if swallowed up by the positive terminal4 ,the amount of electricity that passed through the tube appeared to be materially increased by exciting the electro-magnet2 the discharge was so intense on one occasion as to fuse half an inch of the positive terminal4 ,a very powerful magnet is also capable of extinguishing a stratified discharge4 ,in fact1 according to the law of the reciprocal action of magnetism1 the forces are equal in intensity and opposite in direction4 ,the electric discharge from an induction coil is discontinuous1 or eruptive sparks of high tension are given out producing stratified discharges4 ,the discharge of the voltaic battery had hitherto been considered absolutely continuous2 and so it is for chemical action1 whether of analysis or combination2 nevertheless certain phenomena gave reason to doubt its continuity4 ,mr4 ,gassiot has proved that the tension of a single cell of a galvanic battery increases in force according to the chemical energy of the exciting liquid1 and in all his experiments he found that #8the higher the chemical affinities of the elements used1 the greater was the development of evidence of tension4' ,these observations induced him to institute a series of experiments with galvanic batteries of different chemical affinities1 and to compare the resulting phenomena with those produced by the induction coil1 whose sparks are of high tension4 ,the same carbonic acid vacuum tubes were made use of in all the experiments2 a copper wire formed the positive terminal1 and a copper plate was fixed at the extremity of the negative terminal4 ,in other tubes platinum terminals extended into the interior1 coated with glass1 except the points1 to which charcoal balls were fixed4 ,one end of the tubes was of small diameter and contained caustic potash4 ,when a discharge from an induction coil was sent through these tubes1 there were either minute luminous spots1 narrow stratifications1 or a well defined cloud-like discharge at the positive pole1 according to the size and structure of the terminal1 but the characteristic phenomenon in all the tubes was a large cloud-like luminosity or circular glow on the brass plate or charcoal ball at the negative terminal4 ,with #eab insulated cells of copper and zinc of ,daniell's constant battery1 the exciting liquid being dilute sulphuric acid1 a brilliant glow appeared round the charcoal ball of the negative terminal on the passage of the electric discharge through the tube1 with very trifling luminosity of the positive pole4 ,two copper plates that could be separated or closed by a screw1 were placed between the poles of a nitric acid battery1 so that the circuit could be made or broken gradually1 and spark discharges were obtained between them4 ,the vacuum tubes were placed between one of these plates and a pole of the battery2 one of these tubes was #bd inches long1 #ah in circumference1 and had a circular copper disc #d inches in diameter on its negative terminal4 ,on completing the circuit1 the discharge of the battery passed with a display of magnificent strata of dazzling brightness2 on separating the plates by the screw1 the luminous discharges presented the same appearance as when taken from an induction coil1 but brighter4 ,on the copper disc within the vacuum tube1 there was a white layer1 then a dark space about an inch broad1 and then a bluish atmosphere curved like the disc1 evidently three negative envelopes on a great scale4 ,when the disc was made the positive pole1 the effect was feeble4 ,in vacuum tubes #f inches long and #a inch diameter1 with carbon balls on the terminals1 the discharge of the nitric acid battery elicits extreme heat4 ,in one of these the discharge presented a stream of light of intolerable brightness1 but when viewed through a plate of green glass strata could be seen4 ,this soon changed to a sphere of light on the positive ball1 which became red hot1 the negative being surrounded by magnificent envelopes2 with a horse-shoe magnet the positive light was drawn out into strata4 ,the needle of a galvanometer in circuit was violently deflected and the polarity reversed4 ,when the caustic potash was heated1 the discharge burst into a sunlike flame1 subsequently subsiding into three or four large strata of a cloud-like shape1 but intensely bright4 ,this is called the arc discharge3 it occurs in vacuum tubes with charcoal balls2 when the potash is heated intensely1 dazzling stratifications suddenly emanate from the positive ball1 and powerful chemical action takes place in the battery1 after which the discharge ceases4 ,this process facilitates the discharge and assists the disintegration of the carbon particles1 and these in a minute state of division are subsequently found attached to the sides of the glass4 ,it is these particles which produce the arc discharge with its intense vivid light so suddenly observed with far more brilliant effects than the usual stratified discharge4 ,during its passage the conducting power of the vacuum tube is greatly enhanced4 ,it was already mentioned that a stratified discharge was obtained from #c1ebj insulated cells of a water battery1 which differs but little in intensity from #djj cells of the nitric acid battery4 ,on one occasion the electricity seemed to pass through the vacuum tubes in a continuous stream1 but when examined with ,mr4 ,wheatstone's revolving mirror it was decidedly stratified4 ,mr4 ,gassiot never could obtain a continuous discharge in air1 whether between the points or metallic plates of the water battery4 ,the discharge was invariably in the form of minute clearly defined and separate sparks4 ,thus it was proved by the preceding experiments that a spark discharge could be obtained in air from both the nitric acid and water battery2 and that when these discharges were passed through the highly attenuated matter contained in carbonic acid vacua1 the same luminous and stratified appearance was produced as by an induction coil2 a proof that whatever may be the cause of the phenomena it could not arise from any peculiar action of that apparatus4 ,mr4 ,gassiot finally concludes that the cause of the stratified discharge arising from the impulses of a force acting upon highly attenuated but resisting media is also applicable to the discharge of the voltaic battery in vacuo2 while the fact of this discharge even in its full intensity having been now ascertained to be also stratified leads to the conclusion that the ordinary discharge of the voltaic battery1 under every condition1 is not continuous but intermittent1 that it consists of a series of pulsations or vibrations of greater or less velocity1 according to the resistance in the chemical or metallic elements of the battery or the conducting media through which the discharge passes4 ,caustic potash absorbs the carbonic acid gas by degrees1 and at last so completely exhausts a vacuum tube that electricity cannot be conducted4 ,air is a non-conductor1 and an electric discharge that will not pass through an inch of air1 will pass through more than #cj or #dj inches of attenuated gas4 ,it has already been mentioned that the stratified discharge can be obtained by a single discharge of the primary current of an inductive coil1 however long may be the vacuum tube through which the discharge is passed4 ,if no addition be made to the battery and no alteration be made in the arrangement of the coil so as to increase or diminish the intensity of the discharge1 the stratifications will always present the same appearance and form1 occupying the same spaces and positions in the vacuum tube2 but if any change be made so as to alter the intensity1 then a corresponding alteration will appear in the discharge1 the stri assuming a different shape1 and the bright and dark divisions occupying different positions4 ,in order to try what effect a change of intensity would produce1 three separate insulated voltaic batteries1 in which the exciting liquid was brine1 formed an electric circuit which was completed by two long wires4 ,it was so arranged that the discharge of one1 two1 or all the three batteries could be separately employed4 ,in order to vary the resistance at pleasure1 two tubes #ah inches long containing distilled water and connected at their base were introduced into the circuit4 ,by varying the depth to which the terminal wires of the circuit were plunged into the water1 the resistance could be regulated at pleasure1 and it was immaterial in what part of the circuit the vacuum tube was introduced provided the circuit was completed4 ,the first experiments were made with a carbonic acid vacuum tube #bj inches long and #d inches in diameter4 ,the negative terminal at one extremity of the tube was of aluminium1 cup-shaped1 about #c inches in diameter2 the positive terminal was a wire of the same metal fused into the other extremity of the tube2 the point of the wire and cup were about four inches and a half apart4 ,with this tube and #b1bdj cells of the battery the discharge when the resistance was introduced had the appearance of a positive and negative discharge1 impinging on and intermingling with each other1 without any dark space intervening4 ,around the negative terminal the luminosity extends to the sides of the tube and tapers to the point of the positive wire4 ,the light round the negative terminal becomes brighter1 a dark space appears next to it when the resistance is diminished1 and increases as the resistance decreases1 by the rolling back of the light in bright clouds to the point of the positive terminal4 ,these changes can be perfectly regulated by the resistance1 and various luminous phenomena occur at each stage4 ,with #b1bdj cells distinct sounds were heard in the tube2 with the whole battery of #c1cfj series the sounds were not heard till a magnet was applied to the stri1 when they again became audible and the stri were spread over the surface of the tube4 ,a carbonic acid vacuum tube with platinum terminals fused into the same side far apart was now put into the circuit1 the part of the wires that penetrated within the tube being coated with glass up to the carbon balls in which they terminated4 ,when a discharge from all the three batteries passed through the tube1 changes occurred in the form and number of the stri corresponding to the greater or less amount of the resistance offered in the circuit4 ,at the commencement of the experiments there were #ah inches of water in each of the tubes1 which formed the maximum resistance4 ,the wires attached to the terminal wires of the battery were placed inside of these tubes1 and as soon as they touched the surface of the water a faint luminous discharge was seen at each ball in the vacuum tube4 ,as the wire attached to the negative end of the battery was slowly depressed1 the two luminous discharges appeared to travel towards or attract each other1 and at times a portion of the positive luminosity passed over and mingled with the negative2 in this state the discharge was extinguished by a magnet4 ,when the wire was pressed farther into the water a dark space about an inch in length divided the light into two parts1 the positive glow being sharply defined1 the negative glow having an irregular edge4 ,when the wire had been about three inches deep in the water1 the positive and negative glows became more brilliant1 and a single clearly defined luminous disc burst from the positive side and occupied the middle of the dark space4 ,when the wire was pressed down till #ac inches of it were in the water1 a second luminous disc travelled from the positive side1 and then the two luminous discs or stri occupied the dark space at a little distance from one another4 ,as the wire was pressed more into the water1 three parallel luminous stri appeared1 then four1 then five1 and so on till as many as thirteen or fourteen striped the dark central space4 ,with the full power of the battery1 the adjacent disc impinged on the glow that surrounded the negative ball4 ,this disc was of a pale green1 those adjacent were reddish1 while the negative glow was of a bluish white2 minute bright scintillations emanated from the negative ball1 while distinct luminous flash discharges took place through the stri4 ,thus by the amount of resistance introduced into the circuit1 the number of stri can be regulated1 their position fixed1 separating or closing up the dark space between the luminous glows round the balls4 ,in these experiments there is indication of a force emanating from the negative wire4 ,the actual disruption of the particles from the negative terminal also indicates a force1 and the disruption is as freely obtained by the continuous discharge of the battery as it is by the intermittent discharge of the induction coil4 ,besides1 when ,mr4 ,gassiot sent discharges from the induction coil through ,torricellian vacua1 he several times observed that while a cloud-like discharge issued from the positive terminal1 a long tongue of the most brilliant blue phosphorescent light emanated from the upper part of the negative terminal1 and a brilliant white tongue of light was also seen close to the negative wire3 so there is reason to believe that force emanates from both terminals4 ,some of the preceding striated discharges #8present an appearance somewhat analogous with the stationary undulations 7or nodes7 which exist in a column of air when isochronous progressive undulations meet one another from opposite directions1 and on the surface of water by mechanical impulses similarly interfering with each other4'#aa #8,may not the dark bands be the nodes of undulations arising from similar impulses proceeding from positive and negative discharges8 or can the luminous stratifications which we obtain in a close circuit of the secondary coil of an induction apparatus1 and in the circuit of a voltaic battery1 be the representations of pulsations which pass along the wire of the former1 and through the battery of the latter1 impulses probably generated by the action of the discharge along the wires8' ,the action of magnetism and electricity on light is similarly illustrated by the rotation of the plane of polarization4 ,sir ,john ,herschel was the first who tried to rotate the plane of polarization of a ray of light by surrounding it with a spiral wire electrized by the great battery of two enormous plates of copper and zinc at the ,london ,institution1 but he obtained no evidence of any such action4 ,long afterward ,professor ,faraday succeeded by sending a ray of light through a piece of silico-borate of lead1 which formed the core of a magnetic helix4 ,the silico-borate took on a quasi-crystallised state during the passage of the electric current round it1 giving it for the moment the property of circular polarization1 analogous to that of glass in a state of tension or compression4 ,substances vary exceedingly in the facility with which they transmit electricity2 even the same substance under another form differs remarkably in that property3 charcoal1 which next to the metals is the best conductor known1 when under the form of diamond is quite impervious to electricity4 ,in general1 substances that are the best conductors of heat are also the best conductors of electricity1 as for example the metals1 which however1 possess the transmissive property in very different degrees4 ,silver and copper are the best conductors1 lead one of the worst2 its resistance to the passage of electricity is twelve times greater than that of silver and copper1 consequently it becomes twelve times as hot1 for when a current of electricity is impeded it is changed into heat4 ,so great is the resistance offered by a fine platinum wire1 that the heat amounts to #cbhj and the wire is melted1 a striking instance of the correlation of electricity and heat1 and of the power of the cohesive force4 ,when electricity is passing through conducting substances or when it is static1 it induces an electric state in bodies at a distance by transmission through non-conducting substances or air1 for it gives polarity and tension to the adjacent atoms1 and these to the next1 and the next in succession1 throughout the whole intervening mass1--a strong proof of the individuality and polarity of the atoms of matter4 ,motion1 which is the result of all the physical powers1 has itself a strong action upon the ultimate elements of matter2 in cases of unstable equilibrium it accelerates and even determines their chemical union4 ,some substances will remain merely mixed as long as they are at rest1 but no sooner is their inertia disturbed by a slight motion than they rush into permanent combination4 ,in newly sublimed iodide of mercury the vibration impressed by the scratch of a pin is so rapidly transmitted through the mass that its colour is immediately changed from yellow to bright red4 ,by a new arrangement of the molecules their action on light is altered4 ,catalysis or the chemical decomposition and composition of substances by the contact of a foreign body1 is well illustrated by the chloride of nitrogen1 that explodes when touched by substances which at ordinary temperatures would neither combine with the chlorine nor with the nitrogen4 ,the iodide of nitrogen explodes if touched by a feather1 and ,m4 ,becquerel decomposed the iodide of nitrogen by the vibrations of sound4 ,when substances only exist in consequence of the inertia of their atoms1 the instability of their chemical attractions and repulsions is only increased by an external agent1 so that a great effect is produced by a slight cause1 as in an avalanche1 the snowy mass is on the point of falling1 and the smallest motion1 a breath of wind1 hurls it down4 ,in such cases the potential energy of the unstable mass is in a moment changed into vis viva or impetus4 ,daguerreotype impression shows the power of the chemical rays on substances in unsteady equilibrium1 and the length of time required to make the impression under the same circumstances is a measure of the instability4 ,most of the fulminates are compounds of nitrogen2 of that the fulminate of aniline is a recent instance1 since it is formed by the slow action of nitrous acid on aniline4 ,explosion takes place on the sudden evolution of gas1 or the sudden change of a solid into vapour4 ,in these cases fire or percussion are the foreign causes of change4 ,they are all particular instances of the general principle of catalysis1 which is the chemical combination of heterogeneous atoms by the action of a substance that does not participate in the change4 ,thus it has long been known that when platinum is plunged into a mixture of oxygen and hydrogen it combines these gases into water4 ,acids in some cases seem to have the same effect2 for when rags or starch are dissolved in an acid the starch is changed to dextrine and the liquid has acquired the power of turning the plane of polarised light to the right4 ,the acid has undergone no alteration1 but it has changed the properties of the starch though not its chemical composition4 ,after a time1 a second transformation takes place1 the liquid ceases by degrees to turn the plane of polarisation to the right1 and ends by turning it to the left4 ,the acid is still unchanged1 but the dextrine has now disappeared3 it has combined with the water and is transformed into glucose or sugar of grapes4 ,the quantity of the physical powers1 active and latent1 is inappreciably great4 ,the quantity of heat or potential energy generated by chemical combination alone is enormous4 ,,section ,,iii4 ,,atomic ,,theory1 ,,analysis ,,and ,,synthesis ,,of ,,matter1 ,,utility ,,of ,,waste ,,substances--,,coal-,,tar ,,colours1 ,,etc4 ,,the chemical combination which forms the infinite variety of substances in the organic and inorganic creation consists in an intimate union of their ultimate atoms which produces substances differing from their constituent parts in every respect except gravitation1 the sum of the weights of their constituent parts being invariably equal to the weight of the resulting substance4 ,thus the chemical union of oxygen and hydrogen forms water1 and the weight of the water so formed is exactly equal to the sum of the weights of the two gases4 ,all chemical changes whether of analysis or composition are subject to definite unalterable laws of weight1 measure and number2 nothing is by chance or casual1 the relative weights of the invisible atoms of matter1 and their combination in definite proportions reveal the laws which prevailed in the primeval structure of created things4 ,by the wonderful discovery of these laws ,dr4 ,dalton has placed chemistry on a strictly numerical basis4 ,the chemical union of different kinds of atoms and volumes of matter in the definite proportions of whole numbers entirely changes their character and properties1 as for example the chemical combination of one atom of hydrogen and one atom of oxygen into water4 ,the condensation is often unexpected and wonderful2 two different liquids are often condensed into a solid1 and the result of the chemical combination of two different gases or vapours in quantitative proportions may be solid1 liquid or ariform1 a fact which could only have been discovered by experiment4 ,the powers of the atoms are changed and often highly exalted by chemical union as in ammonia1 a chemical compound of three atoms of hydrogen and one of nitrogen1 which absorbs #a1aie times more radiant heat than its constituents whether simple or mixed4 ,during chemical combination light and electricity are often evolved1 heat always4 ,the quantity given out is exactly proportional to the energy of the chemical action1 and is often so great and so rapidly evolved as to produce an explosion by the sudden expansion of the air around4 ,whatever the temperature may be1 which is given out during the union of the atoms1 the very same quantity of heat is requisite to dissolve their union1 and the atoms are separated in the same definite proportions in which they were combined4 ,voltaic electricity both combines and resolves substances into their component parts1 strictly according to the law of definite proportions4 ,it combines eight parts by weight of oxygen and one part by weight of hydrogen into water2 and again when it decomposes water1 one part by weight of hydrogen is given out at the negative pole of the battery1 and eight parts by weight at the positive or zinc pole4 ,for an electric current weakens or neutralizes the force of affinity in one direction and strengthens it in the other1 so that the heterogeneous atoms of the substance under its influence have a tendency to go in different directions and appear at opposite poles4 ,mr4 ,faraday has established as a general law1 that the quantity of electricity requisite to unite the atoms of matter1 is precisely equal to the quantity requisite to separate the same atoms again4 ,electro-chemical action1 or the power of electricity to combine and separate the heterogeneous atoms of matter1 is in direct proportion to the absolute quantity of electricity that passes in the current4 ,hence the superior analytical power of voltaic over static electricity1 which has enormous intensity1 but is very small in quantity4 ,the electric current separates molecular combinations which yield to no other means3 it is the most powerful instrument of analysis2 light is the most delicate4 ,two simple substances are only capable of a certain number of chemical combinations1 which form a regular series of new substances2 as for example oxygen and nitrogen4 ,two measures of nitrogen gas will unite with one measure of oxygen to form the protoxide of nitrogen2 with two measures of oxygen it unites to form the binoxide of nitrogen2 with three measures of oxygen it forms the hyponitrous acid2 with four it forms nitrous oxide2 and with five measures of oxygen it forms nitric acid4 ,thus there are five compounds of nitrogen and oxygen1 no more4 ,affinity of kind is merely the attraction of one element or atom of matter for another2 affinity of degree consists in the grades and limits of combination2 the preceding series is of the fifth degree2 the limit is the last term1 for no further combination of these two gases can take place1 and these are accomplished by art4 ,all the five substances are deleterious1 most of them deadly poisons1 for the protoxide of nitrogen1 which is the laughing gas1 could not be long inhaled with impunity4 ,for a long time the middle term of the preceding series was wanting1 but ,gay-,lussac formed it by attending to the laws of definite proportion and sequence4 ,the atoms of different kinds of matter possess an affinity1 or attractive force1 which binds them together chemically in different and very unequal degrees4 ,two substances may unite and form a third differing from both1 as water does from oxygen and hydrogen2 but if a new substance be added which has a greater attraction for one of the substances than for the other1 it will dissolve their union1 combine with that for which it has the strongest attraction1 and set the other free4 ,thus the metal potassium1 which has a greater attraction for oxygen than it has for hydrogen1 decomposes water1 combines with the oxygen1 and sets the hydrogen free4 ,both chlorine and ozone have the property of liberating the iodine in a weak solution of the iodide of potassium2 the liquid stains starch blue1 a proof of the free iodine4 ,the facility with which acids and alkalies combine affords the means of eliminating either the one or the other from a compound so as to liberate what remains4 ,the constituents of compound substances may be separated from one another by a variety of means depending upon their greater or less fusibility1 volatility1 and other properties4 ,water1 acids1 alcohols and other liquids hot or cold1 different degrees of temperature1 sublimation1 solution1 distillation1 evaporation1 together with static and voltaic electricity1 are the most powerful means of analysis4 ,but the animal and vegetable creation rear their fabrics by a synthetic process4 ,a plant after having absorbed carbonic acid and water1 decomposes the carbonic acid1 returns the oxygen to the atmosphere1 and combines the carbon and water into wood1 leaves1 and a variety of organic substances4 ,now ,,mm4 ,berthelot1 ,whler1 and other distinguished chemists1 by following this example of nature1 have established a system of synthetic chemistry1 by which they have produced from the chemical combination of the three elementary gases and carbon alone more than #a1jjj complete organic substances1 precisely the same with those formed within the living plants and animals4 ,yet we are as far as ever from any explanation of the mystery of life1 whether animal or vegetable4 ,carbon and hydrogen will not combine at any artificial heat however great2 but when the electric arc between highly purified charcoal terminals passes through hydrogen gas1 acetylene1 a new carburet of hydrogen1 is formed1 consisting of four equivalents of carbon and two of hydrogen4 ,this substance1 which no organized being is capable to form1 was discovered by ,m4 ,berthelot1 and being assumed as a base1 yielded an extensive series of organic substances4 ,thus when two atoms of carbon are added to acetylene it becomes olefiant gas2 when two equivalents of oxygen are added to olefiant gas1 the result is alcohol1 which is transformed into acetic acid by the addition of two atoms of oxygen1 and from this by a similar process have been obtained the malic1 tartaric1 succinic1 and the other acids2 glycerine also1 which is the sweet principle of the oils1 wax1 essential oils1 the perfumes of fruit and flowers1 the principle of the balms1 the essential oil of mustard1 and numerous other organic substances1 simply from carbon1 oxygen and hydrogen2 but nitrogen was introduced by combining alcohol with ammonia1 an inorganic substance consisting of three equivalents of hydrogen and one of nitrogen1 from whence a vast number of nitrogenized substances were derived1 both animal and vegetable4 ,chemical combination1 which has from the beginning of created things1 and still is1 building up organic and inorganic matter in the earth1 in the air1 and the ocean1 exerts forces of transcendent power1 though silent1 unperceived1 and for the most part unknown4 ,professor ,tyndall has given a striking instance of this in water1 the most simple compound of oxygen and hydrogen1 a constituent alike of organic and inorganic nature4 #8,in the combustion of the two gases to form a gallon of water weighing ten pounds1 an energy is expended1 the atoms clash together with a force1 equal to that of a ton weight let fall from a height of #bc1geg feet2 and in the change from the state of vapour to water1 an energy is exerted equal to that of a ton weight falling from a height of #c1gjj feet1 or of a hundredweight falling from a height of #gd1jjj feet4 ,the moving force of the stone avalanches of the ,alps is but as that of snowflakes compared with the energy involved in the formation of a cloud4 ,in passing finally from the liquid to the solid state1' that is from water to ice1 #8the atoms of ten pounds exercise an energy equal to that of a ton weight falling down a precipice of #eej feet of perpendicular height4' ,from ,mr4 ,joule's investigation of the relation existing between chemical affinity and mechanical force1 it appears that when affinity is feeble it can be overcome mechanically4 ,he formed amalgams of different metals1 that is he combined them with mercury1 by electricity4 ,the affinity of iron for mercury is so feeble that the amalgam is speedily decomposed when left undisturbed by the pressure of the atmosphere1 and if a greater pressure be added1 almost all the mercury is driven out4 ,the efficacy of mechanical force to overcome feeble chemical affinities is strikingly illustrated by the amalgam of tin1 out of which nearly the whole of the mercury is driven by long continued pressure4 ,in these cases the force of affinity did not amount to chemical equivalency1 otherwise the mercury could not have been driven out by so small a force4 ,instances from the weakest to the strongest affinity show that it is only when the power reaches a definite point that the law of chemical equivalents comes in4 ,the intense energy which then begins to be exerted has just been shown4 ,it is vain to hope for a knowledge of the absolute weight of the ultimate atoms of matter1 and nothing seems to be more beyond the power of man than to determine even their relative weights2 yet the definite proportions in which they combine have enabled him to do so4 ,thus1 an atom of oxygen unites with an atom of hydrogen to form water2 but as every drop of water1 however small1 contains eight parts by weight of oxygen1 and one part by weight of hydrogen1 it follows that an atom of oxygen is eight times heavier than an atom of hydrogen4 ,now1 since hydrogen gas is the lightest body known1 its atom has been assumed as the unit of comparison4 ,hence1 if the unit of hydrogen be represented by #a1 that of oxygen may be represented by #h4 ,again1 carbonic acid gas contains six parts by weight of carbon1 and eight parts by weight of oxygen1 and as an atom of oxygen is eight times heavier than an atom of hydrogen1 therefore an atom of carbon is six times heavier than an atom of hydrogen1 and consequently may be represented by #f4 ,in this manner the relative weights of many substances have been determined4 ,but the property of isomorphism also affords the means of ascertaining the atomic weights of certain substances with unerring certainty4 ,it is exactly the contrary of dimorphism1 for in the latter substances are chemically the same under different forms2 whereas isomorphic bodies are chemically different under the same form4 ,now the peroxide of manganese contains one atom of oxygen for one atom of metal2 but in #ajj parts of the protoxide there are #baid parts of oxygen and #ghjf of manganese4 ,comparing these numbers with #h the atomic weight of oxygen1 the result is #bh the weight of an atom of manganese4 ,the same number is obtained from two other isomorphic compounds of oxygen and manganese1 which proves the accuracy of this result4 ,the atomic weights of many bodies have been determined1 of which the following are the most important4 ,atomic ,weights1 an ,atom of ,hydrogen being the ,unit4 ,hydrogen #a ,carbon #f ,oxygen #h ,nitrogen #ad ,sulphur #af ,phosphorus ,sodium #bc ,iron ,nickel #bh ,manganese ,bromine #hj ,copper #cb ,zinc #cbe ,chlorine #cee ,potassium #ci ,rubidium #hf ,csium #acc ,iodine #abg ,thallium #bjd ,in the determination of atomic weights a few cases have occurred of fractional numbers1 and although it cannot yet be affirmed that no such cases exist1 yet it seems to be established by the new and more perfect analyses of ,,mm4 ,dumas1 ,isidore1 ,williamson1 and others1 that the atomic weights of substances compared with an atom of hydrogen are in whole numbers4 ,this law leads to very important results4 ,for example1 the equivalent weights of the chemical elements of bodies derived from their specific gravities are either identical with1 or simple multiples or sub-multiples of1 their relative weights4 ,thus the specific gravity of hydrogen is #jjfic1 and that of oxygen is #aaaa2 hence taking hydrogen as the unit of comparison1 it is easy to see that #jjfic 3 #aaaa 33 #a 3 #af1 the simple multiple of #h1 the relative atomic weight of oxygen4 ,in fact since each substance has its own specific gravity or weight1 that weight must depend upon the weight of its atoms1 so that the weights of equal bulks of different substances are proportional to the weights of their atoms1 and thus a relation is established between the atomic weights and specific gravities of bodies1 so that one being given the other may be found4 ,atoms like their substances have many different capacities for heat and electricity4 ,it was proved by ,,mm4 ,petit and ,dulong1 that specific heat1 or the quantity of heat required to raise a simple substance to a given temperature1 is inversely as the weight of its atoms1 so that the specific heat or repulsive force of simple substances multiplied by their atomic weights is a constant quantity4 ,such is the condition requisite for the equilibrium or equality of force2 or the law may be thus expressed3 ,a given quantity of heat will raise to the same number of degrees a portion of every simple substance represented by its atomic weight4 ,for instance1 the atomic weight of sulphur is #af1 that of zinc #cbe2 hence it requires twice as much heat to raise a pound of sulphur ten degrees as it does a pound of zinc4 ,it has also been proved that the atoms of compound bodies of analogous composition are endowed with the same capacity for heat1 so that there is a perfect correspondence between the weight of atoms and their specific heat4 ,the numbers representing the atomic weights derived from the specific heat of bodies are connected with their equivalent atomic weights by the simple ratios of equality1 multiples or sub-multiples4 ,mr4 ,j4 ,croll has made experiments showing that the specific heat of compound gases and liquids is generally less1 and those of solids more1 than that of their component elements1 which is contrary to the hitherto received opinion4 ,moreover it appears that the changes in the specific heat of bodies which occur during combination are not only due to chemical action1 but also to molecular changes2 the real specific heat of a simple atom probably remaining the same under all conditions4 ,mr4 ,faraday has proved that the specific electricity of different substances is also in proportion to their atomic weights1 that is to say1 a given quantity of electricity will separate combined substances into parts represented by their atomic weights4 ,for example1 #cbe parts of zinc will generate voltaic electricity enough to separate nine parts of water into eight parts of oxygen and one part of hydrogen gas4 ,the weights thus derived from decomposition are exactly the same with those determined by composition1 and thus the atomic weights derived from electro-decomposition accord exactly with those obtained from chemical composition4 ,moreover1 ,mr4 ,faraday1 as already mentioned1 proved that the very same quantity of electricity necessary to decompose a body into its elementary atoms1 is requisite to unite them again4 ,the analysis and synthesis of compound matter1 solid or fluid1 show a constant and definite proportion of the component elements expressed by number1 and by an equivalent or multiple ratio of parts in every chemical change4 ,the atomic theory unites1 by a common bond1 specific gravity1 chemical affinity1 heat1 and electricity4 ,taking atmospheric air at the temperature of #fj ,fahr4 and a barometric pressure at #cj inches as the standard unit of specific gravity2 the quantity of heat required to raise a volume of water #a ,fahr4 as the unit of specific heat2 hydrogen gas as the unit of atomic weight2 and atomic electro-chemical electricity as the unit of specific electricity1 the following numbers have been established3 ---------------------------------------- --------------- ,specific ,equivalent ,specific ,specific gravity atomic heat electricity weight ---------------------------------------- --------------- ,hydrogen #jjfic #a #jbicf #ajjj ,oxygen #aaaa #h #jbcfa #abe ,carbon #acb #f #jbfca ,nitrogen #jigh #ad #jbgej ---------------------------------------- --------------- ,the distances between the atoms of the gases are equal1 hence the atomic weights of simple gases are proportional to their densities2 and for the same reason1 equal volumes of the same fluid contain an equal number of atoms1 and the number of atoms in the same volume of different fluids is in the simple ratio of one to one1 one to two1 one to three1 c4 ,it follows from the atomic theory that the number of atoms in equal weights of any two solid substances1 is in the inverse ratio to the weights of these atoms4 ,now since the bodies that have the greatest specific gravities are the heaviest1 if the specific gravities and atomic weights of equal bulks of two simple substances be known1 the relative number of atoms they contain may be found4 ,for the density divided by the atomic weight of the one1 is to the density divided by the atomic weight of the other1 as the number of atoms in the first to the number of atoms in the second4 ,by the preceding law it is found that in equal bulks of the three metals1 sodium1 platinum1 and potassium1 platinum contains five times as many atoms as sodium1 and ten times as many as potassium4 ,when substances which have strong analogous qualities are compared in this manner1 the results are either equality1 or a simple ratio4 ,it has already been mentioned that the protoxides of iron1 copper1 zinc1 nickel and manganese1 have the same form1 and contain the same quantity of oxygen1 but differ in the respective metals that are combined with it2 and by the preceding law it appears that equal bulks of these isomorphous bodies contain also the same number of atoms4 ,mr4 ,hermann ,kopp has proved that the atomic weight of a substance divided by the specific gravity1 that is to say1 its atomic volume1 is the same for all isomorphic bodies simple and compound1 and as a general law that the atoms of isomorphous substances are not only the same in form1 but equal in dimensions4 ,it follows1 therefore1 that any one of the preceding metals might be substituted for any other in the respective protoxides1 and on that account1 according to the modern theory1 they are the chemical equivalents of each other1 for that expression is used now in a different sense from what it formerly had4 ,chemical equivalency between two or more substances consists in their capacity for being exchanged one for the other4 ,direct or indirect substitution forms the basis of the modern doctrine of chemical equivalents4 ,substances which are capable of replacing one another in compounds1 and which are endowed with qualities mutually analogous1 are said to be isomeric4 ,many isomeric compounds are formed of the same materials1 in the same proportions1 and yet differ essentially both in their physical and chemical properties2 whence ,m4 ,daniel observes1 that a specific and definite arrangement of the constituent molecules in space appears to be no less essential to the individual constitution of bodies than a certain proportion between their heterogeneous ingredients4 ,successive substitution in isomeric bodies does not alter the character of the chemical formul of these bodies2 thus chlorine1 bromine and iodine1 are chemically equivalent with an atom of hydrogen1 for they may be put for one or more atoms of hydrogen in various compounds without changing the character of the chemical formul of these compounds4 ,the peroxide of hydrogen consists of one atom of hydrogen and two of oxygen2 hence if #cbe parts of zinc1 #bh of manganese1 and #cb of copper be successively put for the atom of hydrogen1 the result will be the peroxides of zinc1 manganese and copper respectively4 ,here the character of the chemical formula of the original compound remains the same1 and the three metals are chemically equivalent to one another1 and to the atom of hydrogen4 ,in many compounds organic and inorganic1 one or more atoms of hydrogen may be replaced by an equal number of atoms of sodium1 potassium1 zinc1 c41 without altering the character of the chemical formula of the compound4 ,olefiant gas1 olefiant oil and paraffin1 form an isomeric series of a gas1 a liquid and a solid1 consisting of carbon and hydrogen4 ,the gas contains #hf parts in #ajj of carbon1 and forms the most luminous part of coal gas4 ,m4 ,dumas has proved it to be a general law1 that when three isomeric bodies are arranged in the sequence of their chemical properties1 there will also be a sequence in their respective atomic numbers1 and that whenever this symmetry of chemical properties and atomic weights obtains1 any one of these substances may be substituted for the other without changing the chemical character of the formula4 ,sulphur1 selenium1 and tellurium1 form an isomeric group2 that is1 they form a sequence1 with analogous qualities1 for sulphur is the most volatile2 selenium1 a simple substance found in iron pyrites in ,sweden1 is less volatile2 and tellurium is the least volatile and with regard to their atomic sequence1 the atomic weight of sulphur is #af1 that of tellurium is #fd1 and half the sum of these numbers is #dj1 the atomic weight of selenium1 the mean term4 ,hence selenium might be put in any compound for the sulphur1 and the tellurium for the selenium1 without changing the chemical character of its formula4 ,the metallic group of calcium1 strontium1 and barium1 are endowed with analogous properties1 perfect harmony in their chemical qualities1 and in the numbers expressing their atomic weights4 ,that of calcium is #bj1 that of barium is #fh1 and the half sum is #dd1 the atomic weight of strontium4 ,so calcium might be put for strontium1 and strontium for barium1 in any compound without altering the character of its formula4 ,professors ,johnson and ,allen have shown that the new metalloids csium and rubidium form an isomeric triad with potassium1 for the atomic weight of csium is #acc1 that of rubidium #hf1 and that of potassium #ci4 ,transmutations of one isomeric substance for another may also be made in organic bodies1 but chlorine1 bromine1 and iodine form an exception to ,m4 ,dumas's law1 because the arithmetical relation is wanting4 ,there are certain groups of substances1 especially among the metals1 whose atomic weights are in regular arithmetical series1 as those of titanium1 tin1 and tantalum1 which are #be1 #ei1 and #ib1 the common difference being #cd4 ,certain groups of combined atoms called compound radicles are much more important than the preceding4 ,they unite chemically with one another1 and with other substances in definite proportions1 precisely as if they were ultimate atoms4 ,they are even capable of being substituted one for the other1 forming groups of infinitely varied properties1 and thus chemical equivalency extends to them4 ,cyanogen1 amidogen1 and the peroxide of hydrogen are compound radicles which combine with other substances and with simple atoms as if they themselves were simple elements2 though the first is a chemical compound of two atoms of carbon and one of nitrogen1 the second a chemical compound of one atom of nitrogen and two of hydrogen1 and the peroxide contains as before mentioned two atoms of oxygen and one of hydrogen4 ,all three are capable of replacing hydrogen1 chlorine1 and metals by equivalent substitutions4 ,for example1 the chlorate of potash consists of one atom of potash1 an atom of chlorine1 and five atoms of oxygen2 if then an atom of cyanogen whose weight is #bf1 be put for the atom of chlorine1 the result would be the cyanate of potash4 ,cyanogen1 formed by passing nitrogen over red-hot carbon1 consists of two equivalents of carbon and one of nitrogen4 ,it is a frequent constituent of organic and inorganic compounds1 and travels in the voltaic circuit as if it were a simple substance4 ,ammonia consists of three equivalents of hydrogen and one of nitrogen2 now1 when the radical phenyle1 which consists of twelve equivalents of carbon and five of hydrogen1 is put in the ammonia for one equivalent of hydrogen1 the result is aniline1 whence most of the coal tar colours are obtained4 ,in like manner carbazotic acid1 a beautiful yellow dye from coal tar1 is carbolic acid1 three of whose equivalents of hydrogen have been replaced by three equivalents of an oxide of nitrogen4 ,compound radicles1 consisting of carbon and the three elementary gases1 have been discovered which enter into combination in definite proportions as simple atoms1 and all compound radicles travel in the galvanic circuit as equivalents to the elementary substances4 ,hitherto they have been regarded as representatives or equivalents of one atom of hydrogen4 ,now it is generally admitted that each has the property of replacing two1 three1 or more atoms of hydrogen by equivalent substitution4 ,this multiple equivalency among compound radicals forms the basis of what is called the polyatomic theory1 now so much employed by ,,mm4 ,hofmann1 ,berthelot1 and other great modern chemists4 ,water is the most common radicle both in the inorganic and organic world4 ,though a compound of oxygen and hydrogen1 it enters1 according to the law of definite proportion1 into the composition of various amorphous bodies in a dry state1 that is in the form and proportion of its gases4 ,it is an essential element in the greater number of crystals1 and abounds in organic matter4 ,in certain cases the same substance crystallizes at different temperatures1 unites with different quantities of water under the form of oxygen and hydrogen1 and assumes corresponding forms4 ,for example1 the seleniate of zinc unites with three different portions of water and takes three different forms1 according as its temperature is hot1 lukewarm1 or cold4 ,thus each particle of water1 containing one atom of oxygen and one of hydrogen1 combines with one atom of zinc in three different proportions as if it were a simple atom4 ,the water of crystallization may be driven off from many substances by heat1 as from the hydrates of lime1 iron1 copper1 c41 but when combined with the oxides of certain metals1 potassium for instance1 it cannot be driven off by any means whatever4 ,in general a heat of #bab ,fahr4 is sufficient1 but some crystals lose their water of crystallization at the ordinary atmospheric temperature4 ,crystals whose atoms are in unstable equilibrium1 are readily altered both externally and internally by a very moderate degree of heat4 ,arragonite and calcareous spar are isomeric1 that is1 they are chemically the same but differ in form and hardness1 which shows that their molecules are grouped differently4 ,when the arragonite is heated1 the inertia of its atoms is overcome1 the crystal explodes with force1 and becomes a mass of crystals of calcareous spar4 ,the expansive force of the heat suddenly overcoming the force of cohesion causes the explosion1 and at the same time disturbs the unstable repose of the atoms1 which immediately obey their natural attractions and assume the stable form of calcareous spar4 ,dialysis is a method of separating and analysing substances by means of their diffusion in alcohol or water4 ,if a wide-mouthed vial nearly full of a solution of common salt be placed in a jar of water1 after a few days it will be found that the particles of salt have come out of the vial and have diffused themselves through the superincumbent water1 even to its surface4 ,now ,professor ,graham1 ,master of the ,mint1 with whom this subject originated1 made three arrangements precisely like that described2 the three vials were exactly similar and equal1 the three jars exactly the same in size and form1 and contained the same quantity of water2 but the first vial contained a solution of gum arabic1 the second a solution of ,epsom salt1 and the third a solution of common salt4 ,after fourteen days the diffusion of the gum had risen through one half of the superincumbent water1 while the particles of both the salts had risen to the surface4 ,however the common salt would have risen much higher1 for when the strata of water at the two surfaces were drawn off by a siphon and evaporated to dryness1 there was fifteen times as much common salt as ,epsom salt4 ,the three solutions are heavier than water1 yet they rise notwithstanding their gravitation1 whence ,mr4 ,graham thinks that there is probably an attraction between the particles of the dissolved substances and those of the water4 ,the force of molecular attraction is more powerful than gravitation1 hence the particles must rise by the difference of the two forces4 ,after many comparative experiments the professor concluded that most substances differ in diffusibility1 and that crystalloids or crystalline substances such as salts1 sugars1 c41 are much more diffusible than colloids or amorphous sticky bodies1 such as gum1 caramel1 jellies1 and substances that combine with the hydrogen of the water to form gelatinous hydrates4 ,the partial decomposition of definite chemical compounds may be effected by diffusion4 ,alum1 which is a double sulphate of the two metals potassium and aluminium1 furnishes an example2 when allowed to diffuse itself from its aqueous solution1 the diffusive tendency of potassium compounds is so much greater than the diffusive property of aluminium compounds1 that a portion of the sulphate of potassium actually breaks away from the sulphate of aluminium with which it was combined1 in order to diffuse itself in the superincumbent external water more freely than the sulphate of alumina can do4 ,common salt diffuses itself in a solid mass of jelly almost as easily and extensively as in the same bulk of free water4 ,thus colloid bodies do not interfere with the diffusion of crystalloids such as salts1 but they almost entirely arrest the diffusion of one another4 ,solutions of salts1 sugars1 and other crystalloids pass freely through colloid substances1 such as parchment-paper1 vellum1 and membrane into water1 although they have no pores1 because the particles of the crystals unite diffusively with the water combined in these substances1 which solutions of gum1 caramel1 and other colloids cannot do4 ,these colloid substances are permeable to solutions of crystalloids1 impermeable to solutions of colloids4 ,this constitutes ,dialysis4 ,the instrument used by ,mr4 ,graham was a little tray formed of vellum or membrane stretched tightly over a hoop of gutta-percha and capable of holding a liquid and floating on water4 ,when a mixed solution of equal parts of salt and gum is put into the tray1 after a time all the salt will have passed into the water below1 leaving nothing in the tray but an aqueous solution of gum4 ,the following is one of the most extraordinary results of dialysis4 ,mr4 ,graham took a silicate of soda1 a soluble crystalline salt formed by fusing quartz with carbonate of soda at a red heat1 which diffuses readily4 ,he acidulated the aqueous solution of the salt with hydrochloric acid1 which changes the constituent silica from being a crystalloid substance into a colloid form4 ,when the liquid was poured into the tray floating on water1 after four days1 the whole of the acid and the chloride of sodium had been diffused in the water and nothing remained in the tray but an aqueous solution of quartz4 ,there remained in fact1 a solution of sand in water1 a substance so hard that no pure aqueous solution of it had ever been obtained4 ,many other crystalline substances besides quartz can exist both in the colloid and crystalloid states4 ,all colloid substances are characterized by non-crystalline habits1 low diffusibility1 chemical inertness1 high atomic weight1 and above all by their mutability4 ,the aqueous solution of quartz is limpid and liquid1 even if it contains #ad per cent4 of silica1 but after a time it becomes opalescent1 viscous1 and ultimately sets into a firm insoluble jelly1 capable however of solution by chemical means4 ,this jelly gradually shrinks1 exudes pure water1 and when perfectly dry it forms a glassy1 transparent1 but not anhydrous substance1 and the residue left by ignition has a specific gravity of #bb1 that of crystallized silica being #bf4 ,mr4 ,graham has obtained many pure aqueous solutions of organic and inorganic matter1 most of them being unstable4 ,ice near or at its melting point is believed to be a colloid body1 consequently it is unstable and resembles a firm jelly1 having a tendency to rend and recombine4 #8,the constant intervention of colloid septa in so many of the phenomena of animal and vegetable life gives to the subject of dialysis a high physiological interest1 and it will doubtless exercise an important influence on the progress of physiological research4'#ab ,subsequently to these researches ,mr4 ,graham published a memoir on a new method of analysing gases which he had called atmolysis4 ,the memoir may be regarded as consisting of four parts1 the first of which is preliminary1 being on the reciprocal diffusion of gases through porous plates4 ,the next three parts relate to effusion1 or the passage of gases under constant pressure through a minute opening in a very thin plate into a vacuum2 transpiration1 or the passage of gases through capillary tubes into vacuo2 and lastly atmolysis1 which is the partial separation of a mixture of gases and vapours of different degrees of diffusibility by permitting them to diffuse themselves through a porous plate into a vacuum3 a new kind of analysis1 which possesses a practical character of extensive application4 ,the diffusing instrument employed by ,mr4 ,graham was a cylindrical glass tube about an inch in diameter1 ten inches long1 with one end closed by a very thin porous disc of compressed artificial graphite fixed by a resinous cement4 ,while the tube was being filled with hydrogen gas over a trough of mercury1 the escape of the gas was prevented by covering the graphite very carefully with a thin sheet of gutta percha4 ,as soon as the gutta percha was removed1 the reciprocal diffusion of the gases began1 and in from forty to sixty minutes the whole of the hydrogen had escaped from the tube1 and a quantity of atmospheric air amounting to about one fourth of the volume of hydrogen had entered the tube and taken its place1 according to the ordinary law of the diffusion of gases4 ,during this time the mercury rises in the tube so as to form a column several inches high1 a fact which is a striking demonstration of the intensity of the force with which the reciprocal penetration of different gases effected4 ,natural plumbago or graphite has little or no porosity and cannot be used in these experiments1 but the pores of artificial graphite of which pencils are made1 appear to be so minute that only isolated molecules of gas are able to pass1 without however being at all impeded by friction2 for the smallest pores that we can suppose to exist in the graphite must be real tunnels compared with the minuteness of the ultimate atoms or molecules of a gaseous body4 ,the cause of motion appears to reside solely in that internal movement of molecules which is now generally admitted as an essential condition of matter in a gaseous state4 ,the molecules and atoms are assumed to be perfectly elastic and to move in all directions with different velocities according to the nature of the gas4 ,enclosed in a porous vessel the moving atoms constantly strike against its walls and against one another1 but in consequence of their perfect elasticity1 no loss of movement results from the collision4 ,when the gases inside and outside of the tube are of the same density and molecular movement1 an exchange takes place without any perceptible change of volume2 but when the two gases are of different densities and molecular velocities1 then the reciprocal penetration ceases to be equal on the two sides4 ,reciprocal diffusion of gases is accelerated by heat and retarded by cold2 the tension of the gases is increased in the first case1 and diminished in the second4 ,in ,mr4 ,graham's experiments relating to effusion1 a gas under a constant pressure was on one side of a minute opening in a very thin plate1 and a vacuum on the other4 ,the rapidity with which air or gases enter the vacuum depends upon their specific gravity4 ,a gas rushes into a vacuum with the speed acquired by a heavy body in falling from the height of an atmosphere of the gas in question supposed to be everywhere of the same density4 ,the height of this uniform atmosphere will be in an inverse ratio to the density of the gas4 ,an atmosphere of hydrogen1 for example1 will be #af times higher than one of oxygen4 ,but the velocity acquired by a heavy body not being in direct proportion to the height1 but to the square root of the height1 it follows that the rate of flow of different gases into a vacuum will be in an inverse ratio to the square root of their respective densities4 ,the rate of flow of oxygen being represented by #a1 that of hydrogen will be represented by #d the square root of #af4 ,this law has been verified by experiment1 and is quite analogous to that which regulates molecular diffusion1 but the phenomena are essentially different4 ,it is the gas en masse which partakes of the movements of effusion1 whilst only the molecules or atoms of a gas are affected by the movements of diffusion4 ,for that reason the swiftness of the effusion of a gas is many thousand times greater than that of diffusion4 ,the swiftness of the efflux of atmospheric air is as rapid as the velocity of sound4 ,the rate of the flow of different gases under constant pressure through capillary tubes into a vacuum1 constitutes the capillary transpiration of gases4 ,these rates bear a constant proportion to one another1 but they are singularly unlike the rates of effusion4 ,they are independent of the material of the tube2 they are not governed by specific gravity2 and #8they appear to be in constant relation with no other known property of the same gases2 and they form a class of phenomena remarkably isolated from all else at present known of gases4' ,the pores of graphite are so fine that it is incapable either of effusion or transpiration1 but it is readily penetrated by means of the molecular or diffusive movements of gases1 as appears on comparing the time requisite for the passage of equal volumes of different gases under constant pressure into a vacuum4 ,for oxygen1 hydrogen and carbonic acid gas1 the times are nearly as the square roots of their densities4 ,the atmolysis or partial separation of mixed gases and vapours of unequal diffusibility1 can be effected by allowing the mixture to penetrate through a graphite plate into a vacuum4 ,the amount of separation is in proportion to the pressure1 and attains its maximum when the gases pass into a perfect vacuum4 ,one of the results of atmolysis was the concentration of oxygen in atmospheric air4 ,when a portion of air confined in a vessel was allowed to penetrate into a vacuum through graphite or unglazed earthenware1 the nitrogen passed more rapidly than the oxygen in the ratio of #ajffh to #a1 and the portion of oxygen is proportionally increased in the air left behind in the vessel4 ,the increase of oxygen actually observed when the air in the vessel was reduced from #a volume to #je was #jdh per cent4 ,the diffusion was continued till the air in the vessel was reduced to #jjfbe and the concentration of the oxygen in it amounted to #bjb per cent4 ,the molecular or diffusive mobility exercises a certain influence on the heating of gases by contact with heated liquid or solid substances4 ,the more rapid the molecular movement of a gas is1 the more frequent will be the contact of the molecules and the quicker will be the communication of heat4 ,the greater cooling power of hydrogen compared with that of oxygen or air is probably owing to that cause4 #8,oxygen and hydrogen gas have the same specific heat for equal volumes2 but a hot object placed in hydrogen is really touched #ch times more frequently than it would be if placed in oxygen gas4 ,dalton had already ascribed this peculiarity of hydrogen to the high mobility of the gas4'#ac ,it appears that isomorphic substances such as chloride1 bromide1 and iodide of sodium1 have a similar diffusibility1 another of the many analogies between these singular marine substances4 ,modem chemistry is essentially experimental2 the unprecedented magnitude to which ,british manufactures have risen is chiefly owing to experiments conducted with consummate skill and dexterity4 ,in these investigations1 accidental circumstances have sometimes occurred which led to other researches quite different from that originally in view1 which have had unexpected and invaluable results4 ,although the simple elements are few1 they are capable of an infinite variety of combinations1 so that by analysis and new combinations1 the most useful and valuable materials are now obtained from obnoxious or useless substances1 formerly thrown away4 ,the instances are numerous2 but sawdust may be mentioned as one of the most remarkable4 ,it was not even fit for fuel1 but now oxalic acid1 a bleaching principle most extensively used in the various processes of calico printing1 is procured from it2 the quantity required may be imagined1 since the cotton cloth annually printed in ,great ,britain previous to the ,american war1 would surround the earth's equator nineteen times4 ,oxalic acid1 which is a vegetable substance1 found combined with potash in wood sorrel or ,oxalis acetosella1 used to be made from sugar or starch1 by the action of nitric acid4 ,now starch1 sugar1 and woody fibre or fibrine1 all contain twelve parts of carbon and different portions of oxygen and hydrogen1 always in the proportions that form water2 hence the name of carbohydrates4 ,their composition is so similar that the one may be changed into the other by the addition or subtraction of one or two atoms of water under its atomic form2 thus when fruits ripen1 the starch they contain is changed into sugar by the addition of one atom of water under its dry form4 ,now sawdust is woody fibre1 and might be changed by nitric acid into oxalic acid like the others4 ,but a less expensive method is actually employed4 ,when sawdust1 mixed with two equivalents of the hydrate of soda and one equivalent of the hydrate of potash1 is exposed to a heat of #djj for a few hours1 the substances are fused1 and when raised to a still higher temperature the hydrates are decomposed3 hydrogen is evolved1 and the carbon combines with the oxygen to form the oxalate of soda and the oxalate of potash4 ,in order to separate these oxalates they are put into a filter1 a solution of carbonate of soda is passed through it2 the oxalate of soda remains in the filter1 the carbonate of potash passes through it2 and when lime is added to the oxalate of soda1 the soda is liberated1 passes through the filter1 and the oxalate of lime remains4 ,sulphuric acid is then added to the oxalate of lime1 sulphate of lime is formed1 and oxalic acid mixed with water remains1 and by evaporation forms into beautiful crystals of oxalic acid4 ,this is an instance of a complicated chemical process2 nevertheless it is carried on to a vast extent in ,manchester1 nine tons a week being furnished by one manufactory alone4 ,two pounds of sawdust yield one pound of oxalic acid4 ,in ordinary distillation a volatile substance such as water1 by absorbing the heat applied to it1 becomes converted into vapour2 by abstracting the absorbed heat from the vapour1 it is reconverted into the original substance4 ,destructive distillation1 on the contrary1 consists of an entire destruction of the original substance and a simultaneous production of new substances4 ,of this the destructive distillation of coal furnishes the most interesting illustration1 and shows at the same time the success of modern chemistry in utilizing waste substances4 ,coal had been distilled for years to furnish gas for the illumination of our cities before it was discovered that the refuse contained principles of the greatest value4 ,the products of the distillation are threefold3 gas1 coal water1 and coal tar4 ,coal gas is a combination of various gases1 whose illuminating properties depend upon1 and are exactly in proportion to1 the quantity of carbon they contain4 ,the particles of carbon raised to a white heat give the light1 for the gaseous part has a feeble flame1 and requires a higher temperature than solid matter1 which becomes luminous at about #gjj in the dark1 and at from #ajjj to #bjjj in bright daylight4 ,coal gas consists of a combination of illuminants3 olefiant gas1 which contains #hf per cent4 of carbon1 carburetted hydrogen or marsh gas1 which contains #ge per cent41 carbonic oxide1 carbonic acid gas1 hydrogen1 sulphuretted hydrogen1 and a very small quantity of nitrogen1 besides the bisulphide of carbon1 and benzol1 a pure hydro-carbon1 consisting of #ab equivalents of carbon and #f of hydrogen4 ,the poisonous quality of coal gas is owing to the carbonic oxide1 which is fatal to life1 and its explosive quality to carburetted hydrogen1 which also is generated by decomposition of vegetable matter in stagnant pools and marshes2 and in the firedamp of mines it still bears testimony to the vegetable origin of coal4 ,that fatal gas increases in explosive force as it mixes with atmospheric air1 and is at a maximum when it amounts to #ab per cent4 ,hydrogen1 carburetted hydrogen1 and carbonic oxide do not add much to the light1 on account of the feeble flame of hydrogen and the small quantity of carbon they contain1 but they force the chief illuminating gases out of the iron retorts in which the coal is distilled before the heat has had time to decompose them1 and they also enable them to burn without smell or smoke4 ,carbonic acid1 bisulphide of carbon1 and sulphuretted hydrogen are impurities from which coal gas is freed before it is fit for use4 ,by passing the gas over lime1 the lime absorbs both the carbonic acid and the sulphuretted hydrogen2 one per cent4 of carbonic acid diminishes the illuminating power six per cent41 and the sulphuretted hydrogen has an abominable smell4 ,the bisulphide of carbon1 consisting of one equivalent of carbon and two of sulphur1 is got rid of by passing the gas over hot lime4 ,the water of the lime is decomposed1 and carbonic oxide and sulphuretted hydrogen are produced2 but the latter may be absorbed by passing the gas again over lime1 or through a mixture of sawdust and the oxide of iron4 ,the oxide of iron decomposes the sulphuretted hydrogen1 forms water and sulphide of iron1 then the air restores the sulphide to oxide1 and the sulphur is deposited in the mixture4 ,after passing the gas through it till none of that impurity remains1 the gas is fit for use4 ,the test is the nitro-prusside of sodium1 which the gas stains purple if any of the impurity remains4 ,paraffin1 already mentioned as isomeric1 is a pure hydrocarbon1 colourless1 transparent1 and of crystalline texture4 ,it melts at a heat of #abj or #acj1 burns like wax without smell or smoke1 and makes beautiful candles1 which give a brilliant light on account of the #hf per cent4 of carbon they contain4 ,paraffin oil is much used for lamps2 the manufacture of these two substances at ,bathgate is one of the largest chemical establishments in the world4 ,the black ftid gas water resulting from the distillation of coals1 formerly thrown away1 is so rich in the salts of ammonia1 that it has become the chief source from which these materials so important in the arts are obtained4 ,ammonia is well known to be a colourless gas1 with an acrid pungent smell1 consisting of one equivalent of nitrogen and three of hydrogen4 ,it has an alkaline character1 combining with acids1 and is extremely soluble in water4 ,now the gas water contains carbonate of ammonia and sulphide of ammonium1 and when any acid strong enough to decompose these substances is put into the liquid1 the carbonic acid and sulphuretted hydrogen being volatile are driven off1 and the acid combines with the ammonia to form a salt4 ,for example1 when muriatic acid is put into the liquid1 it drives off the volatile gases and combines with the ammonia in solution to form muriate of ammonia1 which is dissolved in water and evaporated till it crystallises2 then it is vaporized and sublimed to free it from impurities4 ,when ammonia and muriatic acid are separately vaporized1 the two colourless transparent vapours1 when mixed1 combine into solid muriate of ammonia1 a result so unexpected that as ,mr4 ,playfair justly observes1 it could only have been taught by experiment4 ,about #d1jjj tons of muriate of ammonia are annually made from gas water in ,england for soldering1 and for making alum4 ,sulphate of ammonia to the extent of #e1jjj tons is annually made by adding oil of vitriol to the liquid4 ,it is also used for making alum1 as well as for manure2 it supplies our grain with nitrogen1 an important article of vegetable food4 ,to these may be added #b1jjj tons of carbonate of ammonia1 so that a substance that was considered to be good for nothing yields #aa1jjj tons of valuable materials1 but even this quantity forms only part of the enormous amount annually consumed in the manufactures of ,great ,britain4 ,coal tar is of complicated nature1 containing a variety of substances1 many of which are more or less volatile4 ,when it is distilled by sending a current of steam through it1 the steam collects the volatile parts1 condenses them into naphtha2 the first product is condensed steam or water with naphtha swimming on its surface1 the next product is dead oil1 and the remainder is pitch4 ,by the aid of the crude naphtha thus produced1 ,indian rubber is dissolved and waterproof clothes are made4 ,when purified by sulphuric acid1 it forms a substance like tar which is thrown away1 and the remaining products when clarified are acid oils and neutral hydro-carbons4 ,the carbolic and cressylic acids are the most important of these acid oils4 ,the carbolic acid1 which has the property of arresting the putrefaction and decay of organic matter1 consists of #ab equivalents of carbon1 #f of hydrogen1 and #b of oxygen4 ,the cressylic acid only differs from the preceding by having two more equivalents of hydrogen and two of oxygen in its chemical composition4 ,creosote is a mixture of these two acids4 ,those vast beams of wood that are driven as piles into the sand or mud at the bottom of the sea1 as well as the timbers that form marine superstructures1 are saturated with it to a certain depth to preserve them from the attacks of marine insects1 especially ,limnoria terebrans1 an isopod crustacean1 which is so destructive in some of our harbours4 ,the wood is deprived of its air by heat and the creosote easily enters4 ,carbolic acid is liquid1 but becomes solid when purified and dried2 and as already mentioned the brilliant yellow dye1 carbazotic acid1 one of the coal tar colours1 is a compound radical1 in which the peroxide of nitrogen has replaced three equivalents of hydrogen4 ,the other coal tar colours are obtained from the neutral hydro-carbons1 that is to say1 compounds of hydrogen and carbon1 such as benzol1 toluol1 and other analogous substances4 ,benzol1 which consists of #ab equivalents of carbon and #f of hydrogen1 is very volatile1 boiling at #aag ,fahr41 and when acted upon by nitric acid1 it forms a compound radicle in which one equivalent of oxide of nitrogen takes the place of one of hydrogen4 ,it smells strongly of bitter almonds1 and may be used with safety instead of them4 ,when water and iron are mixed with nitro-benzol1 the iron combines with the oxygen and forms oxide of iron1 and the result is rusted iron and aniline1 which is the origin and foundation of the coal tar colours4 ,now aniline consists of #ab equivalents of carbon1 #g of hydrogen1 and #a of nitrogen4 ,it is a compound radical3 it is ammonia in which one equivalent of hydrogen has been replaced by the radical phenyle1 consisting of #ab equivalents of carbon and #e of hydrogen4 ,it may be remarked that in all these chemical operations the quantity of carbon has remained the same4 ,aniline is a colourless liquid1 and1 being an analogue of ammonia1 it readily combines with the different acids to form the beautiful coal tar dyes1 for which the world is indebted to the brilliant researches of ,dr4 ,hofmann1 professor of chemistry4 ,by combining a solution of the chloride of lime with the colourless liquid aniline1 he obtained the beautiful colour mauve1 but it could not be used as a dye till it was rendered permanent by his pupil1 ,mr4 ,perkins4 ,his next discovery was the rich crimson crystalline dye magenta1 which ,m4 ,verguin first introduced into trade at ,lyons as a dyeing agent4 ,it may be produced by mixing the anhydrous bichloride of tin with aniline and then driving off the excess of aniline by heat4 ,other metallic chlorides1 nitrates1 and many oxidizing agents1 have the power of converting aniline into magenta2 as for example when the two colourless liquids acetic acid and aniline are mixed and heated1 a chemical combination takes place in which three atoms of ammonia have coalesced into one1 a salt is formed which is the acetate of aniline or magenta4 ,here two liquids unite to form a solid and as in many other instances the resulting substance has the power of decomposing light which neither of its constituents can do4 ,magenta has a redder tint than mauve1 and on that account it is sometimes called aniline red4 ,professor ,hofmann has discovered quite recently that pure aniline has not the property of producing these colours1 but that they originate in an impurity of the aniline called toluidine4 ,rosaniline or roseine1 a white substance1 is the base of aniline4 ,it is a powerful alkali1 readily combining with acids to form highly coloured salts1 many of which have a tendency to crystallize1 like magenta4 ,this base is most easily extracted from the acetate of aniline4 ,the boiling solution of that salt decomposed by a large excess of ammonia1 yields a crystalline precipitate of a reddish colour1 and when the colourless liquid is separated by filtration from the precipitate1 it deposits on cooling perfectly white needles and tablets of pure rosaniline4 ,this substance unites to acids in three different proportions forming three kinds of salts4 ,the salts that contain one equivalent of acid are extremely stable compounds2 for the most part they have a green metallic reflection like some insects' wings2 by transmitted light they are red1 and their solutions in alcohol have the magnificent crimson colour of magenta4 ,a bright purple dye is furnished by mixing equal weights of magenta and aniline4 ,when this mixture is kept at the temperature of #cbi for some hours and then mixed with water and hydrochloric acid to remove any excess of magenta or aniline1 the result is an insoluble purple residuum or precipitate1 but which when well washed with water becomes soluble in alcohol and boiling water slightly acidulated with acetic acid4 ,when the insoluble purple residue is boiled several times with dilute hydrochloric acid1 a fine blue dye is formed2 azuline1 the most beautiful of the blue dyes1 which resists the action of the strongest acids1 and which is produced by oxidizing aniline under high pressure4 ,it was first prepared at ,lyons from phenic acid1 a product of the distillation of coal2 when pure it appears under the form of copper bronze-coloured crystals soluble in alcohol1 to which they communicate a magnificent blue colour tinged with red2 but most of the blue dyes are derived from carbolic acid and from creosote4 ,a blood-red colour is the direct result of mixing the muriatic and phenic acids4 ,aniline1 the great source of the coal tar colours1 yields also a fine yellow4 ,a vast deal of talent has been employed in the research of colouring dyes both at home and abroad1 in which the manufacturers themselves have shown great scientific knowledge4 ,attempts have been unsuccessfully made to obtain a green dye from chlorophyll1 the green colouring matter of plants4 ,the want was for a short time supplied by ,lo-hao1 a ,chinese dye1 but being unstable it was given up4 ,however the very same substance has been procured from the ,rhamnus cathartica 7,buckthorn71 one of the commonest ,european trees4 ,m4 ,charwin of ,lyons1 who made the discovery1 has utilized a waste substance1 and rendered it permanent as a dye4 ,it is the only known substance which with proper reagents is capable of producing all the seven colours of the spectrum4#ad ,the coal tar colours have nearly superseded those from lichens which incrust rocks1 walls and stems of aged trees with brilliant colours1 which do not however furnish dyes directly2 they yield a colourless crystalline substance which combines with alkalies to furnish very beautiful dyes2 it is exactly the opposite of rosaniline1 which is a base4 ,the ,variolaria dealbata yields litmus or orchil1 from which the beautiful ,french purple is made4 ,the ,rocella tinctoria and fusiformis give blue and purple1 and the pale yellow lichen1 ,parmelia parcolerina furnishes a bright yellow dye1 which a little ammonia changes to a rich red1 inclining to purple4 ,mauve was first made from orchil1 but was not permanent4 ,the fine dyes1 alizarine blue1 ,turkey red and garancine1 are still much in use4 ,they are derived from madder1 the dried roots of the ,rubia tinctorum2 the madder dyes most extensively employed are alizarine and flower of madder4 ,mauve and other dyes are derived from guano1 the offal of seabirds1 which is imported in large quantities for manure4 ,the coal tar colours are manufactured on a highly scientific plan and most extensive scale in ,great ,britain1 to supply the enormous quantity annually consumed in dyeing silk and printing cotton4 ,in general1 animal substances such as silk and wool can be permanently dyed at once1 because they have a strong affinity or attraction for coloured dyes4 ,if silk is destined to be a moir1 the silk before it is woven undergoes a chemical process in order to introduce fatty matter into it which gives a softness to the silk when woven and renders it fit to receive the moir by intense pressure4 ,cotton cloth has no affinity for dyes1 which are washed out at once if not fixed by art1 because cotton fibre consists of minute tubes generally open at the extremity1 which imbibe the dye by capillary attraction1 but cannot retain it unless fixed by a mordant1 such as the white of a raw egg1 which readily absorbs any dye that is mixed with it1 and being then laid on the cloth in any pattern it is absorbed by the tubular fibres1 and when coagulated by steam or any other application of heat it is immovably fixed4 ,both animal and vegetable substances afford a variety of mordants4 ,caseine or cheese1 the curd of milk1 which may also be obtained from pease and beans1 is the mordant most used by calico printers2 for if caseine be dissolved in twice the quantity of alkali necessary for its solution1 it coagulates like white of egg and may be used in the same manner4 ,skimmed milk cheese from ,scotland and ,holland when purified is extensively used in calico printing4 ,the quantity of mordants required is very great1 for of all the cotton that was imported into ,britain before the late ,american civil war1 one seventh only was manufactured into muslin and printed calico1 yet as already mentioned that was sufficient to envelope the earth's equator nineteen times1 and twenty-seven millions of pieces were exported annually4 ,atmospheric electricity and ozone affect the process of dyeing1 and east wind has a retarding and injurious effect4 ,the ,lyons manufacturers1 not less celebrated for their scientific skill and taste than for the brilliancy of the colours1 have an advantage in their fine climate and bright sun4 ,it is a singular circumstance that petroleum has existed in enormous quantities throughout the ,north ,american ,states and a great part of ,canada1 unnoticed and neglected till the year #ahei1 when its value was discovered1 and it almost immediately formed a new and extensive branch of commerce1 for during the succeeding year at least #a1jjj wells were dug1 some of which enriched the proprietors2 others were a failure4 ,petroleum from the fountains of ,is1 on the banks of the ,euphrates about #abj miles from ,babylon1 furnished the asphaltic mortar for building ,nineveh #b1jjj years before the ,christian era4 ,there are many sources of naphtha1 petroleum1 and asphalt in ,europe and ,asia1 which like those in ,trinidad and ,venezuela occur for the most part in rocks of the newer1 secondary and tertiary formations1 though sometimes in the lower4 ,but in the northern part of the ,united ,states and ,canada these substances occur in rocks of all ages from the lower silurian to the tertiary period inclusive2 they are usually found in the limestones and more rarely in the sandstones and shales4 ,petroleum collects in the fissures of the rocks1 chiefly in those that have a tendency downwards2 in wells dug for it near one another1 an abundant supply is furnished at all depths from #gj to #cjj feet4 ,in some parts of ,ohio and ,canada the ground is saturated with petroleum1 so that it is believed there is enough in ,north ,america to supply the world for ages4 ,in #ahfa no less than #db1jjj1jjj gallons of petroleum were sent to ,england4 ,the wells are not without danger1 for when they pass through the coal strata1 the petroleum is accompanied by a highly inflammable gas which on one occasion was accidentally set on fire2 it ignited the petroleum1 which was forced out as from the mouth of a volcano1 and covered the ground with liquid fire far around2 at the same time the burning gas formed an incandescent atmosphere which extended to a still greater distance4 ,the distillation of petroleum yields substances for the most part identical with those arising from the distillation of coal4 ,the crude petroleum is put into an iron retort connected with a coil of iron pipes surrounded by cold water1 called the condenser4 ,heat is applied to the retort1 and from the open extremity of the condenser1 a pale coloured liquid with a strong smell flows1 which is very volatile and explosive naphtha4 ,after the naphtha has passed over1 an oil of excellent illuminating quality is distilled over4 ,steam is then forced into the retort1 and a heavy oil is driven over1 and there remains a black1 oily1 tarry matter1 and a black cake used for fuel4 ,after the naphtha has been repeatedly distilled1 benzol is formed1 and when the heavy oil is cooled to #cj ,fahr41 crystals of paraffin appear1 which are separated from the oil by pressure1 and when they are purified by alternate pressure and agitation in a melted state1 they are moulded into candles4 ,this paraffin is identical with that from coal4 ,among the products of the distillation of petroleum are naphthalin whence aniline is obtained1 which yields mauve1 magenta1 and the other coal tar colours1 also solferino which yields dianthine and other dyes and has been proposed as a substitute for chloroform and ether4 ,many other substances have been separated from petroleum which like some from coal have not yet been chemically examined4 ,most of the substances obtained from petroleum and the distillation of coal are common also to distilled peat1 and now it is proposed to utilize sea weeds1 in which the northern coasts of ,scotland and ,ireland are so rich4 ,they were burnt for many years chiefly to furnish soda1 but as that substance is obtained at a cheaper rate from salt1 kelp or sea weed ashes has only been made lately to obtain iodine for medical purposes1 and more than one half is wasted in the process4 ,besides iodine and six other substances generally procured from kelp1 ,mr4 ,stanford has discovered that it contains naphtha1 paraffin oil and volatile oil rich in benzol1 which yields aniline and magenta dyes and shows that marine vegetation as well as terrestrial abounds in colouring matter4 ,every substance is now of use1 no substance is without its value1 but it would be a vain attempt to mention the innumerable discoveries made by experimental chemistry1 which is daily extending its empire over the three kingdoms of organic and inorganic nature4 ,composition of some of the preceding ,substances4 ,acetylene ,c#b;,h#b ,olefiant gas ,c#b;,h#d ,ammonia ,h#c,n ,benzol ,c#ab;,h#f ,phenyle ,c#ab;,h#e,n ,aniline ,c#ab;,h#g,n#c ,rosaniline ,c#dj;,h#i,n#c ,carbolic acid ,c#ab;,h#f,o#b ,cressylic acid ,c#ad;,,ho#b ,,section ,,iv4 ,,the ,,solar ,,spectrum1 ,,spectrum ,,analysis1 ,,spectra ,,of ,,gases ,,and ,,volatilized ,,matter1 ,,inversion ,,of ,,coloured ,,lines1 ,,constitution ,,of ,,sun ,,and ,,stars4 ,,to the unrivalled genius of ,sir ,isaac ,newton we owe the solar spectrum1 and the laws of coloured rings1 by aid of which1 ,dr4 ,thomas ,young proved and established the undulatory theory which forms the basis of the whole science of light4 ,the visible part of the solar spectrum forming a band of seven colours was supposed to be continuous till the year #ahjb1 when ,dr4 ,wollaston looking with a prism whose axis was parallel to a narrow slit in a window shutter1 at a sunbeam passing through it1 discovered seven dark lines crossing the coloured band1 at right angles to its length4 ,twelve years afterwards1 ,fraunhofer of ,munich1 a celebrated optician1 magnified the spectrum of a vertical line of light passing through an upright prism by receiving it upon the object glass of a telescope1 and discovered #fjj dark lines4 ,having ascertained that the position of the lines in the spectrum1 and their distances from one another1 are invariable under every circumstance1 he determined their places accurately and drew the diagram known as ,fraunhofer's lines1 which is universally referred to as a standard of comparison4 ,for that purpose1 the principal lines are designated by letters2 thus the dark line ,a is in the red near the least refrangible end of the spectrum1 ,b and ,c are in the orange1 the very remarkable double line ,d is in the yellow1 b and ,e are in the green1 ,f is at the limit between the green and the blue1 ,g is in the blue1 and the double line ,h is in the violet4 ,the instrument used by ,,mm4 ,bunsen and ,kirchhoff1 though more complicated1 is constructed on the same principle as the preceding4 ,a sunbeam transmitted by a very narrow vertical slit passes through four prisms1 which disperse it so much1 that if drawn on the scale seen with the magnifying telescope which receives it1 the spectrum would extend over twenty feet4 ,by means of a micrometer screw1 the telescope can be turned round a vertical axis1 and as the dark lines come successively under the cross wires in its eye-glass they are seen to pass over a graduated scale1 so that the distances between two thousand of them have been measured in millimetres with unerring accuracy1 but that is only a small part of the whole4 ,when viewed through the telescope1 the retina of the eye is the screen on which this wonderful spectrum falls1 crossed by innumerable dark rayless lines of various breadths and intensities4 ,black bands given by the inferior refraction of one prism are here resolved into numerous dark lines as fine as a spider's thread4 ,mr4 ,glaisher during his tenth scientific balloon ascent devoted his attention for a time almost entirely to the dark lines on the solar spectrum4 ,at a height of about four miles and a half1 they were almost innumerable2 all he had seen on the earth were there1 and many more4 ,the nebulous lines ,h were both seen1 the spectrum was a good deal lengthened at the violet end1 and at the red end the line ,a was visible4 ,the light from the sky near the sun gave a shorter spectrum2 the lines were only visible from ,b to ,g4 ,besides these cosmical or permanent lines1 ,sir ,david ,brewster observed that certain dark bands and lines in the red and green parts of the spectrum are only visible when the sun is near the horizon1 whence he concluded that they are occasioned by the absorption of the solar light while traversing a thicker stratum of air than when the sun is in the zenith4 ,various groups of these absorption bands are to be seen at times on the solar spectrum1 especially a remarkable one near ,fraunhofer's line ,d1 and ,dr4 ,miller observed that temporary dark lines appeared during a heavy shower1 which vanished when the rain ceased4 ,when the sun was high1 ,m4 ,kirchhoff mentions that he had noticed traces of lines and nebulous bands in different parts of the spectrum1 which he thinks might be resolved by a greater number of prisms than those in his apparatus4 ,sir ,david ,brewster was led to his discovery of atmospheric bands by observing that the brownish red vapour of nitrous oxide has the property of absorbing solar light1 resolving the spectrum into a series of bright and dark bands1 alternating4 ,professors ,daniel and ,miller found that bromine1 iodine1 and chlorous acid do the same1 and ,sir ,john ,herschel observed a multitude of similar bands in the flame of cyanogen2 but ,dr4 ,w4 ,a4 ,miller1 who has particularly studied the phenomena of absorption bands1 has proved that the colour of a vapour does not necessarily determine the position or even the existence of dark bands4 ,he has shown that some simple substances which do not occasion dark bands produce them abundantly by the absorptive power they acquire when in composition1 while lines that are produced by a simple vapour1 vanish when it is in combination4 ,dr4 ,w4 ,a4 ,miller has proved also that none of the preceding vapours exist in the atmosphere4 ,he computed that if free bromine constituted only one in a thousand million parts of atmospheric air1 it would betray its presence by absorptive bands2 nevertheless he suspects that there may be some substance in the air that occasions certain unaccountable changes4 ,possibly ozone1 so intimately connected with atmospheric electricity1 may produce some unknown effect4 ,the spectra from glowing solids and liquids1 such as ,drummond's light1 which is incandescent lime1 the still more brilliant flame of the electric arc between charcoal points1 glowing solid and fused metals1 and coal-gas flame1 are continuous2 the spectra exhibit the seven colours1 but they are not crossed by dark rayless lines1 because such incandescent substances give off light of all refrangibility4 ,but solids and liquids reduced to glowing vapours1 and incandescent gases1 only give out rays of certain refrangibilities1 which cross their spectra at right angles1 as bright lines of various colours and intensities4 ,each glowing vapour and gas has bright lines on its spectrum peculiar to itself4 ,in order to compare these bright lines with ,fraunhofer's dark lines1 solar light is transmitted through one half of the vertical slit in ,kirchhoff's apparatus1 and the light of the luminous vapour or gas through the other half4 ,then by prismatic refraction two spectra are seen in looking through the telescope1 the gaseous one immediately below the solar one1 and only divided from it by an almost imperceptible dark line4 ,so that the bright lines appear to be continuations of the dark lines if they occupy the same position in the two spectra2 if not1 the deviation is at once visible4 ,the coincidence or deviation of the bright lines on the spectra of two volatilized substances may be determined by the same method4 ,the coloured light that has so beautiful an effect in fire-works is owing to the combustion of the salts of different metals3 as soda1 or common salt1 which gives a perfectly pure homogeneous yellow2 potash gives a violet light1 strontia red1 baryta green4 ,the colour is given out by the glowing atoms of the vaporized metals sodium1 potassium1 strontium1 and barium in a state of violent ignition2 for as the salt and its metal give the same colour and the same spectrum when ignited1 it is evident that the colour is independent of the oxygen of the alkali4 ,sir ,david ,brewster appears to have been the first who analysed coloured light with a prism2 and in #ahbb ,sir ,john ,herschel1 besides having made a series of observations on coloured flames1 had determined the spectra of the muriates of strontia and lime1 the chlorides and nitrate of copper and boracic acid2 and observes that #8the colours thus communicated by different bases to flame afford1 in many cases1 a ready and neat way of detecting extremely minute quantities of them4'#ae ,the same opinion was afterwards formed by ,mr4 ,fox ,talbot1 who after many experiments on metallic salts1 says in his paper1#af that a glance at the prismatic spectrum of a flame may show it to contain substances which it would otherwise require a laborious chemical analysis to effect4 ,in that paper this gentleman noticed that the glowing salts of lithium and strontium give a crimson or red colour to flame so exactly of the same tint that if these metals were in combination it would be impossible to decide to which metal the colour is due4 ,but when he passed their respective lights through a prism1 he found that the bright lines on their spectra are entirely different4 #8,the strontia flame1' he observes1 #8exhibits a great number of red rays well separated from each other by dark intervals1 not to mention an orange1 and a very definite bright blue ray4 ,the lithia exhibits one single red ray1' ,whence ,mr4 ,fox ,talbot observes1 #8,i hesitate not to say that optical analysis can distinguish the minutest portions of these two substances from each other with as much certainty1 if not more1 than any other known method4' ,thus ,sir ,john ,herschel and ,mr4 ,fox ,talbot laid the foundation of a spectrum analysis of unrivalled delicacy and beauty1 since carried to perfection by ,messrs4 ,bunsen1 ,kirchhoff and other experimenters1 presently to be mentioned4 ,m4 ,bunsen detected the characteristic crimson lithium line in the spectra of numerous substances2 in granite1 in the earliest geological strata1 in meteoric stones1 in the ashes of most land plants1 in blood and other animal matter2 so that instead of being one of the rarest metals1 it exists in all the three kingdoms of nature4 ,in the year #aheg ,mr4 ,swan gave an instance of the extreme minuteness of spectrum analysis1 by detecting the #a_/b1cjj1jjjth part of a grain of salt by its yellow light2 but by the same reaction ,m4 ,bunsen not only recognised the #ahj millionth part of a grain of sodium1 but found that there is hardly any substance that does not contain it4 ,it exists in the dust on our clothes and furniture1 particles of it float in the air we breathe1 so that while examining the spectra of other incandescent substances1 flashes of yellow light appear as these atoms are volatilized and instantly burnt up1 which shows that common salt is perhaps more universally diffused than any other kind of matter4 ,by spectrum analysis1 ,m4 ,bunsen has discovered the two new metals1 rubidium and csium4 ,while examining with a prism the spectrum of the hundredth part of a grain of an alkaline substance separated from the residuum of the ,durckheim mineral water1 he saw coloured lines1 which he had never seen before on the spectrum of any other alkali1 and at once concluded that they belonged to a new metal2 and having obtained about #bjj grains of the substance by the evaporation of forty tons of the water1 he found that they contained the chlorides of the two new metals in question4 ,moreover he perceived that these metallic chlorides resemble the chloride of potassium so nearly in spectrum and chemical character1 that a refined prismatic analysis could alone determine the difference4 ,he thus ascertained that the spectra of all the three have two red lines in the red part of their spectrum1 and two violet lines in the indigo1 while the middle part is occupied by a continuous diffused light4 ,the only difference is that the two red lines in the rubidium spectrum are less refrangible than the red lines in the potassium spectrum1 and that the csium spectrum is distinguished by two bright blue lines in the diffuse middle part4 ,rubidium received its name from rubidus1 on account of the dark red of its lines1 and csium from its sky-coloured blue lines4 ,m4 ,bunsen thinks that there can hardly be a doubt of rubidium having been mistaken for potassium1 but he has shown that they may be distinguished by the difference in the solubility of the double salts which the chlorides of these two metals form with the chloride of platinum4 ,an aqueous solution of the bichloride of platinum and potassium gives an insoluble yellow precipitate1 consisting of the bichlorides of platinum and potassium4 ,an aqueous solution of the bichlorides of platinum and rubidium gives an insoluble yellow precipitate of the bichlorides of platinum and rubidium4 ,these two precipitates are undistinguishable to the eye4 ,now if a solution of platinum be added to the first1 no further precipitate can take place1 but if a solution of rubidium be added to it1 a yellow precipitate is formed consisting of the bichloride of rubidium and potassium1 because the chloride of rubidium resolves the precipitate1 combines with the chloride of potassium1 and sets the chloride of platinum free4 ,thus the precipitate of the bichloride of rubidium and potassium is the least soluble of the two4 ,the yellow colour is evidently due to the potassium4 ,csium may be distinguished from potassium by the same process4 ,the carbonates1 hydrates1 and other salts of the two metals were determined2 their carbonates were shown to be readily separated1 because the carbonate of csium is soluble in alcohol1 which the carbonate of rubidium is not1 and finally the metal rubidium was separated4 ,it has an extreme avidity for oxygen1 and burns in water like potassium1 and possesses many other analogous qualities4 ,it melts at the temperature of #che ,cent41 and has a specific gravity of #aeaf4 ,rubidium is abundant in the mineral lepidolite in many parts of ,europe and ,north ,america1 and ,m4 ,grandeau has detected it in the ashes of beetroot1 tobacco1 coffee1 tea1 and grapes by spectrum analysis4 ,it exists in various mineral waters1 and in fact is very general4 ,traces of various metals are met with in the same vegetable2 thus the spectrum of tobacco gives lines characteristic of lithium1 potassium1 rubidium1 and lime4 ,mr4 ,w4 ,crookes discovered the new metal thallium by means of its spectrum1 which differs from every other in having one bright green line upon a dark ground4 ,he obtained its various salts1 and the metal itself1 which he describes as being heavy1 dense1 and very like lead1 but of greater specific gravity4 ,its fresh surface has a bright metallic lustre1 not so blue as that of lead1 but it tarnishes more easily4 ,it is so soft that it can be indented by the nail1 yet it can be drawn into wire1 and in chemical properties it resembles mercury1 lead1 and bismuth4 ,altogether it is more like a metal than a metalloid1 perhaps something between the two4 ,thallium is completely volatilized at a temperature below red heat1 whether single or in composition4 ,if the quantity be small1 the green line appears in a sudden flash1 lasting but the fraction of a second4 ,if a larger quantity of the metal be gradually put into the flame1 it lasts a little longer1 appearing as a single green line of extraordinary purity and intensity1 sharply defined on a black ground4 ,with respect to volatility1 thallium is analogous to the non-metallic element selenium1 which is so volatile that its beautiful blue light only lasts a few seconds4 ,the green light of thallium comes out more rapidly1 and with less of the substance1 than the blue light of selenium1 a quantitative distinction which accords with ,dr4 ,miller's observation that the rapidity with which a result is obtained1 and the minuteness of the quantity required for the examination1 gives this method a superiority over every other for the qualitative analysis of the alkalies and alkaline earths4 ,thallium has been detected in mineral waters1 wine1 treacle1 tobacco1 and chicory4 ,drs4 ,reich and ,richter discovered a fourth new metal in the zinc-blende at ,freiberg in ,saxony1 which has been called indium1 from two beautiful indigo-blue lines in its spectrum1 which have a greater refrangibility than the blue lines in strontium4 ,the chemical relations of indium resemble those of zinc1 with which it is associated in nature4 ,the metal can be reduced before the blowpipe into a bead1 which marks paper and has the colour of tin4 ,the practical importance of spectrum science has been beautifully illustrated by ,professor ,roscoe by its application to overcome a difficulty in ,bessemer's process for the manufacture of steel4 ,according to that process1 steel is made by sending a blast of air through a quantity of melted iron2 the difficulty was when to stop the blast1 for if stopped too soon1 the metal retains so much carbon that it crumbles under the hammer2 if continued a few minutes too long1 the molten metal is so viscid that it cannot be poured into the moulds4 ,experience had hitherto enabled the manufacturer to judge of the right time from the appearance of the flame which issued from the mouth of the converting vessel1 but now ,professor ,roscoe has determined the exact moment for cutting off the blast by a spectral examination of the flame1 the light of which is most intense4 ,the flame spectrum in its various phases revealed complicated masses of dark absorption bands and bright lines1 showing that a variety of substances were present in the flame in a state of incandescent gas2 and by a simultaneous comparison of these with well-known spectra of certain elementary bodies1 ,mr4 ,roscoe ascertained the presence of sodium1 potassium1 lithium1 iron1 carbon1 phosphorus1 hydrogen1 and nitrogen in the flame4 ,both ,dr4 ,wollaston and ,fraunhofer noticed that the spectrum of the electric spark was crossed by bright-coloured lines2 and in the year #ahce1 ,professor ,wheatstone determined the spectra of the electric spark taken from fused zinc1 cadmium1 tin1 bismuth1 lead1 and from mercury1 and found that each is crossed by bright lines differing in number1 position1 and colour1 but which are the same whether the electric spark be from a static1 voltaic1 or magneto-electric machine4 ,having given a plate showing the colours of these bright lines on the respective spectra1 he proved that they are not owing to the electricity1 but to the incandescent atoms of the metals1 for by using different metals as terminals to the conducting wires1 he determined the spectra of these metals in vacuo1 which proved that they were due alone to the volatilization of the metallic terminals1 and concluded that any one metal may be distinguished from another by the appearance of the spark4 ,wheatstone discontinued his spectrum researches1 for he had invented the electric telegraph1 and was busy in extending the first telegraphic wire that ever carried the thought of man to man between ,london and ,manchester4 ,soon after he laid the first aquatic line across the ,thames1 and he has lived to see his telegraphic lines spread over the surface of the earth and the bottom of the ocean4 ,mr4 ,wheatstone had perceived that the bright lines on the spectra of the metals are different and more complicated when taken in air than in vacuo1 and ,professor ,angstrm made the important remark that the electric spark gives two superposed spectra1 one due to any metal that may be under examination1 the other to the incandescence of the air through which the spark passes4 ,hence the importance of the spectrum analysis of gaseous substances1 especially of those which constitute our atmosphere1 a subject that has been ably and successfully investigated by ,professor ,plcker4 ,for that purpose he made use of the ,geissler or vacuum tubes1 similar to those he used in his experiments on the stratification of electric light4 ,when electricity was sent through a tube containing oxygen gas1 the gas combined so rapidly with the platinum of the negative terminal of the battery that there was little time to examine the spectrum4 ,the electral light in the tube was too red at first1 but as the attenuated gas gradually disappeared it changed through flesh-colour to green1 then through blue to reddish-violet1 and at length there was too little gas to convey the electricity4 ,however1 the oxygen spectrum has a remarkably bright red band at its red extremity1 two bright orange lines divided by a black one in the orange1 and some bright bands in the green4 ,the electric light of attenuated hydrogen is red1 and almost the whole light in its spectrum is concentrated into six bright bands of nearly equal breadths4 ,there is a dazzling red band near the red end of the spectrum1 which1 however1 does not coincide with the oxygen band2 then comes a very beautiful yellow band1 in which the whole of the yellow rays seem to be concentrated1 followed by a grey interval which separates the yellow from three bright lines in the green1 the first of which is yellowish green1 the last a beautiful greenish blue2 a black and a dark space separates the latter from the violet in which there is a bright line4 ,the electric light in a tube containing highly rarefied aqueous vapour is red1 the vapour is resolved into its simple elements by the electricity1 the oxygen combines with the platinum of the negative or heat pole1 and the spectrum is that of pure hydrogen with the three most prominent bands only4 ,the nitrogen spectrum is brilliant with all the seven colours2 there are no broad dark spaces like those which divide the bright bands in the hydrogen spectrum1 but it is crossed by numerous very fine black and grey lines4 ,fifteen of the latter stripe the red and orange2 the green is separated from the yellow by a black narrow band2 it is terminated by two bright blue lines1 and very fine dark lines cross it and the rest of the spectrum4 ,the tube light is yellowish red4 ,the spectrum of highly rarefied atmospheric air is chiefly that of nitrogen1 for the oxygen combines with the platinum of the negative terminal1 and is in too small a quantity to transmit the electricity through the tube4 ,the rarefied vapours of chlorine1 bromine1 and iodine are so rapidly combined with the platinum of the negative terminal1 that it is difficult to determine their spectra2 but they have peculiarities in common1 which distinguish them from all other spectra4 ,the bright lines that cross them are first at rest1 but soon become flickering4 ,in the iodine spectrum1 five of those lines of flickering light of great beauty are in the green1 two of them close together4 ,the bromine spectrum shows a greater number1 which extend across the colours of its middle part1 accompanied by dark lines2 and in the chlorine spectrum there are many lines1 both of flickering light and darkness4 ,new lines are brought out in the iodine spectrum by increase of temperature4 ,at a low heat it is crossed by a number of dark lines1 but with a higher temperature the vapour has a greenish hue1 which is resolved by the prism into green lines at some distance from one another1 and fainter blue light1 crossed by groups of luminous bands4 ,rarefied compound gases are resolved by the electricity into their component parts1 and the result is superposed spectra1 one belonging to each element4 ,m4 ,seguin considers the aspect of the electric spark to be a sure indication of chemical action1 for while the decomposition is in progress1 the electric spark is encompassed by a halo1 and the bright lines of the double spectrum are less distinct2 but when the reaction is finished1 the spark becomes slender1 and the spectrum bands distinct4 ,in the decomposition of highly carburetted and attenuated hydrogen gas1 the spark resembles a flame1 and the spectrum is like that of white light4 ,when the gas is decomposed1 the hydrogen is disengaged1 and the carbon deposited on the extremities of the conducting wires2 the spark becomes slender1 and then the lines of the hydrogen1 the lines belonging to the hydro-carbon and to carbon itself may be seen on the spectrum4#ag ,the bright and coloured lines on the spectra of the gases1 and the vapours of a great number of the metals and metallic salts1 were known before ,,mm4 ,bunsen and ,kirchhoff began their systematic researches1 during which they added many more1 some so difficult and analogous1 that it required all their skill and experience to make them out4 ,of all the spectra that have been determined1 those of sodium and iron are the most important and interesting4 ,in that of sodium1 the only light is of the purest yellow condensed into a double line of intense brilliancy on a dark ground4 ,the iron spectrum on the contrary is crossed by bright lines of all intensities and colours in such multitudes1 that their number has not been ascertained4 ,the calcium spectrum has one very bright green band in the orange1 a red line in the yellow1 and a well-defined yellow line in the indigo4 ,as already mentioned1 the red and orange parts of the strontium are crossed by many red lines separated by dark intervals2 there is a bright blue line between the orange and yellow1 and an orange line in the blue4 ,one intense crimson band in the orange characterises the lithium spectrum4 ,seven broad green bands stripe the yellow and a part of the green1 in the barium spectrum1 and that of magnesium has many green bands and lines4 ,all of these were determined by the heat of white coal gas flame1 which amounts to #bcej ,cent41 and at the time ,,mm4 ,bunsen and ,kirchhoff were not aware that by an increase of temperature new bright lines were added to some of the spectra4 ,that discovery was made by ,professor ,tyndall1 while examining the spectrum of chloride of lithium1 which with the low temperature has only one crimson band in the orange1 but with the hotter flame of hydrogen gas1 amounting to #cbei ,cent41 an orange line appeared in the yellow1 and when ,mr4 ,tyndall employed the electric lamp1#ah the spectrum acquired a broad brilliant blue band between the orange and yellow1 while the crimson band remained unchanged4 ,professors ,roscoe and ,clifton confirmed ,tyndall's discovery1 and upon comparing the spectra of strontium and lithium1 they found where only one prism was employed that the blue line of lithium appeared to coincide with the blue line1 delta1 of strontium2 but with an apparatus having several prisms like that of ,kirchhoff1 they saw that the two blue lines differed by one division of the measuring scale1 the lithium line being the most refrangible4 ,a great change was produced on the strontium spectrum by increased electric temperature3 three of the red bands vanished1 and new bright lines appeared1 that were not coincident with those they replaced2 the blue line was not affected1 but four new violet lines were added4 ,with the intense heat of the electric spark1 the broad green band of the calcium spectrum is replaced by five green lines of less refrangibility1 the well-defined yellow line vanishes1 and instead of the red band three red or orange lines appear1 of greater refrangibility than those that have vanished4 ,six of the bright green bands in the spectrum of barium entirely vanish1 and bright new non-coincident lines appear4 ,thus1 not only new lines appear at very high temperature1 but the broad bands1 characteristic of the metal or metallic compound at a low temperature of the flame or a weak spark1 totally disappear at the higher temperature4 ,the new bright lines1 which supply the part of the broad bands1 are generally not coincident with any part of the band1 sometimes being less and sometimes being more refrangible4 ,the gentlemen who made these experiments add1 that possibly the cause of the disappearance of the broad bands and the production of the bright lines may be1 that at the lower temperature of the flame or weak spark1 the spectrum observed is produced by the glowing vapour of some compound1 probably the oxide of the difficultly reducible metal1 whereas1 at the enormously high temperature of the intense electric spark1 these compounds are split up1 and the true spectrum is obtained1 namely1 the narrow bright lines4 ,no such changes take place in the easily reducible metals1 potassium1 sodium1 or lithium1 which remain unaltered by change of temperature4 ,in these experiments1 a bead of the metallic salt on a platinum wire was placed between the platinum terminals1 from which the spark of a powerful inductive coil could be passed1 but in order to have a more intensely hot spark the coating of a ,leyden jar was placed in communication with the terminals of the secondary current respectively4 ,by this addition of static electricity1 the intensity of the current was increased four-fold1 and must have been beyond estimation4 ,by high temperature the csium spectrum has been so changed1 that for number1 colour and distinctness of its lines1 it is the most beautiful of those of the alkaline and earthy metals1 for besides its characteristic blue lines1 it has six red and an orange-red line in the red part of its spectrum1 a fine yellow line1 and nine green lines1 the last coinciding with ,fraunhofer's ,e4 ,the thallium spectrum also acquires more lines when evaporated by electricity1 for besides the remarkable green line in the green1 it acquires a faint one in the orange1 two of nearly equal intensity in the green1 a third fainter1 and a fifth in the blue4 ,,mm4 ,plcker and ,hittorf1 in recent experiments1 proved that many non-metallic bodies1 such as nitrogen and sulphur1 give two distinctly different spectra on change of temperature1 and that the transition from one spectrum to the other is sudden4 ,the change is particularly striking in sulphur1 for at the moment the first spectrum attains its maximum brightness1 it disappears1 and gives place to the second or high temperature spectrum1 which is one of the richest in brilliant rays known4 ,when the temperature is lowered the first spectrum reappears4 ,these changes ,m4 ,plcker ascribes to the existence of the elements in two allotropic conditions4 ,m4 ,plcker has also found that each metalloid possesses a peculiar and characteristic spectrum3 as hydrogen1 which has three bright lines1 all of which are coincident with dark solar lines1 and nitrogen1 which exhibits a complicated series of bands4 ,the experiments of the ,rev4 ,dr4 ,robinson on a variety of gases and vapours1 inclosed in glass tubes1 show that a greater change is produced by pressure than by heat4 ,at the ordinary atmospheric pressure1 the spectra show a number of bright lines on a coloured ground1 the light of which is1 in general1 stronger towards the red than the violet end1 and strongest in the green4 ,in some the ground is so bright as to efface all but the most luminous lines4 ,this is especially the case with hydrogen4 ,on gradually exhausting the tube in which the vapour is contained1 the spectra rather suddenly fade away1 leaving only a suspicion of one or two lines1 but upon exhausting the tube still more1 these transition spectra become bright again1 fresh lines appear1 and they are changed into new spectra which are never so bright as those at ordinary pressure4 ,fewer lines are visible in the rarefied spectra1 and of these four-tenths are not found in the spectra of atmospheric pressure4 ,the difference between the common pressure spectra1 the transition1 and the rarefied spectra shows1 that the character and even the existence of certain lines depend upon the mere density of the media1 the chemical circumstances remaining unchanged4 ,dr4 ,robinson also observed that spectra are not superposed without a change2 the spectrum of atmospheric air does not always exhibit all the lines of oxygen and nitrogen1 and occasionally there are some lines not visible in either of them4 ,it appears also that for certain lines the actions of bodies may be antagonistic4 ,metals do not always give the same spectrum1 whatever may be the combinations in which they are found4 ,among various instances ,m4 ,mitscherlich mentions that the spectra of copper and the chloride and iodide of copper present essential differences1 and ,mr4 ,roscoe has found that a similar difference prevails in the spectra of carbon compounds when in a state of incandescent gas1 which have hitherto been supposed to yield the same spectrum4 #8,the spectrum obtained from the flame of olefiant gas is different from that obtained by the electric discharge through a vacuum of the same gas2 while the spark passing through a cyanogen vacuum produces a spectrum identical with that of the olefiant gas flame1 and through the carbonic oxide vacuum a spectrum coincident with that of the spark through olefiant gas vacuum4' ,the chlorides1 bromides1 and iodides are the most easily vaporized of all the metallic salts1 and give the most brilliant flames and the most intense spectra1 especially the chlorides4 ,a small piece of the chloride of barium volatilized by a colourless gas flame tinges the flame green1 and the red and green lines on the spectrum stand out with extreme brilliancy4 ,the scattered yellow light on the spectrum of the chloride of sodium is comparatively dark by contrast with the bright lines1 and upon shading off the more luminous part of it1 traces of lines are visible in the more refrangible portion4 ,chloride of lithium gives the red and orange lines on its spectrum2 the brilliant blue band discovered by ,mr4 ,tyndall1 and another more refrangible blue line is seen when the ignition is at its greatest intensity4 ,chloride of calcium gives a blue band very brightly1 and several other lines4 ,the light of the chloride of copper is very vivid1 and its spectrum is remarkable for changing its appearance with the decomposition of the chloride4 ,the chlorides of lead and cadmium1 also1 give very bright and definite spectra1 and chloride of bismuth shows numerous brilliant red and blue rays which quickly disappear4 ,thus the chlorides give spectra with lines1 such as the blue lithium and strontium lines1 hitherto only brought out by an intense electric spark4#ai ,m4 ,bunsen produced a beautiful effect by vaporizing a mixture of equal parts of the chlorides of sodium1 potassium1 lithium1 calcium1 strontium1 and barium1 and passing the light through the slit of his apparatus4 ,for on looking through the telescope the spectrum of each substance with its characteristic coloured lines in all their brilliancy came successively into view1 and gradually faded away as each substance was volatilized and driven off4 ,the sequence showed the time required to vaporize each metal1 and by spectrum analysis each metal could be recognized1 although the mixture only contained the #a_/ajjj part of a grain of each chloride4 ,the position1 colour1 and nature of the bright lines on the spectra of more than thirty metals have been determined1 besides those of the elementary gases and that of the electric spark4 ,to these ,m4 ,louis ,grandeau has added the spectrum of lightning4 ,by a particular arrangement the light passed at once through the slit in the instrument1 and a glass tube containing nitrogen and the vapour of water4 ,the general appearance of the lightning spectrum at first recalled that of the electric spark1 but on a closer examination1 ,m4 ,grandeau noticed in the spectrum of almost every flash the coincidence of a certain number of the rays of the lightning spectrum with those of the spectra of nitrogen and hydrogen4 ,m4 ,grandeau remarks that this result is not surprising1 since all admit the production of ammonia and nitric acid under the influence of electrical discharges4 ,besides the rays of nitrogen and hydrogen1 the lightning spectrum contains the ubiquitous yellow ray of sodium4 ,fraunhofer had noticed a coincidence between the double yellow sodium line and the double dark line ,d of the solar spectrum1 though he was not aware to what it was due4 ,this coincidence1 observed by ,m4 ,kirchhoff many years afterwards1 was fully appreciated by him1 and became the foundation of one of the most brilliant discoveries of modern times4 ,during a systematic comparison between the spectra of volatilized substances and the solar spectrum1 he discovered a perfect coincidence between ,fraunhofer's dark lines and all the bright and coloured lines on the spectra of the volatilized substances1 sodium1 calcium1 magnesium1 chromium1 iron1 and nickel4 ,to these ,m4 ,angstrm has added aluminium and manganese1 and ,m4 ,plcker has very recently found that all the three bright lines in the hydrogen spectrum are coincident with dark solar lines1 and that none of the potassium lines correspond with any solar lines4 ,drawings have been made of ,fraunhofer's spectrum placed above the spectra of the principal metals and metallic salts1 in which the coincidence of the bright and dark lines is shown from the line ,a in the extreme red to the line ,g in the indigo1 and as the length of an undulation of the extreme violet light of the solar spectrum is the #ag_/a1jjj1jjj of an inch1 and the length of an undulation of the extreme red is the #bf_/a1jjj1jjj of an inch1 the length of the undulations of the intermediate rays can be computed by the undulatory theory of light4 ,the length of the waves corresponding to ,fraunhofer's seven principal lines and many of the intermediate ones have been computed1 so that when a bright or coloured line is coincident with any of these1 the length of its waves is at once known4 ,there are other tables of ,fraunhofer's lines1 and the coincident bright ones in which each dark line is marked by its own number1 as the two principal lines in the double line ,d1 which are expressed by the numbers #ajjbh and #ajjfh1 and so with the others2 thus the coincidence of the spectra of volatilized substances with the solar line forms a regular system4 ,professor ,j4 ,p4 ,cooke1 junior1 has recently constructed a spectroscope which shows that the lines of the solar spectrum are as innumerable as the stars of heaven1 that at least ten times as many are distinctly seen as are given by ,kirchhoff in his chart1 besides an infinitude of nebulous bands just on the point of being resolved4 ,yet even with this greatly increased power1 the coincidences between the bright lines of the metallic spectra and the dark lines of the solar spectrum remain perfect4 ,m4 ,kirchhoff had seen a fine yellow line between the double lines ,d of the sodium spectrum4 ,m4 ,merz of ,munich found four additional lines1 but ,professor ,cooke has discovered that there are in all seven intermediate lines and a nebulous band4 ,although the two members of the sodium line ,d could be spread so far apart that the #a_/bjjj part of the intermediate space could be readily distinguished1 yet the coincidence with the two dark ,fraunhofer lines was absolute4 ,the spectroscope #8shows that many of the bands of the metallic spectra are broad coloured spaces crossed themselves by bright lines4 ,this is the case with the orange band of the strontium spectrum1 and with the whole of the calcium and barium spectra to a remarkable extent4'#bj ,as early as the year #ahdi1 ,m4 ,foucault discovered that the sun's light when shining through the electric light gives black bands on that part of the spectrum where the electric light alone would have produced bright bands1 so that the black and bright bands could be produced alternately by admitting or excluding the solar light2 whence he concluded that the electric arc emits the same lines which it absorbs when they come from another luminous source4 ,m4 ,angstrm also observed that the bright lines on the spectra of volatilized metals could be reversed by a stronger light shining through their flames4 ,neither of these gentlemen was aware of the importance of a discovery which enabled ,m4 ,kirchhoff to apply his delicate and refined analysis of terrestrial matter to the sun and stars4 ,he had already determined the coincidence of the double yellow sodium line with ,fraunhofer's dark line ,d1 but while looking with a prism at a bright solar beam passing through a yellow sodium flame1 he was surprised to see a strong and well-defined double dark line instead of the double yellow sodium line which he expected4 ,he obtained the very same result1 more strongly1 with ,drummond's lime light1 which is brighter than the flame of any volatilized metal1 and as he found that he could produce the dark and yellow lines alternately1 by admitting and shutting out the brighter light1 he concluded that the sodium flame is subject to the law of exchange1 in consequence of which it absorbs rays of the same refrangibility with those that it emits4 ,in fact1 the soda flame is pervious to all the rays in solar light and ,drummond's flame1 except those of the same refrangibility with its own2 these it absorbs and it may be supposed changes them into heat4 ,hence ,m4 ,kirchhoff came finally to the conclusion1 that the double dark line in the solar spectrum is the reverse or negative of the double yellow line seen on the spectrum of the sodium flame4 ,quite recently1 ,m4 ,fizeau has discovered that the spectrum of sodium burning in air is reversed during the combustion4 ,at first it is black1 with the usual double yellow line2 at last1 when the light is at its maximum1 the double yellow line becomes black on a continuous spectrum with all the seven colours4 ,after ,m4 ,kirchhoff had ascertained that the bright lines in the spectra of calcium1 chromium1 magnesium1 iron and nickel coincide with dark lines in the solar spectrum1 he reversed them by sending ,drummond's light through their respective flames1 thus proving that the coloured flames of these six metals are subject1 like the sodium light1 to the law of exchanges4 ,m4 ,kirchhoff infers by analogy that the vapours of all these six metals exist in the luminous atmosphere of the sun1 and that they absorb and change into heat such rays of the continuous light of the incandescent solar globe as have the same refrangibility with their own1 so that the corresponding dark rayless lines on the solar spectrum are the reverses of the bright lines in the spectra which these vapours would give were it not for the brighter light of the sun shining through his luminous atmosphere4 ,the dazzling white light of the incandescent body of the sun containing rays of all refrangibilities would give a continuous spectrum shaded with all the seven colours1 but for his luminous absorbent atmosphere1 which comes like a veil between him and the earth1 and crosses his spectrum with thousands of dark lines1 which are the reverses or negatives of the bright lines in the spectra of the innumerable vapours it contains1 all of which must doubtless be the gases of substances existing in the solar mass itself and vaporized by his intense heat4 ,every metal1 and almost every elementary substance in a state of gaseous combustion1 gives its own peculiar luminous lines to its spectrum1 but no volatilized matter can be proved to exist in the sun's atmosphere except such as have bright lines in their spectra coincident with some of its dark lines4 ,the bright lines in the spectrum of iron1 coincident with the dark lines of the solar spectrum1 are so numerous that many yet remain unknown4 ,m4 ,kirchhoff counted seventy in the small space between ,fraunhofer's lines ,d and ,f1 in which the coincidence extends even to shade1 the deepest dark lines corresponding to the most brilliant bright ones1 and he computed that the chances are as #a to the ninth power of #aj1 that the coincidence of these seventy lines is not fortuitous1 but owing to a definite cause1 whence he concluded that the presence of iron vapour in the solar atmosphere is proved with as much certainty as can be attained in any question of natural science4 ,in a later publication1 ,m4 ,angstrm observes that1 although the coincident iron lines between ,d and ,f are not so numerous as ,m4 ,kirchhoff affirmed1 they are quite sufficient to establish beyond a doubt the presence of iron in the solar atmosphere4 ,the iron lines are the most characteristic in the whole solar spectrum1 and if a magnifying power be used1 or if the light be refracted through several prisms1 these lines1 or at any rate the stronger ones among them1 appear to be perfectly black4 ,m4 ,angstrm noticed that on a careful examination of the solar spectrum1 certain lines can be discovered1 imbedded in a mass of fainter ones1 which1 with increased illumination1 seem to withdraw themselves and disappear1 while the first mentioned lines1 on the contrary1 only stand out in a stronger relief4 ,these are metallic lines of high fusion temperature2 the most remarkable among them almost invariably belong to iron4 ,the substances common on earth that have their vapours in the atmosphere of the sun1 though they have fewer bright lines in their spectra than that of iron1 are quite as characteristic1 and quite as distinctly coincident with their reverses1 whether they be single1 in groups1 or double1 as the sodium line1 which is brighter and its reverses darker than that of any other substance1 because volatilized sodium gives out a greater quantity of light1 and consequently absorbs a greater quantity4 ,m4 ,angstrm has added aluminium and manganese to the seven metals whose vapours ,m4 ,kirchhoff has shown to exist in the atmosphere of the sun1 but he thinks it doubtful whether barium1 zinc1 or copper are solar metals1 for although their brighter lines correspond with distinct dark solar lines1 their weaker lines do not4 ,strontium is doubtful also1 for one of its strongest bright lines is not coincident with any dark line4 ,though both iron and nickel are decidedly solar metals1 yet as cobalt is doubtful1 it cannot be presumed that meteorites are of solar origin4 ,the spectrum of luminous magnesium has many green lines perfectly coincident with those in the solar spectrum1 so there is no doubt of that metal being a constituent of the sun's atmosphere4 ,but there are magnesium rays as well as some of iron of such high refrangibility that in ,mr4 ,stokes's long spectrum they are situated ten times as far from ,h as the whole length of the visible spectrum from ,a to ,h4 ,these highly refrangible rays only become visible at the exalted temperature of the electric spark1 and as they are not found in the solar spectrum1 it is inferred that the heat of the sun is inferior to that of the electric spark4#ba ,mr4 ,roscoe observes that this conclusion would only be legitimate if we knew that these rays of high refrangibility are not absorbed in passing through the atmosphere4 ,these are some of the most striking results of the numerous investigations that have been made since ,m4 ,kirchhoff published his discoveries1 for the subject is anything but exhausted4 ,the intensely vivid light of a magnesium flame is rich in violet and extra-violet rays1 partly due to the incandescent vapour of magnesium1 and partly to the intensely heated magnesia formed by the combustion4 ,the properties of this light having been examined and compared with those of the sun by ,professors ,roscoe and ,bunsen1 with a view to photographic purposes1 they came to the conclusion that #8the steady and equable light evolved by magnesium wire1 burning in the air1 and the immense chemical action thus produced1 render this source of light valuable as a simple means of obtaining a given amount of chemical illumination1 and that the combustion of this metal constitutes a definite and simple source of light for the purpose of photochemical measurement4' ,bright lines of two different metals sometimes coincide with the same black line1 that is1 they appear to have the same reverse as an iron and a magnesian line1 an iron and a nickel line1 and some others2 but it is not known whether the coincidence be real or apparent4 ,m4 ,kirchhoff has proved that neither gold1 silver1 tin1 lead1 antimony1 arsenic1 mercury1 lithium1 cadmium1 and some others are constituents of the sun1 because none of their bright lines are coincident with any of the dark lines of the solar spectrum4 ,this negative discovery does no less honour to ,m4 ,kirchhoff than the proof of so many substances being common to the earth and sun4 ,since all incandescent solid and liquid bodies give a continuous spectrum which exhibits no dark lines1 ,m4 ,kirchhoff conceives that the sun consists of a solid or liquid nucleus1 heated to the temperature of the most dazzling whiteness1 and that it is surrounded by a luminous gaseous atmosphere of somewhat lower temperature1 endowed with the law of exchanges4 ,the spectra of ,arcturus1 ,capella1 and many other fixed stars are crossed by dark lines similar to1 and often coincident with1 the dark lines in the solar spectrum2 therefore1 it may be concluded that their structure is to a certain extent the same with that of the sun4 ,numerous observations have been made on the spectra of the fixed stars1 both in ,britain and on the ,continent4 ,in ,england1 ,mr4 ,huggins and ,professor ,w4 ,a4 ,miller have published tables of the measures of about ninety dark lines in the spectrum of ,aldebaran1 nearly eighty in that of ,orionis or ,betelgeux1 and fifteen in that of ,pegasi1 with diagrams of the two first which include the results of a comparison of the spectra of various terrestrial elements with those of the stars4 ,thus coloured lines of sodium1 magnesium1 calcium1 hydrogen1 iron1 bismuth1 tellurium1 antimony and mercury were found to be coincident with some of the dark lines in the spectrum of ,aldebaran1 and besides these there are numerous lines in the spectrum of this star which are probably due to forms of matter unknown to us4 ,coloured lines of sodium1 magnesium1 calcium1 iron and bismuth1 coincided with dark lines in the spectrum of ,orionis2 and ,pegasi had a spectrum closely resembling that of ,orionis1 but much fainter4 ,between forty and fifty stars were examined1 and it was observed that the solar lines ,c and ,f corresponding to hydrogen1 which are present in the spectra of nearly all the stars1 are wanting in those of ,orionis and ,pegasi4 ,with a few exceptions1 the terrestrial elements hydrogen1 sodium1 magnesium1 and iron1 which appear to be most widely diffused through the stars1 are precisely those which with the exception of magnesium are essential to life as it exists upon the earth4 ,besides1 the elements hydrogen1 sodium1 and magnesium1 represent the ocean1 which is an essential part of a world similar to the earth4 ,should any planets revolve round ,orionis and ,pegasi1 they probably would have no hydrogen1 consequently1 no ocean and no water3 therefore1 they could not be inhabited by beings constituted as we are4 ,padre ,secchi1 the ,roman astronomer1 divides the stars into three types2 the first and most dominant type includes ,sirius1 ,lyr1 and other white stars1 which invariably contain hydrogen of high temperature1 and are denoted by a black line in their spectra1 which coincides with the solar line ,f2 and there is another band also probably due to hydrogen in the violet half of the stars visible to the naked eye belonging to this group4 ,a singular modification of this group1 however1 occurs in the stars of the constellation ,orion1 which so rarely show any deviation from one type1 that1 with the exception of ,orionis or ,betelgeux1 they may be said to form a family distinguished from all the other stars in the sky2 their spectra are crossed by fine lines1 faint in the violet1 with a band more or less visible in ,f4 ,cassiopei and ,lyr differ from the stars of the first type in having a bright band near the solar line ,f1 instead of a black one4#bb ,padre ,secchi's second type includes ,orionis1 ,tauri1 ,antares1 ,pegasi1 c41 which have coloured bands in the red and orange4 ,according to ,m4 ,secchi1 the most remarkable star in this section is ,herculis4 ,it gives a spectrum which has the appearance of columns illuminated on one side2 #8the stereoscopic effect of the convexity of these bands due to the shading is so surprising1 that it cannot be beheld without astonishment4' ,the spectrum of the star #b ,lyr has a similar appearance1 only instead of convex it has concave bands4 ,the third type consists of stars whose spectra are crossed by fine lines1 as ,arcturus1 ,capella and our own sun4 ,the colours of the stars are produced by vapours existing in their atmospheres1 one colour predominating over the others1 which are absorbed by the number of dark lines4 ,messrs4 ,huggins and ,miller obtained extraordinary results from the examination of temporary and periodic stars4 ,temporary stars suddenly shine forth with great brilliancy and soon vanish or nearly vanish4 ,a temporary star which suddenly appeared on the night of ,may #ab1 #ahff1 when examined with a spectroscope1 had two spectra1 showing that its light emanated from two distinct sources4 ,one spectrum1 analogous to that of the sun1 was formed by the light of an incandescent solid or liquid photosphere1 which suffered absorption by the vapours of an envelope cooler than itself4 ,the second spectrum consisted of a few bright lines1 indicating that the light by which it was formed was emitted by luminous gas3 the position of some of the lines denoted hydrogen2 whence the observers believed the phenomena to result from the burning of hydrogen with some other element1 and that the photosphere was heated to incandescence by the resulting temperature4 ,the variation in the brightness of periodic stars has by some been supposed to be due to an opaque body periodically obscuring the light4 ,should that body be surrounded by an atmosphere like our planet's1 its presence would be revealed by the absence or presence of additional lines of absorption in the spectrum of the star4 ,now three lines determined in the spectrum of ,betelgeux were no longer found when the star arrived at its maximum of brightness1 indicating it may be the presence of an atmosphere round the opaque body4 ,with regard to our own planets1 ,jupiter has lines in his spectrum which indicate the existence of an absorptive atmosphere2 one band indicates the presence of vapours similar to those existing in our atmosphere1 another band has no counterpart among the lines of absorption of the earth's atmosphere1 and tells of some gas which it does not contain4 ,in the feeble spectrum of ,saturn there are lines similar to those in the spectrum of ,jupiter4 ,these lines are less strongly marked in the ans of the rings1 and show that the absorptive power of the atmosphere about the rings is less than that of the atmosphere which surrounds the ball4 ,m4 ,jansen has found lines denoting aqueous vapour in the atmospheres of both ,jupiter and ,saturn4 ,some very remarkable lines have been seen in the more refrangible part of the spectrum of ,mars supposed to be connected with his red colour4 ,though the spectrum of ,venus is brilliant1 and the dark lines distinct1 no additional lines indicate the existence of an atmosphere differing from our own4 ,the phenomena resulting from an examination of the nebul are most wonderful2 their light is very feeble1 even that of the brightest4 #8,the total light of the whole nebula in ,orion1 the largest and brightest of them1 makes so small an impression on the naked eye1 that you may look twenty times at its place and not perceive any nebulous light at all4'#bc ,besides1 the brightness of a surface cannot be increased by a telescope1 however good4 ,notwithstanding difficulties which seem to be almost insurmountable1 ,mr4 ,huggins in ,england1 and ,padre ,secchi at ,rome1 have been1 and still are1 engaged in these researches4 ,the planetary nebul are beautiful objects2 they are like planets with a round or oval disc1 equable1 slightly mottled and of enormous magnitude2 one near ,aquarii is twenty seconds1 and another is twelve seconds in diameter4 ,sir ,john ,herschel computed that if these objects be as far from us as the nearest of the fixed stars1 their magnitude1 on the lowest estimation1 would fill the orbit of ,uranus4 ,he discovered twenty-eight or twenty-nine of them1 some of a beautiful blue tint1 in the southern hemisphere2 and from the uniformity of the discs in both hemispheres1 and their apparent want of condensation1 he presumed that they may be hollow shells emitting a feeble light from their surfaces only4 ,the spectrum analysis of that light1 by ,mr4 ,huggins1 in six of the planetary nebul1 showed that their structure is utterly unlike anything else in creation1#bd for instead of an ordinary spectrum he found1 to his infinite surprise1 that the spectra of the feeble light of these bodies consist only of three bright lines1 such as those which proceed from an intensely heated gas1 and that the lines exhibited some of those of the hydrogen and nitrogen spectra and an unknown gaseous substance3 whence he draws the astounding conclusion1 that planetary nebul are probably composed of hydrogen1 nitrogen1 and some unknown gas1 without any solid nucleus whatever4 ,the annular nebula in ,lyra1 which is probably nearest to the earth1 and the dumb-bell nebula1 gave a spectrum indicating matter in a gaseous form4 ,the annular nebula appears to be a hollow elliptical ring of nebulous matter of enormous magnitude4 ,the interior opening of the ring is not entirely dark1 but filled with a faint hazy light1 like fine gauze stretched over a hoop4 ,the dumb-bell nebula in the constellation ,vulpecula is like an hour-glass of bright matter surrounded by a thin hazy atmosphere1 which gives the whole the form of an oblate spheroid4 ,both of these nebul when viewed with a very high telescopic power seem to consist of minute clustering stars1 but the spectra of these two nebul have one bright line1 the structure of both being of the same gaseous constitution4 ,the great nebula on the sword handle of ,orion was then examined4 ,the spectrum of the light from the brightest parts of this nebula1 near the trapezium1 was crossed by three bright lines1 in all respects similar to those on the spectra of the planetary and other nebul4 ,other portions of the great nebula were then brought successively under examination1 but the spectra of the whole of those portions which still were sufficiently bright for this method of observation remained unchanged1 and exhibited the three bright lines only4 ,the whole of the great nebula1 as far as it lay within the power of ,mr4 ,huggins' instrument1 emits light which is identical in its characters2 the light from one part differs from the light from another part in intensity alone4 ,the brighter portions of this nebula have been to a certain extent resolved into stars1 by the powerful telescopes of ,lord ,rosse and ,professor ,bond1 of the ,united ,states of ,america2 the whole1 or the greater part1 of the light from that portion of the nebula must therefore be regarded as the united radiation of numerous stellar points4 ,the spectrum of this radiation being crossed by the three bright lines reveals its gaseous source2 ,mr4 ,huggins therefore infers that at least some of these stellar points are merely denser parts of a gaseous matter1 and that the nebul which he examined are enormous gaseous systems4 ,the spectrum of the great nebula in ,orion was subsequently examined by ,padre ,secchi4 ,he describes the light of the spectrum as of a uniform green1 crossed by three bright lines2 one tolerably wide and perfectly sharp1 a very slender one close to it1 and the third at a little distance from the latter4 ,this spectrum afforded a striking contrast to the spectra of the small stars in the brighter parts of the nebula4 ,as soon as the light from one of these stars entered the slit of the instrument1 its continuous spectrum was seen to flash across the field of vision in a long coloured band4 ,this shows that the mass of matter in this immense nebula is in a different state from that of the stars themselves1 as ,mr4 ,huggins had already observed4 ,padre ,secchi does not draw any inference from his observations as to the structure of nebul in general1 probably thinking it premature1 but he expresses astonishment at their results4 ,since the preceding lines were written1 ,mr4 ,huggins and ,professor ,w4 ,a4 ,miller have continued their researches on the constitution of the celestial bodies by a method of direct simultaneous comparison of the lines in their spectra with the lines in the spectra of many of the terrestrial elements4 ,the spectra for comparison were obtained from the spark of the induction coil taken between points of various metals2 and sometimes a platinum wire was used1 surrounded with cotton1 moistened with a solution of the substance required4 ,the telescope of the instrument was mounted equatorially1 and followed the star by clockwork4 ,by this arrangement the spectrum of the star1 and the spectrum of the metal compared with it1 are seen in juxtaposition2 and the coincidence or relative position of a dark line in the stellar spectrum with a bright line in the metallic spectrum can be determined with great precision4 ,it was found that ,jupiter's atmosphere has a much greater absorptive power than the terrestrial atmosphere2 that they have some gases or vapours in common1 but that they are not identical4 ,some of the lines seen in the atmosphere of ,saturn appear to be identical with those seen in the spectrum of ,jupiter4 #8,the lines characterizing the atmospheres of ,jupiter and ,saturn are not present in the spectrum of ,mars4 ,groups of lines appear in the blue portion of the spectrum2 and these1 by causing the predominance of the red rays1 may be the cause of the red colour which distinguishes the light of this planet4'#be ,all the stronger lines of the solar spectrum were seen in the brilliant light of ,venus2 but no additional lines indicating an absorptive action of the planet's atmosphere4 ,the authors are of the opinion that in most of the planets the light is probably reflected from clouds floating at some distance from the surface1 so that it is not subject to the strong absorptive action of the lower and denser strata of the planet's atmosphere1 which1 like our own1 are most effective in producing atmospheric lines4 ,the results of the observations on the fixed stars are exceedingly interesting1 for they show that their elementary constituents are similar1 but not identical2 and that although they contain many of the sixty-five terrestrial elements1 there are probably new unknown substances also4 ,when seventy dark lines on the spectrum of the star ,aldebaran1 and eighty on that of ,orionis 7,betelgeux7 were compared with the bright lines on the spectra of the vapours of a variety of the terrestrial simple elements1 it was found that ,aldebaran contained nine terrestrial substances and ,orionis five3 that is1 there were only nine out of seventy of the dark lines of ,aldebaran coincident with bright lines1 and five out of eighty of those of ,orionis4 ,yet the seventy and eighty dark lines that were compared represented some of the strongest only of the numerous lines which were seen on the spectra of these stars4 ,some of those remaining were probably due to the vapours of other terrestrial elements which were not compared with these stars1 but ,mr4 ,huggins concludes that many of those dark lines are due to new unknown elements existing in these stars1 and that we cannot assume that the sixty-five simple terrestrial elements constitute the entire primary material of the universe4 ,a community of matter1 however1 exists throughout the visible creation2 for the stars contain many of the elements common to the sun and earth4 #8,it is remarkable that the elements most widely diffused through the host of stars are some of those most closely connected with the living organism of our globe1 including hydrogen1 sodium1 magnesium and iron4 ,may it not be that1 at least1 the brighter stars are like our sun1 the upholding and energizing centres of systems of worlds adapted to the abode of living beings8' ,with regard to the nebul ,mr4 ,huggins's observations show that nine are gaseous1 the spectra of six exhibiting three bright lines1 one shows an additional faint line also1 while the spectra of the dumb-bell nebula and the annular nebula in ,lyra show the brightness of three green lines only4 ,the spectra of eight other nebul were continuous1 showing that their light has not undergone any modification on its way to us4 ,mr4 ,huggins has been able to discriminate between the light of the nucleus of a comet and that of its tail4 ,the nucleus is self-luminous1 and its substance is in the form of ignited gas4 ,the coma shines by reflected light as clouds do1 and observations of the spectra give reason to believe that comets chiefly consist of nitrogen and another elementary body different from nitrogen combined with it4 ,the terrestrial elements found in the fixed stars show that1 like the sun1 they have an intensely luminous nucleus3 but if it be taken for granted that highly heated gases are non-luminous internally1 the planetary nebula and the great nebula in ,orion itself being thus considered to be gaseous1 must emit their feeble light from their surfaces alone4 ,all the true clusters of stars which are resolved by the telescope into distinct bright points of light1 give a spectrum which does not consist of separate bright lines1 but is apparently continuous in its light4 ,the great nebula in ,andromeda1 which is visible to the naked eye1 has an apparently continuous spectrum1 but the whole of the red and orange part is wanting1 and the brighter parts have a mottled appearance4 ,the easily resolvable cluster in ,hercules has a similar spectrum2 ,lord ,rosse discovered dark streaks or lines in both4 ,there is a striking correspondence between the results of prismatic and telescopic observations2 half of the nebul which have a continuous spectrum have been resolved into stars1 while none of the gaseous nebul have been resolved even by ,lord ,rosse's telescope4 ,thus it appears probable that primordial nebulous matter does exist1 according to the theories of ,sir ,william ,herschel and ,la ,place4 ,the structure of the sun himself1 which forms one amidst the multitude of stars which constitute the ,milky ,way2 and the maintenance of his light and heat without apparent waste1 are still in various respects involved in mystery4 ,the luminous gaseous atmosphere of the sun is of great extent and of lower temperature1 at least in its upper regions1 than the photosphere on which it rests4 ,mr4 ,de la ,rue's photographs of the sun show that the light from the border of the solar disc is less intense than that from the equator1 on account of the greater depth of solar atmosphere it has to pass through before it reaches the earth1 by which a larger portion of the light is absorbed4 ,the photosphere of the sun has a mottled appearance1 exhibiting minute masses1 which must be of enormous magnitude to be visible at such a distance4 ,they have been examined with a very high telescopic power by ,mr4 ,nasmyth1 who describes them as lens-shaped bodies of wonderful uniformity1 and likens them to willow leaves crossing each other in all directions1 and moving irregularly among themselves4 ,mr4 ,de la ,rue and ,padre ,secchi say they have seen something similar1 and others liken them to rice grains4 ,sir ,john ,herschel#bf is of opinion that they consist of incandescent matter sustained at a level corresponding to their density in the solar atmosphere1 an atmosphere which he considers as varying from a liquid state below to the highest tenuity of a rarefied gas above4 ,in a memoir read at the ,institute of ,paris1#bg by ,m4 ,faye1 something of the same kind is suggested4 ,there are comparatively brighter waves of the sun's disc1 called facul1 which are portions of the sun's photosphere thrown up into the higher regions of his atmosphere2 for ,mr4 ,de la ,rue took a stereoscopic impression of a solar spot and some facul1 in which the spot appeared to be a hollow and the facul elevated ridges4 ,being elevated above the photosphere1 their light is less absorbed by the sun's atmosphere1 and by contrast they are brighter at the less luminous border of the solar disc than at the equator4 ,it appears that the red flames and protuberances seen round the edge of the sun during a total eclipse are gaseous or vaporous luminous bodies which certainly belong to the sun2 for during the total eclipse in #ahfj it was observed1 that as the moon moved over the sun's disc1 the red flames and part of the corona discovered themselves at the side which she had left1 and were covered by her disc at the side towards which she was approaching4 ,besides1 the illuminating effect of the red light of these flames is so inferior to its photographic power1 that ,mr4 ,de la ,rue photographed one of the protuberances1 although it was invisible to the naked eye4 ,the sun spots which are situated in that region of the sun which lies below the photosphere consist of a central darkness or umbra1 surrounded by a penumbra which is less dark4 ,professor ,wilson1 of ,glasgow1 proved that the spots are cavities1 of which the umbra or darkest part forms the bottom1 and the penumbra the sloping sides1 by observing that the umbra encroaches on that side of the penumbra which is next to the visual centre of the sun4 ,hence the umbra of a spot is at a lower level than the penumbra2 and since luminous ridges and sometimes detached portions of luminous matter cross over the spots1 it is concluded that the whole phenomenon is below the surface4 ,the spots have an apparent motion from east to west1 due to the rotation of the sun2 and ,mr4 ,carrington discovered that they have a proper motion also from east to west1 those nearest the solar equator moving fastest4 ,they are confined to the equatorial regions4 ,no reason has yet been assigned for the periodicity of the spots1 which go through a cycle of maxima and minima every ten years nearly4 ,they are singularly connected with terrestrial magnetism2 the maximum of the spots coincides with the period of the greatest disturbance of terrestrial magnetism4 ,the spots seem to be influenced by the planet ,venus in such a manner that when a spot comes round by rotation to the ecliptical neighbourhood of this planet1 it has a tendency to dissolve2 and1 on the other hand1 as the sun's surface recedes from the planet it has a tendency to break out into spots4#bh ,,part ,,ii4 ,,vegetable ,,organisms4 ,,section ,i4 ,,microscopic ,,structure ,,of ,,the ,,vegetable ,,world4 ,,the ,,study of the indefinitely small in the vegetable and animal creation1 is as interesting as the relation between the powers of nature and the particles of matter4 ,the intimate organic structure of the vegetable world consists of a great variety of different textures indeterminable by the naked eye1 and for the most part requiring a very high magnifying power to discriminate4 ,but ultimate analysis has shown that vegetables are chemical combinations of a few very simple substances4 ,carbon and the three elementary gases constitute the bases of all4 ,no part contains fewer than three of these universal elements1 hence the great uniformity observed in the chemical structure of vegetables4 ,the elements unite according to the same laws within the living plant as in the inorganic creation1 and the chemical laws acting upon them are the same4 ,for1 as already mentioned1 ,m4 ,berthelot having combined carbon and hydrogen into acetylene1 which no plant is capable of doing1 he assumed it as a base from which he deduced1 by the common laws of synthetic chemistry1 hundreds of substances precisely similar to those produced by vegetables4 ,although it may be inferred from this that chemical action is the same within the vegetable as it is in the inorganic world1 yet it is accomplished within the plant under the control of the occult principle of plant-life4 ,no mere physical powers are capable of forming directly out of inorganic elements1 the living organism whose passage through the cycle of germination1 growth1 reproduction and decay1 serves so pre-eminently to distinguish between it and inert matter4 ,plants1 indeed1 borrow materials from the inorganic1 and powers from the physical world1 to mould them into living structures1 but both are returned at death to the great storehouse of nature4 ,all other circumstances being the same1 the vigour and richness of vegetation are proportionate to the quantity of light and heat received4 ,the functions of light and heat are different1 but their combined and continued action is indispensable for the perfect development of vegetation4 ,light enables plants to decompose1 change into living matter1 and consolidate1 the inorganic elements of carbonic acid gas1 water1 and ammonia1 which are absorbed by the leaves and roots1 from the atmosphere and the earth2 the quantity of carbon consolidated being exactly in proportion to the intensity of the illumination1 which accounts for the darker green tint of the tropical forests4 ,light acting in its chemical character is a deoxidizing principle1 by which the numerous neutral compounds common to vegetables are formed4 ,it is the principal agent in preparing the food of plants1 and in all the combinations and decompositions the law of definite quantitative proportions is maintained4 ,it is during these chemical changes that the specific heat of plants is slowly evolved1 which1 though generally feeble1 is sometimes very sensible1 especially when the flowers and fruit are forming1 on account of the increase of chemical energy at that time4 ,to the same cause1 the phosphorescence of certain flowering plants and a few fungi1 is supposed to be due4 ,the action of heat is manifested through the whole course of vegetable life1 but its manifestations take various forms suited to the period and circumstances of growth4 ,upon it depends the formation of protein and nitrogenous substances1 which abound in the seeds1 buds1 the points of the roots1 and all those organs of plants which are either in a state of activity1 or are destined to future development4 ,the heat received1 acting throughout the entire organism of a plant1 may augment its structure to an indefinite extent1 and thus supply new instruments for the chemical agency of light1 and the production of new organic compounds4 ,the whole energy of vegetable life is manifested in this production1 and1 in effecting it1 each organ is not only drawing materials1 but power1 from the universe around it4 ,the organizing power of plants bears a relation of equivalence to the light and heat which act upon them4 ,the same annual plant from germination to the maturation of its seed receives about the same amount of light and heat1 whatever be the latitude1 its rate of growth being in an inverse ratio to the amount it receives in any given time4 ,for one of the same species1 the more rapid the growth1 the shorter the life4 ,the living medium which possesses the marvellous property of being roused into energy by the action of light and heat1 and which either forms the whole or the greatest part of every plant1 is in its simplest form a minute globe consisting of two colourless transparent concentric cells in the closest contact1 yet differing essentially in character and properties4 ,the external one1 which is the strongest1 is formed of one or more concentric globular layers of cellulose1 a substance nearly allied to starch1 being a chemical compound of carbon1 hydrogen1 and oxygen in the proportions of #ab1 #aj1 and #aj1 respectively4#bi ,it forms the universal framework or skeleton of the vegetable world1 but it has no share whatever in the vital functions of vegetation4 ,it only serves as a protection to the globular cell within it1 which is called the primordial cell because it is first formed1 and because it pre-eminently constitutes the living part1 since the whole phenomena of growth and reproduction depend upon it4 ,in its earliest stage the primordial cell is a globular mass of an azotized colourless organizable liquid1 called protoplasm1 the life blood of vegetation1 containing albuminous matter and dextrine or starch-gum4 ,it is sufficiently viscid to maintain its globular form1 but its surface becomes slightly consolidated into a delicate soft film4 ,the viscid albuminous liquid within it is mixed with highly coloured semi-transparent particles containing starch2 besides cavities or vacuoles full of a watery vegetable sap of highly refractive power are imbedded in it4 ,by degrees the coloured particles become more and more condensed within a globule of mucus1 which constitutes the nucleus of the primordial cell4 ,the watery sap in the cavities increases so much as ultimately to fill nearly the whole of the cell at the expense of the viscid protoplasm1 which then merely forms a lining to the cell either coloured or hyaline4 ,the primordial cell then secretes and envelopes itself with the strong protecting coats of cellulose already described4 ,on account of its high colour1 which is chiefly green1 the whole contents of the primordial cell are called the endochrome4 ,the minute globular nucleus contains a liquid of high refractive power1 and is coated with a delicate film4 ,its structure1 which is best seen in the hairs and young parts of plants1 is not always the same1 nor is it always in the centre of the primordial cell1 being sometimes attached to the internal cell wall4#cj ,on the minute but complicated organ1 the primordial cell1 vegetable life depends4 ,it will be shown afterwards that the primordial cell sometimes constitutes the whole plant1 with or without its cellular coat4 ,by its continual bisection when so coated1 linear plants1 such as the conferv1 are formed and lengthened 7fig4 #c74 ,when bisection is about to take place1 the cell increases in length2 the nucleus1 which always plays an important part in cell formation1 spontaneously divides into halves2 at the same time the cell wall becomes constricted in the middle and gradually folds between them1 and divides the original cell into two new ones1 in which the nuclei become perfect and assume their normal position4 ,the terminal cell may undergo the same process1 so that the plant may be lengthened indefinitely4 ,illustration3 ,fig4 #c4 ,development of ,ulva3--,a1 isolated cells2 ,b1 ,c1 clustered subdivided cells2 ,d1 ,e1 confervoid filaments2 ,f1 ,g1 frond-like expansions4 ,plants which spread in two directions are formed and increased by the successive division of the cells into four equal parts1 as in some of the fuci1 and the solid vegetable mass is formed and augmented upon the same principle1 so that it consists of a congeries of primordial cells or globules coated with cellulose1 which by mutual pressure take a many-sided cellular form4 ,six or eight sides are most common2 when six-sided1 a section of the solid is like honeycomb1 but it frequently resembles a very irregular fine lace or network4 ,the form of the cells1 which not only depends upon the number of sides but on the direction of the pressure1 varies exceedingly in different plants1 and in different parts of the same plant4 ,the size of the cells averages from the three to the five hundredth part of an inch in diameter4 ,some are very large1 as in the pulp of the orange and lemon2 but in the pollen of flowering plants1 and other cases1 they are not more than the thousandth part of an inch in diameter1 consequently invisible to the naked eye4 ,occasionally the cells are elongated in the direction of least pressure1 as in the stems and hairs of plants1 or sometimes they have a stellar form4 ,in the looser and fleshy parts they retain their globular form and only touch one another1 leaving triangular spaces between them filled with air in water plants2 but in general the cells are held together by a viscid liquid4 ,when these intercellular spaces1 whether left by globular or polyangular cells1 are placed the one over the other for some distance1 they constitute intercellular passages or channels1 and sometimes they form lacun or large empty spaces4 ,notwithstanding its great variety of forms1 this solid congeries of cells1 called cellular tissue1 is the universal basis of vegetable structure2 it forms the principal part of all plants1 and the entire mass of many4 ,though often highly coloured1 as in flowers1 green leaves and young shoots1 it is frequently hyaline and colourless4 ,the dark cells in fig4 #d represent the green part of a leaf1 the white ones are those of the colourless skin4 ,since the primordial cell is the medium in which light and heat act1 cellular tissue is present wherever growth is in progress1 for all the vital operations take place within its cells4 ,all the organs of plants in their earliest stage consist entirely of cellular tissue1 and even in full grown trees the bark and pith of the stem1 as well as the soft parts of leaves and flowers1 are generally composed of the cells of this tissue1 which though assuming a great variety of forms never deviates far from the original type4 ,every important change in the structure of the cell diminishes or destroys its power of contributing to the nourishment of the plant1 as appears in all the tissues derived from it1 and which1 according to ,m4 von ,mohl1 is a necessary consequence of the disappearance of the vital part of the primordial cell from those parts of the cellular tissue destined to undergo the change4 ,illustration3 ,fig4 #d4 ,vertical section of the cuticle of ,iris germanica3--a1 cells of the cuticle2 b1 cells at the sides of the stomata2 c1 small green cells placed within these2 d1 openings of the stomata2 e1 lacun of the parenchyma2 f1 cells of the parenchyma4 ,the fibro-vascular bundles which constitute the wood of trees1 and form consecutive cylinders round the stem between the pith and the bark1 consist of vascular ducts and woody fibre4 ,the vascular ducts are formed of large wide cells each standing upon the other's flattened end1 their cavities being thus separated from each other by septa or partitions directed at right angles to their longitudinal axis4 ,this vascular tissue when young conveys the sap from the roots through the stem and branches to the leaves4 ,it forms part of the stems of all climbing and quick-growing plants1 in which the circulation of the sap is rapid1 and the perspiration great4 ,the sap in this crude state passes freely through the partitions1 being probably a dialysable liquid2 but in the autumn1 when the sap ceases to rise1 the septa are either absorbed or destroyed1 as appears from the fragments of them that sometimes remain1 and then the ducts become filled with air1 which they convey to mature the sap in the leaves and all parts of the plant4 ,some of the vascular ducts have very narrow parallel fibres of a bluish colour twisted in a more or less elastic spiral from end to end of their internal surface1 which in by far the greater number of cases turns in the same direction as a left-handed screw4 ,in some ducts they merely cross the inner wall of the cell at regular distances as circles4 ,the reticulated form from the crossing of right and left-handed spirals is still more frequent than the simple spiral2 there is scarcely a plant1 from the mosses upwards1 in which that structure cannot be found4 ,in a vast majority of cases the secondary internal membrane of some of the ducts is perforated by orifices of numerous forms1 sometimes irregularly1 and sometimes in a regular pattern like a sieve1 and on that account they are called the pitted tissue4 ,in the stem of a tree the vascular cylinders alternate with cylinders of woody fibre1 as may be seen in a section perpendicular to the axis1 in which the two tissues form a series of alternate rings4 ,the woody or ligneous tissue1 which gives strength and solidity to all vegetable structures1 consists of bundles of nearly parallel spindle-shaped tubular fibres1 having their attenuated extremities applied end to end to the extremities of those above and below them1 so that they form groups of nearly straight lines2 but although the ends of these tubular fibres overlap each other they do not prevent a free circulation of the sap4 ,the different layers of these combined tissues which form the wood do not convey the rising sap in equal quantity4 ,the outermost layers that are nearest the bark1 which are always the last formed or youngest1 convey it in greatest quantity1 and on that account are called the sap-wood3 the older the layers the less they convey1 because the interior walls of the cells of both tissues are coated with successive layers of a mucilaginous substance which is the colouring matter of the wood 7lignin71 and is called sclerogen1 which becomes hard1 is ultimately united to the cell walls1 and fills or nearly fills the tubular fibres and vascular ducts1 so that those nearest the centre of the tree lose or nearly lose the power of conducting the sap1 as in hard wood like the oak1 though in softer wood1 as the lime tree1 it is not entirely lost4 ,ligneous tissue forms the chief part of the stems1 branches1 and shoots of trees and shrubs2 it gives firmness to leaves1 flowers1 and all their parts1 and strength to the stems and skins of herbaceous plants2 it is found in the bark of all trees1 and constitutes the strong fibre of hemp1 flax1 the agave1 and many other plants1 whence linen1 canvas1 and cordage are made4 ,cells lined with sclerogen form the shells of nuts1 cocoa-nuts1 and walnuts1 as well as cherry1 peach1 and plum stones1 the brown coat of apple and pear seeds1 the gritty particles in the heart of the pear1 the white coats of the pips of the orange and lemon1 the husks of peas1 c4 ,all the tissues are represented in fig4 #e1 which is a longitudinal section of the ,italian reed1 much magnified4 ,it consists of three parts3 at a the cellular tissue of the pith is represented2 b is a fibro-vascular bundle containing annular ducts 7#a71 spiral ducts 7#b71 a pitted duct 7#c71 besides the long spindle-shaped threads of woody fibre2 c is the exterior part of the reed1 which consists of cellular tissue1 the two surface rows being rather compressed and filled with coloured particles4 ,besides the spiral vessels that are attached to the interior walls of the vascular ducts1 there are groups of independent spiral vessels of great beauty and elasticity1 of which the seeds of the wild clary afford a remarkable instance4 ,they consist of cylindrical tubes with conical extremities twisted into a right or left-handed screw1 which can be unrolled without breaking4 ,they are found in the leaves of almost all plants1 in the petals and stamens of flowers1 in the stalks of all fruits1 even in the minutest seeds2 large parallel bundles of them imbedded in hexagonal cellular tissue may be seen in the veins of the kernel of the hazel nut1 and they constitute the medullary sheath which surrounds the pith in trees4 ,they are all hollow1 and capable of conducting liquids4 ,illustration3 ,fig4 #e4 ,longitudinal section of stem of ,italian reed3--a1 pith2 b1 fibro-vascular bundles2 c1 cuticle4 ,the laticiferous vessels or vasa propria1 those which contain the proper juices of plants whether milky or coloured1 are exceedingly varied in their forms and arrangement in different plants1 and in different parts of the same plant4 ,in the leaves they generally form a delicate capillary network1 in the bark they constitute a system of long vascular ducts forming an elongated irregular network pervious to the proper juices throughout2 sometimes they are formed of cells joined end to end1 and frequently they are thin branching flexuous tubes1 meandering through the passages or interstices of the cellular tissue1 and occasionally filling the lacun4#ca ,every one of the preceding tissues may be found in many of the highest class of vegetables--those which are distinguished by having seeds with two lobes or seed leaves1 such as our common trees1 shrubs1 and most of the herbaceous plants4 ,palms1 the cereals1 grasses1 canes1 and all plants having seeds with but one lobe1 which form the second class1 consist of cellular tissue mixed with fibro-vascular bundles2 whilst in the third or flowerless spore-bearing class1 there is a general tendency to a more and more simple structure1 from the tree fern to the lichens and alg1 which last consist of cellular tissue alone1 and contain the lowest germs of vegetable life4 ,in seeds the miniature plant is enclosed between the two lobes1 as in peas and beans1 or in a cavity of a lobe1 as in a grain of wheat or barley2 and all the parts of the embryo are merely developed into the perfect plant during the progress of vegetation4 ,a spore1 on the contrary1 which is the seed of a ,cryptogam1 or flowerless class of plants1 is a most minute globular cell1 full of granular matter1 in which no embryo has yet been discovered1 so that the parts of the future plant are supposed to be formed during the progress of vegetation1 instead of being developed4 ,seeds1 and spores also1 sometimes produce new varieties1 while buds and offsets only transmit the parent plant1 with all its peculiarities4 ,in the higher classes1 the organs of nutrition and reproduction are always separate2 in the lowest grades of vegetable life they are often the same4 ,seeds bear no proportion to spores either in size or number2 the latter are often so extremely small that they are invisible to the unaided eye1 and are not to be counted even by thousands4 ,it appears that beings1 whether animal or vegetable1 are prolific in the inverse ratio of their size4 ,the incredible multitudes of the lowest grades of vegetable life1 the rapidity of their growth1 the shortness of their existence1 and their enormous fruitfulness1 make them powerful agents in preparing soil for the higher classes which are nourished by their decay4 ,but no sooner do even the monarchs of the forest fall than the work of destruction begins2 the light and heat which in their chemical form brought them to maturity1 now in their physical character accelerate their decay2 the moss and the lichen resume their empire1 and live at the expense of the dying and the dead1 a cycle which perpetuates the green mantle of the earth4 ,notwithstanding the important part these inferior beings perform in the economy of nature1 they were imperfectly known till they became a test for the power of the microscope4 ,then indeed not only were the most wonderful organisms discovered in the ostensible tribes of the ,cryptogamia1 but a new and unseen creation was brought under mortal eye1 so varied1 astonishing1 and inexhaustible1 that no limit can be assigned to it4 ,this invisible creation teems in the earth1 in the air1 and in the waters1 innumerable as the sand on the seashore4 ,these beings have a beauty of their own1 and are adorned and finished with as much care as the creatures of a higher order4 ,the deeper the research1 the more does the inexpressible perfection of ,god's works appear1 whether in the majesty of the heavens1 or in the infinitesimal beings on the earth4 ,,section ,,ii4 ,,alg4 ,,the principal objects in the study of plant-life are the organs by means of which they obtain and assimilate substances that are essential for their nourishment and growth1 and those by which the perpetuity of their race is maintained and their type transmitted from age to age4 ,in the lowest group of plants1 represented by the ,alg1 which come first into consideration1 the two properties are combined2 in the highest they are distinctly different1 but the progress from one to the other may be traced through an ascending series of vegetable structure4 ,in the simple grades of vegetables1 the primordial cell frequently constitutes the whole plant2 it appears first1 and then envelopes itself with a coat either of cellulose or of a gelatinous substance4 ,many instances of this are to be found amongst the ,alg1 which are all aquatic plants1 and are found growing either attached to other bodies1 or floating independently1 and live1 some species in fresh water1 and others in the sea and its estuaries4 ,the ,alg absorb carbonic acid and give out oxygen1 under the influence of sun-light1 exactly as do the flowering plants2 and the quantity of oxygen disengaged by them is said to be enormous4 ,before proceeding to trace the structure and development of the ,alg1 it may be desirable to indicate something of the classification of this curious group of plants4 ,as already stated1 they are without exception aquatic plants4 ,they comprise three distinct orders1 the ,chlorosperme1 having green spores2 the ,rhodosperme1 having red spores2 and the ,melanosperme1 having olive-coloured spores4 ,these groups embrace all the varied plants known as sea-weeds1 as well as the cellular plants which are developed in fresh water4 ,the ,chlorosperme are separable into three groups1 namely1 those which are simply cellular1 including the ,palmelle1 the green ,desmidiace1 and the yellow-brown silicious-coated ,diatomace2 those which are filamentous1 called generally confervas1 and including the true ,confervace1 in which the threads have no compound axis1 the ,batrachosperme1 in which the threads are partially incorporated with an axis1 the ,nostochine1 in which the slender moniliform threads are invested with a mucous or gelatinous mass1 the ,oscillatori1 and some others2 and those which are foliaceous1 comprising the ,ulvace4 ,all these are moncious plants1 whose reproductive bodies are zoospores provided with ciliary appendages1 or motionless cysts filled with endochrome1 true spermatozoids being rarely present4 ,the ,rhodosperme divide primarily into two groups defined by the nature and position of their spores3 one having the spores indefinite1 produced within mother cells2 the other having the spores single in the upper joints of the threads of the nucleus4 ,the first group includes the ,ceramiace1 which are filiform articulate plants1 with the nucleus naked1 and the ,rhodymeniace1 which are compound inarticulate plants1 with the spores generated within the cells of moniliform threads4 ,the second group includes1 amongst others1 the ,rhodomeliace and the ,laurenciace1 the former articulate1 the latter inarticulate1 and both bearing terminal spores1 and having the nucleus conceptacular4 ,to this group also belong the calcareous ,corallinace and the cartilaginous or membranaceous ,sphrococcoide4 ,the plants of this group are dicious1 with two kinds of fruit1 spores and tetraspores1 and they bear antheridia filled with active spermatozoids4 ,the ,melanosperme divide into two series1 the articulate and inarticulate4 ,the former comprise the ,ectocarpe1 which are filiform plants with external cysts1 and the ,chordari1 which are interlaced cylindrical plants with immersed cysts4 ,the latter include the ,laminari1 flat1 often strap-shaped1 sometimes gigantic plants1 having the spores superficial and indefinite1 and the ,fucace1 which constitute a large proportion of the shore-weeds of our seas and estuaries1 and which bear their spores in elliptic or spherical conceptacles sunk in the frond4 ,the ,melanosperme are either moncious or dicious1 and spermatozoids are general amongst them1 though occasionally propagation is effected by means of zoospores resembling the spermatozoids4 ,having thus indicated the several groups of the great ,algal family1 their structure and development will now be traced1 commencing with the most simple forms1 which occur among the ,,chlorosperme4 ,spring water absorbs oxygen1 nitrogen1 and a large proportion of carbonic acid gas from the earth and the atmosphere1 without losing its limpidity1 but notwithstanding this apparent purity1 if exposed for a time to the sun1 green slime appears1 and this the microscope shows to be full of globules or vesicles filled with green matter--the primordial cell in its earliest form4 ,no green slime is formed in spring water if kept in darkness1 so solar light is the principal agent in this growth1 which is by no means a spontaneous birth2 it is merely the development of one or more of the many kinds of germs1 invisible to the naked eye1 that exist in the earth1 air1 and water in myriads1 waiting till favourable circumstances enable them to germinate4 ,illustration3 ,fig4 #f4 ,palmogla macrococca3--,a1 full grown cell2 ,b-,e1 successive stages of binary division2 ,f1 row of cells produced by a succession of subdivisions2 ,g-,i1 cells treated by iodine2 ,k-,m1 cells in conjugation4 ,the slime that covers damp walls or stones1 and moist cliffs or rocks in the sea1 also the slime or mucus that sometimes swims on the surface of water1 are said by ,m4 ,bory de ,st4 ,vincent to be provisional creations waiting to be organized4 ,of this the conferva1 ,palmogla macrococca 7fig4 #f71 is an example4 ,it is a green slime covering damp places1 consisting of microscopic primordial cells1 each of which is surrounded by a gelatinous envelope1 and filled with green granular matter occasionally concentrated into a nucleus4 ,this singular plant is propagated in two different ways4 ,the endochrome or green matter within the cell spontaneously divides into two equal parts1 the thin coat of the cell bends round the two ends1 separates them1 then each half takes a globular or ovoid form1 and secretes a gelatinous substance round itself which completes the separation1 so that they form two distinct and independent plants1 in every respect similar to that from whence they were derived4 ,after a little time1 each of these plants undergoes a similar bisection1 so that four new plants are formed with their gelatinous envelopes2 by the same process eight are produced and so on indefinitely1 the organ of nutrition being the same with that of reproduction4 ,again1 the membrane or film that covers each of these primordial cells is so thin and soft1 that occasionally two adjacent cells of the series unite into one mass by a fusion of their sides and internal matter1 which is then coated by a membrane1 and after various internal changes becomes a spore which terminates a generation4 ,by and by the spore germinates1 produces a green primordial cell which secretes a gelatinous coat1 and becomes by the process of bisection the parent of a new generation1 which terminates by the union of two adjacent cells to produce a spore1 a cycle of alternate modes of reproduction that may be continued till ended by some external circumstance1 as the cold of winter4 ,when the matter in two adjacent cells joins to form a spore1 it becomes granular1 and mixed with minute particles of oil1 which unite in a drop2 and the spore1 which is at first green1 gradually assumes a yellow brown colour2 conversely when the spore begins to grow1 the oil disappears1 and the green matter takes its place4 ,this is a frequent occurrence during the formation of spores in this class of plants1 for the endochrome or internal matter1--which consists of a small variety of elements probably in a state of unstable equilibrium or change1--is easily decomposed and recombined into new substances by chemical action1 but the bisection of the cells of the ,palmogla so as to form new individuals is probably owing to heat alone4 ,there is no apparent difference between the cells selected to produce spores by their union1 and the others4 ,it seems that in every plant certain cells are reserved for certain purposes4 ,professor ,karsten conceives the nucleated cells to be reserved for reproduction1 while those destitute of nuclei are designed for secretion4 ,the ,protococcus pluvialis 7fig4 #g71 one of the unicellular ,conferv1 is frequently met with in rain-water cisterns4 ,the spore of the plant 7fig4 #g ,a7 is a globular primordial cell invested with a double coat of cellulose1 sometimes separated by an aqueous fluid1 sometimes not4 ,the cell is filled with protoplasm1 a colourless watery liquid in which red and green particles are scattered4 ,when this spore begins to grow1 the endochrome1 or solid matter in the primordial cell1 divides spontaneously into two similar and equal parts1 round at one end1 and tapering to a point or beak at the other1 each being coated by a very thin film of the transparent colourless protoplasm4 ,illustration3 ,fig4 #g4 ,protococcus pluvialis3--,a1 encysted cell2 ,b1 ,c1 cells divided into two2 ,d1 cell divided into four2 ,e1 cell divided into eight2 ,f1 cell divided into thirty-two2 ,g1 escaped motile gonidia2 ,h-,l1 primordial utricles furnished with cilia4 ,after various changes1 the green matter with several red spots is condensed into the thick round half1 while the tapering beaked part is left transparent1 being only filled with the watery liquid4 ,both bodies are then coated with cellulose1 and two vibratile filaments called cilia1 from their resemblance to eye-lashes1 proceed from a point near the beak4 ,the whole of these changes take place while the two bodies are still within the common cellulose covering2 the moment they come out of it1 by a rupture in the cell-wall1 they swim about with the greatest velocity by means of their cilia1 which lash the water so rapidly that they are invisible even with a microscope4 ,the activity of these zoospores1 as they are called1 continues for about an hour and a half2 the motion then becomes gradually less rapid2 the cilia may now be seen1 and soon fall off2 then the bodies acquire a firmer coat of cellulose1 and sink to the bottom of the water1 where they remain at rest as still1 or winter spores4 ,there is great variety in the ,protococcus1 for the matter in the primordial cell sometimes divides not only into two equal and similar parts1 but into #d1 #h1 #af1 #cb equal and similar parts consecutively2 each brood is developed into zoospores1 which ultimately become resting spores4 ,when a spore is to be formed in a primordial cell1 the starch and green matter condense into a nucleus in its centre1 and a membrane envelopes the liquid and the nucleus within it1 so that a spore in its first stage is a free and independent cell containing azotized matter swimming in a formative liquid4 ,if the spore is to be motile it remains of a green colour1 and gets cilia2 but if it is to be a winter spore1 the internal matter forms into granules1 mixed with particles of red oil1 which coalesce into a drop1 and it generally undergoes the same transformations as those which take place after the conjugation or union of two adjacent cells into one as already described4 ,the zoospores may lose their cilia1 fall to the bottom of the water as green spores1 and reproduce a facsimile of the parent plant as buds do1 or they may acquire a cellulose coat1 undergo the transformations and change of colour mentioned1 and sink to the bottom of the water as red winter spores4 ,under certain circumstances which do not seem to be perfectly known1 it happens that during the formation of some of the zoospores the green matter is gradually changed into a red oily substance2 they lose their cilia1 acquire by secretion their cell-walls and a mucous envelope1 and float on the water as winter spores4 ,should they be left dry1 they may remain in that state for an indefinite length of time without losing their vitality1 and as they are extremely small1 they are carried by currents of air into the atmosphere1 from whence they are brought down in the rain1 and having fallen occasionally in places where they were never seen before1 have given rise to the idea of spontaneous generation4 ,many cycles may be accomplished from the still cell to the zoospores1 and back again1 producing numerous generations from the same plant before it returns to the red thick-walled cell1 which may again be dormant for an unlimited time4 ,these cycles1 however1 do not finish the history of the plant1 for there can be little doubt that1 in some stage of its existence1 a conjugation of two cells occurs1 as in the ,palmogla4 ,sometimes when the division of the endochrome of the spore of the ,protococcus is successively divided into sixteen parts1 or even sooner1 the new cells thus produced get two long cilia1 as in fig4 #g ,h1 and are liberated before they acquire their cellulose coat4 ,this motile primordial cell soon acquires a bag-like investment 7fig4 #g ,i1 ,k1 ,l17 of cellulose1 through which the cilia pass1 and thread-like extensions of the protoplasm are not unfrequently seen to radiate from the primordial cell to the surrounding bag1 as in fig4 #g ,i1 showing that the transparent space is only occupied by a watery liquid4 ,the varieties of this plant are very numerous1 and all related to one another4 ,sometimes the whole of the matter within the primordial cell of the spore divides at once into #d1 #h1 or #af parts1 giving rise to as many minute primordial cells4 ,the cilia are extensions of the colourless transparent film which covers the zoospores1 and their vibrations are generally believed to be a consequence of the vital contractibility of that film1 and intimately related to the changes taking place in the cell on which they are borne4 ,the persistence of their motions after a cell is detached from a compound body covered with them1 being like the persistence of the contractibility of muscle fibre after being detached from a living animal1 proves that we must look to a contractile energy in the film of protoplasm for the maintenance of these curious operations4 ,it appears that a cell cannot perform two functions at the same time1 and that one must either precede or follow the other4 ,thus1 the zoospores have two distinct periods of action2 the first is that of mechanical motion alone1 which is followed by one of growth and multiplication1 manifestations which1 though very dissimilar1 are really modes of action of the same vital energy that formed these bodies while they were yet in their parent cell4 ,in fact1 it seems to be a general law1 that each cell is endowed1 altogether or for a time1 with its own mode of action1 and is incapable of any other4 ,of the ,volvocine1 by some regarded as fresh-water microscopic plants1 the ,stephanosphra pluvialis may be taken as a type4 ,this plant consists of a colourless transparent globe not more than the #dh_/ajjjth of an inch in diameter1 containing eight green primordial cells arranged in a circle in its equator4 ,each primordial cell is furnished with a pair of cilia2 these #af cilia pierce through the hyaline globe1 and by their vibrations1 they make it rotate about an axis perpendicular to the plane of its equator1 and move actively through the water4 ,each of the primordial cells1 which are green with a spot of red in the centre1 secretes a cellular covering1 and they swim about in the interior of the globe as free cells4 ,eventually they escape either by fissure of the globe1 or by its gradual dissolution4 ,after swimming about for a short time they become motionless1 lose their cilia1 and sink to the bottom as green still spores4 ,if1 after being dried1 water be poured on one of these green still spores1 it takes up the water1 its contents become closely granular1 and fill the whole membrane of the spore4 ,then it divides1 first into halves1 then into quadrants or heart-shaped segments1 meeting in a point in the centre of the membrane4 ,these quadrants are ultimately divided into #h wedge-shaped segments1 whose contour lines1 like the spokes of a wheel1 meet in the centre1 and each gets a pair of cilia4 ,the coloured matter is driven back in each individual towards the thick end of the wedge as if by centrifugal force1 and a colourless plasm remains in the points or beak4 ,these disappear1 a cavity is formed in the centre of the disc1 the eight bodies assume the form of a wreath in close contact1 and the original cilia1 which continue to vibrate1 cause the rotatory and progressive motion of the whole organism4 ,sometimes the eight globular bodies have been seen to divide into a number of extremely minute motile cells1 while yet within the parent globe4 ,these gonidia1 as they are called1 are1 with a few exceptions which may reproduce the plant1 believed to perish when they come into the water4 ,the division of the primordial cell of this plant is confined to a certain time of day2 it begins towards evening1 and is completed the following morning1 and according to ,mr4 ,f4 ,currey1 the exact time is the same in ,lapland1 where there is no night1 and at ,berlin in spring when the day and night are almost equal4 ,the fertility is enormous4 ,it is calculated that in eight days1 under favourable circumstances1 #af1ggg1baf families of the ,stephanosphra pluvialis may be formed from one resting spore4 ,the transmutation of chlorophyll in the ,protococcus and ,volvocine1 from green to red and vice vers1 which so frequently occurs in the lowest class of plants1 shows that its molecules must be united by very feeble affinities1 and easily converted into new combinations either by direct chemical action1 or by other substances also in a state of change4 ,illustration3 ,fig4 #h4 ,volvox globator4 ,the ,volvocine consist of various species according as the internal matter of the primordial cell divides into #b1 #d1 #h1 #cb1 or a greater number of equal parts1 forming respectively as many free cells which ultimately become ciliated spores1 by means of which the globe either rotates on the spot1 or in straight lines4 ,the ,volvox globator found in fresh-water pools is one of the most remarkable of these1 both for its peculiarity and beauty of structure and for its comparatively large size1 since in some lights it is visible to the naked eye while swimming in a drop of water4 ,when viewed with a microscope1 it is a pellucid sphere whose surface is studded with green spots1 often connected by green threads2 each of the spots has two cilia1 so that the surface is bristled with these filaments1 whose vibrations give the sphere either a rolling or smooth motion1 or make it spin like a top in the same place4 ,in the interior of the sphere there are from two to twenty dark green globes of different sizes2 the smaller are attached to the internal surface1 while the larger rotate freely by their cilia in the internal cavity4 ,after a time the sphere bursts open and its inhabitants swim forth1 and soon assume the form and character of that which gave them birth4 ,the growth and development of the ,volvox globator are peculiar1 for in the primordial cell the red and green endochrome breaks up into numerous angular masses1 and a central globe rather larger than the rest4 ,the angular masses are connected by green threads1 the interstices between all the bodies are filled with a hyaline substance secreted from their surfaces1 and the whole is enclosed in a distinctly membranous globular envelope4 ,as this young ,volvox increases gradually in size1 the hyaline matter is increased1 the green threads lengthen1 and the angular masses assume the form of a flask the #a_/cjjjth of an inch in diameter exactly as in the ,protococcus2 for the green matter with a few red spots is collected in the thick end1 while the hyaline beak is turned towards the circumference of the sphere1 which is pierced by their long cilia4 ,each of them is invested with a pellucid envelope of considerable thickness1 the borders of which are flattened against those of similar envelopes4 ,while these ciliated bodies are approaching maturity their endochrome exhibits vacuoles or apparently empty cavities of a spherical form about one-third of its own diameter4 ,mr4 ,g4 ,busk discovered that these vacuoles expand and contract at regular intervals of about forty seconds4 ,the contraction1 which almost obliterates the cavity of the vacuole1 is rapid and sudden2 the dilatation is slow and gradual4 ,this action ceases when the body comes to maturity4 ,when this mass of zoospores connected by green threads is immature and begins to expand into a hollow sphere1 then the central globe is continually bisected so as to form #d1 #h1 #af1 #cb1 #fd1 or a greater number of equal and similar parts1 each of which is ultimately developed into a zoospore exactly the same with the matured green zoospores on the surface of the primary sphere1 so that the #8,volvox globator is a composite fabric made up of a repetition of organisms in all respects similar to each other1' which ,professor ,ehrenberg the first to discover1 though he did not investigate the development of the plant4 ,it appears that certain spheres of the ,volvox are moncious1 that is1 each sphere contains male and female cells1 though the greater number of cells are neutral4 ,the germ or female cells are larger and of a deeper green than the others2 the male cells resemble them1 but the endochrome within them breaks up symmetrically into a multitude of linear particles aggregated into discoid bundles beset with vibratile cilia1 which move about within their cells and soon become decomposed into their component corpuscles4 ,each of these corpuscles has a linear body1 thicker at its posterior end1 and furnished with two long cilia4 ,the female cell1 when fertilized1 gets a smooth envelope1 and then a thicker one1 beset with conical-pointed processes1 and the contained chlorophyll gives place1 as in ,palmogla1 to starch and a red or orange coloured oil4 ,it appears that the ,volvox stellatus and ,v4 aureus are only phases of the ,volvox globator4 ,the ,desmidiace are minute green alg inhabiting fresh-water pools or slow running streams1 never those that are muddy4 ,they are free unicellular plants1 sometimes triangular1 sometimes cylindrical1 crescent or bow-shaped1 smooth or spined4 ,so varied are their microscopic forms that a description would be tedious4 ,in plants of such extreme minuteness1 the only means of ascertaining the nature of their component materials is by chemical tests4 ,a solution of iodine turns starch blue1 and cellulose brown1 and thus it is found that the interior of the ,desmidiace is occupied by a mass of starch granules1 covered with chlorophyll1 and mixed with a formative fluid4 ,this mass1 enclosed in a delicate membrane1 constitutes the primordial cell2 it has an exterior coat of firm cellulose1 and the whole is more or less enveloped in a gelatinous substance4 ,like other plants1 when in bright sunshine1 the ,desmidiace decompose carbonic acid gas1 give off the oxygen1 and assimilate the carbon into chlorophyll4 ,illustration3 ,fig4 #i4 ,various species of ,staurastrum3--,a1 vestitum2 ,b1 aculeatum2 ,c1 paradoxum2 ,d1 ,e1 brachiatum4 ,these plants are frequently distinguished by projections from their cellulose coat above their surface1 these being sometimes short and conspicuous1 but often projected in spines1 which form a beautiful symmetrical hyaline border round the green internal cell1 as shown in fig4 #i4 ,another peculiarity of the ,desmidiace is the appearance of their being divided into two symmetrical parts by a satural line1 as the name implies1 though there is no real division4 ,many of the ,desmidiace1 but more especially the genus ,closterium1 are remarkable for having a double circulation of the internal fluid in opposite directions1 maintained by a vital contractile energy4 ,one current flows between the cellulose horny coat1 and the thin film covering the chlorophyll1 while the other spreads in a broad stream in the contrary direction between the thin film and the chlorophyll mass1 carrying from the latter some of its coloured particles to the extremities of the frond1 where there seems to be a connection between the two streams4 ,illustration3 ,fig4 #aj4 ,economy of ,closterium ,lunula3--,a1 frond showing central separation2 ,d1 frond in a state of self-division4 ,the type of the ,desmidiace is continued by various modes of bisection1 depending upon the genus and species of the plant4 ,in the ,closterium ,lunula1 which has an elongated crescent shape1 as in fig4 #aj ,a1 the endochrome or internal matter divides into two equal parts1 which retreat from one another at the middle line2 and a constriction of the cellulose coat takes place between them1 which increases till it closes entirely round the extremities1 as in fig4 #aj ,d2 then one of the halves remains at rest while the other moves from side to side1 and finally detaches itself from the other with a jerk4 ,in each of these halves a constriction of the endochrome may be seen1 dividing it into an obtuse and an elongated part1 and for some time the circulating fluid flows round the obtuse end1 but the latter gradually assumes the form of the elongated end1 the regular circulation of the fluid is established1 and in five or six hours after the separation1 two young desmids are formed precisely similar to their parent1 the ,closterium ,lunula4 ,the ,cosmarium1 another ,desmid1 consists of a cell of two lobes united by a narrow isthmus4 ,when about to multiply1 the isthmus swells into two globular expansions1 separated from each other and from the two lobes of the cell1 by a narrow neck4 ,these enlargements increase and assume the appearance of half segments of the original cell4 ,in this state the plant consists of four segments lying end to end1 the two old ones forming the extremes1 with the two new ones in the middle4 ,at last1 each of the middle segments gets a new half1 which soon acquires the full size and characteristics of the old one4 ,this process1 which is accomplished in twenty-four hours1 is repeated ere long1 and being continued indefinitely1 the extreme lobes of the row are thrust farther and farther asunder1 and the whole constricted thread or chain of ,cosmaria is enclosed in a gelatinous sheath4 ,the last two central lobes contain no portion of the original frond or plant1 and may thus be considered to be entirely new individuals4 ,many of the ,desmidiace multiply by the subdivision of their endochrome into a multitude of granular particles called gonidia1 which are set free by the rupture of the cell wall1 and of which every one may develop itself into a new cell4 ,the gonidia may be zoospores with cilia and active locomotion1 or they may be enclosed in a firm envelope1 and become resting spores4 ,the movement of the zoospores at first within the cavity of the cell which gave them their origin1 and afterwards externally to it1 has frequently been observed in the varied species of the genus ,cosmarium1 and has been described under the name of the #8swarming of the granules1' from the resemblance of the moving mass to a swarm of bees4 ,their subsequent history is unknown4 ,in the ,pediastrum1 a plant consisting of a cluster of cells1 the zoospores are not emitted separately1 but those formed by the subdivision of the endochrome of one cell into #d1 #h1 #af1 #cb1 or #fd parts1 escape from the parent plant still enclosed in the inner tunic of the cell1 and it is within this that they develop themselves into a cluster resembling that in which they originated4 ,mr4 ,thwaites discovered that the ,desmidiace are also propagated by conjugation1 which would be impossible if the hard coat of the adjacent cells about to unite did not split open2 then the whole endochrome in one cell passes into and blends with that in the other cell1 so as to form one mass1 which soon acquires a delicate membranaceous envelope4 ,at first the mass consists of granular green matter1 but when the membrane becomes thicker1 it changes to brown or red4 ,this body1 which is called a sporangium1 is sometimes smooth1 sometimes granular1 covered with tubercles or rough with spines1 according to the nature of the original plants4 ,the filamental species are propagated by conjugation1 but the subsequent history of the produce is still obscure1 though there is reason to believe that they give rise to plants of different forms1 while all the other modes of increase only reproduce a facsimile of the parent4 ,desmidiace exist in ,america1 but their distribution is little known4 ,in ,europe1 their maximum seems to be in the south of ,england4 ,they abound in small shallow pools that do not dry up in summer1 and also on boggy moors4 ,the larger kinds are spread out as a thin gelatinous stratum at the bottom of water1 or collected in little tufts2 others form a dirty cloud upon the stems and leaves of aquatic plants4 ,they have been found in a fossil state in flint1 their spores have been discovered in the grey chalk at ,folkestone1 and the cells of various species of ,closterium and ,euastrum are imbedded in the marls of the ,united ,states of ,north ,america4 ,the ,diatomace1 or ,brittleworts1 are unicellular microscopic plants so numerous that there is hardly a spot on the face of the earth1 from ,spitzbergen to ,victoria ,land1 where they may not be found4 ,they abound in the ocean1 in still and running fresh water1 and even on the surface of the bare ground4 ,they extend in latitude beyond the limits of all other plants1 and can endure extremes of temperature1 being able to exist in thermal springs1 and in the pancake ice in the south polar latitudes4 ,though much too small to be visible to the naked eye1 they occur in such countless myriads as to stain the berg and pancake ice wherever they are washed by the swell of the sea2 and when enclosed in the congealing surface of the water they impart to the brash and pancake ice a pale ochreous colour4 ,although the diatoms have a vast variety of forms1 they all consist of a simple primordial cell whose external coat of cellulose is so deeply interpenetrated with silex that it is indestructible1 a structure which constitutes the peculiar characteristic of the tribe4 ,this primordial cell1 as in other plants1 contains organizable liquid or protoplasm1 through which golden-brown granules are pretty regularly distributed1 except in the centre1 where they are collected into a nucleus4 ,round this nucleus they commonly form a ring from which radiating lines of granules diverge to the interior wall of the cell4 ,in each of these there is a double current of granules1 similar to the circulation in the ,desmidiace2 it was discovered by ,professor ,smith in some of the comparatively large diatoms4 ,at times oil globules are seen in the protoplasm4 ,the golden-brown matter is supposed to be chlorophyll1 whose green tint has been changed by the presence of iron1 which is assimilated in this group4 ,such is the internal structure of a race of plants altogether invisible to the naked eye4 ,their external forms1 reproduction and movements1 are no less wonderful4 ,the silicious envelope of the simple cell of a ,diatom or frustule1 as a single plant is usually called1 consists of two valves or plates1 commonly of the most perfect symmetry1 closely applied to each other along a line of junction like the two valves of a bivalve shell1 and each valve being more or less concavo-convex1 a cavity is left between the two which is occupied by the golden-brown cell described above4 ,the form of the cavity differs greatly1 for sometimes each valve is hemispherical1 so that the cavity is globular2 sometimes it is a small segment of a sphere1 resembling a watch-glass1 so that the cavity is lenticular2 in short1 the form of the cavity depends upon that of the valves1 which may be heart-shaped1 or much elongated1 square1 triangular1 boat-shaped1 or furnished with outgrowths1 which1 however1 is rare4 ,illustration3 ,fig4 #aa4--;,a1 ,diatoma vulgare3--a1 side view of frustule2 b1 frustule undergoing self-division4 ,b4 ,grammatophora serpentina3--a1 front and side view of single frustule2 b1 front and end view of divided frustule2 c1 frustule about to undergo division2 d1 frustule completely divided4 ,the diatom or frustule is considered to present its front view when the joint or suture of the valves is turned to the eye1 as in fig4 #aa ,b1 b1 whilst the side view is seen when the centre of either valve is directly beneath the eye1 as in fig4 #aa ,a1 a4 ,when the diatoms are young the valves are in close contact1 but as they increase in size by a secretion round their edges1 the valves separate from one another1 and the cell membrane which is left exposed is immediately consolidated by silex1 and forms a kind of hoop between the valves1 as in fig4 #ab4 ,this hoop increases in breadth as the cell increases in length4 ,when the two valves are circular discs1 they are separated by a circular hoop1 round the edges of which water is admitted to nourish the plant2 but when the diatom has an elongated form1 the water enters through depressed points in its extremities which are free from silex4 ,illustration3 ,fig4 #ab4 ,biddulphia pulchella4 ,illustration3 ,fig4 #ac4 ,pleurosigma angulatum4--,a1 entire frustule2 ,b1 its hexagonal areolation2 ,c1 the same more highly magnified4 ,numerous as these plants are1 the valves of each genus have their own peculiar ornaments1 consisting of the most beautiful and symmetrical designs1 which are impressed upon the young valves when they are in a plastic state4 ,the genus ,navicula and others are marked with the finest stri1 some diagonally1 others transversely4 ,rows of round or oval spots disposed in parallel lines are peculiar to some2 the valves of others are covered with hexagonal forms of the most perfect structure1 as those of the ,pleurosigma angulatum1 fig4 #ac1 where ,a is the magnified diatom1 and ,b and ,c its hexagonal areolations1 seen under higher and higher microscopic powers2 but the figures on the discoid genera are the most beautiful of all4 ,there is generally a small ornamented circular space in the centre of the valves1 from whence rays extend to the circumference1 dividing the surface of the valves into eight1 ten1 or more equal parts1 the alternate segments being differently and highly ornamented1 as in the ,actinocyclus undulatus 7fig4 #ad71 where ,a is the side view1 and ,b is the front view4 ,the ,arachnoidiscus ,ehrenbergii takes its name from the likeness of the figures on its circular valves to a spider's web4 ,according to the observations of ,mr4 ,shadbolt1 each valve is formed of two superposed layers2 on the uppermost of these1 which is a thin horny transparent substance1 the spider's web is engraven2 and the undermost silicious layer1 which forms the supporting frame-work1 is like a circular ,gothic window4 ,the genus ,triceratium1 nearly allied to the preceding in general characters1 though differing in having a triangular shape1 has many species in a fossil state1 while others are still existing in the ocean1 and in tidal rivers4 ,the ,triceratium favus1 one of the largest and most beautifully marked1 occurs in the mud of the ,thames1 and that of the estuaries of other rivers on our coasts2 it is also frequently found on the surface of uncleaned shells4#cb ,from the few examples given1 a faint idea only can be formed of the variety and beauty of the engravings on the diatoms4 ,it had long been doubted whether those on the valves of ,coscinodiscus1 ,triceratium and others1 were elevations or depressions1 but ,professor ,rood of ,new ,york1 ,united ,states1 has proved them to be depressions by an optical arrangement which will be useful for the investigation of microscopic forms4 ,illustration3 ,fig4 #ad4 ,actinocyclus undulatus4 ,diatoms increase by spontaneous bisection1 by conjugation1 and by the resolution of their endochrome into minute spores1 called gonidia4 ,when bisection is about to take place the cell elongates1 the hoop increases in breadth1 the endochrome divides into two equal parts1 and the coating of the cell bends in between them1 which gives the diatom the appearance of an hour-glass4 ,at last they separate1 and upon each of the new surfaces a new silicious half is formed1 usually the exact counterpart of the old one1 so that there are two diatoms instead of one2 and the process may be continued indefinitely4 ,in most cases1 the new diatoms thus produced are free and independent4 ,sometimes1 however1 they adhere to one another by a fragment or connecting membrane1 and if they happen to be slender and rectangular1 and attached side by side1 they form a slender filament1 or if attached by alternate angles they form a zigzag chain1 as in fig4 #aa4 ,the ,meridion circulare 7fig4 #ae7 is a diatom of exquisite beauty1 millions and millions of which cover every submerged stone1 twig1 or blade of grass1 and even form the mud at the bottom of the streams at ,west ,point1 in the ,united ,states of ,north ,america4 ,its frustule or single diatom is long1 slender1 and rectilinear1 but being broader at one end than at the other1 by continued bisection and adhering to one another they form a circular1 spiral1 or flattened helical screw of several turns4 ,the individual frustules of some marine diatoms have a precisely similar form1 being rectilinear and broader at one end than the other1 but each frustule is attached by its narrow end to the extremity of branching cellulose stems fixed to sea-weeds or stones1 and by a continuous subdivision of which the stem does not partake1 they are spread out at their free ends like a fan4 ,illustration3 ,fig4 #ae4 ,meridion circulare4 ,by continual bisection a diatom is propagated through many generations1 but at some stage or other1 owing to an unknown cause1 propagation by conjugation takes place4 ,when two frustules are near to each other1 two little swellings arise in one1 which meet two little swellings in the other opposite to it4 ,these soon unite and elongate1 the septum or division between them is absorbed so that they form two tubes in which the endochrome of the two frustules becomes mixed1 and a spore is formed in each of the two connecting tubes1 which increase in size and change in form till they resemble in every respect the parent1 except in being much larger4 ,as these young diatoms swell1 they split the two parent frustules1 become free1 and lay the foundation of a twin series of generations4 ,in the ,fragillaria only a single spore is formed4#cc ,in ,surirella and ,epithemia the manner of conjugation is somewhat different4 ,in the former the valves of two free adjacent frustules separate from each other at the suture or line of junction and the two endochromes are discharged2 they coalesce and form a single mass1 which becomes enclosed in a gelatinous envelope1 and in time this mass shapes itself into a frustule resembling that of its parent1 but larger4 ,in ,epithemia1 however1 the endochrome of each of the conjugating frustules divides at the time of its discharge into two halves2 each half of the one coalesces with each half of the other1 and two frustules are formed which become invested with a gelatinous envelope and gradually assume the form and markings of the parent frustules1 but grow to a much larger size1 for the spore masses have the power of self-increase up to the time that their envelopes are consolidated4 ,this double conjugation seems to be the ordinary type of the process among the diatoms4#cd ,but these plants multiply also by gonidia4 ,it is thought probable that as long as the vegetative processes are in full activity diatoms multiply by self-bisection1 but when a deficiency of warmth1 of moisture1 or of some other condition1 gives a check to these1 that they increase by gonidia1 some of which becoming encysted1 possess a greater power of resisting unfavourable circumstances1 and thus the species is maintained in a dormant state till a change enables them to germinate4 ,it is even thought they may be the origin of distinct species4 ,a peculiar spontaneous locomotion is exhibited by some diatoms of a long narrow form1 as the ,navicul1 which by a succession of jerks in the direction of their length1 go to a certain distance1 and then return nearly by the same path4 ,the motion of the ,bacillaria cursoria is still more unprecedented4 ,the frustules1 which are narrow1 lanceolate1 and acute1 are joined end to end in a long line by some highly elastic invisible medium4 ,one of the terminal frustules remains at rest while all the others slide over it till the line is so much stretched that they are nearly detached from one another2 then they all slide back again in the same manner1 and this alternate motion is continued indefinitely at regular intervals of time4 ,the velocity of the diatoms at the free end of the row is very considerable2 in the ,bacillaria paradoxa it is #a_/bjjth of an inch in a second2 the impetus of one has been observed to upset and even to push aside a plant as much as three times its size which obstructed its path4 ,if the frustule at the free end gets entangled1 the fixed frustule takes the lead and continues the motion till the other is free4 ,minute particles in the vicinity are sometimes attracted and dragged after the frustules1 sometimes they are repelled1 possibly by some invisible organs2 but the whole motion of the diatoms themselves may perhaps be attributed to the action of light and heat upon the highly contractile substance1 whatever it may be1 which connects their frustules1 since their motion is exactly in proportion to the quantity of light and heat received1 for it ceases during darkness1 and is renewed on the return of light2 ultimately it may disperse the individual frustules1 which are not more than between the #bh_/aj1jjjth and the #hd_/aj1jjjth of an inch in length and the #d_/aj1jjjth of an inch in breadth4 ,illustration3 ,fig4 #af4 ,bacillaria paradoxa ,this ,bacillaria paradoxa 7fig4 #af7 differs from the preceding species in its motion2 each half of the row of frustules moves in an opposite direction on each side of a central stationary frustule1 and the alternate motion is so regular as to time1 that if in advancing1 the frustules meet with an impediment1 they wait till the proper time comes for their retreat4 ,the jerking motions of the ,navicul are ascribed by ,prof4 ,w4 ,smith to forces acting within the plants1 originating in the vital operations of growth1 by which the surrounding water is drawn in at one end of the frustule1 and expelled at the other4 ,some species of diatoms are so universal that they are found in every region of the globe2 others are local1 but the same species does not inhabit both fresh and salt water1 though some are found in brackish pools4 ,the ocean teems with them4 ,though invisible as individuals to the naked eye1 the living masses of the pelagic diatoms form coloured fringes on larger plants1 and cover stones or rocks in cushion-like tufts2 they spread over the surface as delicate velvet1 in filamental strata on the sand1 or mixed with the scum of living or decayed vegetable matter floating on the surface of the sea2 and they exist in immense profusion in the open ocean as free forms4 ,the numbers in which they exist in all latitudes1 at all seasons1 and at all depths--extending from an inch to the lowest limit to which the most attenuated ray of light can penetrate1 or at which the pressure permits--are immeasurably in excess of what we have been in the habit of assuming4 ,temperature has little to do with the distribution of diatoms in the tropics2 it decreases with the depth at a tolerably fixed rate till it becomes stationary4 ,it increases in the polar regions with the depth1 and approaches the standard1 which is probably universal1 near the bed of the ocean4 ,nothing can exceed the vividness of colour or massiveness of the endochrome or soft internal matter of the floating diatoms1 that matter which diminishes their specific gravity and makes the plant buoyant which otherwise would be weighed down by its silicious coat4 ,at those periods in which the structural and reproductive phenomena proceed most vigorously1 their position in depth must be fluctuating2 hence they approach and vanish from the surface4 ,their growth is perfected by the heat and light which penetrates the sea in calm weather4 ,diatoms are social plants crowded together in vast multitudes4 ,dr4 ,wallich met with an enormous assemblage of a filamental species of ,rhizoselenia1 which is from six to twenty times as long as it is broad1 aggregated in tufted yellow masses1 which covered the sea to the depth of some feet1 and extended with little interruption throughout six degrees of longitude in the ,indian ,ocean4 ,they were mixed with glistening yellow cylindrical species of such comparatively gigantic size as to be visible to the naked eye4 ,other genera constitute the only vegetation in the high latitudes of the ,antarctic ,ocean4 ,dr4 ,hooker observes1 that without the universal diffusion of diatoms in the ,south ,polar ,ocean1 there would neither be food for the aquatic animals1 nor would the water be purified from the carbonic acid which animal respiration1 and the decomposition of matter1 produce4 ,these small plants afford an abundant supply of food to the herbivorous mollusca and other inhabitants of the sea1 for they have been found in the stomachs of oysters1 whelks1 crabs1 lobsters1 scallops1 c4 ,even the ,noctiluci1 those luminous specks that make the wake of a boat shine like silver in a warm summer night1 live on the floating pelagic diatoms1 and countless myriads are devoured by the enormous shoals of salpi and other social marine animals4 ,the silicious shells of the diatoms form extensive fossil deposits in various parts of the globe1 containing species which have long ceased to exist1 and others that are identical with those still alive even in their most minute and delicate engravings4 ,the polishing slate of ,bilin in ,bohemia1 which occurs in beds #ad feet thick1 and the ,tripoli and ,phonolite stones on the ,rhine consist entirely of the silicious coats of diatoms1 while the city of ,richmond in ,virginia stands upon a marine deposit of the debris of diatoms #ac feet thick1 and of unknown extent4 ,near the ,mediterranean1 very extensive strata1 consisting almost entirely of marine ,diatomace1 alternate with calcareous strata chiefly formed of ,foraminifera1 the latter being a race of microscopic mollusca4 ,the fossil ,diatomace at ,oran in ,algeria are particularly perfect and beautiful4 ,in many of these deposits existing species are found4 ,the trade winds bring over large quantities of dust mixed with diatoms1 which sinks through the upper into the lower current1 blowing over ,america1 and at last falls in ,europe4 ,professor ,ehrenberg found that this dust contained chiefly true ,american species1 many of which were identical with forms existing at the bottom of the ,antarctic ,ocean1 where an area of #d1hjj square miles was discovered by ,sir ,james ,ross skirting the volcanic coast of ,victoria ,land1 consisting of the remains of these microscopic plants1 which have deposited their silicious valves at death for countless generations1 producing geological changes of enormous magnitude2 while a still greater area of sea-bed in the ,north ,atlantic is the perpetual grave-yard of myriads of microscopic mollusca4 ,thus the ,supreme ,being1 whose power is stupendously manifested in the motions of the celestial bodies1 creates generations of infinitesimal creatures1 adorns them with exquisite beauty1 and makes them ,his agents to form future continents4 ,the ,confervace are a numerous tribe of pretty little plants1 usually of a green colour1 growing in fresh and salt water1 on moist ground1 wet rocks1 and thermal springs4 ,there is scarcely a gently running stream in which they may not be seen1 like bunches of green threads1 attached to stones and waving in the current2 some are so soft as to become almost a mass of jelly when taken out of the water4 ,they are sometimes branched1 but more frequently simple1 formed of cylindrical cells1 joined in a single long row by their flat ends1 and they increase in length by the bisection of their terminal cells4 ,illustration3 ,cell multiplication in ,conferva glomerata3--,a1 portion of filament with incomplete separation at a1 complete partition at b2 ,b1 the separation completed2 ,c4 formation of additional layers of cellulose wall4 ,in unicellular plants bisection is an act of reproduction2 in the multicellular ,conferv it is an act of growth and extension which is accomplished as follows3--,the terminal cell of the plant grows to twice its length1 the matter within the primordial cell spontaneously divides into two equal parts1 and both the film and cellulose coat which cover it1 bend round1 and form a double layer or cellulose division between them4 ,this cellulose layer extends over the whole exterior of the primordial cell1 so that the new cellulose division or septum becomes continuous with a new layer which is formed throughout the interior of the cellulose wall of the original cell4 ,in this manner two perfect cells are formed out of one1 and as the extreme cell may undergo the same process1 the growth of the plant may be continued indefinitely4 ,branches are sometimes formed by buds springing from any part of the stem2 though apparently so different1 it results from the subdivision of the cell which produces the bud4 ,illustration3 ,fig4 #ah4 ,zoospores4 ,the ,confervace are generally reproduced by zoospores4 ,in most cases the endochrome within a cell divides itself into numerous segments1 each of which becomes a minute zoospore1 and escapes into the water through a rupture in the cell wall4 ,this is the case in a very graceful genus of ,conferv1 of which the ,chtophora elegans is a species4 ,it consists of filamental strings of cells1 ending in a capillary bristle1 with lateral branches like narrow fronds4 ,it is reproduced by zoospores4 ,one half of each zoospore is round1 opaque1 and full of matter2 the other half hyaline1 and tapering to a beak furnished with four cilia4 ,it frequently happens in this genus of ,confervace1 where the filaments are divided at equal distances into little joints or compartments1 that the zoospores issue from the terminal cell first1 then from the next1 and so on in succession till the upper part of the branch is left empty1 while the lower part is still forming zoospores4 ,after moving in water for a time1 the zoospores retreat to a shady place1 fix themselves to some substance1 and begin to grow4 ,these plants rapidly cover a large surface of water2 for each individual cell may produce #ajj zoospores1 and as the development and dissemination of them continues during the whole summer1 one plant may yield an enormous number4 ,the ,sphroplea annulina is a rare and very remarkable ,conferva1 whose cinnabar-coloured spores make the surface of the water in which it floats1 like a pool of blood4 ,it has no root1 being merely a filament with capillary extremities1 formed of elongated cells joined end to end4 ,the spores only grow on the filaments that are exposed to the sun and air2 the filaments that are below the water are green and barren4 ,the spores are filled with red matter1 grains of starch1 and red oil1 the outer or cellulose coat being so plaited1 that the spore looks like a red star with white rays4 ,when a spore germinates1 it produces a minute cell ending in capillary fibres1 which increases in length by the continual bisection of its central cells1 while the other ,conferv grow by the bisection of those that are terminal4 ,during this growth1 the red contents of the spore are so changed by a remarkable succession of chemical processes1 that the primordial cells in the filament of the young plant are filled with a colourless viscous matter1 an aqueous liquid1 granules of starch1 and chlorophyll4 ,in some of the cells the starch disappears1 while the green matter and the other materials arrange themselves into a series of rings1 alternating with empty spaces or vacuoles4 ,after a time1 the green changes to a yellowish red1 and then each ring in succession resolves itself into a multitude of minute active particles1 which move with incredible velocity in the void spaces of the cell1 till at last the whole cell swarms with them4 ,they are analogous to the pollen of flowering plants1 and thence are called spermatozoids4 ,their form is cylindrical1 thick1 broad1 and yellow at one end1 sharp at the other1 with a colourless beak1 and long cilia4 ,the parent cell is at last pierced by their united efforts1 and out they rush in great confusion into the water2 some whirl round their centres1 others swim in a circle1 many describe cycloidal curves by a series of leaps1 and a few swim in straight lines4 ,during the preceding changes another process is in progress1 within what may be called female cells4 ,in these the starch1 mixed with green matter and a plastic substance1 arrange themselves also into green and vacant rings1 and after various and complicated changes1 each green ring forms itself into a kind of plastic primordial free cell1 which1 after being fertilized by the moving bodies1 gets a stronger coat4 ,the green matter becomes first of a red-brown colour1 then red2 and after leaving the parent cell it is invested with a plaited cellulose coat1 and becomes a star-like resting spore which may produce a new plant4 ,no cryptogamic plant exhibits a greater variety in the modes of action of the vital forces1 none more activity in the motile powers4 ,in some of these ,conferv1 the moving male filaments1 or spermatozoids1 instead of escaping singly from their prison cell in confusion into the water1 are discharged in a mass enclosed in a capsule furnished with cilia1 which moves with its lively burden like a zoospore1 till a lid falls off which sets them free4 ,some pretty plants allied to the ,conferv are called ,batrachosperme1 from the resemblance which their beaded filaments bear to the spawn of a frog4 ,they are all inhabitants of fresh water1 chiefly of gently flowing streams1 and are so flexible that they yield to every movement of the water1 and when taken out of it are like a mass of jelly4 ,their colour is usually a brownish-green1 but sometimes it is of a reddish or bluish purple4 ,the central stem of the plant1 though originally formed of a single row of large cylindrical cells placed end to end1 gets an investment of cells1 or rather branches1 which ultimately becomes a thick cylindrical stem1 bearing1 at nearly regular intervals1 whorls of short radiating branches1 each composed of rounded cells1 arranged in a bead-like row1 and sometimes branching again4 ,some of the radiating branches grow out into transparent points1 which may possibly be antheridia1 and contain motile bodies2 for within certain cells in other branches resting spores are found1 which are agglomerated and form the large dark globular masses that are seen in the midst of the whorls4 ,the ,hydrodictyon utriculatum is another allied plant of singular structure1 which grows in fresh-water pools in the midland and southern counties of ,england4 ,it resembles a regularly reticulated green purse1 from four to six inches long1 and is composed of a vast number of tubular cylindrical cells1 which adhere to one another by their rounded extremities1 the points of junction corresponding to the knots or intersections of the network4 ,each of these cells may form within itself from #g1jjj to #bj1jjj gonidia1 which at a certain stage of their development are observed to be in active motion in its interior2 subsequently1 by mutual adhesion1 they form into groups which lay the foundation of new net-plants1 when set free by the dissolution of their envelope4 ,besides these groups1 there are certain cells which produce from #cj1jjj to #ajj1jjj more minute bodies of a longer shape1 each of which is furnished with four long cilia1 and a red spot4 ,these escape from their cell in a swarm1 move freely in the water for a time1 then come to rest1 and sink to the bottom1 where they remain1 heaped together in green masses4 ,their future fate is unknown1 but they are believed to be male filaments similar to those described1 and are generally called spermatozoids4 ,the ,nostochine are either an assemblage of cells loosely united into numerous green chaplets1 or distinctly beaded filaments1 generally twisted1 and occasionally branched2 they are imbedded in a firm gelatinous frond of different form1 sometimes globular1 sometimes spreading in branched masses1 often of considerable size4 ,they are frequently seen on damp shady walks in gardens3 they shrink to a film in dry weather1 and reappear so suddenly in rain that they have been called fallen stars4 ,they are reproduced by spontaneous division of their filaments2 the segments escape from the gelatinous mass1 move slowly in the direction of their length1 after a time come to rest1 secrete a gelatinous envelope1 and not only grow in length by transverse bisection1 but split longitudinally into new filaments which are separated by their gelatinous secretions4 ,these movements1 discovered by ,m4 ,thuret1 are evidently intended to disperse the plant4 ,vesicular cells1 destitute of endochrome1 sometimes furnished with cilia1 and of a larger size than the others1 are occasionally seen at the end or middle of a filament of the ,nostocs1 sometimes situated at intervals along their length2 and near to these are sporangial cells1 a little larger than the ordinary cells4 ,from analogy1 it is believed that the vesicular cells are antheridia1 and that the sporangial cells contain germs which1 after being fertilized by the spermatozoids1 are set free and become resting spores4 ,in some species1 the sporangial cells are oblong1 and contain vividly green matter2 in others1 the cells are elliptical and brown4 ,the species are widely distributed4 ,hormosiphon arcticus1 a species consisting of a modification of cellulose1 abounds to such a degree in the herbless polar regions1 that it affords a welcome variety of food4 ,each plant lies on a small depression of the snow1 which covers the soft and almost boggy slopes bordering the arctic seas1 but it is carried by the winds in every direction1 rolling over the snow and ice to a distance of several miles4 ,two northern species of ,nostoc were found by ,dr4 ,hooker in ,kerguelen's ,land1 growing on wet rocks near the sea2 one of them was the common ,nostoc commune4 ,other species occur in the warm springs in ,india1 as well as in the arctic and antarctic regions1 and an aquatic species is much used in ,china as a wholesome food4 ,the genus ,monormia forms floating masses of jelly on the surface of brackish water4 ,the necklaces are of vast length1 and1 together with the jelly in which they are imbedded1 wave with the slightest motion of the water4 ,floating masses grow on large ponds or lakes1 which give the water a green tint4 ,the structure of the ,oscillatori is microscopic4 ,they are minute filiform plants closely allied to the ,nostocs2 and consist of transparent colourless tubular filaments containing colour cells of various forms1 more or less separated from each other1 and visible through their transparent tubes2 the colour is usually some shade of green1 yellowish1 or purple4 ,in the genus ,rivularia these tubular filaments have a globular transparent cell at the base1 and are closely packed into little balls1 either forming small groups1 as in the ,rivularia nitida1 or singly attached to stones and rocks4 ,in ,rivularia nitida1 the filaments radiate from a centre4 ,some ,oscillatori form velvety cushion-like patches upon rocks1 others are attached in tufts as parasites to other sea weeds1 while many are arranged in free or attached stratified bundles4 ,lingbya furnishes a beautiful specimen of the latter4 ,the filaments in the stratified group are usually much twisted and interwoven1 and some of them exhibit singular oscillating motions1 as the ,oscillatoria littoralis and spiralis1 ,spirulina tenuissima and others2 one end of the filaments remains at rest1 while the other extremity is in constant vibration4 ,with a microscope the movement in some species is seen to be from side to side like a pendulum1 in others it is spiral or twisting1 and when a fragment of the plant is set free when vibrating the movement is progressive4 ,if a fragment be put into a glass of water1 its edge in a little time becomes fringed with short filaments radiating from central points with their tips outwards4 ,they soon detach themselves from the fragment by their oscillations1 and as their vibrations continue after they are free1 they swim with a spiral motion to the edge of the water1 and even ascend the glass till arrested by the dry part above4#ce ,during these motions there is a corresponding alteration in the form of the filamental tubes believed to arise from rhythmical periods of vital contractibility1 which are affected by light and heat1 because the motions are more rapid in sunshine than in shade2 besides1 they are checked by strong chemical agents4 ,some of the species have a tuft of delicate cilia at the extremities of their filaments4 ,the free stratified bundles contain the simplest form of the ,oscillatori4 ,each filament is a straight or slightly curved chain of cells1 full of coloured matter1 and enclosed in a common transparent colourless tube4 ,multiplication takes place in these by division2 when about to multiply1 two adjacent coloured cells1 or the two halves of a divided cell1 recede from one another1 and the outer tube contracts at the point of division1 and separates them into two distinctly new filaments4 ,sometimes the transparent outer tube does not yield1 so that the divided parts retain their places in the tube1 which dilates when these new parts are again divided4 ,the manner of division varies with the species1 and the generic characters of the ,oscillatori depend upon the different conditions of the external tube1 and the form and arrangement of the coloured cells within it4 ,the tube often contracts to the finest point during division1 and frequently consists of distinct coats1 the number of which increases upwards1 sometimes with such regularity as to produce a beautiful streaked effect4 ,like their allies1 the ,oscillatori are reproduced by zoospores4 ,while these parts are growing1 but especially during their dissolution1 the endochrome undergoes various changes of colour1 staining the water they die in1 and rendering it putrid2 some of the common kinds emit a strong odour of sulphuretted hydrogen4 ,in the compound gelatinous ,oscillatori1 the jelly is of very different degrees of tenacity4 ,the mass of the ,dasygla is so slippery that it can scarcely be taken hold of2 ,rivularia nitida 7fig4 #ai7 is equally so1 its tubes being so thick and tender4 ,many species of the genus ,rivularia have a peculiar mode of oblique alternate branching2 species of that genus grow on the stems of aquatic plants1 on rocks in rapid streams1 on cliffs when washed by cataracts1 or sometimes in calcareous water1 in consequence of which crystals of carbonate of lime are deposited on their substance4 ,the ,rivularia nitida occurs among ,alg exposed at low tides1 and a species of another genus floats on fresh-water lakes like green stars4 ,illustration3 ,fig4 #ai4 ,threads of ,rivularia nitida4 ,the ,oscillatori are found in every part of the world1 most abundantly in the temperate zones4 ,they chiefly inhabit fresh water1 but these minute plants attain their greatest size in the sea4 ,numerous species grow in warm springs1 and one species1 ,trichodesmium erythrum 7fig4 #bj71 spreads for many square miles over the surface of the ,indian seas in faggots of red-brown threads1 like fragments of chopped hay2 the same species is said to abound in the ,red ,sea also4#cf ,the ,conjugat are fresh-water plants of numerous species1 which have almost the same structure as the ,conferv1 but the green endochrome within the cells of their articulated threads is more highly organized1 and the manner of reproduction is altogether different and very peculiar4 ,these plants consist of strings of cylindrical cells joined end to end by their flat ends1 and generally float freely on or near the surface of still water1 especially when buoyed up by the bubbles of gas which are liberated from them by the heat and light of the sun4 ,in the early stage of their life1 while as yet the cells are undergoing multiplication by self-division1 the endochrome is diffused pretty uniformly in each cell2 but as the plant approaches towards maturity1 it undergoes various modifications1 according to the species4 ,in some it consists of large granules disposed in rows2 in others it is formed into broad spiral bands with large granules in binary or stellar groups placed at intervals on it2 and1 in the dogonium capillare and others1 the granules are united in spiral lines which cross one another and form a network4#cg ,illustration3 ,fig4 #bj4 ,trichodesmium erythrum4 ,the act of conjugation by which spores are formed1 usually takes place between the cells of two distinct parallel filaments which happen to be adjacent to each other1 and all the cells of the two filaments generally take part in it at once4 ,the cells that are opposite to one another put out little protuberances1 which come into contact with each other2 the intervening partitions disappear1 so that a tube is formed which establishes a free communication or passage between the cavities of the conjugating cells4 ,in the genus ,mesocarpus and others1 the conjugating cells pour their endochromes into a dilatation of the passage that has been established between them1 and it is there that the matter mingles to form a spore or embryo cell4 ,but in the ,zygnema 7fig4 #ba71 which is the commonest form of these plants1 the endochrome of one cell passes entirely over into the cavity of the other1 and within the latter the two endochromes coalesce into a single mass1 round which a firm coat is developed1 and it becomes a spore4 ,all the cells of one filament are thus left empty1 while spores are formed in all the cells of the other4#ch ,sometimes cells in the same filament conjugate1 and occasionally the endochrome in a cell divides into two parts1 each of which becomes a spore4 ,illustration3 ,fig4 #ba4 ,conjugation of ,zygnema quininum3--,a4 two filaments in the first stage of conjugation2 ,b1 completion of the act of conjugation4 ,some of the spores are quiescent1 others have cilia and are motile1 but both after a time become attached at one end by two or three root-like fibres1 and grow into filaments by repeated bisection4 ,according to the observations of ,m4 ,itzigsohn1 the endochrome in certain filaments of ,spirogyra breaks up before conjugation into little spherical aggregations1 which are gradually converted into nearly colourless spiral filaments1 having an active spontaneous motion1 and therefore corresponding precisely to antherozoids4 ,with the exception of ,south ,america1 the ,conjugat are widely dispersed in warm and temperate climates4 ,the genus ,vaucheria may be assumed as a type of the ,siphone1 whose essential character is1 that the plant consists of one single tubular cell1 however branched and complicated its form may be4 ,the ,vaucherias form tufted masses of branching tubes1 filled with bright green granular matter1 on mud and damp soil2 they abound in fresh-water pools1 and some grow in the sea4 ,when about to produce fruit1 the extremities of some of the tubes swell out in the shape of a club1 in which a portion of the green matter collects1 takes a darker hue1 and is separated from the rest by a transparent space and a new envelope4 ,after various changes1 the darker green matter forms itself into a zoospore1 which is so active that it breaks open the top of its club-shaped cell1 and comes into the water2 sometimes several come1 one after another4 ,they are egg-shaped1 with a colourless beak1 and as their whole body is bristled with cilia1 they leave a long current in their wake when they swim1 which they do with such impetus that they are flattened against any obstacle they meet with1 even to the discharge of their green endochrome4 ,they escape from their cell about eight in the morning1 move for two hours1 then come to rest1 and begin to grow into a new plant4 ,m4 ,pringsheim discovered another mode of reproduction in the ,vaucherias1 which are moncious plants1 that is to say1 the same plant produces snake-like fertilizing spermatozoids and female germ cells4 ,for example1 the ,vaucheria sessilis consists of one long branched cell2 on the same side of it two swellings appear near to each other1 one of which elongates1 curls round like a horn1 and is soon filled with snake-shaped filaments having long cilia at their thin end1 with which they move rapidly both within the horn1 and after they come out of it into the water4 ,they are perfectly colourless1 and correspond to the pollen of flowering plants4 ,the other protrusion which swells into a globose germ cell1 and which corresponds to the pistil of a flower1 contains a mass of green endochrome1 which1 after being fertilized by the snake-like filaments1 becomes a primordial cell which has no motion1 but after having secreted a strong coating of cellulose1 it sinks to the bottom of the water1 becomes a winter or resting spore1 and lays the foundation for a new generation of plants4 ,the resting spores produce new forms1 while the zoospores1 like buds1 only multiply the type of the individual plant with all its peculiarities4 ,the marine genus ,bryopsis grows in ,new ,zealand1 the ,falkland ,islands1 and the seas about ,cape ,horn4 ,the species are mostly parasites on other ,alg1 and produce innumerable zoospores4 ,the genus ,codium is found in high latitudes1 and appears under four different forms on the ,british coasts2 one of these inhabits turfy banks exposed to the spray of the sea1 the others grow in deep water1 or on rocks never uncovered but at spring tides4 ,species of this genus are found as far south as ,kerguelen's ,land1 and in most of the intervening latitudes4 ,the ,caulerpas inhabit the warmer districts in the northern hemisphere1 and furnish five species in ,new ,zealand4 ,the numerous species afford almost the whole food of turtles on many coasts1 and other genera furnish nutriment to a host of smaller animals4#ci ,the ,achlya prolifera is also a unicellular plant1 much smaller than the ,vaucheria1 but whether an ,alga or a ,fungus is not very clearly settled4 ,to the naked eye it appears as a cluster of colourless threads on dead flies floating in water1 on the gills of fishes1 and sometimes on frogs4 ,with a microscope the tufts are seen to consist of tubes extending in all directions1 filled with a nearly colourless granular matter1 the particles of which are seen to move slowly in streams along the walls of the tubes1 the currents sometimes anastomosing with each other4 ,when the plant is about thirty-six hours old1 the endochrome begins to accumulate in the dilated ends of the tubes1 and is cut off from the remainder by a transverse division1 the motion of the particles being still visible in the part cut off4 ,the endochrome breaks up into a number of long masses1 each of which acquires a cell wall and two cilia1 and begins to move about within the parent cell2 when mature they are set free by the rupture in its wall1 and germinate1 and produce a facsimile of the parent4 ,it appears that1 in some species1 the transverse dividing film becomes convex as soon as the motile bodies are discharged1 a new fertile articulation is formed and new motile spores are set free1 and this process is continued till the vital powers of the plant are exhausted4 ,the ,achlya has resting spores1 which may remain long in the water without change1 but if a dead insect be put into it1 they fix on it and germinate immediately4 ,it is supposed that these resting spores are fertilized by filamental bodies4 ,the ,achlya prolifera goes through all its changes in an hour and a half or two hours4 ,it is found in the thermal springs at ,vichy1 ,nevis1 and ,vaux1 where it contains an alkaline iodide4 ,the whole of the plants which have been described in the preceding pages belong to the group of green ,alg1 although many are inhabitants of fresh water4 ,the structure of the marine ,alg is entirely cellular4 ,deprived of vascular tubes1 they can have no circulation of sap1 consequently they derive their nourishment by absorption throughout their whole surface from the medium in which they live1 for their root1 or rather fulcrum1 only serves to fix them to the rocks and stones to prevent them from being buffeted by the waves4 ,since solar light and heat decrease rapidly with the depth1 each family of ,alg has a zone peculiar to itself4 ,the first zone extends from high to low water mark1 and is inhabited by plants periodically exposed to the atmosphere1 to the direct light and heat of the sun1 and occasionally to rain4 ,some of the ,alg that are long left dry are believed to derive some nourishment from the substances to which they are fixed4 ,the second zone1 which extends from low water mark to a depth of fifteen fathoms1 is the region of the great marine forests which encircle the globe in both hemispheres4 ,other two zones follow at greater and greater depths1 but all are divided into various minor regions1 below the last of which the ,alg decrease as the depth increases1 till1 as far as we know1 vegetation ceases altogether2 that depth1 however1 must be very great1 as diatoms are sometimes found1 and in great quantities1 three hundred fathoms deep4 ,the marine ,confervas1 like those growing in fresh water1 are slender-jointed filaments formed of one series of cells joined end to end4 ,the cells become more or less flattened on the surface of contact1 while the side walls retain their natural curvature1 which may be cylindrical or oval4 ,the filament may1 therefore1 be cylindrical or beaded4 ,the cells are almost always longer than they are broad1 and for the most part equal and similar in the same plant1 although there are exceptions to uniformity of size4 ,the cells contain a transparent liquid through which minute solid particles of various shades of green are pretty evenly scattered4 ,the conversion of these particles into zoospores has already been described4 ,since these ,alg have no roots1 and the cell wall no opening1 each cell of a ,conferva elaborates independently the nutriment it absorbs from the water4 ,some species form a fleecy layer over rocks1 and on the bottoms of salt-water pools and estuaries1 others extend in bundles in salt-water ditches1 and some are found on rocks1 between tide marks1 rising in long1 straight1 stiff1 and wiry tufts1 from three to eight or twelve inches high4 ,the genus ,hormotrichum1 which forms tufts several inches long1 of bright grass green1 differs from the ,confervas in being soft and gelatinous1 and even more by its mode of increase1 which1 however1 is still by zoospores4 ,the ,h4 collabens may be taken as the type of this genus4 ,it forms a long and large tuft of soft gelatinous and slippery filaments of glossy green4 ,the joints of the filaments are once1 or once and a half1 longer than they are broad1 and the green granular matter within them is collected into a round sac or sporidium in the centre of each1 and after being converted into zoospores1 the sac comes through a rupture in the joint into the water1 opens1 and sets the zoospores free4 ,the genus ,cladophora1 which has twenty-five species in the ,british seas alone1 forms tufts of jointed filaments from four to eight1 ten1 or even twenty inches high4 ,in some species the filaments are rigid1 bristly1 and wiry2 in others they are soft and silky2 but they are always richly1 variously1 and sometimes densely1 branched and rebranched4 ,in some the branches and branchlets are forked1 in others tripartite2 the ,cladophora pellucida1 which is a rigid1 wiry plant1 combines both these forms4 ,the genus ,bangia consists of purple filamentous jointed and unbranched ,alg1 which are distinguished from all others by the microscopic arrangement of their endochrome1 which is enclosed in little cells placed according to a definite plan within the transparent and tubular joints of the filaments4 ,in the ,bangia fuscopurpurea1 whose blackish purple tufts1 several inches long1 cling closely to the rocks near high-water mark1 the tubular joints contain rows of minute colour cells radiating from a centre4 ,in the narrow filaments there is but one colour cell in a joint1 but in the broader filaments there are from three to five1 forming a tesselated line across it4 ,in this plant one spore is produced in each joint4 ,the ,bangia ciliaris forms a scarcely perceptible rosy pink fringe of hair-like jointed filaments on the ,zostera marina1 and also on other ,alg4 ,the filaments are not more than the tenth or fifth of an inch long1 consequently their joints are most minute1 yet the microscope shows that they contain from two to three colour cells set as if radiating from a centre1 and that the granular endochrome in each cell is converted into two zoospores4 ,the ,bangia ceramicola1 which forms purplish pink tufts on small ,alg in rock pools1 differs from both of the preceding4 ,the joints of its filaments are once or twice as long as they are broad1 and contain colour cells like long upright lines4 ,by aided vision zoospores are seen to be formed within the linear colour cells1 then the cells run together into a globular mass1 which bursts through the cell wall1 leaving the joint empty4 ,the whole genus is soft and sometimes gelatinous4 ,the ,enteromorpha genus is characterized by a cylindrical and tubular stem and branches4 ,these plants form two groups1 one whose filaments and branches swell from a narrow base upwards and terminate in a blunt extremity1 while in the other group the tips of the branches are pointed4 ,the ,enteromorpha intestinalis1 which is an inhabitant of many seas1 has a thin membranous1 tubular1 cylindrical1 and unbranched stem1 inflated upwards into a broad round head1 being more or less wrinkled and curled throughout4 ,downwards it tapers to a fine thread1 and although attached at first1 at last it becomes floating4 ,several of these plants rise from the same root1 sometimes to the height of two feet1 at others not more than an inch1 and they are of every width1 from the tenth of an inch to three inches1 their colour being grass green4 ,the typical form of the other group is much branched1 and all the branchlets are finely pointed4 ,the three genera ,codium1 ,bryopsis1 and the marine ,vaucherias are all soft plants characterized by their filaments being tubular1 however much they may be branched4 ,they agree also in being reproduced by zoospores developed from the green matter within little sacs attached to the exterior of their filaments4 ,the species of the genus ,codium differ much1 although formed of similar elements4 ,in the ,c4 tomentosum1 which is from three to twelve inches long1 the dark green stem is thicker than a crow's quill and much branched2 while ,codium ,bursa1 on the contrary1 is a dark green round spongy lump of tubular filaments1 densely interwoven and matted together4 ,these masses1 which are from one to eight inches in diameter1 become hollow when old1 and different sizes and ages grow together in a group4 ,the ,bryopsis is a yellowish green tubular plant1 from two to four inches high1 plumed like a feather1 and sometimes replumed4 ,it is a rare plant in ,england1 and grows on the larger ,alg in deep water4 ,the ,vaucheria marina forms soft limp tufts of hair-like filament filled with bright green matter1 which often runs partially out4 ,it is from one to three inches high1 and has a few long upright branches1 to which are attached small stalked pear-shaped sacs containing zoospores4 ,both this plant and the ,vaucheria velutina1 grow on muddy shores4 ,illustration3 ,fig4 #bb4 ,ulva latissima3 a1 portion of ordinary frond2 b1 cells in which the endochrome is beginning to break up2 c1 cells from the boundary between the coloured and colourless portion1 some containing zoospores2 d1 ciliated zoospores2 e1 development of zoospores4 ,the ,ulvas1 which are the grass green layers seen on all our coasts1 originate in the simple vegetable cell1 whatever form their foliaceous fronds may ultimately assume4 ,when the cell is divided in one direction only1 a confervoid filament is the result2 and if the filament should increase in breadth as well as length1 according to a determinate law1 a ribbon-shaped frond may be produced2 but when the original cell is divided into four cells1 and each of these four and all their successors undergo similar division1 the increase being as the series #a1 #d1 #af1 #fd1 c41 a membranous expansion is formed1 in which all the cells are firmly attached to one another1 and every portion is the exact counterpart of another4 ,the cells of the ,ulvas frequently exhibit an imperfect separation of the granular endochrome into four parts preparatory to multiplication by double division1 and the entire frond or leaf shows the groups of cells arranged in clusters containing some multiple form of four1 as in fig4 #c1 page #aga4 ,the frond membrane of the true ,ulvas1 as that of the ,ulva lactuca1 is formed of but one layer of cells2 the frond itself is thin as cambric paper1 almost transparent1 and of a pretty light green4 ,when young it is a puckered inflated bag1 which afterwards bursts and opens into a flat1 ribless1 wavy1 more or less rounded expansion1 three to six inches long1 and as many broad4 ,this plant1 which is attached to the rocks between the tide marks on our shores1 is rare in the ,mediterranean2 nor is it so common in ,britain as the ,ulva latissima 7fig4 #bb71 which is cosmopolite1 and abundant everywhere4 ,it is found as a ribless irregular expansion of a full bright green in deep water1 and of a yellow apple green when in shallow water1 and exposed to the light4 ,the base and stem are very short1 and the frond1 which the microscope shows to be formed of two layers of cell membrane1 spreads so rapidly into crisp wide-lobed foliations1 that the parts often overlap each other in stiff bulging folds4 ,it is from six inches to a foot in height1 and from three to twelve inches wide4 ,the frond of the ,ulva ,linza is also formed of two layers of cells1 but so small and so closely pressed together that the two layers can only be detected by the microscope4 ,this plant1 which is from six inches to two feet long1 is a ribless1 narrow1 ribbon-shaped expansion with curled wavy edges tapering to a base1 and either blunt or pointed at the top4 ,its colour is the same as that of the ,ulva lactuca4 ,in the ,ulvas1 which are multilocular plants1 some cells are selected to bear fruit1 and others not4 ,the granular endochrome of these chosen cells divides into several parts1 which are at first in close contact and at rest2 then they become restless1 acquire four or a greater number of cilia1 and pass through a fracture in the cell wall into the water1 in which they swim freely as zoospores4 ,after a time they come to rest1 attach themselves to some object1 and begin to grow4 ,the walls of the cells which have thus discharged their endochrome in the form of zoospores1 remain as colourless spots on the frond4 ,the whole colouring matter of a portion of the frond may escape as zoospores1 leaving behind it nothing but a white membrane4 ,with a microscope1 this process may sometimes be observed in all the different stages of its progress4 ,every full-grown ,ulva has its own precise and definite form1 but whatever that may be1 the young plants on their first appearance from the shore are in all respects similar to ,confervas2 the top cells soon divide1 and a plane or sac-like frond is formed4 ,certain ,ulvas1 which have a yellow tint1 produce small zoospores with only two cilia1 but in the ,ulva bullosa and the ,ulva latissima four zoospores are produced in the same cell1 each having four cilia4 ,the same fructification prevails also in the purple ,ulvas--,porphyra laciniata and vulgaris4 ,the latter is seen in winter and the early spring1 covering the rocks near high water mark1 with its tiny bright purple lanceolate leaves4 ,later in the season it grows into a flat narrow ribless frond with a pointed end1 and about two feet long1 the margin of the frond becoming waved and plaited as the plant increases in growth4 ,at a later period1 it is seen mixed with the ,porphyra laciniata1 which is a ribless flat frond of a dull purple2 sometimes it is very thin1 divided or torn1 and occasionally growing in a circle round its root4 ,both forms are sold as laver4#dj ,the ,,rhodosperme1 ,floride1 or ,rosetangles1 are the most beautiful of the marine vegetation4 ,no sea plant surpasses them in delicacy and grace of form or richness of colouring1 but the most beautiful are seldom seen1 because they grow below the line of ebb tides1 or under the shelter of other sea weeds in the rock pools left at low water1 their crimson tints being deepest when sheltered from strong light4 ,the ,rhodosperms1 which have representatives in every sea1 are much more numerous than the green ,alg both in genera and species4 ,thirteen orders1 comprising sixty-seven genera1 inhabit the ,british coasts4 ,many are exceedingly minute1 forming patches and velvety cushions on rocks and other ,alg2 a vast number have jointed filamentous fronds1 while others consist of tubular filaments1 and many exhibit a shrub-like collection of firm branches2 some are flat and foliaceous expansions without a midrib1 either thin and delicate1 or thick and strong1 while a very brilliant group of both narrow and spreading fronds possess a midrib as a distinguishing character4 ,the structure of the frond varies from a simple membranous to a cartilaginous or even horny substance1 caused by a greater development of the cellular tissue1 which in the higher kinds of ,floride divides the epidermal layer or skin from the parenchyme or spongy matter within4 ,the mode of reproduction by tetraspores1 as well as by simple spores1 distinguishes the ,rhodosperms from the other two great divisions of the marine ,alg4 ,these bodies are produced by the division of the red or crimson endochrome into four parts1 which remain in the cells till they acquire an envelope2 their form1 which is much varied1 depends upon that of the endochrome4 ,some are produced by the breaking up of a globe of endochrome from the centre into four pyramidal segments2 or should the endochrome be elliptical1 by dividing it into four by three parallel segments1 or a mass may be divided into four by horizontal and vertical sections4 ,some of these are represented1 greatly magnified1 in fig4 #bc4 ,the tetraspores are lodged in wart-like excrescences1 immersed either partially or wholly in some part of the frond4 ,illustration3 ,fig4 #bc4 ,a1 ,polyides rotundus3--a1 thin slice showing the wedge-shaped spores2 b1 tetraspores4 ,b1 ,furcellaria fastigiata3--c1 thin slice showing a nucleus with the dividing spores2 d1 one of the large cells2 e1 a tetraspore4 ,the simple spores are produced within colourless tubercules called nuclei1 variously situated upon the plant1 as at fig4 #bc a1 c4 ,these nuclei contain many microscopic spores4 ,sometimes the nuclei are enclosed in conceptacles or ovate sacs1 which are either perforate or not at the apex4 ,these contain many microscopic strings of cells like jointed threads1 and the endochrome in each joint of these threads is converted into a spore successively from the summit downward4 ,sometimes the endochrome in one or two joints only1 becomes a spore whether terminal or central1 and when the spores break through the joint wall and fall off from the threads1 they are collected without any definite order into a mass within the nuclei4 ,sometimes new joints or cells are produced on the threads when the old ones have yielded their fruit4 ,occasionally a globose nucleus contains several secondary nucleoli full of spores4 ,in every instance1 the perfect spore is a dense grumous mass surrounded by a hyaline sub-gelatinous coat consisting of at least two membranes4 ,the situation1 mode of growth1 and structure of the nuclei vary almost infinitely1 and together with the structure of the frond afford the distinctive marks by which the genera are separated from each other4 ,the spores and tetraspores are equally capable1 like buds1 of reproducing their species2 but the spores are believed to be in some cases fertilized by spindle-shaped particles1 and consequently are considered to be the true fruit4 ,antheridia1 or sacs containing these particles1 have been discovered in various genera of ,rhodosperms4 ,although1 as a rule1 the red ,alg have two modes of vegetative reproduction1 yet there are various species in which tetraspores only have hitherto been met with4 ,illustration3 ,fig4 #bd4 ,vertical sections of conceptacles3--a1 ,gracilaria armata2 b1 ,grinnelia americana2 c1 ,corallina officinalis1 the membrane of which1 more highly magnified1 is shown at d4 ,a large proportion of the higher ,rhodosperms is distinguished from those possessing the preceding mode of fructification by the internal structure of their reproductive nuclei4 ,in some of these ,alg the nuclei are divided into two equal chambers by a fibro-cellular substance to which the spores are attached2 in others1 pear-shaped spores radiate from a fibro-cellular substance at the base of the nucleus4 ,there are1 moreover1 ,alg which have nuclei containing conical spores whose broad bases radiate from the centre1 and other arrangements occur4 ,the ,rhodosperms are comparatively small plants4 ,some which form velvety cushions on stones1 or minute tufts on small ,alg1 are only the fraction of an inch high1 but the larger kinds range from one to four1 six1 ten1 or twenty inches2 probably none exceed two feet4 ,in thickness1 some fronds are fine1 like jointed and branched hairs1 while others are thick1 like hog's bristles or crow quills4 ,numerous as the forms are1 the simple jointed filamentous frond is connected by a series of forms with the highest order of the class4 ,a great portion of the ,rhodosperms on the ,british coasts is composed of the exquisitely beautiful order of the ,ceramiace4 ,they abound in every rocky pool1 on every piece of wood that has been long exposed to the waves1 on rocks and stones1 and1 above all1 they fringe the ,zostera marina1 or sea wrack1 as well as the firmer ,alg1 with every shade of red from bright crimson to purple4 ,they are articulated filiform plants1 approaching in simplicity of form to the ,confervas4 ,the genus ,callithamnion1 which has thirty species in the ,british seas1 consists of cylindrical jointed threads more or less profusely branched1 and distinguished by having the divisions between the joints opaque and of various shades of red and purple1 while the joints themselves are transparent and colourless1 so that the stem and branches appear to be striped across by alternately white and coloured bands which are often visible to the naked eye1 notwithstanding the smallness of the plants and the delicacy of their filaments1 as the ,c4 sparsum1--which is a soft purple tuft of jointed threads scarcely one-tenth of an inch high4 ,the ,callithamnion corymbosum has a soft jointed filamentous stem1 hair-like below1 fine as a cobweb above1 and excessively branched1 with dichotomous branches4 ,in fig4 #be a represents a thread of this plant with tetraspores1 much magnified2 b1 a portion of the same1 more highly magnified2 c1 a thread with naked nuclei1 gongylospermous1 that is1 filled with a mass of spores1 magnified2 and d1 a spore1 magnified more highly4 ,the nuclei are naked in all the ,ceramiace4 ,illustration3 ,fig4 #be4 ,callithamnion corymbosum4 ,the genus ,ceramium1 some species of which have spinulose branchlets1 is characterized by the tips of the forks of its terminal branchlets being hooked inwards1 and by the stems and branches being striped by alternate hyaline and coloured bands as in the preceding genus1 though the arrangement of the colours is somewhat different4 ,the ,ceramium ciliatum1 which is a dense tuft of capillary jointed filaments1 from two to six inches long1 repeatedly and regularly forked1 has the tips of the last forks so much hooked inwards1 that the extremities of the branchlets look as if they were heart-shaped4 ,it has minute spores in globular nuclei1 sessile on the branches with two or three branch-like hairs beneath them1 and tetraspores set in the coloured parts of the joints with a thorn between each1 for in this plant the centre of the joint is hyaline1 the rest coloured4 ,the genus ,griffithsia contains various species of bright rose-coloured plants1 which become bleached when put into freshwater1 and form a circle when spread out4 ,soft1 tender1 and gelatinous1 they form dense tufts of jointed and branched filaments on rocks at low water mark4 ,the filaments are slender below1 capillary and forked above1 and the joints contain one linear upright rose-coloured tube1 which is seen throughout their transparent walls3 a distinguished mark of the genus4 ,tetraspores are borne on the hair-like jointed ramuli1 and spores are amassed in coated roundish sessile nuclei1 surrounded by minute hair-like fibres4 ,several species once called ,griffithsia differ so much from the others1 that they are by some referred to ,halurus1 which has the stems and branches thickened by overlapping whorls of tiny forked jointed and curved ramuli4 ,they are propagated by spores1 enclosed in clusters of nuclei borne on the tips of short branches1 with a mass of curved ramuli folding over them1 and by tetraspores attached to the inside of another set of curved ramuli4 ,antheridia have been discovered in several genera of the group ,ceramiace1 especially in ,ceramium1 ,callithamnion1 ,griffithsia1 and ,halurus4 ,they consist of little clusters of cells variously arranged1 in which the active particles known as spermatozoids are generated4 ,the ,polysiphonia are ,alg1 seen in tufts from ten to twelve inches long1 of usually much branched jointed filaments1 on rocks1 corallines1 and the smaller ,alg at low water mark4 ,the joints of the filaments contain upright tubes1 full of purple or reddish brown matter1 which is seen through their transparent walls4 ,the number of these colour tubes vary from four to ten1 eighteen1 or even twenty1 and form the characteristic of the genus4 ,thus there is a similarity of structure between the ,polysiphonia1 a genus of the highest order amongst ,rhodosperms1 and the ,griffithsia1 which is one of the lowest4 ,the ,polysiphonia elongata1 which is from six to twelve inches high1 has four primary and several secondary colour tubes in the transparent joints of its filaments4 ,like many of its congeners1 this plant does not come to perfection or bear fruit till the second spring4 ,in its youth1 it resembles the full grown plant but is smaller1 and the colour tubes are not formed in the capillary threads of the tufts1 which with many of its branchlets are deciduous1 leaving the plant in its naked winter state4 ,with returning warmth1 it assumes its perfect form1 and in ,march and ,april bears fruit1 which consists of nuclei in conceptacles1 sessile on the branches1 either clustered or scattered4 ,the spores are at the top of jointed threads rising from a substance at the base of the nuclei4 ,in some species of this genus1 tetraspores only have been found4 ,the ,cryptonemiace are the most numerous and diversified of all the orders of the ,rhodosperms4 ,thirty-five genera are widely dispersed throughout the world1 chiefly in the northern hemisphere2 twenty-four genera at least occur on the east coast of ,north ,america2 and fifteen genera have representatives in the ,british seas4 ,this multitude of generic forms is divided into two groups of gelatinous structure1 the one having inarticulate fronds composed of articulate threads closely incorporated1 the other membranaceous1 formed of cells closely incorporated into a foliaceous expansion4 ,most of these plants have a stratum of cellular tissue1 interposed between a spongy matter in the interior of the frond1 and the epiderm or external skin1 which for the most part consists of a simple layer of minute cells firmly united by their sides1 generally forming a mere film2 but it may be thin and flexible1 thick1 tough1 or leathery1 according to circumstances4 ,the ,furcellaria fastigiata 7fig4 #bc ,b7 has an intermediate layer of cellular tissue between its skin1 and a pulpy interior4 ,the frond is cylindrical1 smooth1 strong1 and opaque1 repeatedly forked with long narrow forkings4 ,the root is fibrous1 and the stem short and tapering4 ,masses of spores nestle under the skin and swell out the upper forkings1 and oblong tetraspores are deeply imbedded in the same4 ,in the ,dumontia filiformis the simple undivided stem and branches are filled with a watery jelly4 ,the stem of the ,chylocladia kaliformis is a cylindrical tube1 from four to eighteen inches high1 constricted at intervals of half an inch or more into long hollow joints2 branches of the very same construction but smaller spring from each constriction either opposite to one another or in whorls2 these again have lesser branches1 all tapering more or less to each end4 ,the plant1 which is of a pink colour fading to greenish yellow1 is propagated by tetraspores imbedded in the branches1 and by transparent conceptacles sessile on the branchlets1 enclosing nuclei containing pyramidal spores4 ,we neither possess the ,constantinea rosa marina1 nor the ,c4 sitchensis1 some of the largest and finest plants of the group1 both being inhabitants of high latitudes1 but there are some very pretty species on the ,british coasts4 ,they are supposed to be annuals4 ,the red dulses belong to the foliaceous and gelatinous part of this order4 ,the ,chondrus crispus1 or ,irish moss1 sold as ,carrigeen1 is very common on rocky coasts in the northern seas4 ,it is from three to eight inches high1 and exceedingly varied in form4 ,the frond is thickish1 firm1 and elastic1 with a stratum of cellular tissue under the skin1 which is probably much developed1 as the plant becomes horny when dried4 ,it is reproduced by tetraspores1 in large oval groups scattered all over the surface1 often prominent on one side only1 and1 in some rare instances1 spores in prominent oval conceptacles are immersed in the lesser frond divisions4 ,besides these are warts composed of radiating threads1 possibly antheridia1 but not made out4 ,illustration3 ,fig4 #bf4--;,a1 ,rhabdonia ,coulteri1 portion of nucleus4 ,b1 ,sphrococcus coronopifolius2 portion of nucleus and single spore4 ,c1 ,wrangelia penicillata1 spore threads4 ,d1 ,cruoria pellita1 tetraspores4 ,the ,rhodymeniace are sometimes filiform1 but for the most part they are compressed flat cellular fronds1 spreading widely from a short delicate stem4 ,they are usually of a blood red1 but ,rhodymenia palmata1 or common ,scotch dulse1 is of a dark purple4 ,the tetraspores are variously disposed1 and simple or compound globular conceptacles containing nuclei are either attached externally to the filiform fronds1 or partly immersed in those that are foliaceous4 ,the spores are produced in the joints of moniliform threads within the nuclei1 which are sometimes divided into two chambers by threads running from wall to wall4 ,rhabdonia 7fig4 #bf ,a7 belongs to this group4 ,the ,wrangeliace are filiform1 many species consisting of a central thread coated more or less with smaller ones1 sometimes so disposed as to form a most elegant lacework4 ,each joint of the stem1 branches1 and branchlets is beset with whorls of short slender forked and jointed ramuli4 ,they have clusters of spores in stalked capsules4 ,the spore threads of ,wrangelia penicillata 7fig4 #bf ,c7 are surrounded by a whorl of ramuli composed of radiating pyriform spores arising from the endochrome of terminal cells4 ,the ,squamari resemble lichens in spreading themselves in a red crust over stones and rocks4 ,they have roots below1 and warts1 on their upper surface1 in which there are tufts of moniliform spore-bearing threads4 ,the tetraspores of ,cruoria pellita are shown in fig4 #bf ,d2 its repeatedly forked filaments taper upwards1 and the tetraspores are formed in the swollen centre cell of the filaments4 ,the ,peyssonnelia grows on shells and other marine objects1 and extends from the ,mediterranean to ,ireland1 and the east coast of ,north ,america4 ,the ,polyides rotundus 7fig4 #bc ,a71 representing the only genus of the ,spongiocarpe1 has a dark purple solid gristly cylindrical stem1 repeatedly and regularly forked1 all being of the same thickness4 ,the tips of the last forkings1 which are small and equal1 give the top of the plant a rounded form4 ,the microscope shows that the stem and branches are composed of a central column of interlaced threads and radiating cells2 it shows1 moreover1 that hyaline nuclei containing a cluster of conical spores whose broad bases radiate in all directions from a centre1 as in fig4 #bc a1 are scattered among the articulated threads of oblong irregular spongy warts which clasp or embrace the stem and branches4 ,the tetraspores are buried in the ends of the last forks4 ,this plant is so like the ,furcellaria fastigiata 7fig4 #bc ,b71 that it affords a remarkable instance of similarity of form and total diversity of fructification1 not only in the spores and their arrangements1 but in the form of the tetraspores2 for in the ,polyides they are formed by two sections1 one vertical and the other horizontal1 while in the ,furcellaria the endochrome is divided by three annular sections1 as in fig4 #bc ,e4 ,the ,gelidium corneum1 common in ,britain and almost everywhere1 representing the group ,gelidiace1 is opaque1 firm1 and of a dark purple4 ,the axis with its alternate and repeated branches lying all in one plane1 is composed of confervoid threads4 ,this plant is distinguished by having its spore-cases or nuclei divided into two chambers by a fibro-cellular substance2 the spores are either attached to this or to a network of threads2 these bodies and the tetraspores are lodged in the tips of the branchlets4 ,it is one of the most variable of all ,alg4 ,the ,sphrococcoide comprise some of the most common and beautiful ,alg1 remarkable for their brilliant rose and purple tints4 ,this section consists of those red ,alg which have their nuclei lodged in an external subglobose conceptacle1 the spores being formed at the tips of jointed threads rising from a substance at the base of the nucleus4 ,a portion of a nucleus of ,sphrococcus coronopifolius1 and a single spore magnified1 is shown at fig4 #bf b4 ,the tetraspores are variously disposed4 ,the fronds in this family are either gristly or membranaceous1 and totally different from those which follow4 ,they often assume a leafy aspect from the regularity of the nerves1 which sometimes perform the functions of a stem when the membraneous border has decayed1 and then they give rise in turn to new fronds4 ,that happens in some species of ,nitophyllum3 a very short stem rises from a minute disc1 and spreads widely into a flat ribless expansion1 more or less deeply slit into broad rounded divisions4 ,wavy nerves from the top of the stem spread through the fronds1 which are left bare in winter1 and give rise to new fronds in spring4 ,the leaves of the ,delesseria sanguinea1 from two to eight inches long and from one to six inches broad1 are of the richest colour and most delicate structure1 with evenly curled edges1 and a firm solid stem1 with prominent midrib and nerves4 ,in winter globose stalked spore conceptacles are borne on the skeleton midribs of the summer's leaves from which the margin has decayed1 which thus become the stems of the next year's plant4 ,in this plant tetraspores in small special stalked leaflets fringe the skeleton midribs2 in the ,nitophyllums they are either scattered in dots over the frond1 confined to the centre1 or in lines round the margin4 ,as regards the internal structure of this order1 nothing can be more various1 but they never acquire a truly articulate form4 ,the genera and species of this group are widely distributed2 they have many representatives in the ,mediterranean4#da ,the genus ,sphrococcus is confined to ,europe1 while numerous genera are exclusively tenants of the southern hemisphere4 ,the ,gracilaria lichenoides1 the ,ceylon moss1 is celebrated for its gelatinous qualities2 and the ,gracilaria compressa on our own shores is excellent as a pickle or preserve1 and very ornamental4 ,one of the most beautiful ,alg known is the ,grinnelia americana1 which abounds on the eastern coast of ,north ,america2 fig4 #bd b1 is a vertical section of its conceptacle1 showing the rudimentary placenta and spore threads4 ,it differs singularly from the ,delesseria sanguinea1 of which it is an exact analogue1 in the capsules being scattered over the surface of the frond instead of being situated on the midrib4#db ,the ,delesseria sanguinea is now known as the ,wormskioldia sanguinea4 ,the ,corallines are florid ,alg1 which absorb such a quantity of carbonate of lime from the surrounding water1 that they become rigid1 hard1 and often stony4 ,they are purple or pink when fresh1 white and sometimes brittle when dry1 and are propagated by strings of spore threads rising from the base of the nuclei which are enclosed in conceptacles or spore cases1 open at the top4 ,some are articulate1 composed of closely compacted threads1 as the ,corallina officinalis1 a pretty little branched and bushy plant1 most luxuriant in deep water1 and particularly abundant in the rocky pools4 ,its urn-shaped spore sacs are attached to the tips or sides of the branches2 fig4 #bd c is a vertical section of one of them magnified1 and d is a membrane of the same1 more highly magnified1 with impressions of the external cells4 ,the joints of the articulate corallines1 which are flexible and vary much in length1 are either free from carbonate of lime1 or ornamented with calcareous plates2 it is through these open spaces that the plant is believed to obtain nourishment4 ,the forms of the corallines are varied beyond description2 many are mere amorphous crusts on stones and sea weeds1 increasing from the centre outwards as in the lichens1 others are lobed and branched like real corals4 ,corallines ascend to very high latitudes1 but abound most in warm and tropical seas3 either free1 or coating pebbles at vast depths1 they form the last zone of vegetable life4 ,the ,laurenciace have fronds which are soft and thread-like1 or solid1 fleshy1 and inarticulate2 both are repeatedly branched4 ,the colour of these plants is purple or a dullish red1 but they are extremely sensitive to the influence of light and air1 changing through every shade of orange1 yellow1 or green1 according to the exposure1 and like many other florid ,alg they lose their colour in fresh water4 ,they are amongst our commonest sea weeds4 ,the ,laurencia pinnatifida is the pepper dulse of ,scotland1 and is also native on the eastern and western coasts of ,north ,america4 ,species have been found at the ,cape of ,good ,hope1 ,australia1 and ,new ,zealand4 ,the fructification in this section is quite peculiar4 ,they have tetraspores lodged in the branchlets2 and egg-shaped conceptacles with a terminal pore1 enclosing nuclei with pear-shaped spores radiating from a fibro-cellular mass at their base4 ,the antheridia1 which differ in the different species1 attain a greater degree of complication than in other tribes4 ,in ,laurencia tenuissima they form curious lateral twisted plates of a greyish tint1 bordered with large cells4 ,the plate is occupied by the productive cells of a much smaller size1 evidently springing from a cellular branched axis4 ,in ,laurencia pinnatifida instead of a plate there is a somewhat hollow cup-shaped disc1 formed of dart-like vertical groups of pale cells surmounted by two or three larger oily-looking sacs filled with yellow pigment4 ,these bodies are sometimes forked1 and appear to shoot out from the mass4 ,l4 dasyphylla presents a third modification1 the antheridium being a sac1 and the dart-like groups of cells being ejected from the minute terminal orifice4 ,the moving particles produced in the cells of these three forms1 differ a little in shape1 and as they do not germinate they are believed to be spermatozoids1 though no cilia have been found on them4 ,the ,rhodomelace1 the last and highest family of florid ,alg1 are1 as the name implies1 of a rich red brown colour4 ,none of the other ,rhodosperms can vie with them in peculiarity or variety of structure4 ,the fronds may be areolate or reticulate1 filiform or variously leafy1 articulate or inarticulate4 ,illustration3 ,fig4 #bg4 ,dictyurus purpurascens4 ,some genera1 as for example ,dasya1 have slender1 often elegantly branched threads1 while such genera as ,amansia and ,odonthalia have instead a flat and pinnatifid frond4 ,the latter1 which has a very conspicuous cellular reticulation1 is a genus of high latitudes1 but is common on some parts of the ,scotch and ,north ,american coasts4 ,the ,british seas are rich in many genera of this order1 and analogous forms occur in the southern hemisphere1 where there are at least twenty-three genera4 ,many are remarkable for their singularity of structure3 the ,claudea for example1 which is one of the most elegant of the ,alg1 has a cancellated frond and is the ornament of warm seas2 the ,amansia and ,leveillea which are distinguished by the beautiful reticulation of their fronds caused by large hexagonal cells2 and the ,dictyurus1 in which the net forms a spiral web round the principal stem4 ,fig4 #bg shows a portion of the network of ,dictyurus purpurascens magnified4 ,all the genera of this order possess free areolate hollow conceptacles perforated above1 and containing nuclei1 from the base of which short tufts of threads arise1 each bearing a large obovate spore at its apex4 ,the tetraspores are arranged in series either within the frond1 or in distinct pod-like receptacles called stichidia4 ,fig4 #bh shows the ,polyzonia cuneifolia with its tetraspores arranged in rows in their pod-like stichidia1 together with the areolated conceptacle and spores1 all highly magnified4 ,the antheridia differ in form in the different genera4 ,in the ,dasya they assume that of pods full of cells1 in which the motile particles are generated2 in the ,rytiphla tinctoria the antheridia resemble those of the ,dasya except in being elliptical1 and in the ,rytiphla pinastroides they are cellular bodies1 without any investing membranes1 clothed with delicate hairs4 ,the form of the ,rhodosperms1 as well as the limits of the species1 like those of other ,alg1 are affected by many circumstances known and unknown1 such as the depth1 temperature1 saltness1 and currents in the water4 ,the ,gelidium corneum varies to such an extent that its forms may not only be considered as distinct species1 but even as belonging to different genera4 ,the ,delesseria alata is sometimes destitute of its margin1 and then its midribs alone being left1 it has the form of the ,delesseria angustissima4 ,several species of the florid ,alg1 which in their natural state have the tips of their fronds even and straight1 occasionally produce hooked and clasping tips4 ,illustration3 ,fig4 #bh4 ,polyzonia cuneifolia4 ,brackish water is often a cause of change4 ,the ,irish moss1 ,chondrus crispus1 when exposed to the fresh water of an estuary acquires great breadth and thickness1 while at low water mark it is thin and has narrow forked branches1 and there are many intermediate forms4 ,the fruit rarely varies with these changes2 its disposition and intimate structure1 as well as that of the frond1 are the points of prime importance for the determination of genera and species in the ,alg4 ,the ,,melanosperme1 or ,melanosperms1 are olive-green ,alg1 sometimes inclining to brown4 ,they have fewer species than the ,rhodosperms1 but the individuals exceed in abundance and in magnitude all the other ,alg4 ,these large ,melanospermous ,alg1 which form marine forests in both hemispheres1 are excessively strong and tough on the exterior but of a looser texture within1 so that the cells of their tissue are of different sizes and forms1 according to the degree of pressure4 ,the stems and branches are more dense than the leaves4 ,this highest order1 however1 has small and delicate ,alg united to the largest by many intermediate forms4 ,the ,melanosperms are either moncious or dicious1 and bear their olive-green spores in cases1 that is cysts1 variously disposed on the plants4 ,many have two kinds of zoospores differing in nothing but size2 they are produced in different organs2 in some species both are fertile1 in others only one1 and1 in these cases1 the other is therefore supposed to be a fertilizing body1 but however that may be1 there are certainly antherozoids in this group of ,alg1 especially in the order ,fucace4 ,the ,ectocarpe have many representatives on our coasts1 all of which are tufts of articulated threads from one to eighteen inches long1 branched or simple4 ,they are generally soft1 some so flaccid that they cling together1 but sometimes they are firm and stiff4 ,the cysts which are attached to these threads have various forms2 they are spherical1 siliquose 7that is1 like long pods71 or of other shapes1 according to the species2 but whatever form they may assume1 they are filled with a dense endochrome4 ,besides these they have active granules contained in other distinct organs4 ,m4 ,thuret has decided beyond a doubt that the latter are small zoospores1 and it is presumed that the endochrome in the cysts is resolved into zoospores1 but of a different order1 as in the ,ulvas4 ,these two organs are for the most part situated on different individuals2 in ,ectocarpus pusillus 7fig4 #bi b7 they are on the same4 ,the different forms of fruit carpels are represented magnified in fig4 #bi4 ,illustration3 ,fig4 #bi4 ,fruit of ,ectocarpus3--a1 ,e4 sphrosporus2 b1 ,e4 pusillus2 c1 ,e4 fenestratus2 d1 ,e4 fasciculatus4 ,the ,ectocarpe contain little or no gelatine1 whereas the genera of the group ,chordari have soft gelatinous fronds of many forms1 either incrustations1 convex lumps1 or tubers1 like the ,leathesia so common on our coasts2 small plants as the ,mesogloias1 which have soft slippery filiform stems beset with myriads of moniliferous worm-like branches2 or lastly the ,chorda filum1 a simple unbranched slimy cylindrical cord1 varying from a quarter of an inch to the thickness of a pencil1 and from one to twenty or even forty feet in length in deep water4 ,the cord is tubular1 divided into chambers by transverse partitions1 formed of interlaced vertical and horizontal articulated threads4 ,it tapers at each extremity1 and the exterior1 which is brown1 is clothed with pellucid hairs4 ,vertical spores are immersed throughout the whole surface of the cord1 and ,dr4 ,harvey says that1 mixed with these1 there are numerous narrow1 elliptical1 transversely striated cells1 which according to ,m4 ,thuret produce zoospores4 ,each plant rises solitary from its own little disc1 but as the ,chorda filum is a social plant1 vast assemblies of it cover extensive areas of sand and mud1 and form dense thickets in our northern seas4 ,there are bands of it in the ,north ,sea #ae to #bj miles long1 and more than #fjj feet wide2 there is a submarine forest of it in ,skapta ,bay1 ,orkney2 and in passing through the sounds of the western islands1 as between ,kerrera and the mainland1 there are others4 ,the long cords always lean in the direction of the tide1 and must oscillate between two zones of rest1 one at the turn of the flood1 and another at the turn of the ebb4 ,when dried the people use them for fishing lines4 ,in the ,chordaria divaricata both kinds of spore cysts are external1 and give rise to zoospores4 ,in the preceding divisions of the ,melanosperms the fronds consist of articulated threads2 in the succeeding divisions the fronds are inarticulate4 ,the latter comprise four very remarkable groups1 of which the ,dictyote are distinguished by a leathery or membranous frond1 sometimes cylindrical1 but mostly flat1 the surface of which is reticulated and sprinkled with groups or little patches of naked spores or cysts4 ,the endochrome in the cysts is sometimes quadripartite1 or even divided into eight parts4 ,in one of the genera only1 anything like antheridia have been found4 ,the zoospores produced from the quadripartite endochrome are large1 of a dark colour1 and have two lateral cilia1 while the bodies in the filiform much divided antheridia seated variously in the tufted threads are far more minute and pale1 but with similar cilia4 ,this order obtains its maximum of development in the tropical and subtropical regions2 several species are found in the ,mediterranean1 while a few occur on our coasts1 and on those of ,north ,america4#dc ,the genus ,dictyota begins the zonarioid group1 whose structure is very curious4 ,every band 7lacinia7 of the frond terminates in a single cell1 by the constant division of which at the lower side1 the other cells of the frond are formed1 the terminal cell of the frond being thus continually pushed onwards4 ,hence it results that the longitudinal lines of superficial cells converge1 thus affording a ready method of ascertaining the genus in default of fructification4 ,when a new centre of growth is to be made1 that is1 when the frond is to become forked1 the terminal cell divides longitudinally and then each half-cell grows according to its own law4 ,fig4 #cj shows the tip of the frond of the ,dictyota dichotoma magnified2 the cells on its surface are square1 and the interior of each has a spiral structure4 ,illustration3 ,fig4 #cj4 ,dictyota dichotoma3--a1 tip of young frond2 b1 cell showing spiral structure2 c1 threads from marginal cells2 d1 sorus of spores2 e1 f1 terminal cells dividing into new centres of growth4 ,the ,padina ,pavonia1 or ,peacock's-tail laver of our southern coast1 and those of ,north ,america and the ,mediterranean1 is sometimes included in the genus ,zonaria4 ,the species is remarkable for its wedge-shaped fronds1 which are olive green shaded with rust colour1 and1 when in fruit1 they are striped across with dark concentric zones1 which are merely lines of spores immersed in the frond and seen through its transparent superficial membrane4 ,each zone is ornamented with a fringe of orange-coloured hairs4 ,parallel to1 or rather concentric with1 the spores1 is a row of articulated threads1 which bear so strong a resemblance to the antheridia of the ,cutleria that a similarity of function is suspected by ,mr4 ,berkeley4 ,species of ,zonaria1 ,padina1 and ,haliseris1 which is the most highly developed of the ,dictyote1 are most abundant in tropical and low latitudes4 ,the ,cutleria multifida is a small plant not exceeding eight inches in length1 of an olive green varied with rusty tints4 ,the frond is a flat ribless expansion many times variously slit in the upper part4 ,it is beautifully marked by prominent dot-like tufts of fructification scattered over both sides of the frond1 and grows on rocks and shells in from four to fifteen fathoms water4#dd ,the great ,laminari form the principal part of those vast submarine forests which encircle the globe in the arctic and antarctic oceans4 ,none of these gigantic ,alg are to be met with in low latitudes1 but there are several smaller species4 ,the ,laminaria debilis of the ,mediterranean is not more than five inches high1 and we have some ribbon-shaped species also of small size4 ,besides1 many small individuals of the large species grow on our coasts at low water mark or below it2 but the largest individuals are only found at depths suited to their size1 so that the great ,laminaria1 or tangle forests1 extend from low water mark to a depth of fifteen fathoms4 ,the fronds of these ,alg are for the most part leathery and of a fibro-cellular consistence4 ,the ,laminaria bulbosa is the largest of our sea weeds4 ,mr4 ,berkeley says that individuals are sometimes found which are a sufficient load for a man to carry4 ,a flat stem1 often more than a foot long1 rises with a twist from a round hollow bulb a foot in diameter1 throwing out numerous stout fibrous roots below2 the stem is bordered by a thin wavy membrane1 whence these plants are commonly called sea furbelows4 ,at the top of the stalk there is a broad leafy expansion cut into straps or segments1 twelve or more feet long1 and from one to two feet wide4 ,the ,laminaria digitata1 commonly called the great tangle1 oar weed1 or sea girdle1 has a fibrous root1 a stem six or more feet long1 with a wide expansion at its top cut into very long narrow segments4 ,the fronds of some ,laminari are deciduous2 the stem increases in size year by year1 a new frond springing from the apex and replacing the old one1 which at last separates from the point of junction with the new frond1 to which it is attached till the latter has attained its natural form and dimensions4 ,the ,laminaria saccharina1 called the devil's apron on our northern coasts1 is of a greenish olive when young1 brownish when old4 ,it has a fibrous root1 a stem several feet long1 ending in a flat ribless ribbon-like expansion1 always very much longer than the stem1 and terminating in a point4 ,the margin of the frond is even1 but wavy or puckered4 #8,the fruit of these three great ,laminari is imbedded here and there in the surface of the frond1 thickening it and forming cloudy patches4'#de ,it consists of thick club-shaped perpendicular cells in which the endochrome is ultimately divided into four parts4 ,this is certainly the case in the ,laminaria bulbosa1 and also in the ,alaria ,pylaii1 a species of which latter genus1 the ,alaria esculenta of our own coasts1 is a much esteemed ,british dulse4 ,abundance of colossal ,alg are found in the ,north ,pacific1 about the ,kurile and ,aleutian ,islands1 and along the deeply indented and channel-furrowed northwestern coast of ,america4 ,the ,nereocystis ,lutkeana forms dense forests in ,norfolk ,bay1 and all about ,sitka4 ,its stem resembles whipcord1 and is sometimes #cjj feet long4 ,it is exceedingly slender at the top1 where it terminates in an enormous air-bladder six or seven feet long1 and about four feet and a half in diameter at its widest part1 the lower extremity passing into the stem4 ,this huge air-vessel1 which is the usual seat of the sea otter1 is crowned with a tuft of twin leaves mostly rising on five stalks4 ,these leaves1 which are membranous and lanceolate when young1 and from one to two feet long and two inches broad at the centre1 are only marked with a few faint nerves1 but they ultimately split lengthwise1 cover a large space1 and attain a length of twenty-seven or thirty feet1 or even more4 ,the growth of the ,nereocystis must be enormously rapid1 since it is an annual1 and must therefore develop its whole gigantic proportions in one summer4#df ,boats cannot pass through the floating masses of this plant1 whose stem is used for fishing lines1 and whose cylindrical air-vessel serves as a siphon for pumping water out of boats4 ,the ,thalassiophyllum ,clathrus is also an inhabitant of the ,russian coast of ,north ,america4 ,it is about six feet high1 very bushy and branched1 each branch bearing a broad leaf at its extremity which unfolds spirally1 and by this gradual development produces the stem with its branches and lateral divisions4 ,a spiral border wound round the stem indicates the growth of the frond1 which presents a large convex bent lamina without nerves1 or a leaf of which one-half is wanting4 ,numerous long narrow perforations1 arranged in a radiating form1 give it the appearance of a cut fan4 ,the ,macrocystis pyrifera and the ,laminaria radiata are the most remarkable of marine plants1 for their gigantic size and the extent of their range4 ,they are met with on the antarctic coasts two degrees nearer the pole than any other vegetable1 except the ,diatomace4 ,the stem of the ,macrocystis is slender1 smooth1 round1 and slimy1 rising from a fibrous root1 like other ,laminari1 and bearing at its tip a lanceolate or oblong lanceolate frond4 ,this frond divides at the base2 the fissures extend upwards so as to form two petioles1 each of which swells into an oblong or pyriform air-vessel4 ,another fissure is formed in a similar way a little above1 and so on1 till a single frond may at the same time have eight or ten fissures1 each of which will ultimately gain the common apex4 ,the margins of the fissures are at first perfectly smooth1 but they soon become ciliated like the outer edge4 ,the continuity with the fibrous base is at last broken1 and the divisions of the leaves going on indefinitely1 the whole reaches the length of some hundred feet1 forming enormous floating masses which are wafted by the waves hundreds of miles from their origin4 ,fructification only takes place in young plants2 consequently in such as are still attached to their native rocks4 ,even in that youthful state1 ,mr4 ,darwin mentions that such is the buoyancy of this powerful weed1 that there is scarcely a loose block of stone on the coasts of ,cape ,horn that is not buoyed up by it4#dg ,the ,macrocystis is native on the shores of the ,atlantic1 from ,cape ,horn to #dc ,s4 latitude2 but on the ,pacific coast1 according to ,dr4 ,hooker1 it extends to the river ,san ,francisco in ,california1 and perhaps to ,kamschatka4 ,the plant is reproduced by pyriform cells1 full of endochrome1 in nearly parallel rows imbedded in the fronds4 ,the rocky coasts of the ,falkland ,islands are covered with a vast growth of the gigantic ,macrocystis mixed with forests of the arborescent ,lessonia1 which forms large dichotomous trees with a stem from eight to ten feet high and a foot in diameter4 ,the leaves are two or three feet long1 drooping from the forked branches like weeping willows4 ,in the ,lessonia nigrescens the quadripartite endochrome1 ultimately resolved into spores1 is contained in thickened club-shaped cells springing vertically between the surfaces of the frond4 ,a transverse section of the stem of many of the larger sea weeds presents zones1 formed period by period1 corresponding with the development of the lamin1 roots1 and branches4 ,the stem of the ,lessonia bears a strong analogy to that of dicotyledons in having rings of growth1 though there is a great difference4 ,as increase in ,lessonia takes place by the constant division of a flat leaf1 the basilar portion of which becomes the petiole and ultimately swells into a branch1 the stems have always a more or less elliptical form1 and their section exhibits an elliptical core4 ,this form of the core is not however peculiar1 but exists in other ,alg4 ,it is probable that the ,lessoni1 although attaining so large a size1 are really of rapid growth4#dh ,the ,ecklonia is essentially a southern genus1 though one species ascends to ,spain and the ,canaries4 ,the frond is pinnatifid1 the segments arising from the evolution of marginal teeth4 ,the stem of the ,ecklonia buccinalis1 which is three or four inches thick and strongly inflated above1 exhibits rings of growth with an orbicular central pith4 ,the group of the ,fucace exhibits the highest structure of all the olive-green ,alg1 and forms a large portion of the sea weeds on our coasts1 but they abound more in individuals than in the number of genera and species4 ,a few have cylindrical stems and branches swelling out at intervals into large oblong inflated air-vessels1 which gives them buoyancy in the water4 ,the rest have a flat1 ribbon-like stem1 and for the most part dichotomous branches with a decided midrib1 but no air-vessels1 because they chiefly grow at half-tide level1 and are exposed twice every twenty-four hours4 ,the most common of our fuci1 the ,fucus vesiculosus1 or bladder-wrack1 has a midrib with air-vessels1 generally in pairs on each side of it1 formed by the inflation of the frond2 these vessels1 however1 are frequently wanting1 for it is the most variable in form and most widely spread of the ,fuci4 ,the fructification of this group is contained in large clavate receptacles or expansions of an orange or greenish yellow colour situated at the extremities or borders of the branches4 ,,mm4 ,thuret and ,decaisne discovered1 by microscopic investigation1 that the fuci have a truly sexual fructification1 consisting of male and female cells inclosed in these receptacles4 ,in the common ,fucus vesiculosus it was found that the male and female cells are either in different individuals1 or in different conceptacles on the same individual2 whilst in the ,fucus platycarpus1 both the male and female cells were found to be contained in a globular cavity enclosed in the flattened receptacles which grow at the extremities of the branches4 ,the cavity is lined with jointed hair-like filaments formed of cells1 some of which are so long as to project through a pore on the surface of the receptacle in a spreading brush 7see fig4 #ca1 where the whole is highly magnified74 ,towards maturity1 the cells of some of these filaments assume an ovoid form2 the white viscous1 granular matter in their interior acquires an orange hue1 and is divided into a multitude of hyaline particles1 each having an orange spot and two cilia of unequal lengths1 which enable these spermatozoids to swim with great vivacity in the water as soon as they are set free by the rupture of the cell in which they are inclosed4 ,besides these1 dark olive-green female cells1 of a large pyriform shape1 are fixed to the walls of the same cavity by very short stems2 their contents spontaneously divide into eight spore cells1 never more2 each contains a colourless viscous liquid1 which is mixed with protein and yellow-green matter1 and is inclosed in a double coat4 #8,the coats are united at the base1 and when the spores are ready for dispersion1 the inner coat bursts through the apex of the outer one1 dragging with it a portion of the latter in the form of a little peduncle4 ,the immediate covering of the spores at length bursts1 and they are set free4'#di ,in ,fucus serratus1 vesiculatus1 and nodosus1 swarms of spermatozoids are produced1 but ,m4 ,thuret has proved by experiment that they never come to anything of themselves1 and the unfertilized spores perish4 ,illustration3 ,fig4 #ca4 ,vertical section of receptacle of ,fucus platycarpus4 ,when a fertilized spore begins to grow1 it assumes a pear shape1 and sends out from its narrow end filaments or footstalks containing solid yellow grains at their extremities1 where a hook or claw is formed by which it fixes itself to rocks or stones4 ,the spore then divides itself into four equal cells of a brown colour1 and by the continued subdivision of these into four1 the plant increases in size1 and assumes a form corresponding to the genus and species of the spore4 ,dr4 ,carpenter mentions that in the ,fucace there is also a multiplication by zoospores4 ,these bodies are produced within certain of the cells that form the superficial layer of the frond1 and swim about freely for a time in the water after their emission1 until they fix themselves and begin to grow2 but these are merely gemm4 ,all the ,fucace are tough leathery plants4 ,this is even characteristic of the genus ,cystoseira1 various species of which may be seen on our coasts at low water mark1 or in the tide pools4 ,they are little shrub-like and somewhat thorny plants1 not more than three feet high1 with a cylindrical stem and many branches1 near the extremities of which there are inflated air-vessels1 sometimes two or three together2 in some species they are lower down4 ,long spiny conceptacles are situated at the tips of the branches1 but the endochrome does not divide in the germ cells as it does in the ,fuci1 so that each cell produces but one spore4 #8,throughout all latitudes the two divisions of ,fucace--,fucoide and ,cystoseire1 form the prevailing marine vegetation to which the name of sea-weed is commonly applied1 and the different genera so arrange themselves as to present1 with a few exceptions1 a most harmonious assemblage4' #8,none of these approach the tropics2 the ,fucoide abound towards the poles1 and there attain their greatest bulk1 diminishing rapidly towards the equator1 and ceasing some degrees from the line itself2 while the immense genus ,sargassum finds its maximum in lower latitudes and under the equator itself4 ,in the opposite cold and frigid zones the waters are inhabited by certain genera of ,fucoide1 which are in a great measure representatives of one another4'#ej ,the huge ,d',urvilla and the ,sarcophycus in the ,antarctic ,ocean represent the ,himanthalia and ,fucus proper in the north1 and the ,cystoseire and ,halidrys of the northern seas are represented by the ,blossevillea and ,scytothalia in the southern4 ,the frond of the ,himanthalia lorea is a knob about an inch high1 somewhat like a small mushroom2 by degrees the top of the knob sinks in1 and the frond becomes cup-shaped4 ,in the second year of growth it throws out from its centre strap-shaped receptacles from two to three feet long and the sixth of an inch wide2 they are slimy1 forked1 and entirely covered with fruit4 ,the true frond sometimes becomes hollow and swells into a bladder4 ,this singular plant1 which grows on our coasts1 extends from ,norway to ,spain4 ,in the ,d',urvilla1 its representative in the southern hemisphere1 the frond and receptacle are united1 for the plant1 which is of large dimensions1 has dichotomous fronds ten feet long1 and an inch or more in breadth4 ,their surface is ornamented with large cavities like a honeycomb1 and the fruit imbedded within them consists of antheridia and club-shaped germ cells with four spores in each4 ,these plants form a large portion of the wrack and also of the living ,alg which surround the ,falkland ,islands and ,cape ,horn2 and they extend to ,western ,chili1 where the poorer class make a sweet mucilaginous soup of them4 ,the ,sarcophycus potatorum1 the only species of its order1 is nearly allied to the ,d',urvilla by the structure of its fruit1 and is so named from pieces of its frond being used to carry water4 ,many other olive-green ,alg are peculiar to the southern hemisphere--among them the ,hormoseira1 in which the frond1 at first even and filiform1 becomes inflated so as to produce moniliform chains of vesicles1 parts of which are at length rough with the apertures of the conceptacles2 this plant has bladder-like air-vessels formed by swollen parts of the frond1 like many of our ,fucace4 ,those genera which have distinct organs containing air1 as the ,sargassum1 of which there are numerous species1 are either of low latitudes or tropical1 but are sometimes drifted by currents to the extra-tropical shores4 ,the ,sargassum vulgare1 however1 grows on the rocks in the ,mediterranean4 ,the whole plant is of a translucent reddish brown2 the stem has alternate branches1 bearing lanceolate serrated leaves with a midrib1 and generally dotted with dark pores4 ,the air-vessels are small translucent round balls about the size of a currant1 borne on flat stalks in the axils of the branches1 and the spores are in conceptacles borne on the branchlets just above the air-vessel4 ,in one variety of this most variable plant1 the ,uva di mare1 the main stem ends in a loose bunch of these little air-balls4 ,the ,sargassum bacciferum is often found in the ,mediterranean1 but only as a wanderer drifted in from the ,atlantic1 where masses of it1 like floating meadows1 occupy an area west of the ,azores equal in extent to that of ,france1 which has never changed its position since the time of ,columbus1 on account of the surrounding currents4 ,fields of it cover the seas near the ,bahama ,islands1 and another permanent area of ,sargassum of great extent occurs in the ,south ,pacific4 ,the ,sargassum bacciferum is of a pale translucent olive colour1 having branched stems1 with lanceolate1 midribbed1 and serrated leaves1 destitute of pores1 and little stalked air-balls in the axils of the branches4 ,the same individual continually produces new branches and leaves1 and thus multiplies its species1 but it never produces fruit2 consequently its habits exactly resemble those of the ,macrocystis1 and as that plant becomes detached and floats after fructification1 it is supposed that the ,sargassum bacciferum may grow on rocks at the bottom of the ,atlantic1 between the parallels of forty degrees north and south of the equator1 and when detached after fructification that it is uniformly drifted to particular spots which never vary4 #8,multiplication is so rapid in the floating beds of the ,sargassum and ,macrocystis1 as to render fruit needless2 and even the common ,fucus vesiculosus occurs in the ,mediterranean under a peculiar form consisting entirely of specimens derived from sea borne weed carried in by the current which sets in towards the ,mediterranean from the ,atlantic4'#ea ,kelp1 the ashes of sea weeds1 is the commercial source of iodine4 ,alg growing in deep water contain most of that substance2 consequently the kelp made at ,guernsey1 consisting chiefly of the ashes of ,laminaria digitata1 is richer in iodine than that made elsewhere4 ,marine vegetation varies both horizontally and vertically with the depth1 and it seems to be a general law throughout the ocean1 that the light of the sun and vegetation cease together4 ,it consequently depends upon the power of the sun1 and the transparency of the water2 so that different kinds of sea weeds affect different depths1 where the weight of the water1 and the quantity of light and heat1 suit them best4 ,one great marine zone lies between high and low water marks1 and varies in species with the nature of the coasts1 but exhibits similar phnomena throughout the northern hemisphere4 ,in the ,british seas this zone does not extend deeper than thirty fathoms1 but it is divided into two distinct provinces1 one to the south and another to the north4 ,the former includes the southern and eastern coasts of ,england1 the southern and western coasts of ,ireland1 and both the ,channels2 while the northern flora is confined to the ,scottish seas1 and the adjacent coasts of ,england and ,ireland4 ,the second ,british zone begins at low water mark1 and extends below it to a depth of from seven to fifteen fathoms4 ,it contains the great tangle sea weeds or marine forests mixed with fuci1 and is the abode of a host of animals4 ,a coral-like sea weed is the last plant of this zone and the lowest in these seas1 where it does not extend below the depth of sixty fathoms2 but in the ,mediterranean it is found at seventy or eighty fathoms1 and is the lowest plant in that sea4 ,the same law prevails in the ,bay of ,biscay1 where one set of sea weeds is never found lower than twenty feet below the surface1 another only in the zone between five and thirty feet1 another between fifteen and thirty-five feet4 ,in these two last zones they are most numerous2 at a greater depth the kinds continue to vary1 but their numbers decrease4 ,the distribution in the gean sea was found by ,professor ,e4 ,forbes to be perfectly similar1 only that the vegetation is different and extends to a greater depth in the ,mediterranean than in more northern seas4 ,he also observed that sea weeds growing near the surface are more limited in their distribution than those that grow lower down1 and that with regard to vegetation1 depth corresponds with latitude1 as height does on land4 ,thus the flora at great depths in warm seas is represented by kindred forms in higher latitudes4 ,there is every reason to believe that the same laws of distribution prevail not only throughout the ocean1 but in every sea4 ,,section ,,iii4 ,,fungi4 ,,the ,fungi are enormously numerous4 ,no less than #b1jjj of the highest and most conspicuous of these plants have been figured2 many more have been described2 multitudes of those inhabiting the torrid zone are unknown2 and the microscopic and parasitic tribes are innumerable4 ,though with a few exceptions entirely formed of cellular tissue1 the fungi resemble animals in respiration and chemical constitution4 ,they contain more azote than any other of the ,cryptogamia1 and obtain it chiefly from their food1 which consists of animal and vegetable substances alive1 dead1 or decomposed4 ,they inhale oxygen1 and exhale carbonic acid gas1 so that they never form true chlorophyll4 ,no plants are more dependent on heat and moisture2 many perform all the functions of life and reproduction independently of light1 preferring dark and shady places to sunshine4 ,the ,fungi form two principal groups1 distinguished by their mode of fructification4 ,in the higher group1 ,sporiferi1 the fungus produces naked spores either single or compound1 by means of which it may be multiplied4 ,in the lower group1 ,sporidiiferi1 the fructification consists of sporidia1 enclosed in a distinct sac4 ,the ,sporiferi include the following orders1 ,hymenomycetes1 ,gasteromycetes1 ,coniomycetes1 and ,hyphomycetes4 ,the ,sporidiiferi include the ,ascomycetes and the ,physomycetes4 ,these various groups we may now proceed to examine4 ,the most important family of ,fungi is1 without question1 that of the ,,hymenomycetes1 the species of which far excel all others in their richness of colouring1 and beauty of form4 ,in this group the hymenium is free and mostly exposed4 ,it comprises six orders1 of which the ,agaricini hold the first place4 ,the genus ,agaricus alone comprises #a1jjj distinct species1 which assume as many different forms and colours1 with only slight modifications of substance1 and it surpasses in number of species all the other generic groups known4 ,the ,agaricus campestris1 or common mushroom1 is a type of that vast group2 it consists of two distinct parts1 the nutritive and reproductive4 ,the nutritive part is the mycelium or mushroom spawn of gardeners1 which resembles a mass of white spider's threads mixed in inextricable confusion1 and carries on for a time all the functions of the plant4 ,mycelia may exist for years without bearing the reproductive part1 but fruit never can be produced without spawn4 ,the mushroom itself1 which springs from the spawn1 is the fruit-bearing part1 in which the spores are formed and ripened4 ,it is distinguished by a kind of hat or bonnet called the pileus1 supported by a stem4 ,the pileus is lined by a number of gill-shaped plates or lamell radiating from a common centre2 they are the reproductive organs in which the spores are produced by free cell formation1 a process always preceded by a concentration of the matter within the parent cell1 which is then divided into as many nuclei as there are to be spores4 ,in the higher fungi1 the number of spores thus formed is definite2 in the ,agarics they are in groups of four placed at the extremity of a stem1 springing from the summits of these reproductive gills4 ,most of the ,agarics rise from the ground without any cover2 the pileus or cap may show every variety from a smooth polished surface to hairs or shaggy scales1 but some of the more highly organized have a general wrapper or volva1 which encloses the whole plant1 and bursting at last1 it leaves some traces behind4 ,in others1 the pileus is at first clothed with fibres1 which vanish or leave traces on its margin forming a veil or curtain4 ,some have a membrane attached to the stem1 either connected with the volva1 or spread under the gills when young1 and1 when more or less persistent1 it is called a ring4 ,the spawn1 which is the earliest product of the spore1 has a great variety of forms4 ,sometimes it is filamentous1 sometimes tubular1 creeping extensively1 or concentrated in a felted mass1 sparingly developed1 or produced in abundance4 ,besides1 it is developed in a great variety of situations often difficult to detect4 ,the fructification is alone evident1 under innumerable forms1 which are as rapid in their growth as they are for the most part ephemeral in their duration4 ,some species have been known to acquire several square inches of surface in a single night2 the plant1 however1 is often far advanced before it appears above ground4 ,some ,agarics grow most readily after thunder storms and abundant rains2 certain species are always single2 others grow in dense aggregations2 while in several species there is a tendency to assume a circular arrangement1 and that not merely when the spawn is perennial1 but when the whole existence of the fungus is confined to a few days or weeks4 ,a mass of spawn is not always produced by a single spore1 but by a collection of spores1 from whence it spreads in every direction1 and forms a common belt4 ,in the ,agaricus arvensis1 ,marasmius ,oreades1 c41 it spreads in a circle and bears fruit2 and1 as it continues to spread1 the same process takes place at each circumference4 ,in this way are formed the ,fairy ,rings so frequently seen in pasture lands4 ,the fairy rings are sometimes of very ancient date1 and attain enormous dimensions1 so as to be distinctly visible on the side of a hill from a considerable distance4 ,it is believed that they originate from a single fungus1 whose growth renders the soil immediately beneath unfit for its reproduction4 ,the spawn1 however1 spreads all around1 and in the second year produces a crop1 whose spawn spreads outwards again1 for the soil behind forbids its return in the opposite direction4 ,thus the circle is continually increased1 and extends indefinitely till some foreign cause destroys it4 ,the manure arising from the dead fungi of the former years makes the grass vigorous around1 so as to render the circle visible even when there is no external appearance of the fungus2 and the contrast is often the stronger from that immediately behind it being killed by the old spawn4 ,this mode of growth is far more common than it is supposed to be4 ,the depth to which spawn penetrates and the rapidity of its growth even in the hardest timber if exposed to damp is quite astonishing4 ,instances occur in which the spawn of dry rot not only enters wood1 but penetrates solid structures of brick4 ,it overcomes an immense resistance4 ,the genera of the ,agaricini differ in substance2 some are almost ligneous1 others leathery or tough1 occasionally they are delicate and deliquescent1 and although most of them are entirely formed of cellular tissue1 the ,lactarii and ,russul form remarkable exceptions in having laticiferous vessels mixed with their cellular structure4 ,these vessels exist in all parts of the plants1 especially in the gills1 where they give out the liquid on the slightest touch4 ,in the ,russul it is watery2 but in the ,lactarii1 in which it is either mild or acrid1 according to the species1 it is also of different colours1 which sometimes change their tint upon exposure to the air1 probably from ozone4 ,in all fungi there is a small amount of poisonous matter1 and the quantity in any given species is extremely uncertain1 so that the same fungus which may be eaten with safety in one country1 is deleterious in another4 ,in the dark coal mines at ,dresden1 luminous ,fungi cover the roof and pillars with the most dazzling phosphorescent light1 which increases with the temperature of the mine4 ,agaricus ,gardneri1 a species parasitic on the ,pintado palm in ,brazil1 is highly luminous2 and the ,agaricus olearius in the south of ,france also possesses that rare quality4 ,the gills under the pileus shine as brightly as a glow-worm1 in the dark crevices of the olive stems in ,november and ,december4 ,m4 ,tulasne found that the light was extinguished in vacuo or non-respirable gases1 whence he concludes that it is due to a slow combustion without heat1 arising from a chemical combination of the oxygen of the atmosphere1 inhaled by the fungus1 with a substance peculiar to the plant4 ,in a few ,agarics the cells are so connected by veins or lateral branches1 that they assume the character of pores1 as in the ,chantarelle1 a sweet-scented lemon-coloured fungus1 whose gills pass into mere veins1 and its inferior fruit-bearing surface is all but even and uniform1 so that it forms a connection between the ,agarics and the ,polyporei1 a most extensive order of the higher fungi1 essentially distinguished by having a multitude of pores in the smooth under-surface of the pileus1 instead of gills4 ,the pores are generally small2 in some species they are hexagonal1 and so large that they look like a honeycomb4 ,in all1 they are the mouths of cellular tubes1 packed closely together side by side1 or more closely connected1 sometimes easily separated1 sometimes inseparable4 ,they constitute the fructiferous surface or hymenium of the fungus1 and contain the spores4 ,this structure gives the pileus a thick heavy appearance1 and a vast variety of characters2 besides1 the substance itself varies in density and colour4 ,the stem also may be long or short1 sometimes wanting altogether1 when the pileus or cap is attached to the surface on which the fungus is growing4 ,the growth of individual fungi1 whether ,polyporei or ,agarics1 is centrifugal1 that is1 they spread from the centre of the pileus1 as in the ,polyporus fraxineus1 which involves every stick and blade of grass it meets with as it increases in diameter1 and continues to increase for years1 till it is occasionally a yard across4 ,the fructiferous surface in the higher fungi is essentially turned away from the light1 yet1 although in many of the lower ,agarics it is uppermost and exposed1 such is the tendency to produce the fructification on the lower side1 especially in the ,polyporei1 that if the position of the plant be reversed the hymenium or fructiferous surface is gradually obliterated and a new one is formed on the other side4 ,the ,polyporei abound in the tropical forests1 but species are found in all latitudes4 ,the higher fungi are more or less plentiful in forests everywhere1 and every genus of trees seems to have one or more species of fungus peculiar to itself4 ,the ,boleti1 a genus of the ,polyporei1 which are thick fleshy fungi of various forms1 and for the most part brilliantly coloured1 grow under trees in the temperate zones1 sometimes in conspicuous circles4 ,when a slice of the ,boletus luridus1 cyanescens1 or other species is exposed to the air1 the white fleshy part acquires a blue tint in consequence of the action of ozone upon the acetate of aniline1 which was ascertained by ,dr4 ,phipson to be a constituent of these fungi4 ,according to ,m4 ,dutrochet more heat is evolved by the ,boletus neus than by any other vegetable except the ,arum4 ,the ,polyporei destroy decaying trees and timber1 and the ,merulius lacrymans or common house fungus1 attacks and induces the decay of timber previously sound4 ,the cap is large1 fleshy1 spongy and moist1 but delicate and velvety on the under-side1 with wide porous dentate folds4 ,the plant is yellow with a white woolly margin4 ,it grows in a circle1 and its mycelium attracts moisture from the atmosphere1 which falls down in drops from the pileus4 ,the decay of wood induced by the attacks of this mischievous fungus1 is what is called dry rot4 ,the four principal sub-orders of the ,hymenomycetes1 or highest fungi1 have a cap or pileus1 and an inferior fructiferous surface characterized by gills1 pores1 or tubercles1 and are connected by intermediate species2 but the other two sub-orders are quite different4 ,the ,clavariei are club-shaped1 upright1 branching fungi1 with the fructification surrounding the uppermost extremity of some of the stems4 ,the finest species grow in the ,swiss forests where they form an article of food2 some are edible in ,britain1 but of smaller size4 ,the ,tremellini consists of plants forming a gelatinous mass of a bright orange1 purple1 or dark brown colour1 which may be seen on rotten sticks in hedges1 and in enormous masses resembling the convolutions of an animal's brain on the stumps of dead trees1 or at the base of living ones4 ,they are mostly plants of temperate climates1 but the ,exidia ,auricula ,jud1 or ,jew's ear1 is universal4 ,all fungi have a mycelium1 but in this order it is not apparent4 ,the structure of the fruit1 as determined by the microscopic observations of ,mr4 ,berkeley and of ,m4 ,tulasne1 is unusual4 ,the fructiferous part is very extensive1 being uppermost and spread over the surface of the gelatinous mass1 so as to follow all its inequalities4 ,threads rise from this fructiferous surface bearing on their extremities globular cells exhibiting a concentration of coloured matter generally divided into four lobes1 and from the upper surface of these globular bodies1 a number of flexuous threads spring1 carrying on their tips cymbiform spores4#eb ,in the preceding family 7,hymenomycetes7 the fruit-bearing surface has free access to the air1 but in the group of the ,,gasteromycetes1 which consists of five or six sub-orders1 it has neither access to air or light till the fruit is ripe1 for the fructification is enclosed in a rind of one or two coats1 and springs without a stem from a gelatinous thready1 or cellular mycelium4 ,the most important group1 ,trichogastres1 includes the puff-balls1 which grow on the ground4 ,of these the ,lycoperdon1 found everywhere on pasture grounds and meadows1 is a familiar instance4 ,when young it has a milk-white coat filled with closely packed cells1 some of which bear naked spores set upon spicules4 ,when mature1 the whole of the interior vanishes1 leaving nothing but a mass of threads and fruit2 the coat becomes brown1 bursts open at the top1 and gives vent to a cloud of microscopic spores like the finest dust4 ,in general the ball is sessile1 or it has merely the rudiment of a stem4 ,the ,lycoperdon giganteum1 an exceedingly large species1 is a native of a warm climate4 ,the tops of some of the branched threads of its hymenium swell into pear-shaped cells surmounted by short spicules ending in spores2 when young it is edible1 when dry it is used for tinder and as a styptic1 and when ignited its fumes possess a property similar to that of chloroform4 ,the ,batarrea forms a contrast to the common puff-balls1 being mounted on a stem sometimes a foot and a half high4 ,it has several coats enclosing a thick gelatinous substance in which the threads carrying the spores are distinctly spiral and closely twisted4 ,the sub-order ,hypogi is subterranean1 as the name implies4 ,the exterior coat of these fungi is inseparable from the internal matter1 which is for the most part fleshy4 ,in some species it is dry1 in others it abounds in milky juice2 but in all the fruit is formed in hollows excavated in the interior mass4 ,in some species these cavities are traversed by threads1 and in many species the spores accumulate in such multitudes within the cavities1 as to make it certain that the spicules1 on which the spores are borne1 produce successive crops4 ,they are set free by the rupture of the rind4 ,a species of the genus ,melanogaster1 abundant in the south of ,england1 is edible and sold as the red truffle of ,bath2 but it is far inferior to the real truffle4 ,the order ,phalloidei has a club-shaped or globose head1 composed in the interior of large cells mixed with fruit-bearing cavities4 ,this head has a coat consisting of a jelly inclosed between two heterogeneous strata4 ,the whole interior of the fungus deliquesces1 changes to a mucilage1 and drips out of the exterior coat in drops dark with microscopic spores4 ,the colour of these fungi is often beautiful1 but their smell is most loathsome1 tainting the air to a considerable distance2 yet the gelatinous volva of more than one species--an ,ileodictyon--is eaten by the ,new ,zealanders under the name of thunder dirt1 and ,phallus ,mokusin is an article of food in ,china4 ,certain species of these fungi have a rudimentary stem in their early stages1 but it becomes full of deep pits or cavities and suddenly acquires an enormous development when the plant approaches maturity4 ,the cavities are at first strongly compressed1 but as the stem increases1 they acquire a rounder form1 till at length their vertical tendency is so strong that the coat or volva of the fungus is ruptured1 which could only be effected by a very strong force4 ,moreover1 the stem is fixed to the base by so small a point that the plant could not remain erect were it not for the tubes of the volva which contract on the stem and act as a sustaining force4 ,thus these very revolting fragile plants afford a very striking instance of mechanical power exerted by vegetable matter4 ,the ,myxogastres are an anomalous group of fungi which often appear as black or coloured spots on dead leaves and twigs4 ,sometimes their mycelium or spawn is large and conspicuous1 as that of the ,reticularia maxima1 which overruns cucumber beds1 choking up the breathing pores1 and killing the plants4 ,species of these fungi are found upon mineral and vegetable substances dead and alive1 and the same species grows upon plants of very different affinities1 so that they depend upon the atmosphere for their nourishment1 and not on their matrix4 ,like the puff-balls they end their lives in myriads of microscopic dust spores1 but they begin it as a gelatinous mass1 sometimes sparkling as a gem1 brilliant with the metallic tints of gold1 silver1 steel1 or copper4 ,the gelatinous or creamy mucilage of which these fungi consist1 forms a mycelium which is either diffuse1 or creeps over the matrix on which it grows in anastomosing filaments like a network1 or it is arranged without any definite order4 ,this spawn gives rise to many bodies having an envelope of one or more concentric membranes1 technically called a peridium1 enclosing a gelatinous fertile substance which1 when mature1 becomes a mass of scales or threads mixed with spores2 the spores are mostly attached to short threads singly or in groups1 sometimes surrounded by a firm coat or cyst4 ,these bodies are either sessile on the mycelium or stalked1 and are either free or confluent4 ,in their soft state the tissues are so delicate that they exhibit no structure1 but just as they are passing from the puffy to the dry dusty state there are indications of it4 ,it would be tedious to describe the variety of forms assumed by the fruit-bearing bodies in the different genera of these fungi1 or the manner in which they are ruptured to give egress to the spores1 which differ in colour according to the species1 though they are for the most part red4 ,the forms of the chaffy scales and threads are equally diversified3 in the species of ,trichia1 the threads contain one or more spiral filaments1 a form peculiar to the vegetable kingdom4 ,botanists are now generally of opinion that the ,myxogastres are vegetables1 although the singular ,amba-like motions some of them exhibit1 and the nature of the motile bodies they produce1 seemed to assign them a place in the animal kingdom2 indeed1 even now little is known of the reproduction and final life-history of these singular fungi4 ,motions precisely similar to those of the ,amb1 the lowest class of animal existences1 were observed by ,,mm4 ,hoffmann and ,tulasne1 and more especially by ,m4 de ,bary1#ec in the thalium septicum4 ,it is a yellow pulpy mass1 produced upon a spawn or mycelium consisting of semi-fluid gelatinous anastomosing filaments1 often widely spread through the moist tan in hothouses4 ,m4 de ,bary describes the filaments of the mycelium as full of a multitude of small colourless corpuscles mixed with large yellow ones2 moreover the branches of this mucous network are described as continually changing their form1 in a manner closely resembling the pseudopodia of the animal ,amba4 ,they push out new branches1 others are withdrawn1 and the whole mycelium frequently advances with a creeping motion of translation4 ,the yellow pulpy mass produced by the mycelium is entirely composed of similarly constituted soft filaments about the thickness of a bristle closely interlaced4 ,they anastomose in all directions1 in long or short meshes1 and their upper free extremities form groups of projections which bristle the exterior surface of the pulpy mass4 ,when that mass is about to form spores1 all the asperities on its surface are withdrawn and replaced by a bright yellow network of irregularly interlaced filaments1 which constitutes an envelope to the interior spore-forming part1 consisting of a white central liquid or plasma containing an innumerable multitude of colourless granules4 ,both of these parts are formed at the expense of the filaments which are decomposed1 the yellow granules are absorbed in the envelope1 while the colourless granules retire with the gelatinous matter towards the centre to constitute the plasma1 which is the fruit-producing part4 ,transparent globular cells containing nuclei are generated simultaneously in every point of the plasma1 round each of which a portion of the granular matter is consolidated2 it takes a dark purple colour and constitutes a spore1 myriads of which1 fine as dust1 are thus generated4 ,the whole of the plasma is consumed in the spores1 except a very small quantity1 which forms the threads found mixed with the spore dust4 ,according to ,m4 de ,bary the complete development of the thalium1 from the instant it appears above the tan in a hothouse of high temperature to the maturity of the spores1 is accomplished in about fifteen hours4 ,the rapidity of growth of this fungus is therefore astonishing4 ,mr4 ,berkeley mentions that a mass of it two feet long1 formed of many confluent individuals1 was formed upon a piece of iron that had been red-hot twelve hours before--a proof among many others of the meteoric nature of these fungi1 the atmosphere affording them a sufficient supply of food4 ,the motions of the plastic matter contained within the dust-like spores of the thalium septicum exhibit amban motions of the same character as its mycelium4 ,for when ,m4 de ,bary placed ripe spores of that fungus in water1 their skin burst open and the plastic granular matter was set free under the form of a coherent globular mass without any exterior membrane4 ,these globular corpuscles exhibited amba-like changes of form2 processes were pushed out1 and then drawn in1 till at last they assumed an elongated cylindrical shape round at one end1 prolonged at the anterior end into a long cilium with which they turned convulsively round their axis4 ,at the same time vacuoles were frequently seen to expand and contract alternately in the round extremity4 ,ultimately these bodies lost their middle1 and at last were divided into two equal parts1 each of which went through the same changes as the primary globule1 and at length assumed the ciliated active form4 ,besides these active bodies1 there were others which never acquired cilia4 ,the motile bodies were also discovered in other species of these fungi by ,m4 ,hoffmann2 there can be no doubt that they are either zoospores1 or of the same nature as the eel-shaped motile bodies in some of the ,alg2 possibly the bodies which never acquire cilia may be germ cells4 ,there is still much obscurity with regard to the ,myxogastres1 inasmuch as the origin of their mycelium is unknown1 whilst in all other fungi mycelium or spawn are produced by the germination of the spores4 ,the spiral vessels found in the threads of the ,trichia prove that the members of this singular family are truly vegetables4 ,professor ,fries places the geographical maximum or centre in the temperate zone1 but different species are found from ,new ,zealand to high northern latitudes4 ,the ,nidulariacei constitute a beautiful order of this family of fungi4 ,the plants are exactly like a bird's nest with eggs1 sometimes with a stem1 sometimes without4 ,at first the nest or cup has a cover consisting of several coats1 which either burst open with a stellate or irregular figure1 or by the separation of a little lid2 then the hollow of the cup or nest is exposed1 and at the bottom are seen one or more sporangia1 that is spore cases1 often immersed in jelly and either free or fixed to the nest by an elastic string4 ,the spore-coats at first contain a compact circular mass1 but a cavity is afterwards formed in the centre1 and the cells which terminate in the walls of the cavity bear spores on their tips4 ,when ripe the spore cases are ejected by elastic power4 ,the force with which the sporangium of the species of ,sphrobolus is ejected1 far exceeds in proportion the force with which a shell is projected from a large mortar2 this fungus sometimes grows in damp hothouses4#ed ,many ,nidulari are widely spread1 but they thrive best in warm climates4 ,the intimate structure and fructification of the higher fungi are for the most part microscopic but an innumerable mass of the lower fungi are themselves invisible to the naked eye1 living upon all kinds of vegetable and animal substances1 dead1 alive1 fresh or putrid4 ,they vegetate upon decayed linen1 flannel1 leather1 and even on metallic and poisonous solutions4 ,they yield myriads of minute spores wafted by every breeze4 ,they float in the air we breathe1 seeking a nidus in anything that will supply them with suitable food4 ,there is scarcely a spot on the earth where these minute spores may not exist1 and being insoluble1 they wait where they fall for the growth or decay of the plant or animal which suits them4 ,as parasites they are most destructive1 producing disintegration1 disease1 and even death1 both in vegetables and animals4 ,it is the mycelium or spawn which does the mischief1 by supplying the fungus with food at the expense of the victim4 ,the spores of the ,botrytis ,bassiana find a nidus in the breathing pores which open into the trachea of the silkworm2 they develop their mycelium in the air-tubes1 which are soon filled up2 it then extends into the fatty matter under the skin1 which nourishes the worm during its dormant state1 and1 as soon as that matter is exhausted1 the victim dies4 ,in autumn1 the common fly1 though quite dead1 may be seen adhering to many parts of a room1 especially to the window glass1 as if it were alive4 ,in this state it is always surrounded by a halo about an inch in diameter of whitish dust1 consisting of the spores of the ,empusa ,musc1 or fly fungus4 ,the body of the fly is much distended1 the rings of its abdomen are separated by the growth of the mycelium from within1 and all the contents of the body having been consumed by the parasite1 nothing remains but a hollow shell with a thin felt-like layer of the interlaced mycelia of innumerable fungi1 for the fly fungus increases with wonderful rapidity within the insect4 ,mr4 ,berkeley believes the fly fungus to be merely a condition or phase of one of those anomalous moulds which grow on dead fish1 making them conspicuous as they float on the surface of the water1 by the foggy halo which surrounds them4 ,different kinds of parasitic fungi may exist at the same time4 ,dr4 ,leidy found a variety in the stomach of the ,passalus cornutus1 a beetle that lives upon decayed wood4 ,fungi do not attack the carnivorous beetles4 ,man is not exempt from these parasites4 ,fourteen different species of fungi were discovered by ,mr4 ,hogg in as many cutaneous diseases4 ,there cannot be the smallest doubt of cutaneous disease being induced by inoculation with fungi2 merely rubbing certain species on the skin is sufficient4 ,fungi cause baldness by fixing themselves on the roots of the hair1 and destroying the internal structure of the bulb4 ,our eyes are not exempt from attacks of these parasites1 for in performing an operation upon a diseased eye ,dr4 ,hannover found several species of fungi in it2 one of them was globular1 and strongly refracted the light4 ,there is a fungus consisting of from four to sixty-four cells united in square groups1 which infests the stomachs of men and animals1 even in a healthy state2 but although fungi produce certain cutaneous diseases1 there is no proof as yet that fever1 cholera1 or any other epidemic1 is owing to the spores of the fungi which we inhale from the atmosphere4 ,the family of ,,coniomycetes consists of six groups1 two of which are parasites on living vegetables1 the other four growing on those which are dead1 decaying1 or dying4 ,they are microscopic plants1 and their mycelium is filamentous1 or vesicular1 often obsolete2 short threads rising from it bear on their tips either septate spores1 or spores like fine dust1 inclosed in oval or bottle-shaped cases1 called perithecia1 or in cells united in a cell1 like a necklace of beads4 ,we are chiefly indebted to ,m4 ,tulasne and his brother for the obscure and extraordinary life-history of these fungi4 ,the parasites on living plants form the two vast groups of ,epiphytes and ,entophytes4 ,the ,epiphytes exhibit their fructification on the surface of the plant1 while their mycelium penetrates the moist texture of its interior1 which feeds them4 ,all parts are liable to be attacked by these fungi2 they may insinuate their mycelium into the leaves1 stem1 flowers1 stamens1 anthers1 and the very heart of the seeds4 ,the mycelium is generally annual1 but sometimes it is perennial1 and leaves a crop of fungi year after year2 it disintegrates the tissues of the plant on which it feeds1 and distorts or kills it4 ,occasionally1 the chlorophyll in the leaves is oxidized1 and becomes yellow by the oxygen which the parasite absorbs4 ,the ,entophytes1 which constitute the second group of parasites on living plants1 form microscopic congregations in the interior of the leaves and tender shoots1 the only indication of their existence being a white1 red1 or orange coloured spot1 which usually becomes black or brown when the fungus attains maturity4 ,it appears that the same individual of these entophytes may assume two or more different forms during the course of its life1 and bear two or more totally dissimilar types of fructification4 ,of these1 the sub-orders ,puccini and ,uredines furnish many examples4 ,illustration3 ,fig4 #cb4 ,puccinii3--a1 ,aregma speciosum2 b1 ,xenodochus paradoxus2 c1 ,puccinia ,amorph2 d1 ,triphragmium dubens2 e1 ,young spores of an unknown ,puccinia2 f1 ,puccinia lateripes4 ,fig4 #cb represents various species of ,puccinii1 which consist of a thread ending in club-shaped or elongated cells called asci1 containing a definite or indefinite number of septate conidia or spore dust cells4 ,each order of plants1 as the ,rosace1 has its own form of these entophytes4 ,in the tissue of a rose leaf1 immediately beneath a bright golden coloured surface spot1 ,m4 ,tulasne found two distinct forms of fungi1 living together in a small cavity4 ,the forms were exactly those of a ,puccinia and ,uredo4 ,the ,puccinia consisted of a short colourless stem1 ending in a club-shaped cell1 containing two conidia or spore cells4 ,these fungi were crowded together in multitudes in a small space so as to form a solid rounded mass1 with their broad tops immediately under the skin of the upper-side of the leaf1 but sometimes they were arranged in concentric circles4 ,the ,uredines1 on the contrary1 had colourless branching stems1 like threads1 bearing on their tops pointed spore sacs4 ,in some species these ,uredines are scattered through the mass of ,puccinia1 in others disposed in a circle round it1 or in the centre of the concentric ring where the ,puccinia takes that form4 ,it was long believed that these two forms of fungi living together in the same cavity were totally different plants1 but as in various instances ,m4 ,tulasne perceived that the ,uredo had sprung up1 shed its spores1 and vanished before its companion had ripened its fruit1 he concluded that the two different forms are merely two states of the same plant1 that the larger spores of the ,uredo thus early matured1 immediately germinate and produce the ,puccinia1 whose fine dust-like spores are merely the secondary fruit of the ,uredo4 ,these minute spores issue through a pore in the conidia or dust cell and a puncture in the upper skin of the leaf into the air1 whence they are wafted in myriads by the winds2 and1 if not too late in the season1 they enter into the pores of the leaves and tender parts of the same or other plants that may suit them1 and within these they form a mycelium1 and produce a young ,uredo4 ,even if the autumnal leaves fall in a moist place before the spores have germinated1 the entophyte will grow on the approach of spring1 and ultimately send its dust spores to enter into young leaves1 and grow with their growth4 ,although there cannot be a doubt of the existence of the ,uredines as a numerous natural family1 ,m4 ,tulasne considers the species of certain genera to be only secondary forms of certain genera of ,puccini4 ,many of these minute fungi have a third and even a fourth order of fruit2 the principle being carried to a maximum in the order ,comacei4 ,these entophytes have a delicate mycelium1 which gives rise to short or obsolete fertile threads1 terminated by single spores or chains of spores4 ,these spores when they germinate produce a second order of spores2 these occasionally produce a third order1 and so on successively even to a fourth or a fifth order4 ,it is always the last and smallest spores which reproduce the plant4 ,the object of the successive orders seems to be to diminish the size of the spores and to increase their number1 that they may more easily enter the stomates of the plants they live upon1 and be more easily and widely dispersed by the winds4 ,the ,uredo candida1 or ,cystopus candidus1 which takes its name from the white spot it forms on the leaves of the cabbage and other vegetables1 is found to produce both female or germ cells and spermatozoids4 ,long before the white spot is formed on the leaf1 the presence of the abundant spawn may be perceived by swellings and deformities in the victim plant4 ,its filaments1 which creep exclusively in the intercellular canals of the cellular tissue1 are tubular1 of unequal diameter1 and exceedingly branched1 and are always formed of cellulose1 either thick-walled and gelatinous1 or thin-walled and membranous4 ,from this mycelium1 little threads hang down1 ending in globular vesicles containing a nearly homogeneous colourless matter1 and ultimately an aqueous liquid2 they are supposed to fix the mycelium to the cells of the victim4 ,according to the examination of ,mr4 ,berkeley1 ,m4 ,tulasne1 and others1 the branches of the mycelium accumulate in a hollow immediately under the white spot in the skin of the leaf of the plant attacked4 ,from these branches spring bundles of club-shaped tubes1 directed perpendicularly towards the upper skin of the leaf1 and forming a tuft or little cushion of variable extent4 ,the summit of each of these club-shaped tubes is formed into a conidium1 or spore dust cell1 which separates itself from that below it by taking a globular form4 ,in the upper end of the remainder of the tubes1 new spore dust cells are formed1 and so on indefinitely4 ,these conidia remain attached to one another in a string by slender constrictions which become thinner1 and at last give way from above downwards1 and they escape in succession through a crack in the skin of the leaf4 ,the quantity of spores that are generated by the dense mass of these club-shaped tubes must be enormous4 ,the ,cystopus has female reproductive cells1 which had escaped notice from being hid in the plastic matter which nourishes them4 ,they appear before the spore dust bearing cells1 and are formed by terminal or interstitial swellings in the tubes of the mycelium1 which become large oval cells1 separated ultimately by a closure from the rest of the tube that bears them2 they are filled with a granular liquid mixed with large granules of a coloured fatty matter4 ,the tips of some branches of the mycelium swell into oval or club-shaped cells containing spermatozoids1 which fertilize the female cells2 then the matter within the latter assumes a globular form1 gets a coat of cellulose1 and becomes the true fruit of the ,cystopus4 ,as early as the year #ahjg1 ,m4 ,b4 ,prvost had seen that the sporangia1 or spore cells of the entophytes produced zoospores1 and recently ,m4 de ,bary has seen them produced1 during the germination of the spores1 collected within a sporangium of the ,cystopus4 ,when they came into the water they had two cilia1 one of which was short and went first1 the other was long and trailed after the zoospore4 ,neither ,m4 de ,bary nor ,m4 ,tulasne have ever seen zoospores in the fungus itself1 but if the drops of rain or dew round the white spot on the leaf of a plant be examined1 empty sporangia are generally found1 and spores in different states of development4 ,the ,puccinia ,fab1 an entophyte on the common bean1 has but one spore in its cylindrical case1 and is considered identical with the ,uromyces appendiculatus4 ,besides male organs like those of the cidium1 ,m4 de ,bary found that the bean entophyte has four kinds of reproductive organs1 of which one alone reproduces the original form1 while the others present a well-marked alternation of generations4 ,the ,puccinia forms a prothallus on which conidia1 or secondary spore dust cells1 arise2 these secondary spores form a mycelium1 on which an cidium appears1 whose orange-coloured fruit gives rise to a ,uredo1 and the dust spores of the ,uredo enter the leaves of beans or peas1 and grow into a ,puccinia4 ,all the species of cidium are similar to one another1 and ,m4 ,tulasne is of opinion that they do not constitute a distinct genus1 but that1 like many of the ,uredines1 they are merely a secondary form of some other fungus1 and inhabit the same cavity1 as in the case of cidium cyparissi and ,uromyces scutellatus1 cidium leucospermum and ,puccinia ,anemones1 and others4 ,illustration3 ,fig4 #cc4 ,puccinia ,graminis4 ,the order ,puccinii comprises epiphytes1 as well as entophytes4 ,the mildew on wheat is caused by the ,puccinia ,graminis 7fig4 #cc71 which attacks the stem of the plant1 and appears on its exterior in a circular cluster of pear-shaped septate spore cases4 ,these spore cases spring from a filamental mycelium1 whose threads interweave themselves among the soft tissue of the stem of the wheat1 and the fertile threads make their way through the stomates to the surface4 ,professor ,henslow has proved that the rust which appears on the leaves and chaff scales of wheat is owing to the ,uredo linearis1 a secondary form of the ,puccinia ,graminis1 and that rust is only an earlier form of mildew2 so that the ,puccinia ,graminis is a dimorphous and epiphytic fungus4 ,it may be a question whether the ,uredo segetum1 which destroys the blossom of wheat1 and reduces the ear to the sooty mass of powder called smut1 may not be the form of some other fungus4 ,the epiphytes of the order ,puccinii often appear on the exterior of plants in tufts of brown1 yellow1 orange-coloured1 or white sporangia4 ,fungi are extensively propagated by fragments of their spawn1 and the threads of the mycelia are sometimes diminished in thickness in order that they may more easily penetrate into the stomates of the plant they invade4 ,this was discovered by ,mr4 ,berkeley while investigating the germination of the spores of bunt1 a ftid rust which attacks wheat and other grasses4 ,it is perfectly analogous to the diminution of the size of the dust spores in the successive orders of fructification4 ,it is thought probable that in many of the parasitic fungi1 new spores are formed at the tips of the fructiferous threads of the mycelium as fast as the ripe spores fall off1 whence that enormous mass of minute spores which a single individual is capable of producing4 ,among the multitudes of known parasitic fungi1 there is not one that does not form a mycelium more or less distinct4 ,they do not arise from a disease in the plant they attack1 though they ultimately cause disease and often death4 ,each parasite has its own mode of penetrating into the tissues1 and its own manner of vegetating2 they attack certain plants1 and avoid others though nearly allied4 ,dust spores1 single or septate1 oozing out of a dark or coloured fungous mass is characteristic of the group ,melanconiei1 which is more remarkable in regard to the mode of fructification than any of the preceding ,coniomycetes1 for instead of successively assuming the form and fructification of two genera1 or two orders1 the plants successively assume the form and fructification of two distinct families4 ,the family of the ,,hyphomycetes takes its name from its filamentous character4 ,the mycelium gives rise to white1 dark brown1 or bright coloured threads1 simple or compound1 bearing naked spores on their extremities4 ,of these there are five sub-orders and many genera4 ,the sub-order ,isariacei has four genera found on the pup of moths1 on dead spiders1 dead fungi1 and dead plants respectively4 ,the group is characterized by compound threads ending in pulverescent spores4 ,most of the caterpillars of the ,bombyx ,rubi1 or bramble moth1 fall victims to a species of ,isaria1 which has several distinctly different periods and modes of fructification1 and at last assumes the form of a very beautiful fungus belonging to a different family4 ,near ,paris1 in the month of ,october1 when the caterpillars of the bramble moth seek for shelter from the cold1 in the earth1 or under long grass and withered leaves1 ,m4 ,tulasne and his brother found that most of them were surrounded by tufts of a whitish down1 which increased so rapidly that it killed the caterpillars and covered the whole of their body except the bristly hairs1 and assumed characters similar to the muscardine fungus that kills the silkworm4 ,this down is a mycelium composed of extremely fine branched filaments felted together1 the upright fertile branches of which bear whorls of branchlets each terminated by chaplets of from ten to fifteen equal and spherical cells filled with dust spores4 ,these most minute spores germinated1 and put out filiform creeping germs which quickly emitted many branches ending in long chaplets of fertile dust-bearing cells4 ,points here and there on the felted envelope of the caterpillars became of an orange colour1 took the form of a mycelium1 and produced little orange coloured club-shaped cells which shed abundance of reproductive dust spores from a ring of white hairs on their summit4 ,each caterpillar had from ten to fifteen of these coloured clubs on its sides1 which lost their brightness when they grew old1 and had shed their dust spores4 ,these fungi possessed all the characters of the ,isaria crassa1 or ,isaria farinosa of ,fries4 ,later in the season other caterpillars on which this club-shaped ,isaria had not been produced1 but which were swollen and white with the felted spawn of the parasite1 gave out orange red club-shaped vessels of a larger size and deeper tint than those of the nascent ,isariacei4 ,they had no terminal ring of hairs1 but some of them had a red spore dust-bearing felt at their base4 ,ultimately they assumed all the characters of the ,sphria militaris of ,ehrenberg or ,cordyceps militaris of ,fries1 which is a bright scarlet fungus half an inch high with a fleshy upright stem ending in a cup-shaped head containing long cylindrical sacs called asci1 in which the spore cells are so numerous as to resemble strings of beads4#ee ,this fungus1 therefore1 begins as a member of the family ,hyphomycetes1 and ends as a member of the family ,ascomycetes4 ,the order ,stilbacei are little globose fungi with or without a stalk1 covered with semi-gelatinous spores4 ,they are united in cushion-like masses1 on decayed wood and dead twigs4 ,the little scarlet masses on dead currant branches so often seen in gardens1 are examples4 ,the order ,dematiei are the black moulds found on damp paper1 old damp linen1 dead wood and plants4 ,their spawn is seldom much developed1 the fertile threads are erect1 rigid1 dark brown approaching to black1 sometimes of an olive green4 ,the spores on their tops are either simple1 in whorls1 or collected into heads1 which are large1 septate1 and even spiral4 ,the ,mucedines are beautiful microscopic objects both as to form and colour2 they are very numerous both in genera and species and are well known as red1 blue1 or green moulds4 ,these fungi spring from many points of a generally abundant mycelium1 in erect coloured threads1 bearing on their tips simple naked spores1 spores collected into little tufts1 or spores strung together like beads forming threads either branched or simple4 ,in this order of fungi there are1 moreover1 instances of dualism1 the second order of fruit being that of the family of the ,ascomycetes4 ,the ,botrytis1 or ,peronospora infestans1 which causes the murrain in potatoes1 shows how destructive the ,mucedines can be4 ,like other entophytes1 its spores enter the stomates in the leaves of the potato1 and fill the cavities of the leaves with spawn1 the ramifications of which are said to be very beautiful4 ,this creeping spawn then insinuates itself into the stem and tuber1 and from thence it finds its way to the exterior of the plant1 or to some internal cavity1 where it fructifies1 bearing large globose sessile bodies yielding fruit of the second order1 and spores on the tips of its fertile branches4 ,the spawn of the ,botrytis spreads rapidly in a circle1 and soon destroys the texture of the leaves and stem1 but although it attacks the tuber or potato generally so called1 it does not penetrate deeply4 ,the destruction of the potato is aided and completed by the ,fusisporium ,solani1 a microscopic fungus1 which takes various forms according to its age and changing conditions1 the last of which seems to be partly gelatinous2 it sometimes hardens the tissues of the potato1 but sometimes causes rapid and loathsome decay4 ,the thread-like fibres of the spawn of the ,peronospora permeate even the branches and wood of trees4 ,wasps are frequently seen to frequent hollow trees1 probably in search of the mycelia of some of these parasitic fungi1 which is identical in structure with the material of which their nests are built4 ,signore ,panceri1 professor of comparative anatomy in the university of ,naples1 has discovered seven species of ,mucedines in the albumen of hens' eggs4 ,chemical changes in preserved animal and vegetable substances afford suitable food for the ,penicillia mould1 if indeed they are not the immediate cause of these changes4 ,the threads rising from the mycelium of these moulds terminate in bundles of branchlets carrying at their summits strings of spores1 like necklaces of small beads collected into bunches like tassels1 white1 yellowish1 blue or red according to their age or kind4 ,figure #cd represents various species of ,mucedines1 in which c is the ,penicillium armeniacum1 and f is a spore of ,helminthosporium ,hoffmanni2 all are magnified4 ,different species of the ,penicillia form the blue and brick-red moulds on cheese1 and the greenish and grey moulds on jam and preserved fruit4 ,they appear as dry rot1 as orange coloured spots on long kept potatoes1 as mildew on cloth1 silk1 sugar1 meat1 and even on weather-beaten window glass4 ,they can exist in metallic and poisonous solutions by decomposing the chemical combination1 rejecting the metal or poison1 and living on whatever nutriment may be found in the remainder4 ,like the larger fungi1 these minute plants are sometimes poisonous2 the fatal effects occasionally produced by sausages and spoilt meat are supposed to be owing to poisonous moulds4 ,the ,mucedines conform to the law prevailing in other low organizations of having their species widely distributed4 ,the ,penicillium glaucum is found in all countries1 especially in the vicinity of man2 it inevitably appears in all saccharine substances1 and1 according to ,m4 ,fries1 it is met with alike in the alps of ,lapland and in the oasis of ,jupiter ,ammon in the ,lybian desert1 an example which has no parallel in the geographical distribution of the higher plants4#ef ,ferment1 that is to say1 the yeast plant1 is a peculiar condition of certain fungi1 including the present species1 and is capable of unlimited propagation4 ,illustration3 ,fig4 #cd4 ,mucedines3--a1 ,aspergillus glaucus2 b1 ,aspergillus dubius2 c1 ,penicillium armeniacum2 d1 ,sepedonium mycophilum2 e1 ,helminthosporium nodosum2 f1 ,helminthosporium ,hoffmanni1 spore2 g1 ,zygodesmus fuscus4 ,the real spore-bearing filaments of the ,penicillium glaucum are only developed in air1 for when the spores of that fungus are kept submerged in a liquid favourable for their growth1 as in a saccharine solution1 or the juice of the grape1 they form an aquatic mycelium on the filaments of which cells are produced1 and carbonic acid gas is given out4 ,these cells increase by budding or division into chains of ferment1 easily separated into single cells4 ,the ,penicillium glaucum is thus developed in all kinds of liquids1 and in almost all kinds of conditions2 even the peculiar knotty filaments observed in its submerged mycelium are not constant in different liquids4 ,m4 ,hoffmann has observed with certainty the passage of ,penicillium glaucum into ,penicillium candidum1 into a sulphur-coloured ,penicillium1 and1 lastly1 into the ,coremium glaucum1 so that this fungus is polymorphous1 although the conditions under which the changes take place are unknown4#eg ,it appears that substances and liquids do not ferment spontaneously1 for upon examining with a microscope the dust obtained by scraping the exterior of gooseberries1 plums1 vine leaves1 potatoes1 c41 ,m4 ,hoffmann found the short chains of the ,torula1 the necklace-like ferments of the ,mucedines1 and the chaplets of others4 ,some had already begun to germinate1 and were developed readily when put into water4 ,they had no doubt been carried by the wind from the dry refuse of fermented substances which are thrown away4 ,illustration3 ,fig4 #ce4 ,torula ,cerevisi1 showing successive stages of cell multiplication4 ,the yeast of beer was at one time considered to consist entirely of the cells and chains of the ,torula ,cerevisi 7fig4 #ce74 ,this1 which is one of the ,coniomycetes of the order ,torulacei1 is in its early stage a colourless transparent globe capable of endless increase by budding4 ,when in a liquid favourable to its growth1 as the wort of malt1 buds in the form of young cells spring from the walls of the globes2 these soon become perfect and acquire buds also1 so that in a few hours the parent cells develop themselves into rows of four or five globes1 which remain in contact while the plant is growing1 but separate if anything checks the fermentation4 ,the full development of the plant only takes place when the fermentation is allowed to continue for some time1 and then it is capable of producing a variety of forms1 which show that it has other modes of reproduction besides budding4#eh ,in fact1 when the fermentation is active in the upper parts of the liquid it appears in chaplets of from four to twelve articulations1 or sometimes it ramifies into little branches4 ,more recent observations show that yeast is a peculiar state of the mycelium of various fungi1 of which1 as already stated1 a large proportion is believed to consist of ,penicillium glaucum1 though it is known that other kinds of mould also enter into its composition4 ,these plants grow naturally in a state of exposure to the atmosphere1 but they have the property of also developing themselves when submerged2 and as in this unnatural condition1 which they bear when developed as yeast1 they cannot produce their proper fruit1 they propagate themselves by means of shoots from the altered mycelium4 ,it has been observed that mechanical injury destroys the vitality of ,german yeast1 which consists of yeast globules in a dried state4 ,thus a fall on the ground1 or a bruise caused by a blow or by careless handling1 will kill the plant1 and such dead yeast becomes dark-coloured and glutinous1 and soon acquires an offensive smell4 ,the form of ,penicillium glaucum which produces acetic fermentation1 known as the vinegar plant1 has a filamental submerged instead of a vesicular mycelium4 ,ferments may be formed in the wort of beer1 in the solutions of grape and cane sugar1 in the juice of gooseberries1 currants1 c41 by means of the submerged spores of the ,uredines segetum and ,ros1 of ,ascophora elegans1 ,mucor ,mucedo1 ,periconia hyalina and others4 ,there are active exchanges continually going on between the contents of the globules of ferments and the exterior liquid1 and therefore a continual chemical action4#ei ,m4 ,pasteur's experiments on the nourishment of the ,mucedines concur with the observations of others in showing that these plants are the origin of all fermentation properly so called4 ,when he put a mere trace of the beer yeast fungus into pure water holding in solution the three crystallizable substances1 sugar candy1 an ammoniacal salt1 and some phosphates1 the globules of yeast were seen to multiply1 deriving their nitrogen from the ammoniacal salt1 their carbon from the sugar1 and their mineral material from the phosphates2 at the same time the sugar fermented4 ,the same results were obtained from lactic yeast4 ,m4 ,pasteur now sowed the spores of the ,penicillium1 or of some other mucedinous fungus in pure distilled water holding in solution the same ingredients1 except that an acid salt of ammonia was employed to prevent the development of infusoria1 which would soon have stopped the progress of the microscopic plant by absorbing the oxygen without which fungi cannot live4 ,the result was the same as in the preceding case4 ,there is consequently a complete analogy between the ferments1 the mucedines1 and plants of more complex structure4 ,if in these experiments any one of the principles in the solution be omitted1 the vegetation is arrested4 ,the quantities of these substances in the air1 the water1 or in the spores themselves1 are not sufficient to make up for the suppression of any one of them4 ,for example1 the carbonic acid in the air or water does not make up for the omission of the sugar4 ,the mucedines and fungi generally obtain their carbon from their food and from rain water1 for rain water holds in solution nitrates and ammoniacal salts together with salts of potash and lime1 and ,m4 ,barral has ascertained the existence of phosphates also4 ,m4 ,barral found that the nitrates and ammonia disappear under the influence of cryptogamic plants4#fj ,in the genus ,oidium1 belonging to the ,mucedines1 the short threads have a string of spores1 like a necklace of beads1 on their tops4 ,species of this genus are found on damp paper and honeycombs2 also on decayed oranges1 and other spoilt fruits4 ,the family of the ,,ascomycetes produces spore-bearing cells1 called sporidia1 enclosed in long cylindrical sacs or asci1 in the definite numbers two1 four1 eight1 sixteen1 thirty-two1 c4 ,the great characteristic of this large group1 consisting of six orders1 is the fleshy soft texture and the more or less complete exposure of the fructiferous surface4 ,in one division the asci are persistent2 this includes the ,elvellacei1 the ,tuberacei1 the ,phacidiacei1 and the ,sphriacei4 ,in the other division the asci are often evanescent1 and this includes the ,perisporiacei and the ,onygenei4 ,the genera ,peziza and ,helvella are the principal fungi belonging to the order ,elvellacei4 ,the ,peziz are a very numerous race1 and consist of brilliantly coloured little cups1 with or without stems1 and more or less concave4 ,they grow in the cooler part of the temperate zone1 many show themselves in spring1 and some of the largest and most beautiful appear during the melting of the snow4#fa ,a few are subterranean1 and #abh species inhabit ,great ,britain1 many growing on the ground1 others on stumps of trees1 dead sticks and timber1 on living plants1 damp walls1 c4 ,they are singularly beautiful1 including #8many of the most elegant fungi1 from the little white and red ,peziza elegans1 which is sprinkled over almost every fallen twig of the larch and other conifers2 the pale toothed cups of the ,p4 coronata1 which abounds on the dead stems of herbaceous plants2 the scarlet ,p4 scutellata with its edge fringed with tawny hairs1 and the graceful mouse-grey ,p4 macropus1 to the gorgeous ,p4 coccinea1 which attracts attention from its elegant form and bright colours2 the more irregular1 but not less brilliant ,p4 aurantia1 and the font-shaped ,p4 acetabulum1 which might form an elegant pattern for an architect or silversmith4 ,fifty others might be mentioned of equal pretensions to grace of form and brilliancy of colouring4'#fb ,some of the genus are peculiar in their fructification1 for in several plants of this group1 besides asci containing eight sporidia1 ,m4 ,tulasne met with cells full of eel-shaped particles like those in the ,alg1 and although without motion he considered them to be analogous to the pollen of flowering plants4 ,in the ,peziza aurantia1 however1 the particles were staff-shaped and motile4 ,the genus ,helvella may be regarded as ,peziza with the cup inverted2 consequently1 it assumes the character of a pileus or hat1 like a common mushroom1 though often very different in shape1 and1 instead of spore-bearing gills1 it has asci containing eight sporidia sunk in its fleshy texture4 ,the pileus is ovate or mitre-shaped in some species and the margin free1 in others it is more or less attached to the stem4 ,when the pileus and stem are perfectly soldered together1 we get the club-shaped species of the group4 ,some obscure forms of this group1 forming the genus ,ascomycetes1 cause the leaves of the peach1 walnut1 and pear to blister4 ,they consist of little more than asci1 accompanied by short necklace-shaped thread4 ,the ,morchella esculenta1 which is the morel1 is so plentiful in some parts of ,england1 that it is used for making katsup2 while the ,cyttaria1 which is indigenous in the southern hemisphere1 is the staple food of the ,fuegians during many months of the year2 its subgelatinous consistence indicates a nutritious principle4 ,this species has the peculiarity of growing upon living branches1 after the manner of the jelly-like fungus of the juniper4 ,m4 ,tulasne has discovered in ,peziza1 and in the genus ,bulgaria and others1 certain minute bodies1 which he considered to be of the nature of the eel-shaped particles or antherozoids in the ,alg4 ,besides1 he has shown that several species of ,peziza have a second form of fruit4 ,fries had long before pointed out the identity of ,fusarium tremelloides and the orange coloured ,peziza common on nettle stems4 ,many of the larger ,peziz and ,helvell eject their sporidia with great elastic force4 ,this is particularly remarkable in the ,peziza vesiculosa1 common in hot-beds1 when the sun is shining2 the least agitation raises a visible cloud of sporidia like vapour4 ,the motions of the sporidia in the genus ,vibrissea1 which grows on twigs partly immersed in water1 is very peculiar4 ,they are exceedingly long and slender1 and1 when partly ejected1 they wave about in the sunshine till they are expelled4 ,the fungi of the order ,tuberacei are nearly all subterranean1 and their fruit-bearing surface1 as in the truffle1 is internal4 ,the asci are either irregularly deposited in cavities1 or in the denser tubers they are sprinkled through a dark substance which is mottled with a paler tissue4 ,the truffle1 which is the most important and best known of the order1 has a dark corrugated exterior1 and the asci are represented by large pyriform sacs containing sporidia covered with a reticulated or spinose coat2 but these spines are only the angles of continuous cells1 and are beautiful microscopic objects4 ,truffles prefer calcareous soil1 and a temperate climate4 ,in ,england1 they are found in ,rutlandshire1 and numerous species grow in ,northamptonshire1 but they are smaller than the continental truffles1 which increase in abundance and size towards the south1 and have their maximum in ,italy1 where they grow on the roots of trees and vines1 and are hunted by dogs1 or traced by the presence of a peculiar fly1 and dug up for sale4 ,sometimes the dogs dig them up1 to the annoyance of the proprietors of vineyards1 from the mischief they do to the roots of the vines4 ,the ,sphriacei1 another order of ,ascomycetes1 are enormously numerous4 ,there are #a1jjj well known species of this order1 and probably twice as many undetermined2 for there is scarcely a twig or dry branch in the forests1 hedges1 or gardens on which they may not be found4 ,the rose tree1 the oak1 and other plants harbour more than one species at a time4 ,the genus ,cordyceps and many so-called species of ,sphria are only the ultimate development of fungi of other families4 ,the ,cordyceps purpurea1 discovered by ,m4 ,tulasne on the ergot of wheat1 has a short1 upright1 slender stem1 with a minute pale purple globose fruit-bearing head4 ,in this ergotized state the white substance of the grain is converted into a firm mass without any appearance of meal1 and having very powerful properties4 ,when sown1 it is found to produce the ,cordyceps4 ,mr4 ,currey found the same plant on the ergot of the common reed1 and there are several other species of ,cordyceps1 all of which are only the second form of ergot4 ,to these may be added the ,cordyceps militaris of ,ehrenberg1 already shown 7p4 #bhc7 to be the ultimate development of the ,isaria1 which attacks the caterpillars of the bramble moth2 and the ,cordyceps ,robertsii1 which grows like a bunch of rushes from the head of the ,hepialus virescens of ,new ,zealand2 whilst a kind of wasp in the ,west ,indies1 which continues to fly about after it is attacked1 is at last killed by branching ,cordyceps1 which project from its head like a pair of antlers4 ,but the largest of all these parasites grows on an enormous larva found on the banks of the river ,murrumbidgee in ,australia4 ,it appears that species of ,sphri are parasitic on insects of very different affinities in ,china1 ,america1 and ,europe4 ,it may be presumed that1 like the ,cordyceps militaris1 they are the ultimate development of fungi belonging to other families4 ,illustration3 ,fig4 #cf4 ,sphriacei3--,sphria ,desmazierii2 a1 ascus2 b1 sporidia2 c1 mycelium with conidia4 ,mucedines3--d1 ,botrytis curta4 ,in the genus ,sphria the fungus springs at once from its mycelium1 and consists of a perithecium or external case1 to the internal walls of which the asci are fixed4 ,each ascus contains eight sporidia or spore cells1 and when the fruit is ripe the asci are emitted through a pore or slit in the perithecium or external coat4 ,fig4 #cf represents the fructification of ,sphria ,desmazierii4 ,sphria bombarda is like an assemblage of minute black beads lying flat and crowded together upon decayed wood2 each bead is an oblong vesicle pierced at the apex for the emission of the microscopic sporidia1 or spore cells4 ,the ,sphria aquila1 found upon decayed wood1 has its fruit-bearing vessels seated upon thickly matted fine threads4 ,in some species they are in tufts2 others have bottle-shaped perithecia sunk into the stems of the berberry1 laburnum1 and decayed oak palings2 and lastly the candle snuff ,sphria may frequently be seen like patches of soot at the bottom of stakes or gate posts4 ,more than two hundred well ascertained species of the genus ,sphria are native in ,great ,britain alone4 ,the genus ,nectria1 which forms a connecting link between the genera ,peziza and ,sphria1 has several interesting species1 as the ,nectria ,peziza1 which grows in a congeries of most minute cups forming a bright orange-coloured patch on decayed stumps of trees4 ,in the order ,perisporacei the perithecia1 or external cases1 are free and become dehiscent at last1 but when young these fungi consist of cellular jointed filaments like necklaces1 rising upright from their mycelia1 and bearing reproductive bodies4 ,in this state they constitute the mildew on the vine1 rose tree1 turnip1 hop1 pea1 c4 ,they are true parasites1 appropriating the juices1 and filling up the breathing pores of the leaves1 so as to cause disease and often death4 ,the vine mildew1 which has been called ,odium ,tuckeri1 but which is now supposed to be an imperfect state of ,erysiphe1 never advances beyond this state1 consequently it never has more than one form of fruit4 ,mr4 ,berkeley has discovered that1 on the contrary1 the hop and pea mildews1 which belong to the genus ,erysiphe1 have five different modes of reproduction4 ,the destructive power of these fungi is strongly illustrated by the extraordinary energy of their mycelia in draining the vital juices of the plants on which they live in order to form such various kinds of fruit2 and the quantity of fruit produced is so enormous1 that if the whole were to germinate no genus of plants for which they have an affinity could escape annihilation4 ,other species of ,erysiphe have at least three different modes of reproduction4 ,the perithecia of some of these fungi are beautiful objects for the microscope4 ,the ,physomycetes1 which form the sixth and last order of the great fungus family1 have bladder-like fertile cells scattered on threads1 the number of sporidia within the cells being indefinite4 ,the ,antennariei are dark coloured felt-like fungi which run over the leaves of living trees1 and have fruit on black threads1 which in some species1 when magnified1 resemble the antenn of certain beetles4 ,the species of this order are not common in ,britain1 and they are supposed to be only a condition of some other fungi4 ,they are certainly spore-bearing plants1 yet the fruit-bearing cells of the ,antennaria ,robinsonii sometimes contain a ready formed miniature of the parent plant waiting to be set free1--a singular analogy between these microscopic fungi and flowering plants4 ,the order ,mucorini1 or moulds1 has threads springing from the spawn1 bearing on their extremities large vascular sacs containing asci with spore cells4 ,the genus ,ascophora contains several remarkable species1 as ,ascophora elegans1 which has two kinds of fruit1 and attacks bread while yet hot from the oven3 however1 the spores were probably in the dough1 for it has been ascertained that the spores of some of the lower fungi retain their vitality after being exposed to the temperature of boiling water4 ,the ,mucors are probably found on decayed and decaying matter all over the world2 they grow on fat1 on greasy walls1 and on decaying fruit and vegetables4 ,the extreme minuteness of the reproductive bodies of the microscopic fungi1 many of which are not more than the #bj1jjjth part of an inch in diameter1 and their extraordinary and varied forms even in the same plant1 have made these fungi one of the most difficult studies in the whole science of botany4 ,there is still some obscurity with regard to those minute motile bodies supposed to be male particles1 and their analogues1 which have not been seen1 or have rarely been seen to germinate4 ,these bodies have been observed in comparatively few genera1 and nothing more than mere molecular motion has been observed in them4 ,one of the most unaccountable circumstances in the history of the lower fungi is their sudden appearance in immense numbers1 and the rapid extension of disastrous and destructive epidemics caused by them among plants and animals1 as the potato murrain and the vine disease1 which1 though widely spread through ,europe and ,madeira1 leaves the ,north ,american vines unscathed1 whether grown at home or abroad4 ,the black mildews at one time raged so much in the ,azores and ,ceylon as to threaten the complete annihilation of the orange and coffee plantations4 ,their ravages have been scarcely less among the olive trees in some parts of ,europe2 and the ,lanosa nivalis1 which grows in the melting snow in spring1 is supposed to be the cause in many instances of the death of the germs of the sprouting rye4 ,the destructive course of most of these has abated1 but the silkworm disease still continues4 ,the fungi require warmth and a moderate degree of moisture for their development1 but the unwonted multitudes in which the parasites occasionally appear1 possibly indicate some meteoric influences of which we are ignorant4 ,,section ,,iv4 ,,lichens4 ,,lichens are essentially air plants1 being nourished1 like the ,alg1 by the medium in which they grow4 ,they vary from a pulverulent or dry papillose crust1 to a leathery or horny expansion1 and even acquire an erect stem4 ,they are independent of the matrix to which they are attached4 ,hence they spread their coloured frond1 or thallus1 in circular or indefinite patches on old walls1 the tiles of houses1 stones1 and rocks4 ,they appear in large expansions of red1 golden yellow1 grey or white1 on barren heaths1 under plantations1 and on the stems of aged trees2 while others of them often hang from the branches like long shaggy grey hair1 and many form forests of miniature bushes on the northern plains4 ,the lichen is the last trace of vegetation on the tops of the mountains1 and on the arctic deserts4 ,some lichens are patient of severe cold1 yet in general they prefer heat and moderate warmth1 and they love bright light so much1 that they are usually barren1 or else yield little fruit under shade4 ,though differing greatly from fungi in slowness of growth1 length of life1 and the power of forming chlorophyll1 they resemble them in having a mycelium in their youth1 and in their ascigerous fructification4 ,a perfect lichen without an ascus would be an anomaly1 for the asci contain the true fruit1 associated with vertical threads or elongated cells called paraphyses1 which sometimes bear secondary spores on their summit4 ,the asci with their paraphyses inclosed in vessels of various shapes1 called perithecia1 are aggregated in discs or shields1 which form projections on the surface of the plant4 ,some of these discs are closed1 and give egress to the spores through a fracture or pore on their surface2 others are open cups of various forms1 either with stalks or sessile on the frond1 and through these the spores have egress4 ,hence the whole order of lichens is naturally divided into two groups1 according as their discs are open 7,gymnocarpei71 or closed 7,angiocarpei71 the first being incomparably the most important4 ,fig4 #cg shows open1 and sections of closed cups1 or perithecia4 ,illustration3 ,fig4 #cg4 ,lichens3--a1 ,trypethelium ,sprengelii1 pustules1 with sporidia2 b1 ,verrucaria variolosa1 section of perithecium with sporidium2 c1 ,endocarpon lacteum1 thallus with section and fruit2 d1 ,stegobolus ,berkeleianus1 portion of plant with ascus1 and sporidia4 ,the highest type of horizontal lichens1 of which fig4 #cg b is a perpendicular section1 has a firm1 spreading1 superficial crust or surface1 formed of oblong coloured cells1 or of coloured filaments closely aggregated1 and which covers two distinct layers of cellular tissue4 ,in the layer immediately below the surface1 the cells are globular and of a paler colour2 the second layer1 or marrow1 which is the origin of fructification1 consists of lax1 detached1 branching rows of elongated cells and gelatinous matter4 ,these branches of cells spring up from a fourth layer1 which is the base of the plant4 ,it is of a strong1 firm1 and tough nature1 composed of interlaced filaments and is often ribbed on the under-side4 ,white fibres fix the base of the plant to the surface on which it is spread2 they are the remains of a mycelium or matted mass of fibres1 from whence lichens spring1 which vanishes when the plant is full grown4 ,illustration3 ,fig4 #ch4 a1 ,sporopodium ,leprieurii1 ascus2 b1 ,coccocarpia smaragdina1 section2 c1 ,lecanora affinis1 section4 ,globular bodies of vegetable green called gonidia1 like those at the base of fig4 #ci a1 are arranged in regular parallel rows1 and placed between the surface and the base of the lichen1 as in fig4 #ch b and c2 they are said to proceed from the medullary layer1 though ,mr4 ,berkeley has seen them springing from the threads of the mycelium of ,parmelia parietina4 ,the gonidia find their way to the air through rents in the surface of the plant1 and are washed off by the rains1 after losing a little of their green colour4 ,when they germinate they only produce a facsimile of the mother plant1 as buds do in the highest classes4 ,but according to the microscopic observations of ,m4 ,tulasne1 the true fruit differs little if at all from the asci-bearing fungi4 ,through the open discs of the higher lichens1 sporidia are discharged from perpendicular septate asci which1 with their paraphyses1 are imbedded in the substance below4 ,the asci are formed by the elongation of some of the cells of that layer into cylindrical septate vessels1 generally containing from four to eight sporidia1 the ultimate result of as many free cells4 ,in whatever part of a lichen the perithecia may be placed1 the asci and paraphyses invariably originate in the medullary layer4 ,illustration3 ,fig4 #ci4 a1 ,paulia perforata1 gonidia1 paraphysis1 and asci2 b1 ,calicium tympanellum1 perithecium and sporidia2 c1 ,graphis ,leprevostei1 with excipulum1 asci1 and sporidium4 ,the thallus or frond of many of these lichens is irregularly covered with thick convex scales1 in each of which are concealed white or grey bodies1 which become flask-shaped1 with pores in their extremities4 ,when mature1 they exactly resemble the bottle-shaped perithecia in the genus ,sphria among fungi4 ,they are lined with branching filaments or other supports1 ending in minute ovoid particles1 which escape in myriads from the flask-shaped vessels long before the spores appear4 ,they are motile1 though not provided with cilia1 and are supposed to be fertilizing particles like pollen1 since they do not germinate as spores do4 ,in this vast family of open-shielded lichens1 which comprises every form and habit of the plant1 the preceding type1 which is the highest1 undergoes many modifications2 but the essential character remains the same1 and the group is so natural1 that the species run into one another so as to leave no very striking distinction4 ,commencing with the ,,gymnocarpei1 the ,parmeliacei first claim notice as containing the highest types which lichens are capable of assuming1 and as abounding in species4 ,the disc1 which is the hymenium1 is orbicular or kidney-shaped1 and surrounded by the frond1 without any proper excipulum or cortical covering4 ,a large portion of our most widely diffused lichens1 whether growing on the ground or attached to rocks and trees1 belong to this tribe2 they form patches two or three feet in diameter1 which are often of marvellous antiquity1 and they grow so slowly that even small patches are of great age4 ,this tribe consists of three distinct groups3 in two of these the plants are horizontal and sometimes foliaceous2 in the third they are vertical1 often branched1 and occasionally pendulous4 ,the latter group of this large division of lichens comprises the genera allied to ,usnea1 which are erect1 centripetal lichens1 that is to say1 their body or thallus is an upright and generally cylindrical stem1 in the centre of which the layer of marrow1 the origin of fructification1 is condensed1 and the open discs1 or hymenia1 are in connection with it1 whether they be situated at the ends of the branches1 or on the surface of the upright stems4 ,the ,usne have three forms1 the pendulous1 the inflated and erect1 and the branched or shrubby4 ,the ,evernia jubata is an example of the first1 and remarkable for its long1 pendulous1 cylindrical branches hanging down like bunches of bluish grey hair4 ,it is often attached to the branches of aged larch trees1 and is exceedingly picturesque4 ,with the exception of ,evernia vulpina and flavicans1 which are brightly coloured1 all the rest of the genus have dull tints4 ,the genus ,ramalina has the dull tints of the ,evernia1 and some species approach very nearly in form to that genus4 ,the ,ramalina polymorphum and ,r4 scopulorum abound in dyes1 while the ,r4 calicaris is rich in gluten4 ,lichens have lost much of their importance since the discovery of the coal tar colours2 nevertheless they afford dyes still in use4 ,in many species the dying principle is colourless like aniline2 but it yields the most brilliant colours by means of alkalies4 ,the ,parmelia parietina1 common on walls and the roofs of houses1 gives the chrysophonic acid1 a colourless liquid which becomes bright yellow when treated with an alkali2 and in like manner the vulpinic acid1 given by ,evernia vulpina1 gives a brown dye4 ,notwithstanding the quiet greyish green tints of the ,rocella fuciformis and ,r4 tinctoria1 no lichens are richer in the purple substance known as orchil1 from which1 by means of soda or potash1 the valuable blue substance litmus is manufactured1 so important as a test for acidity4 ,many of the small moss-like lichens yield orchil1 but none in such abundance as the ,r4 fuciformis1 which grows in ,madeira1 ,angola1 ,madagascar1 and ,south ,america4 ,oxalic and usnic acids are produced by lichens2 indeed the usnic acid combined with green and yellow resins seems to be more or less a constituent of various lichens4 ,it is evident that the colour of the dyes is altogether independent of the colour of the lichen from whence they are obtained4 ,these arial plants have a marvellous power of decomposing the light1 and adorning themselves in brilliant hues4 ,in our own country1 where the colouring is often cold from the excess of verdure1 the lichen affords a happy relief by giving a little warmth to the landscape4 ,even at ,rome1 where nature is so gorgeously coloured1 the ruins owe much of their picturesque beauty to the red1 white1 and golden lichens with which they are clothed4 ,the ,usne are perhaps the most beautiful of the lichens1 the colours being sometimes brilliant1 the forms elegant1 and when the broad discs are amply ciliated1 the appearance is very striking4 ,the same species are widely diffused1 but the colours are brighter in exotic specimens4 ,usnea melaxantha and ,usnea ,taylori are splendid productions4#fc ,the ,usne are cosmopolitan in genera and species4 ,the genus ,cetraria1 of which the ,iceland moss is a well known species1 forms a connection between the vertical and horizontal lichens2 its thallus is neither cylindrical nor quite erect1 though it becomes more so towards maturity4 ,the ,cetraria tristis has only that degree of inclination which arises from its crowded mode of growth1 and springs like a sea-weed from a little peltate disc4 ,the most typical species of lichens occur in the second group of ,euparmeliace1 or ,parmeliacei proper1 in which the disc is at first closed1 and surrounded after expansion by a border arising from the thallus or frond4 ,the thallus is always horizontal1 and expands from the centre towards the circumference4 ,the genus ,sticta1 belonging to this group1 is often highly foliaceous1 and is not excelled by any horizontal lichen in brightness of colouring or elegance of form4 ,even in our own country the ,sticta pulmonacea spreads over a wide area1 and is remarkable for its pitted frond4 ,in this genus the under-side of the plant is covered with a delicate velvety down1 amidst which are scattered round white spots1 which penetrate to the medullary strata4 ,the erratic lichens are among the peculiarities of the genus ,parmelia4 ,the ,parmelia saxatilis1 common on stones and boulders of the primary and metamorphic formation1 curls up into a ball1 only fixed to its matrix by a slender thread1 which soon gives way1 and the ball being dry and as light as a balloon1 is driven bounding by the winds1 over the sheep walks and downs of ,england4 ,the globular ,lecanora esculenta sometimes suddenly covers large tracts in ,armenia1 ,persia1 and ,tartary1 where the plants are eaten by the cattle and by the nomade tribes4 ,this species1 with ,lecanora affinis1 is largely used by the inhabitants of the countries east of the ,levant1 and in some parts of ,africa is mixed with wheat in grinding4 ,these species are found1 scattered over the ground without any attachment1 in the form of rugged truffle-like objects of the size of walnuts4 ,sometimes they are piled together in strata a few inches thick1 by the whirlwinds1 after traversing the air for many miles1 which gives rise to the histories of the miraculous descent of food4 ,during a scarcity1 a shower of these lichens fell at ,erzeroum1 and there are other well-authenticated instances recorded4#fd ,the ,peltigeri1 or the third group of ,parmeliacei1 are so named from the target-like discs on their surface1 covered by a veil1 which afterwards disappears4 ,the species frequently spread their beautifully foliaceous fronds upon the ground1 and as the fruit is marginal1 it gives the thallus a digitate appearance4 ,they are often spotted by a little red fungus4 ,the genus ,solorina has the fruit scattered over the frond2 in the ,solorina saccata it is at first superficial1 but a number of fibres are formed on the under-side of the discs1 which penetrate the soil1 and draw them down below the general surface--a very peculiar structure1 in strong contrast with that of the ,solorina crocea1 which has veins on the under-surface but no fibres1 and as no rootlets are sent out from the base of the disc1 it remains superficial4 ,m4 ,tulasne discovered fertilizing particles in several species of this group4 ,the order of the ,lecidinei contains numerous species of the most varied habits4 ,there is a distinct and regular series upwards in the genus ,lecidea1 the species of which are always crustaceous1 and often form merely a thin1 close1 adherent fibrous stratum on the hardest flint or quartz4 ,some of them disintegrate the hard rocks on which they spread1 possibly by the action of some acid which they contain4 ,from this low type1 the genus rises to the exalted forms with erect branching stems clothed with foliaceous scales1 and brightly coloured4 ,the order is distinguished by an orbicular disc1 contained in a distinct excipulum or cortical envelope1 which is open from the earliest age2 but it is frequently obliterated afterwards by the development of that part of the medullary stratum where the fruit is formed1 the disc in consequence becoming convex and capitate4 ,this transformation takes place in the highest forms of the genus ,lecidea4 ,the genus ,bomyces has rose or chestnut coloured convex discs1 supported on a stem called a podetium4 ,the genus ,cladonia has a foliaceous thallus producing free scale-like fronds1 from the midst of which spring cylindrical or cup-shaped podetia1 which are sprinkled with leaves4 ,the margins of the cups or tips of the branches bear an abundant crop of convex1 irregular brown1 or deep red discs1 often as brightly coloured as sealing wax4 ,the species of ,lecidea bear severe cold1 and are wonderfully long lived4 ,mr4 ,berkeley mentions that there are patches of the ,lecidea geographica which probably date from almost fabulous periods4 ,the fronds of the order ,collemacei are gelatinous2 the medullary stratum seems to occupy the whole1 though in two species of the genus there is a distinct epidermic cellular coat4 ,there are moniliform strings of minute gonidia in the gelatinous matter1 and others that are single1 arising from the division of each gonidium and its supporting thread into two3 both kinds differ from the gonidia in other lichens4 ,the fruit-bearing discs on the surface are open4 ,members of this order occur in ,europe1 ,africa1 and ,australia4 ,the order ,coccocarpei is mainly distinguished by having orbicular discs entirely deprived of the cortical envelope called an excipulum1 or1 if it does exist1 it is confounded with the thin membranaceous thallus4 ,the discs spring at once from the medullary stratum1 and contain asci and sporidia1 similar to those of minute fungi 7,sphri74 ,some species of the genus ,coccocarpia only differ from ,lecidea in the total absence of an excidium4 ,the order is chiefly parasitic1 and in some cases the whole plant is little more than a mass of fructification1 parasitic upon and continuous with the substance of other lichens1 at whose expense they live1 thus forming an exception to the general habit of lichens1 which are fed by the atmosphere alone4 ,m4 ,tulasne has discovered that the genera ,abrothallus and ,scutula1 though consisting almost entirely of fruit1 produce secondary spores--they are the only lichens in which they occur2 while ,phacopsis and ,celidium bear spermatogonia1 which1 analogous to antheridia1 contain minute fertilizing particles4 ,the parasitic genera occur in most parts of ,europe and ,north ,america4 ,the ,pyxinei are horizontal foliaceous lichens1 for the most part fixed by the centre4 ,they have orbicular discs1 and form one of the most singular groups1 both with regard to the superficial fruit1 and the curious convolutions of the perithecia4 ,the fruit-cup1 or excipulum1 is at first closed1 and in the genus ,gyrophora the disc produces a number of partial fructiferous discs on the original fruit-bearing surface4 ,as usual the cells from whence the asci spring belong to the medullary stratum2 the border on the contrary is cortical4 ,the thallus is always foliaceous1 and more or less peltate1 but it becomes dry and brittle when exposed to drought4 ,several of the species have tufts of strong rootlets by which the frond is fixed to rocks1 and some have deep pits1 with corresponding swellings on the upper-surface1 from whence they have their popular name of ,tripe de ,roche4 ,these lichens1 together with some species of ,gyrophora1 afforded a miserable sustenance to ,sir ,george ,back and his companions during their journey along the frozen regions of ,arctic ,america in quest of the north-west passage4 ,it is evident that plants which derive their sustenance solely from the medium in which they live1 whether air or water1 can never become a permanent and wholesome food for man1 though erratic lichens and laver may be eaten from necessity1 certainly not from choice4 ,in the ,gyrophora the perithecia are convolute1 in the ,umbilicaria they are not2 but both of these genera1 which have their seat in ,arctic ,europe and ,america1 possess fertilizing particles like most of their class4 ,in the order ,graphidei the disc is linear1 simple1 or branched1 with or without an excipulum1 which is carbonaceous4 ,many of these lichens are crustaceous1 and in most of the genera the perithecia are much elongated1 pointed at both ends4 ,when they are parallel1 or placed at different angles to each other1 they form groups like ,japanese or ,chinese characters1 whence their name4 ,the genera are determined by the position of these perithecia1 which are much varied4 ,m4 ,tulasne has found linear male particles immersed in the crust of some of these lichens4 ,they have their principal seat in tropical ,america1 though a few species occur in the frigid and temperate zones of both hemispheres4 ,the order ,glyphidei has no true excipulum2 the coloured discs are at first immersed in the medullary stratum of a crustaceous thallus1 the crust then rises into distinct expansions1 in the centre of which the coloured discs are set like gems in a mosaic4 #8,there is in fact no true border to the disc1 the perithecium being reduced to a thick conical base1 from which proceed immediately the asci and paraphyses2 each individual hymenium being surrounded by the intervening medullary matter injected1 as it were1 into the interstices4' ,the whole surface of ,chiodecton monostichum is productive1 and in that genus ,m4 ,tulasne found vessels in the form of little scattered perithecia1 containing filiform curved fertilizing particles4 ,the species of this order are almost wholly tropical1 though the ,chiodecton myrticola has been found in ,ireland4 ,the order ,caliciei consists of horizontal lichens1 with generally an ill-developed crust2 the discs1 which are at first covered by a veil1 are contained in a stalked1 or more rarely sessile1 excipulum1 looking like little flat-headed pins stuck into the crust2 the veil at length vanishes1 and exposes a pulverulent mass of spores1 which adhere so loosely in the ,calicium inquinans1 that they soil the finger if touched2 in other cases they come out of their ascus like little necklaces4 ,the species of these lichens are almost entirely confined to ,europe and ,north ,america4 ,in the second division of ,lichenace1 the ,,angiocarpei1 the discs are enclosed in an excipulum1 which projects from the surface of the plant1 and ultimately discharges the spores from a rupture or pore in its surface4 ,besides the fructification consisting of perithecia containing paraphyses and asci with their enclosed sporidia1 there is a nucleus in each disc1 either of firm or deliquescent matter4 ,some of the lichens of this group are parasitic1 others are aquatic4 ,the order ,limboriei1 like parasitic fungi1 begin their existence under the thick skin of the leaves of tropical plants1 spread their crustaceous thallus over their surface1 and destroy their beauty1 by stopping up their pores1 and preventing the admission of light to their tissues4 ,the excipulum and perithecia are black1 and the latter burst in an irregular fissure1 and are in most cases covered by a beautifully sculptured crust4 ,the crustaceous fronds of the ,verrucariei are often so thin as to be inseparable from the substance over which they spread4 ,the excipula are closed1 the walls of the perithecia are often black1 and in some species more or less crowded round a columella4 ,in the ,verrucaria muralis fertilizing particles have been discovered4 ,the plants are widely distributed1 and at least one species spreads its crust over the smooth stones in running streams4 ,in the group ,endocarpei1 the perithecia are immersed in the substance of the plant1 which has1 for the most part1 a foliaceous horizontal crust1 and a gelatinous nucleus4 ,some species grow on stones1 perpetually or periodically submerged1 or1 if not under water1 continually wet with its spray4 ,the ,lichina1 a genus of the group ,lichinei1 lives on marine rocks1 and is often dripping with salt-water1 and often suddenly dried up4 ,the ,sphrophorei1 or sphere-bearing lichens1 have upright stems bearing globular fruit at the extremity of their numerous branches4 ,at first1 the fruit is only indicated by a swelling1 but in time the outer bark bursts1 and exposes the contents of the perithecium1 which consist of asci and paraphyses seated on a central columella4 ,the sporidia are beautiful objects under the microscope on account of their spherical form1 which is rare among lichens1 and their more or less deep blue tint--a colour by no means peculiar to the sporidia of this order of plants1 for in other orders they are bright scarlet1 olive1 golden yellow1 or brown4 ,,section ,v4 ,,charace4 ,illustration3 ,fig4 #dj4 ,nitella flexilis4 ,,the ,charace are submerged annual water plants1 growing in stagnant pools and ditches rather than in running streams4 ,it is a small order containing but three genera1 but the numerous species are dispersed all over the world1 especially in temperate climates4 ,the genera found in this country are ,nitella and ,chara4 ,the ,nitella flexilis 7fig4 #dj7 may be taken as a representative of the order4 ,its stem or axis is formed of very long cylindrical transparent tubes1 joined by their flat ends1 and surrounded at each junction by a whorl of long tubes which are forked or trifid at their extremities4 ,in some species the branches are jointed1 and have whorls precisely like those on the main axis4 ,on the internal surface of the tubes1 which are sometimes several inches in length1 there are four longitudinal bands parallel to the axis of the tubes1 which are occasionally twisted3 two of these bands are broad and covered with oval green particles2 while the other two are narrow1 transparent1 and colourless4 ,each tube is filled with a limpid semifluid liquid1 in which pale green particles and jelly-like globules of a starchy nature float2 and when these particles are watched with a microscope1 they show that1 in every tube of the plant1 a continual current of that liquid1 with its particles1 ascends one of the green bands and descends by the other1 even when the stem and branches are twisted2 but they never flow in the colourless bands1 though there is nothing to hinder them4 ,according to the observations of microscopists there is probably a gyration of an azotized viscid fluid in all plants originating in1 and maintained by1 vital contractility of structure1 but in none is it so evident as in the ,charace4 ,its rate is increased by heat and diminished by cold1 like the circulation of the blood in animals1 because the activity of the vital energy bears a precise relation to the quantity of heat received4 ,the gyration is instantly arrested by a shock of electricity4 ,the reproductive organs of the ,charace are of two kinds1 both growing in the axils of the branchlets1 namely1 dark-red globules1 which are antheridia1 and nucules or pistillidia1 which contain germ cells4 ,sometimes they are found in different individuals1 but in most of the ,nitellas they are in the same individual1 the globules being placed closely below the nucules1 as in fig4 #da1 ,a1 ,b4 ,the envelope of the nearly spherical globules is formed of eight spherico-triangular valves4 ,from the middle of the interior surface of these valves1 a perpendicular orange-coloured column extends to the centre of the globule1 where its summit is crowned with a mass of confervoid filaments1 which are formed of a linear succession of minute cells2 while from the base of the column1 bands of orange-coloured spherules imbedded in gelatine radiate along the interior surface of the valve to its margin as shown at ,c1 in the same figure4 ,after successive changes in the matter within the confervoid filaments1 7fig4 #db1 ,d-,g71 the microscope shows that #8in every one of the cells there is formed a spiral thread of two or three coils1 which1 at first motionless1 after a time begins to move and revolve within the cell2 at last the cell wall gives way1 and the spiral thread makes its way out1 partially lengthens itself1 and moves actively through the water in a tolerably determinate direction1 by the lashing action of two long and very delicate filaments with which it is furnished'#fe 7fig4 #db ,h74 ,illustration3 ,fig4 #da4 ,antheridia of ,chara fragilis3--,a1 antheridium developed at base of nucule2 ,b1 do41 the nucule enlarged1 and the antheridium laid open by the separation of its valves2 ,c1 one of the valves1 with its group of antheridial filaments4 ,the nucule is an ovoid sac with five long cells spirally twisted round it1 the sac being full of a viscous fluid containing globules of starch and oil4 ,this nucule falls off when fertilized by the spirally-coiled ciliated bodies1 and then germinates4 ,the ,charace may also be artificially reproduced by cuttings2 while under favourable circumstances they are reproduced by nodular bodies rich in starch grains1 which arise from the creeping root1 and also by clusters of cells called bulbils filled with starch grains1 which arise from a modification of the nodes4 ,the ,charas1 properly so called1 are moncious or dicious1 more or less opaque and brittle1 their many-jointed tubular stems bearing whorls of long slender awl-shaped branchlets4 ,the fruit1 accompanied by a cluster of short bracts or ramuli1 is placed at intervals in the hollow side of the branchlets1 one at each joint4 ,in the bristly ,chara the awl-shaped branchlets are simple1 pointed at the extremity1 and composed of about seven joints1 with a whorl of from four to seven short bracts1 and having fruit at each articulation4 ,many of the species of ,charace are thickly incrusted with lime1 and the whole order is exceedingly fetid4 ,illustration3 ,fig4 #db4 ,antheridia of ,chara fragilis3--,d1 ,e1 ,f1 successive stages of formation of spermatozoids in the linear cells of the antheridial filaments2 ,g1 escape of mature spermatozoids1 which are shown detached at ,h4 ,,section ,,vi4 ,,hepatic1 ,,or ,,liverworts4 ,,the ,hepatic are the small herbaceous plants1 which constitute the three distinct natural orders called respectively ,ricciace1 ,marchantiace1 and ,jungermanniace4 ,they are distinguished primarily by the first having the sporangia valveless1 without elaters2 by the second having dependent valvate or irregularly bursting sporangia2 and by the third having the sporangia valvate and erect4 ,both the latter1 moreover1 have the spores mixed with elaters4 ,the ,ricciace1 popularly called ,crystalworts1 which form the lowest grade of ,hepatic1 are inconspicuous plants1 growing in mud1 or floating on water4 ,they have spreading1 horizontal fronds1 of a delicate cellular structure and of indefinite form4 ,their fructification consists of valveless spherical sporangia1 or spore sacs1 imbedded in the frond2 cells are formed within these sporangia1 each of which cells is divided into four parts1 which become spores1 and1 when ripe1 the surface of the sporangia is fractured to give them egress4 ,in some species there are many air passages in the cavities where the sporangia are produced4 ,the under-surface of the frond is often beset with scales4 ,the genus ,riella differs from all the other genera in having an upright branchless stem with a distinct wing or limb forming a continuous spiral round it4 ,in the male plant1 the edge of the frond bears the antheridia containing spermatozoids2 in the female plant the sporangia spring from the stem2 they have a separate envelope1 and the spores are echinate4 ,illustration3 ,fig4 #dc4 ,marchantia polymorpha3--a1 gemmiparous conceptacles2 b1 lobed receptacles bearing pistillidia4 ,the ,marchantiace rank as higher forms of ,hepatic4 ,in the ,marchantia polymorpha 7figs4 #dc1 #dd71 which may be taken as an illustration of the group1 the structure of the horizontal frond is complicated1 for1 besides the colourless transparent skin1 there are three distinct layers1 the uppermost of which consists of cells filled with green matter1 the lowermost 7or base of the frond7 being formed of close-set cells full of very solid matter1 while between the two there is a cavity filled with air and loosely branching filaments1 which spring from the base1 and consist of green cells fixed end to end1 as in fig4 #dd ,b4 ,the surface of the plant appears to be smooth and shining1 but when magnified it is found to be marked with numerous narrow elevated green bands1 crossing one another diagonally so as to mark out the surface into a number of small lozenge-shaped divisions 7fig4 #dd ,a74 ,these elevated bands are merely the tops of very solid walls which descend perpendicularly to the base of the plant1 consequently they divide the internal air chamber into a number of lozenge-shaped compartments1 each of which communicates with the external atmosphere by means of chimneys opening in the centre of each compartment on the surface of the plant4 ,these chimneys are so constructed of four or five superposed rings of cells 7see fig4 #dd ,b71 that by the expansion and contraction of the cells of the lowermost ring1 more or less air can be admitted into the cavity below4 ,this is a very beautiful instance of the contractile vital energy acting for the production of motion1 its object being to supply air1 so essential to the health of all plants4 ,white filaments from the base at once fix the ,marchantia to the earth1 and supply it with food4 ,this is the youthful state of the ,marchantia polymorpha1 but after a time green points appear from under little reddish scales on the surface1 and these are developed into stalks an inch or less in height1 which terminate differently1 some in lobed shields1 others in spoked whorls1 like a carriage wheel without the rim 7fig4 #dc74 ,the lobed shields are rather concave and covered with little elevations1 in each of which there is a flask-shaped cavity with a long neck opening on the surface of the shield4 ,in all of these hollows there is a mass of cells full of an amorphous substance1 which is changed into spermatozoids1 having the form of delicate spiral filaments1 thicker at one end1 and furnished with two cilia1 with which they revolve in a spiral within their cell4 ,at last they emerge from it1 and come through the neck of the flask-shaped hollow to the surface of the shield4 ,illustration3 ,fig4 #dd4 ,marchantia polymorpha3--,a1 portion of frond seen from above1 showing lozenge-shaped divisions 7a71 with central stomata 7b72 ,b1 vertical section1 showing the layers of tissue1 and one of the stomata 7g74 ,illustration3 ,fig4 #de4 ,marchantia polymorpha3--archegonia4 ,illustration3 ,fig4 #df4 ,elater and spores of ,marchantia4 ,in the companion female receptacles at an early age1 certain objects called archegonia 7fig4 #de7 are found to be concealed between membranes which connect the spokes of the whorl at their origin4 ,these archegonia are shaped like flasks with long necks1 and each has a germ cell in its interior1 into which a canal leads down from the extremity of the neck4 ,when this embryo or germ cell is fertilized by the spermatozoids1 instead of producing a new plant resembling its parent1 the embryo cell developes itself into a sporangium containing spores1 which are isolated cells enclosed in firm yellow envelopes and elaters1 or ovoidal cells1 each containing a double spiral fibre coiled up in its interior4 ,this fibre is so elastic1 that when the surrounding pressure is withdrawn by the bursting of the sporangium at maturity1 the spires suddenly extend themselves with such force as to tear open the cell membrane1 and jerk forth the spores which may be adhering to their coils1 and thus to assist in their dispersion4 ,the spores1 when they germinate1 develope themselves into little collections of cells1 which gradually assume the form of a flattened frond4#ff ,it is only when exposed to light and air that the ,marchantias have regular fructification2 in shady places they are reproduced by buds placed in open conceptacles1 which are formed out of green globules that appear in different parts of the frond1 and after a time split open at the summit and expand into singularly graceful cups or baskets1 whose edges are sharply and regularly indented so as to form a glistening fringe of teeth1 while each tooth is adorned with a narrow fringe4 ,when mature1 the basket contains a number of little green round or oval discs raised on footstalks1 and composed of two or more rows of cells4 ,as soon as these objects1 called gonidia1 are ripe1 they are detached from their stalks1 and being washed out of their basket by the rain1 they quickly grow on the moist earth around2 sometimes they germinate before they leave their nest1 and form irregular lobes on the parent plant4 ,the ,marchantia polymorpha1 so admirably constructed1 occurs in all temperate climates1 and can bear considerable heat provided it has abundant moisture4 ,the ,marchantiace are divided into three groups1 containing fifteen genera1 which are distinguished from each other by the character of their fructification4 ,they are minutely described in ,mr4 ,berkeley's #8,cryptogamic ,botany2' and are widely dispersed both in temperate and tropical countries1 most of the genera being represented in ,europe4 ,the ,jungermanniace1 or ,scale ,mosses1 in their lowest forms bear the same resemblance to ,lichens that many of the other ,liverworts do4 ,these lichenoid forms are lobed1 leaf-like masses1 sometimes ribbed and sometimes not4 ,there are forty genera of this group of plants1 distributed amongst fifteen tribes1 and exhibiting great variety of form and structure2 but in external aspect they are so closely connected1 that a graduated series may be traced from the flat-lobed frond to the higher forms of erect-stemmed foliaceous plants1 approaching in size and structure to some of the smaller mosses4 ,the higher groups have a distinct upright stem with symmetrical leaves1 which leaves1 however1 in the lower genera1 are merely fleshy fronds without veins1 of numerous and sometimes grotesque forms1 while in the higher1 they are generally oval1 and disposed in spiral imbricated rows on each side of the stem and branches1 every leaf overlapping part of that which is adjacent to it like a row of tiles4 ,they are disposed after two distinctly different plans4 ,in one1 the leaves are arranged in a spiral1 which turns from left to right2 consequently1 the anterior border of each inferior leaf is covered by the posterior border of that immediately above it4 ,this constitutes the succubous group of frondose ,jungermannie1 which embraces five tribes4 ,in the second case1 the spiral of the leaves turns from right to left1 and the anterior border of each inferior leaf covers the posterior border of that immediately above it4 ,this constitutes the incubous group embracing three tribes of the frondose ,jungermannie4 ,besides the imbricated spiral leaves1 there are small leaves alternating with them1 and applied directly on the stem between them4 ,the male fruit of the ,scale ,mosses consists of antheridia1 which form ovoid masses of cells variously disposed2 in each of these cells1 there is a filiform spermatozoid coiled in a circle in active motion1 which is maintained after leaving the cell4 ,the female fruit consists of archegonia1 containing embryo cells1 which ultimately develope into sporangia2 but the plants arrive at their full development before the archegonia appear4 ,the same plant may produce more than one crop of these objects1 which are occasionally abortive4 ,the stalk of the sporangium is first surrounded by the sac of the archegonium1 then by an involucre or circle of bracts1 placed in a rosette of leaves4 ,the sporangia contain cells which ultimately become spores mixed with long cells containing elaters1 that is1 elastic spiral filaments4 ,when the fruit is ripe1 the sporangia split into four equal parts1 which form a cross on the top of their stems1 and the elaters spring out of their cells1 and disperse the spores4 ,the plants of this order are also reproduced by gonidia1 but in such numerous genera and species the arrangement of the reproductive bodies and their minute details are exceedingly varied4 ,they are chiefly distinguished by the insertion of the fruit1 and the form of the different organs which surround it4 ,they are pretty little plants1 occasionally of a bright green1 but oftener inclined to red1 purple1 and chocolate colour2 a few are fragrant1 but they are of no known utility4 ,they are found in shady woods and moist situations1 throughout all regions of the globe1 but are most abundant in damp1 tropical forests4 ,in all the families of the leafy ,cryptogamia as well as in the ,hepatic1 antheridia exist2 they differ much in form and structure1 but they collectively agree in developing in the interior of delicately walled cells1 an amorphous substance1 coloured yellow by iodine1 in place of which1 at the epoch of maturation1 spermatozoids appear1 thick at one end and running to a very fine point at the other1 and displaying several spiral convolutions4 ,when rolled up like a watch-spring the motion is more or less rotary1 but if it be coiled in the form of a corkscrew1 the movement is at the same time advancing4 ,the thin end of the filament always goes first both within the cell and after it comes out4#fg ,the whole structure of the ,hepatic is full of objects of interest to the microscopic observer4 ,,section ,,vii4 ,,musci1 ,,or ,,mosses4 ,,mosses approach the higher classes of vegetable life in having roots1 and a more or less upright stem or axis of growth4 ,like all other plants1 they are chiefly formed of cellular tissue1 yet1 in the stems1 there is an indication of a separation between the bark and pith by the intervention of a circle of elongated cells approaching to woody fibre1 which passing into the branches and leaves form a kind of midrib1 either extending to the extremity of the leaf or not4 ,the delicate little leaves1 which are arranged with great regularity1 consist of a single or double layer of cells united by their flattened sides1 and rarely exhibiting any epiderm or skin4 ,green is the prevailing colour in this order of beautiful little plants1 but1 when exposed to the sun and much moisture1 they sometimes become red4 ,the urn-like vessels 7fig4 #dg ,b71 containing the spores1 are either terminal or lateral on the stem of the moss1 and rise on a slender stalk from a rosette of narrow leaves possessing a skin perforated by stomata or breathing pores of simple structure4 ,this is the ultimate result of fructification2 for at a very early period1 while the rosettes of narrow leaves are merely buds1 they contain antheridia and archegonia1 the latter or female organs being either inclosed in the same bud1 or in different buds placed on the same or on different plants2 but however that may be1 the buds are invariably placed at the base of the leaves1 close to the axis of the plant4 ,when a male bud is developed1 the antheridia are found to be globular1 ovoid1 or elongated hyaline bodies1 set in a cluster of hairs and paraphyses1 or sterile cellular filaments4 ,fig4 #dh represents the antheridia of ,polytrichum commune1 with the paraphyses and hairs1 from the microscopic observations of ,dr4 ,carpenter4 ,the central antheridium is discharging its spermatozoids2 the one on the right is empty1 that on the left immature4 ,illustration3 ,fig4 #dg4 ,a1 plant of ,funaria hygrometrica3--f1 leaves2 u1 urns or capsules2 ,s1 seta or foot-stalk2 o1 operculum2 c1 calyptra4 ,b1 sporangia of ,encalypta vulgaris3--u1 urns2 o1 opercula2 c1 calyptra2 p1 peristome2 s1 seta4 ,the antheridia are filled with a mass of mucilage containing a multitude of cells1 in each of which there is a spiral filament furnished with cilia1 as in fig4 #di4 ,as soon as the filaments are mature1 the cells open2 the mobile filaments1 or spermatozoids1 are free1 and come out through a pore in the antheridia1 in multitudes like pollen out of an anther4 ,while the antheridia are in process of formation1 the female buds expand and exhibit flask-shaped archegonia1 similar to that in fig4 #de1 seated in a rosette of leaves4 ,when this archegonium is fertilized by the spermatozoids1 its internal germ cell is developed by cell division into a conical body elevated upon a stalk2 and this at length tears across the walls of the flask-shaped archegonium by a circular fissure1 carrying the higher part upwards as a calyptra or hood 7fig4 #dg c7 upon its summit1 and leaving the lower part to form a kind of collar round the base of the stalk4 ,illustration3 ,fig4 #dh4 ,polytrichum commune3--group of antheridia mixed with hairs and sterile filaments 7paraphyses71 the central one discharging its contents4 ,illustration3 ,fig4 #di4 ,polytrichum commune3--,b1 cellular contents of an antheridium previously to the development of the spermatozoids2 ,c1 the same1 showing the first appearance of the spermatozoids2 ,d1 the same1 mature and discharging the spermatozoids4 ,the urn-shaped organ or sporangium has a double wall1 and in its centre a fusiform or deeply winged columella4 ,between these two there is a tissue of a most delicate texture1 divided into spherical cells1 each of which usually produces four unripe spores1 which get an exterior coat when fertilised1 and then it is that the stalk lengthens1 and the flask-shaped archegonium is torn across4 ,the urns are closed by a lid or operculum of a flat1 convex1 or pointed form1 which falls off when the spores are ripe to give them egress4 ,the mouth of the urn in most of the mosses is surrounded by a deciduous annulus of two or three rows of elastic cells1 which are supposed to aid in scattering the spores1 for the mosses have no elaters4 ,although the separation of the lid may at once expose the spores1 they may be covered with a membrane entire or toothed at the circumference1 or there may be one or two rows of teeth surrounding the mouth of the urn like a fringe2 these teeth form the peristome1 and their number is always a multiple of #d1 varying from #d to #fd 7see fig4 #dg p74 ,sometimes they are divided half way down1 sometimes they are prolonged into straight twisted hairs4 ,the teeth arise from the thickening of the walls of two contiguous cells2 when there are two rows of teeth1 the outer row frequently arises from the layer of cells which line the outer wall of the urn1 the inner row from the outermost layer of the spore sac2 sometimes1 when the peristome is double1 three strata of cells are requisite to form the teeth4 ,the urns of the ,encalypta vulgaris are represented at fig4 #dg ,b2 one is covered with the hood or calyptra1 while from the other the lid has fallen off1 showing the mouth of the urn with its toothed peristome4 ,when a spore begins to grow1 its outer coat is ruptured1 its innermost coats protrude and form a projecting extremity1 which becomes developed into a confervoid pro-embryo1 analogous to the mycelium of fungi1 but is distinguished by the chlorophyll contained in its cells4 ,many spores may concur or not in its formation2 but the pro-embryo of each spore is capable of transforming one or more of the cells seated upon its various ramifications immediately into buds1 which grow up into leafy stems1 as the ,funaria hygrometrica1 so that here we have the peculiar condition of one spore giving rise to the development of a number of plants4#fh ,in process of growth each of these plants would produce antheridia and archegonia1 and1 by the process described1 a full-grown ,funaria hygrometrica with its urns and hoods1 as represented in fig4 #dg ,a1 would be the result4 ,if the moss be annual or biennial it dies after bearing fruit2 if perennial1 two or more successive crops of archegonia are formed4 ,the mode of fructification1 therefore1 resembles that of flowering plants1 with this difference1 that the fructification of the latter produces a young plant from each embryonic cell1 while in mosses the fructification of one embryonic cell produces a sporangium or urn containing spores1 that is1 a multitude of reproductive bodies1 which have no trace of cotyledons or axis4#fi ,mosses are also propagated by gemm or buds4 ,they are produced in many situations1 sometimes on distinct organs1 sometimes on the tips of the leaves1 or on rootlets which grow on various parts of the plants1 and which in some of the mosses form a dense woolly or silky mass of a bright yellow or brown colour varying to purple4 ,on the fibres of this mass1 green cells appear1 which are developed into reproductive buds4 ,almost every cell on the surface of a moss is capable of forming1 by continued division1 a cellular nodule1 which falls off and gives rise to a germ which grows into a new plant4 ,these nodules are generally situated at the extremity of the leaves1 or on the leaves themselves1 while pro-embryo fibres spring from the leaf cells of many mosses4 ,m4 von ,mohl observes that since the cells in the different parts of mosses are capable of being developed into a bud or embryonic confervoid structure producing a bud1 it follows that in these plants1 notwithstanding their rather complex structure1 the subordination of the individual cell to the purposes of the whole plant is still but small2 and even here individual life readily acquires the preponderance4 ,this facility of reproduction possessed by the various individual parts of the plants1 accounts for the extensive tracts over which mosses spread themselves2 moreover1 some are dicious1 and as the spores might not always be fertilized1 the gemm ensure the continued existence of the species4 ,mosses are divided into five principal groups1 differing exceedingly in importance1 and in comparative numbers4 ,they are chiefly distinguished by the position of their fruit4 ,the ,pleurocarpi have their fruit lateral1 whether on the stem or branches4 ,they comprise thirteen tribes2 many of them are found in the southern hemisphere1 but a considerable number1 especially of the ,hypnei1 ,drepanophyllei1 and ,hookeriei1 are ,european4 ,the ,cladocarpi are characterised by having their urns seated on the tops of very short lateral branches1 and by their double axis of growth4 ,the ,acrocarpi are distinguished by their main stems ending in fruit4 ,they comprise twenty-seven tribes1 and embrace genera and species having a wide geographical range4 ,in the ,syncladei the branches of the plant are fasciculate2 this group comprises the ,sphagnums4 ,the ,schistocarpi are remarkable for their fruit splitting into valves1 and consist of the tribe ,andrace4 ,the various tribes depend on the structure of the urns and leaves1 as well as on the natural habits of the plants4 ,in this numerous class of plants only a few remarkable for peculiarity of structure can be mentioned4 ,the species of the acrocarpous tribe ,phascei are exceedingly numerous1 and contain the simplest of all mosses2 they grow on newly turned-up soil1 and are chiefly annual4 ,their leaves generally have nerves1 and are bordered by large cells4 ,the urns1 which are either sessile1 or upon a short stalk1 have not a trace of peristome1 and sometimes have a columella1 sometimes not4 ,the spores are large compared with those of other mosses4 ,the tribe ,dicranei contains numerous species1 some of which are the commonest of mosses in ,europe4 ,they are easily known by their single peristome of sixteen teeth divided half-way down4 ,the leaves are extremely crisp and convolute1 and the hood is spoon-shaped4 ,the ,leucobryum is remarkable for pallid leaves2 it has three layers of cells1 a narrow layer of green cells embedded in the centre of the leaf with a broader layer of colourless cells on each side1 whose cell walls are perforated with large round openings1 as in fig4 #ej b4 ,the mosses of this order live on sandstone rocks1 shady banks1 and trunks of trees4 ,fig4 #ej shows the microscopic structure of the leaves of various mosses4 ,in the tribe ,grimmiei we have frequently a sessile urn1 with a single peristome1 and a mitre-shaped hood4 ,the leaves1 which are dark green1 have minute hexagonal perforated cells on their upper surface1 and a white nerve projecting from their extremity4 ,in the tribe ,polytrichei the mouth of the urn is mostly closed by a flat membrane and a hood rough with silky hairs4 ,the leaves are sheathing at their base and spreading at their tips2 except in a few cases they are rigid2 and the nerve often exhibits lamelliform folds4 ,the ,polytrichum dendroides contains scalariform ducts1 and starch granules4 ,the ,bryei are of variable size1 but a number of ,european species are among the finest of mosses1 on account of their large leaves and beautiful double-toothed peristome1 the great distinction of the group4 ,the leaves are margined1 toothed1 and composed of a loose reticulation of large rhomboidal cells2 in the genus ,timmia they clasp the stem at the base and spread widely at the tip4 ,there are thirty-three ,british species of the genus ,bryum1 many of which with their abundant urns are extremely ornamental4 ,illustration3 ,fig4 #ej4 ,microscopic structure of leaves of mosses3--a1 ,octoblepharum albidum2 b1 ,leucobryum glaucum2 c1 ,sphagnum latifolium2 d1 ,hypopterygium ,smithianum2 e1 ,eucamptodon perichtialis2 f1 ,andra subulata2 g1 ,campylopus lamellinervis4 ,the tribe ,splachnei contain many of the most singular and beautiful of the whole class of mosses4 ,they have large-celled diaphanous leaves and a straight urn1 with the spores radiating from the columella4 ,the urn has a swelling at its base1 often of greater dimensions than the urn itself4 ,in the ,splachnum vasculosum it is purple and very large1 but nothing in comparison of that organ in ,s4 luteum and rubrum1 which are the pride of hyperborean ,europe and ,america4 ,the enormous size of the swelling1 the variety of colouring1 the singularity and elegance of form1 and in some cases the unusual dimensions1 make the species objects of great interest4 ,the common ,s4 ampullaceum1 when growing in abundance on the shallow peaty banks of some mountain stream where cattle come to drink1 is scarcely exceeded in beauty by any cryptogam4 ,species of this order are abundant in the two hemispheres1 but the same species rarely occur in both4 ,their habits1 too1 are different1 for while those in the north only grow on manure1 those in the south grow on the trunks of fallen trees4 ,three genera occur in ,great ,britain4 ,gemm are found in the axils of the leaves in most species of this group4 ,the tribe of ,schistostegei consists of but a single most elegant species4 ,it inhabits shady caverns1 which are sometimes lighted by a golden gleam from the refractions of the confervoid shoots of its mycelium-like pro-embryo1 which is perennial1 and produces a new crop year after year4 ,the urn is subglobose without a peristome1 and when young the spore cells radiate from the columella as in the ,splachna4 ,the leaves show various intermediate stages between a vertical and horizontal insertion1 and are sometimes perfectly free1 while at other times they are united4 ,this moss is scarce1 and confined to the northern hemisphere4 ,there are various genera of aquatic mosses in the different tribes1 most of them floating plants4 ,of these are the pleurocarpous ,fontinalei1 which inhabit the northern hemisphere2 their urn1 with its double peristome of sixteen teeth1 forms a beautiful microscopic object1 on account of the latticed work in the inner row1 and the cross bars on the outer teeth1 which are united at their tips by two and two4 ,the common species have sharp-angled triangular stems1 and keeled leaves which clasp the stem at their base1 and are sometimes cleft along the keel4 ,the syncladeous ,sphagnei are aquatic bog mosses of a pale yellowish green colour4 ,they form but one genus1 ,sphagnum1 which consists of some eight or ten species and several varieties4 ,the species of ,sphagnum1 or common bog moss1 hold an important place in the economy of nature4 ,they are floating mosses1 entirely destitute of roots4 ,the stalk of the full grown plant1 like that of land mosses1 is constructed of three kinds of cells2 one forms the exterior or cortical layer1 another forms the central pith or axial system1 while the third1 which is coloured and somewhat ligneous1 comes between the other two4 ,the leaves1 which have their origin in the cortical layer while it is yet soft1 consist of two kinds of cells1 one kind being large1 elongated1 and colourless1 and containing spiral fibres loosely coiled in their interior4 ,the membranous walls of these cells have large round apertures by which their cavities have free communication2 for certain animalcules1 which sometimes live in the cells1 have been seen to pass from one to the other4 ,between these colourless cells are some thick-walled1 narrow1 elongated green cells1 which give the leaf firmness and colour4 ,according to ,mr4 ,wilson1 the fascicles1 or bundles of branches1 are disposed round the stem in imbricated spirals1 so that1 for every complete spiral formed by five of these fascicles1 there are eight spirals formed of twenty leaves1 four leaves being inserted between each pair of fascicles4 ,the fructification in all these floating mosses is immersed in the leaves of the stem1 the antheridia being globose1 and the spermatozoids having spiral motions1 both within the cells of the antheridia and when they come out4 ,the urns1 which are the product of fructification1 and are borne at the top of what appears to be a long footstalk1 but is in reality a pedunculate vaginula1 are globular1 and their lids have been observed to be driven off when the spores are ripe1 with such force as to give a distinctly audible report4 ,the common bog moss grows so rapidly that1 rootless as it is1 it soon covers a pool with its matted bundles of branches1 and as in a few years it has no room to spread1 the lower stems and branches decay1 sink to the bottom1 and begin to form a peat moss1 while the upper parts grow on1 so that new stems and branches are perpetually produced4 ,multitudes of spores no doubt germinate1 and1 in this way1 the pool is filled up1 and a peat moss is at length formed4 ,the ,sphagnum moss has such a power of absorbing moisture from the atmosphere1 that it forms and maintains the peat mosses and quagmires in the mountains which feed the streams at their feet4 ,mosses in general are almost as much indebted for moisture to the absorbing nature of their leaves as to their roots2 but the loose1 large celled1 and perforated leaves of the ,sphagnum suck up water like a sponge2 even during the heat of summer1 a quantity of water may be squeezed out of a handful of them4 ,in fact the plant is a perfect hydraulic machine1 for a small stem of it put into a glass of water with its drooping terminal branch hanging over the edge1 acts like a syphon1 and soon empties the glass1 pouring the water out through its bending top4 ,though the peat from ,sphagnum is often too spongy for fuel at present1 yet that little moss now growing on our mountains will yield aniline1 magenta1 paraffin1 and other illuminating gases to remote generations1 although not in such quantities as the richer vegetation of the coal measures1 the products of a warmer period4 ,like all cryptogams the mosses are exceedingly variable and difficult to distinguish4 ,not only does the same species show great differences in size1 but even in other respects the characters vary on account of climate1 soil1 and exposure4 ,beyond that of becoming converted into peat1 the uses of the moss family are not of any great importance4 ,brooms1 mats1 and other domestic articles are sometimes formed from ,polytrichum1 and in ,lapland ,sphagnum not only sometimes enters into the composition of bread1 but is used in place of clothing for new-born babes4 ,,section ,,viii4 ,,filices1 ,,or ,,ferns4 ,,of all the spore-bearing families1 the ,ferns are the most universally known4 ,they may easily be recognized by the coiling inwards of their young leaves in spring previous to expansion1 and by the arrangement of the fruit on their undersides when expanded4 ,the ,ferns are exceedingly numerous both in genera and species1 and vary from low herbaceous plants of an inch high1 to trees with upright trunks forty or fifty feet or more in height1 bearing a graceful coronet of leaves at their extremity4 ,the tree ferns come to the utmost perfection in the warm1 moist islands of the tropical oceans4 ,their boreal limit is about the thirty-seventh parallel of north latitude1 but1 on account of the vast extent of ocean in the southern hemisphere1 they reach the fortieth or fiftieth parallel of south latitude1 the more copious evaporation1 and the consequently moister air and soil1 being specially congenial to the fern tribe4 ,for that reason a most luxuriant fern vegetation prevails in ,juan ,fernandez1 ,western ,chili1 and ,new ,zealand4 ,in the latter there are one hundred and twenty species1 some of which are subarborescent1 while others form tree ferns of considerable altitude4 ,shade is not absolutely requisite to ferns1 for many of them grow luxuriantly when exposed to the sun1 provided the soil be damp4 ,the range of the non-arborescent ferns is very extensive4 ,according to ,dr4 ,j4 ,d4 ,hooker1 twenty-one species have been found in ,fuegia and the ,falkland ,islands1 and one grows in matted tufts in ,kerguelen's ,land4 ,in the north the ,cytopteris fragilis has been found in the seventieth parallel of latitude at ,minto ,inlet1 and both it and ,polystichum ,lonchitis have been gathered at ,disco1 on the west side of ,greenland1 and ,aspidium fragrans on the eastern side4 ,on account of the extremes of heat and cold in ,north ,america there are only fifty species in all that enormous extent of country2 while in ,britain we are indebted to the humidity of our climate for a rich vegetation of thirty-six species1 which adorn our woodlands1 our valleys and mountains in wild profusion4 ,one-half of our ferns are also native in the ,himalaya mountains1 where multitudes of ,british plants are indigenous4 ,the fern floras of ,great ,britain and ,new ,zealand are the richest in species of their respective latitudes1 and have several species in common4 ,the ferns of ,tasmania are1 with few exceptions1 identical with those of ,new ,zealand2 and the occurrence of the rather common ,australian and ,new ,zealand ,gymnogramma rutfolia in the ,pyrenees1 and no where else in the whole world1 so far as is known1 is a remarkable fact in the distribution of plants4#gj ,whatever the size of a fern may be1 its spores 7fig4 #ea ,a7 are microscopic4 ,they are produced within the sporangium by cell division1 and are therefore free and variously shaped4 ,they consist of a grumous mass enclosed in a double coat2 and when the spore begins to grow1 it sends out from the cell wall of its inner coat a white tubular projection or root fibre 7fig4 #ea ,b71 which passes through the cell wall of its outer coat4 ,this root sucks up liquid till it expands the inner coat sufficiently to burst open the outer one1 and then it begins to increase by the subdivision of its cells1 till the primary green leaf or marchantioid prothallus 7fig4 #ea ,d7 is formed4 ,this prothallus lies flat on the ground1 and is furnished on the under-side with fibrous roots to fix it1 and supply it with food4 ,illustration3 ,fig4 #ea4 ,development of spores of ,pteris serrulata3--,a1 spore2 ,b1 ,c1 early stages of development2 ,d1 the prothallus with radical fibres 7a1 b7 and antheridia 7h1 h74 ,two sets of organs are subsequently developed on the under-side of this prothallus2 one of these is a stalked cell called an antheridium1 and is situated near the roots2 the other is an archegonium containing a germ cell1 which is sunk in the cellular tissue4 ,in each of the antheridia1 which are numerous1 a cell is formed1 which becomes filled with a mass of mucilage mixed with a number of free cells1 containing a flat ribbon-shaped filament1 or spermatozoid1 coiled in a spiral manner1 which1 as soon as set free by the rupture of the cell1 revolves rapidly by means of several long cilia placed close to the large end4 ,fig4 #eb shows the globular antheridium and the spermatozoids of ,pteris serrulata4 ,the archegonia are fewer in number1 and contain the germ cell1 represented in fig4 #ec1 as viewed from above1 and sidewise2 it is placed at a little distance from the antheridia1 and after being fertilized by the active filaments or spermatozoids1 and matured1 it contains the primordial cell of the young fern1 which soon sends forth leaves rolled up and curled inwards previous to expansion1 and a root1 which being sufficient to feed the plant1 the flat pro-embryo1 which was the first stage of development1 perishes4 ,thus in the family of ferns there are two distinct periods of growth1 and one only of fertilization4 ,in flowering plants1 fertilization and its products are the final result of vegetation1 and the maturation of the fructification is frequently followed by death4 ,in the ferns1 on the contrary1 fertilization precedes the development of the plant1 which1 if perennial1 continues to bear fertilized fruit year after year4 ,illustration3 ,fig4 #eb4 ,antheridium and ,spermatozoids of ,pteris serrulata3--,a1 projection of one of the cells of the prothallus showing the antheridial cell 7b72 ,b1 antheridium fully developed1 containing sperm-cells1 each enclosing a spermatozoid2 ,c1 one of the spermatozoids magnified1 showing the cilia4 ,illustration3 ,fig4 #ec4 ,archegonium of ,pteris serrulata3--,a1 as seen from above2 ,b1 side view1 showing at ,a the cavity containing the germ cell2 at ,b1 the walls of the archegonium made up of four layers of cells2 and at ,c1 the spermatozoids within the cavity4 ,it is evident that there is an essential difference between the archegonium of the ,marchantia1 and that of the ferns4 ,the archegonium of the ,marchantia merely produces a sporangium1 while that of the ferns produces a new plant1 and is therefore1 in some sense1 analogous to the seed of one of the higher vascular plants1 though there is no affinity between the two4 ,the roots of ferns1 like those of forest trees1 are delicate fibres1 which descend either from a woody stem called a rhizome1 from rhiza1 a root1 or from a caudex1 so named from the ,latin1 caudex1 a trunk4 ,thus the stems of ferns are of two distinct types4 ,the rhizome generally grows horizontally1 and creeps along the surface of the soil or rock1 or tree trunk to which it is affixed1 but it is sometimes subterranean4 ,in this1 the growing point is in advance of the fronds1 which appear at intervals along the exposed side or sides1 and after they have reached maturity drop off1 leaving a clean scar or cicatrix4 ,the caudex varies from the size of a small wire-like thread to the size of a tree trunk4 ,it is sometimes elongated1 as in the superfine wiry thread-like stems of ,hymenophyllum1 the scandent ivy-like rooting stems of ,stenochlna1 and the subterranean1 horizontal1 widely-creeping stems of ,pteris aquilina1 all of which develop single fronds at intervals1 but fronds which adhere permanently to the stem1 and which do not fall off1 leaving a scar1 as do the fronds borne by the rhizome4 ,the more frequent form of caudex1 however1 is that of a short stocky stem producing fronds on all sides from its apex3 very frequently this is a globose or oblong mass growing erect1 yet scarcely reaching above the surface of the soil2 but sometimes it is more lengthened1 showing a more or less elevated stem1 or turning sideways1 and taking a decumbent position1 the young fronds1 however1 always rising from its apex4 ,it is on the latter plan1 by a continuous erect and upward growth1 that the trunks of tree ferns1 which rise sometimes sixty or eighty feet high1 are formed4 ,the common ,lady ,fern1 ,athyrium ,filix-fmina1 furnishes an example of the ordinary herbaceous caudex2 as also does the ,male ,fern1 ,lastrea ,filix-mas4 ,in the ,hart's-tongue1 or ,scolopendrium1 the caudex is generally compact1 and increases by the formation of new crowns or centres of growth around the older one1 till the whole becomes an almost spherical mass of considerable size4 ,the stipes or leaf-stalk of a fern is often of considerable length1 and in its upper part1 called the rachis1 which bears the leafy portion1 is commonly more or less branched1 as well as furrowed on its upper surface4 ,the fronds1 or parts analogous to leaves1 are sometimes simple1 as in the ,hart's-tongue1 the rachis of which has a symmetrical limb or wing on each side1 so as to form a long1 even-margined1 narrow1 tongue-shaped frond4 ,if the limb on each side of the rachis be deeply divided1 as in the ,polypodium vulgare1 the frond is said to be wing-cleft1 or pinnatifid1 and the divisions are called segments or lobes4 ,in most ferns1 however1 the frond is once1 twice1 or three times winged or pinnate1 and in such cases the first divisions are called pinn1 and the secondary or subsequent ones when present1 pinnul or pinnules4 ,the leafy portion1 whether simple1 pinnatifid1 or pinnate1 is always traversed by veins arranged on some definite plan1 a most important circumstance1 since the sori or fructification of the ferns is always produced in connection with the veins4 ,the fertile fronds1 in certain groups1 differ in form from the sterile1 generally by the greater or less contraction of their parts4 ,in most ferns the full-grown fronds are flat1 that is1 with all their parts lying in one plane2 but1 during their vernation1 that is1 when they first rise from the stem1 they are circinate or curled inwards1 like a crosier4 ,when a fern acquires a considerable stem1 as in ,tree ,ferns1 it consists of a central or medullary part1 consisting of cellular tissue1 and an external or cortical portion1 formed of the consolidated bases of the fronds1 in which may be seen1 on cutting a section of a trunk1 an irregular zone1 formed of fibro-vascular bundles1 scalariform ducts1 and woody fibre4 ,prolongations from this zone pass into the leaf-stalks1 and thence into the midrib of the leaf1 whence they spread into its lateral branches1 and ultimately appear in the leafy parts in the form of veins4 ,it is the arrangement of these bundles of coloured woody tissue in the cellular tissue of the leaf-stalks of the herbaceous ferns1 which give rise to those peculiar figures on their transverse sections1 such as a star1 the letter ,t1 and the heraldic spread eagle1 from which latter the common ,brake ,fern 7,pteris7 takes its botanical specific name of aquilina4 ,fig4 #ed shows an oblique section of the footstalk of a fern leaf with its bundles of scalariform ducts1 as determined by ,dr4 ,carpenter's microscopic observations4 ,illustration3 ,fig4 #ed4 ,section of footstalk of ,fern frond showing scalariform ducts4 ,the fructification of the ferns is arranged with the most perfect symmetry1 usually on the under surface of the leaf1 but sometimes at the margin1 and assuming a great variety of forms and positions4 ,it consists of sori1 that is1 groups of nearly globular spore cases or sporangia1 sometimes sessile on the frond1 sometimes with a footstalk4 ,they are always situated on a vein or its branches1 or at the extremity of the veins on the margin of the frond4 ,in fact the sporangia originate in the cellular tissue immediately in contact with a vein1 beneath the epidermis or skin of the leaf1 which is forced up as the sporangia increase in size1 in the form of a whitish membrane1 which constitutes the indusium1 or protecting cover of the sori4 ,while the fruit is advancing to maturity1 the indusium separates partly or wholly from the surrounding skin or epiderm1 and subsequently either shrivels or falls off altogether4 ,in some few species the opening is in the centre of the indusium1 and then it surrounds the sori like a cup2 in other ferns1 the skin from both surfaces of the leaf extends beyond the margin1 includes the sori between it1 and fulfils the office of an indusium4 ,illustration3 ,fig4 #ee4 ,pinnule of ,polypodium bearing sori4 ,the sori1 as already noted1 take a variety of forms1 and are variously situated4 ,some are round and dot-like1 some are oblong and straight1 some are hippocrepiform or horse-shoe-shaped1 while some are continuous in a line-like band4 ,the indusium1 when present1 takes more or less exactly the form of the sorus4 ,these peculiarities are so well marked that they are taken advantage of in the discrimination of genera4 ,the sporangia or spore-cases are for the most part of globular form1 and are nearly or quite surrounded by a strong elastic ring1 which in some cases is continued so as to form a stalk4 ,when the spores are ripe1 this ring1 by its elastic force1 tears open the sporangia1 and gives free egress to their contents4 ,the ring assumes various forms4 ,in one large group it passes vertically up the back of the sporangium1 and is continued to a point called the stoma1 where the horizontal bursting takes place4 ,this form is seen in fig4 #ef1 a1 b4 ,in other groups it is1 though vertical1 somewhat oblique1 as in fig4 #ef c4 ,sometimes1 though more rarely1 it is transverse and complete2 in which case the rupture is vertical1 as in fig4 #ef d4 ,in a few cases it is apical1 fig4 #ef e2 and in a few others it is obsolete1 fig4 #ef f4 ,these are the true ,ferns4 ,in one or two small groups1 sometimes called ,pseudo-,ferns1 the ring is altogether wanting4 ,illustration3 ,fig4 #ef4 ,sporangia of ,polypodiaceous ,ferns3--a1 b1 ,polypodiace2 c1 ,cyatheine2 d1 ,gleichenine2 e1 ,schizine2 f1 ,osmundine4 ,the systematic arrangement of the ,ferns is chiefly founded on peculiarities of the sori and sporangia1 characters which are quite intelligible by the aid of a good magnifying lens1 these spore-cases being very pretty opaque objects under the microscope4 ,thus some of the primary divisions are founded on the presence or absence of the ring or annulus on the spore-case4 ,another series of divisions are founded mainly on the nature of the ring in those cases when it is present2 and1 for the rest1 the form and position of the sori come in as discriminating characters4 ,in this way the main groups are marked out1 but1 in the case of the genera1 still further recourse is had to the sori and its covering1 and by some modern authors supplementary characters derived from the venation are brought into use4 ,the following is the arrangement adopted by ,mr4 ,moore1#ga and which agrees in its general features with that of most modern observers4 ,the two leading groups are the ,annulate and the ,exannulate ,ferns1 the first being much the larger division1 and consisting of the order ,polypodiace1 which comprises the ,true ,ferns1 while the second includes the two orders ,marattiace and ,ophioglossace1 which are some times called ,pseudo-,ferns4 ,the ,,polypodiace1 distinguished by the ring or annulus1 which more or less completely girts the sporangia1 offer so much variety of structure that it becomes necessary to subdivide them2 and for this purpose characters derived from the form1 number1 or position of the sporangia1 or the structure or development of the ring1 are chiefly relied on4 ,this gives several groups1 e4g4 ,polypodine1 the most comprehensive of all1 including some ten or twelve minor groups1 in which the sporangia are almost equally convex1 and have a vertical and nearly complete ring1 and in which the dehiscence is transverse at a part called the stoma1 where the stri of the ring are elongated1 and apparently weaker2 ,cyatheine1 in which the spore-cases are sessile or nearly so1 seated on an elevated receptacle1 with the nearly complete ring more or less obliquely vertical1 that is1 vertical below1 curving laterally towards the top1 and the dehiscence transverse2 ,matonine1 a single species only1 in which the sporangia are sessile1 bursting horizontally1 not vertically1 the ring being broad1 suboblique1 and nearly complete1 and the dorsal sori oligocarpous1 covered by umbonato-hemispherical indusia1 affixed by a central stalk2 ,gleichenine1 with the ring complete1 transverse1 either truly or obliquely horizontal1 the sporangia globose-pyriform1 forming oligocarpous sori1 i4e4 sori consisting of but few spore-cases 7two or four to ten or twelve71 situated at the back of the frond1 sessile or nearly so1 and bursting vertically1 the fronds1 moreover1 being rigid and opaque1 and usually dichotomously-branched2 ,trichomanine1 with the ring resembling that of the ,gleichenine1 but the sporangia lenticular1 numerous1 clustered on an exserted receptacle1 which is a prolongation of the vein beyond the ordinary margin of the frond1 so that the sori become extrorse marginal1 or projected outwards as well as opening outwardly1 while the fronds are pellucid-membranaceous2 ,schizine1 with the ring horizontal or transverse1 situated quite at the apex of the oval sporangia1 which is1 in consequence1 said to be radiate-striate at the apex2 ,ceratopteridine1 one or two aquatic species1 the sporangia sometimes furnished with a very rudimentary ring1 reduced1 as in ,osmundine1 to a few parallel stri1 sometimes furnished with a very broad and more lengthened ring2 and ,osmundine1 with the spore-cases two-valved1 bursting vertically at the apex1 the ring very rudimentary1 reduced to a few parallel vertical stri on one side near the apex4 ,in all but the last of these groups1 the sporangia are not valvate1 and consequently1 when they open for the liberation of the spores1 they burst partially or irregularly2 but in the ,osmundine they split at the top in two equal divisions4#gb ,a large portion of the ,polypodine are either tropical or subtropical4 ,the genus ,polypodium itself is one of the most extensive and diversified genera of the group4 ,it is chiefly distributed over the tropical regions of the western hemisphere1 but four species are indigenous in ,britain1 and of these the ,polypodium vulgare1 or ,common ,polypody1 is abundant about the trunks of moss-grown trees1 on banks1 rocks1 and old thatched roofs4 ,the young fronds appear in ,may1 and rise from five or six to twelve or eighteen inches in height4 ,they are lanceolate1 deeply pinnatifid1 with obtuse1 linear1 lanceolate1 indistinctly serrated segments4 ,the genus is distinguished by its naked globular sori1 which in this species are regularly disposed in a line on each side of the mid vein1 half way between it and the margin of the leaf4 ,when young1 they are of a yellow or bright orange colour1 which changes to brown when they are ripe4 ,the rhizome1 which branches in all directions1 is at first clothed with a skin densely covered with yellowish brown membranaceous lanceolate scales1 which at length fall or become obliterated1 leaving the surface nearly smooth4 ,the ,polypodium vulgare has many varieties1 several of which are well marked1 especially that called cambricum1 which is twice pinnatifid4 ,the plant is common in temperate climates4 ,illustration3 ,fig4 #eg4 ,pinnule of ,lastrea ,filix-mas with sori4 ,the ,aspidie form an extensive and widely distributed group1 embracing several of our common ,british species4 ,one of these is the genus ,lastrea1 which has1 for the most part1 lanceolate fronds1 bipinnate or tripinnate in division1 with linear lanceolate1 and usually pinnatifid pinn4 ,the sori are nearly circular1 seated upon the back of the veins1 and covered by a reniform indusium1 which is attached by its sinus4 ,in ,lastrea ,filix-mas 7fig4 #eg71 one of our commonest ferns1 the fronds spring up in a rather spreading mass1 from the extremity of a long scaly caudex1 and often present a vase-like tuft hollow in the centre4 ,the rachis1 leafy through a third or a fourth of its length1 is more or less clothed with thin membranaceous scales1 of a pale often brownish-golden hue1 a peculiarity common to the other ,lastre4 ,lastrea ,thelypteris1 the ,marsh ,fern1 however1 has them not1 and differs also from most of its congeners in having its sori submarginal4 ,its rhizome has a widely creeping habit of growth4 ,the ,lastrea mula has globular glands1 sessile over the whole under-surface of the fronds1 which secrete a perfume like new-made hay4 ,from a similar cause1 ,lastrea rigida was botanically known as ,polypodium fragrans4 ,this coumarine odour is possessed by several other ferns1 notably by ,cheilanthes odora4 ,the ,oleandra1 which is a foreign genus1 has simple fronds articulated near to the rhizome1 and its sori are placed on the tips of the parallel veinlets4 ,the ,oleandra neriiformis1 which grows on open spots1 has an erect rhizome1 and assumes quite a shrubby habit1 rising to from four to six feet1 and bearing at intervals whorls of fronds4 ,illustration3 ,fig4 #eh4 ,sorus and ,indusium of ,polystichum or ,aspidium4 ,in the genus ,polystichum1 the fronds spring in tufts from a short slow-growing caudex4 ,they are rigid1 linear or lanceolate1 and either pinnate1 bipinnate1 or tripinnate4 ,the upper terminations of the fronds are sharp and spinous1 while the pinn are auriculate at their base above1 and oblique below4 ,circular sori are seated on the anterior branches of the parallel veins1 and these are covered by circular indusia1 opening all round and remaining attached by a short central stalk4 ,the free venation and this peculiar form of the sorus and indusium are the distinguishing characters of the genus4 ,fig4 #eh shows a sorus and indusium of ,polystichum or ,aspidium1 which differ only in venation4 ,one of the spinous1 serrated pinn of the ,holly fern1 ,polystichum ,lonchitis1 is represented in fig4 #ei2 it is auriculate at its base above and oblique below1 with its sori disposed in regular series on each side the mid-vein2 these often become confluent at maturity4 ,this beautiful ,alpine fern1 which is of a deep glossy green1 has linear lanceolate1 and simply pinnate fronds4 ,the pinn are short1 arranged alternately and obliquely on the rachis1 and extend nearly to its base1 which is rather densely clothed with reddish-brown chaffy scales4 ,the other ,british ferns of this genus are bipinnate4 ,p4 aculeatum is rigid1 but ,p4 angulare is lax1 and drooping4 ,one of its varieties1 named proliferum1 is abundantly viviparous1 producing small bulbils about the bases of the lower pinn and pinnules1 which readily reproduce the plant4 ,illustration3 ,fig4 #ei4 ,pinna of ,polystichum ,lonchitis4 ,all the preceding genera1 from ,lastrea inclusive1 belong to the ,aspidie1 an enormous tribe1 abounding in species1 and almost conterminous with the old genus ,aspidium4 ,the ,nephrolepis tuberosa and other species bear sub-translucent tubers on the rhizome4 ,they are subterranean1 ovoid1 an inch and a half long1 and filled with a nearly translucent mucus4 ,the tubers have a circle of vascular bundles forming a sort of balloon1 proceeding from a common base below1 and converging to the apex4#gc ,most of the species are tropical1 but ,lastrea and ,polystichum include several ,european species1 some of which are extremely variable4 ,the ,onoclea is a remarkable genus from the pinn being contracted into berry-like globes4 ,onoclea sensibilis is a handsome free-growing ,american species and appears to have been named sensibilis1 from the particularly rapid withering of the fronds after being gathered4 ,the genus ,cystopteris1 which has species in both hemispheres1 is the type of the ,cystopteride1 a small group which approaches ,aspidie through ,nephrolepis and ,acrophorus4 ,the ,british species of ,cystopteris are small1 fragile ferns1 growing on walls and rocks in ,alpine and ,subalpine districts4 ,their fronds are for the most part erect1 lanceolate or deltoid1 and bipinnate or tripinnate4 ,they are generically distinguished by having each round sorus covered by a hood-shaped indusium1 which is hollow and attached by its base1 and opens towards the apex of the segment1 its free margin being elongated and fringed2 in this respect it bears some resemblance to ,woodsia1 in which1 however1 the indusium projects from beneath the spore-cases equally on all sides1 becoming incurved in a cup-like form4 ,the ,cystopteris fragilis1 or ,brittle ,bladder fern1 flourishes in most shady mountainous and rocky districts1 but is also found in the lowlands4 ,it has a decumbent caudex1 which extends slowly1 branching and forming new crowns around the old one1 often to the number of several during the summer and autumn4 ,the fronds rise in tufts from these crowns in ,april1 rapidly attain their maturity1 and die away in succession as their place is supplied by others1 till the frost comes and destroys them all4 ,the tufts vary in height from two or three inches to a foot or more4 ,the fronds differ much in form and division even in the same crown1 but both they and the pinn are usually lanceolate2 the pinnules are ovoid or oblong1 always deeply pinnatifid1 and having the segments sharply toothed or serrated4 ,the ,dicksonia group1 ,dicksonie1 contains some of the finest tree ferns4 ,the ,dicksonia antarctica sometimes attains a uniform girth of twelve feet throughout its height of forty feet4 ,in the stem of this fern1 the vascular bundles are symmetrically disposed round the axis so as to form a closed cylinder4 ,the ,new ,zealanders slice the fibrous coating of the trunk1 and use it for constructing their houses4 ,d4 squarrosa reaches the farthest south of the tree ferns4 ,the ,d4 lanata sometimes forms a distinct stem but not always1 for tree ferns vary much with regard to the dimensions and elevation of their stem4 ,the caudex of ,cibotium ,barometz is covered with long tawny hair2 each has its own peculiarity4 ,the species of ,dicksonie belong principally to the tropics and southern isles4 ,the ferns of this group have globose sori1 which are submarginal1 seated at the tip of a vein or veinlet4 ,the indusium is lateral1 persistent1 and bivalved2 the lower valve is formed by the true indusium1 the upper by the altered tooth of the frond folded back4 ,in ,dennstdtia the indusium is cup-shaped1 and curiously deflexed2 while in ,deparia1 another section of the group1 the cup-shaped indusium containing the sorus is extrorse marginal1 as shown in fig4 #fj4 ,illustration3 ,fig4 #fj4 ,sorus and cup-shaped indusium of ,deparia prolifera4 ,the group ,peraneme1 or ,woodsie1 is represented in the ,british ,flora by two species of ,woodsia1 which are amongst the rarest and most curious of our ferns1 and inhabit the crevices in our highest mountain tops4 ,their tufts of fronds are not more than two or three inches high1 sometimes less1 and the fronds themselves are lanceolate1 and pinnate2 in ,woodsia ilvensis they have oblong and usually opposite deeply lobed pinn1 whose under-surface is clothed more or less with jointed hairs and long attenuated scales4 ,the sori in both species are circular1 and situated at the extremity of the lateral veins4 ,when young they are covered with an indusium1 which opens at the centre1 and forms a cup round the sori2 afterwards it is divided into numerous jointed and usually incurved threads4 ,the ,davallie are mostly tropical and subtropical ferns4 ,their sori are submarginal1 placed upon the tip of a vein or veinlet1 and enclosed within a tubular indusium1 which is either short and approaching to cup-shaped1 or more or less elongated4 ,in this group the stem assumes the form of a rhizome1 often creeping extensively1 and the fronds are articulated1 falling off with a clean scar when they perish4 ,davallia canariensis is cultivated in most conservatories1 and is known as the ,hare's-foot fern1 from the stoutish scaly rhizomes resembling the foot of a hare4 ,somewhat allied to these are the ,lindse1 including ,lindsa and its allies2 these have linear marginal sori1 for the most part continuous1 but sometimes regularly interrupted1 in which state they approach some of the ,davallie1 ,microlepia to wit4 ,the indusium opens towards the margin of the frond1 and the sori more or less connect the tips of the veins and veinlets4 ,illustration3 ,fig4 #fa4 ,scolopendrium vulgare4 ,the group of ,asplenie is a very comprehensive one1 including1 besides the extensive typical genus ,asplenium1 the cognate subdivisions of ,diplazie and ,scolopendrie4 ,the latter is represented by ,scolopendrium vulgare1 the ,hart's-tongue fern1 in which the sori are linear1 and situated in pairs on two parallel veins1 so closely approximate that1 though really double1 they seem to form but one straight line2 they are not covered with one indusium splitting down the middle1 but each has its own indusium opening in opposite directions4 ,on the under-surface of the long strap-shaped entire fronds of the common ,hart's-tongue1 which is a type of the genus1 the double sori with their opposite indusia form parallel equidistant straight lines1 diverging on each side from the mid-vein of the frond1 as in fig4 #fa4 ,the fronds are cordate at the base2 sometimes they are forked1 and occasionally crisped and wavy1 and the leaf-stem is shaggy with narrow membranaceous scales4 ,the caudex is very compact and deep-rooted2 it does not much elongate1 but increases slowly by the formation of new crowns round the older1 attaining considerable bulk4 ,from this the fronds rise in circular tufts to the height of a foot or more1 and attain from two to three feet1 in favourable shady localities4 ,at first the tufts are straight1 but ultimately they radiate and bend outwards4 ,this plant is exceedingly variable2 hundreds of varieties have been found or raised in ,great ,britain4 ,though twin sori are characteristic of the ,scolopendrie1 they diverge somewhat in ,camptosorus1 a ,north ,american genus1 sometimes called the ,walking fern1 from its habit of throwing forward a bud on a thread-like prolongation of the point of the frond1 which becomes established as a new growing centre1 and thus carries the plant onwards4 ,the group of ferns called ,diplazie1 another section of the ,asplenie1 typified by the genus ,diplazium1 is altogether tropical4 ,the sori are bilateral or double1 but placed back to back on the vein1 exactly the opposite of ,scolopendrie2 so that the indusia1 instead of opening face to face1 open in opposite directions4 ,the species are rather numerous1 and embrace much variety of form and character4 ,to the ,asplenie proper belongs one of our commonest species1 the ,athyrium ,filix-fmina1 or ,lady ,fern1 which1 when growing in moist shady places1 is one of the most elegant of ,british ferns4 ,its bipinnate frond varies from a broad almost ovate outline to a linear lanceolate form4 ,the numerous fronds often spring from the caudex in a vase-like arrangement1 to the height of four or five feet1 those in the centre nearly erect1 but the outer ones1 drooping around in all directions1 forming a tuft of lovely feathery foliage4 ,the sori have commonly a semilunar outline1 as in fig4 #fb2 but they are occasionally so much curved as to acquire a horse-shoe form1 and more rarely they are linear1 and they become at length reflected by the growth of the sporangia4 ,in some varieties they are distinct1 in others so close as to become eventually confluent and completely cover the surface4 ,the ,filix-fmina is distinguished by the linear junction of the indusium with the frond4 ,it is one of the most variable of all the known ferns1 and is remarkably prolific1 so that new forms may be raised from the spores4 ,there are a very large number found in this country4 ,illustration3 ,fig4 #fb4 ,athyrium ,filix-fmina4 ,all the ,asplenie have linear sori attached to the side of the vein1 so that they are said to be lateral4 ,the indusium opens on its inward side1 and is sometimes ciliated4 ,there are many tropical ferns of this group1 but the genus ,asplenium1 which has representatives in all parts of the world1 yields eight or nine species in ,great ,britain4 ,illustration3 ,fig4 #fc4 ,asplenium ,ruta-muraria4 ,the ,asplenium ,ruta-muraria1 or ,wall ,rue1 is an indigenous mountain plant growing in tufts six or eight inches high in the clefts of the rocks1 but has diminished much in size in migrating to the plains1 where it is found on old brick walls and outhouses4 ,the fronds are deltoid and bipinnate1 the pinnules are wedge-shaped and notched1 or toothed1 on their upper margin2 their colour is deep green1 but in exposed situations they are always covered with a glaucous secretion4 ,the veins diverge from the footstalk at the base of the pinnules1 branch out above1 and extend to the teeth or serratures1 as in fig4 #fc4 ,the sori1 which are produced on the inner side of the veins1 are linear1 elongated1 and eventually become confluent1 covering the whole under-surface of each fertile pinnule4 ,the indusium1 which is only traceable in the earlier condition of the fructification1 is white1 and the free inner margin is somewhat jagged4 ,changes as remarkable take place in the sori of the ,asplenium lanceolatum4 ,at first1 when the sori are covered by their white indusium1 they are oblong1 but they become circular as they enlarge1 and eventually often confluent1 so as to form a line round the whole under-margin of the sharply toothed pinnule4 ,this fern1 which is indigenous in the ,atlantic islands1 and is found in the ,channel ,islands1 as well as in the maritime counties of ,england and ,wales1 grows in the crevices of rocks and old walls1 or clothes the sides of wells and deserted mines4 ,it belongs to the section which has a mid-vein4 ,the genus ,ceterach apparently belongs to that section of ferns which have a vertical ring1 and no indusium2 but its affinities ally it closely with ,asplenium4 ,its want of an indusium is supplied1 perhaps occasioned1 by the abundance of chaffy scales which cover the back of the fronds4 ,the lateral veins are alternate and irregularly branched1 with the branches anastomosing towards the margin4 ,the sori are oblong or linear1 attached to the upper side of the anterior branches except the last1 which is on the opposite side of the lower branch4 ,the ,british species1 ,ceterach officinarum1 or ,scaly ,spleen-wort 7fig4 #fd71 has deeply pinnatifid1 lanceolate fronds1 with oblong1 obtuse1 alternate segments1 and linear sori4 ,the whole of the under-surface is densely clothed with brown1 pointed1 imbricated scales1 finely serrated at their margins1 the outermost of which extend beyond the edges of the segments4 ,they completely cover the sori1 and at first hide them entirely from view4 ,on the unexpanded fronds1 the scales are white and silvery4 #8,this plant has an obscure indusium1 only perceptible at an early stage of fructification1 and subsequently as a nearly erect membrane1 attached to the back of the vein4 ,it is rendered unnecessary by the arrangement of the scales1 which are disposed in regular series along each side of the veins and veinlets1 pointing outwards1 and concealing the sori with their broad bases1 which completely overlap them in their immature condition4' ,illustration3 ,fig4 #fd4 ,ceterach officinarum4 ,it is well known that the seeds of tropical plants have been brought to the western coasts of ,scotland and ,ireland by the great ,atlantic currents2 it might therefore be expected1 that the spores of ,cryptogams brought to our shores by the same means1 and finding a congenial climate1 should become naturalized1 as appears to have been the case in ancient times1 with regard to the ,ceterach and ,asplenium marinum1 from their migrations1 as traced by ,mr4 ,johnson4 #8,the countries bordering on the basin of the ,mediterranean and the islands and eastern shores of the ,north ,atlantic appear to have been the original stations of this remarkable fern4 ,in the ,british islands its distribution is too partial to admit of its being regarded as strictly indigenous1 though probably naturalized here at a period little subsequent to the arrival of ,asplenium marinum4 ,it occurs here on limestone-rocks1 but more frequently on old walls and ruins1 rooted deeply in the decaying mortar1 and often accompanying ,asplenium ,ruta-muraria and ,asplenium ,trichomanes4 ,like other natural importations from the south1 it is found most abundantly on the western maritime counties that receive the more direct flow of the tide1 and has progressed slowly towards the northern and central parts of the kingdom4 ,in ,scotland it has not yet traversed beyond ,perth1 and is still regarded as a rare species2 while in ,ireland its copious distribution seems to indicate an earlier arrival4' ,the group ,vittarie1 consisting mainly of ,vittaria and ,tniopsis1 is essentially equatorial or sub-equatorial4 ,the plants have narrow ribbon-like fronds1 with naked sori immersed in the very margin of the frond1 in a more or less sunken furrow1 there being no indusium4 ,the ,blechnum ,spicant1 which may be taken as a type of the ,lomarie1 is a very ornamental fern1 with its dark green1 linear-lanceolate fronds1 of two forms2 the fertile ones erect1 pectinate1 pinnate1 with distinct narrow linear and acute pinn1 while the barren ones are smooth1 spreading1 and pinnatifid1 with broad linear1 blunt1 approximate lobes4 ,the rachis is generally smooth1 and of a dark purple hue1 its leafless portion being shaggy with membranaceous scales4 ,the barren fronds lie on the ground in the winter1 while the fertile ones are erect1 bear fruit from ,may to ,october1 and wither when they have shed their spores4 ,in the fertile fronds the lateral veins are alternate1 and extend obliquely upwards1 about half way towards the margin of the lobe1 when1 by a sudden turn1 each runs parallel to the mid-vein1 and anastomoses with the one above it1 thus forming an apparently longitudinal vein on which the sorus is placed1 so as to form a line on each side of the mid-vein2 this is covered with a continuous indusium like a hem1 which opens on the interior side 7fig4 #fe74 ,in the barren fronds the veins do not anastomose at the margins of the lobe4 ,this species is common in almost every part of ,great ,britain1 and extends on the ,continent from ,swedish ,lapland to the borders of the ,mediterranean4 ,the species of ,lomaria are marked by having the fertile fronds contracted1 so that the sorus is quite marginal2 but there are many species of ,blechnum in which the elongated sorus1 placed parallel to the midrib1 is quite distant from the margin1 much more so than in ,blechnum ,spicant4 ,illustration3 ,fig4 #fe4 ,blechnum ,spicant4 ,illustration3 ,fig4 #ff4 ,pteris aquilina4 ,the genus ,pteris is the type of another group1 the ,pteride1 in which the sori form a continuous marginal line covered by the attenuated edge of the frond folded over it1 and forming an indusium4 ,this is the structure in most of the species of ,pteris1 a large family abounding in the tropics1 and very widely distributed in almost every part of the globe4 ,in the ,pteris aquilina1 or ,bracken 7fig4 #ff71 however1 in which the lateral veins of the leaf are divided two or three times before they reach the margin1 and the extremities of the branches anastomose and form a vein at the exterior or extreme margin of the leaf1 the sporangia are produced on the upper-surface of the marginal vein1 and are enclosed by an extension of the skin from both surfaces of the leaf2 so that the fructification1 which is folded back on the under-surface of the leaf1 is in the earliest stage of its development enclosed between two thin membranes1 both of which have their margins ciliated with jointed hairs1 while1 under the microscope1 their cellular structure will be found to differ in accordance with that of the upper and under epidermis1 from which they are individually extensions4 ,this fern is so universal in ,britain1 as to exclude in some places almost every other kind of vegetation1 and is so well known1 that it may appear superfluous to mention that the fronds are deltoid1 with an elongated1 stem-like petiole two or three times divided1 the primary pinn opposite1 the ultimate segments oblong1 obtuse1 and confluent4 ,there are exotic forms of ,pteris in every part of the world1 which are mere varieties of the ,pteris aquilina1 so that the ,bracken may be said to rank as the most universally distributed of all vegetable productions1 extending from ,west to ,east1 over both continents and islands1 in a zone reaching from ,northern ,europe and ,siberia to ,new ,zealand1 where it is represented by1 and perhaps identical with1 the well known ,pteris esculenta4 ,the ,allosorus crispus1 ,parsley fern1 or ,curled ,rock ,bracken1 which may be taken as a type of its genus1 is by some authors referred to the same group of ,pteride1 though others regard it as one of the ,polypodie4 ,it is a pretty little fern1 growing in tufts in sheltered crevices of mountain rocks1 from ,lapland to the ,mediterranean4 ,the fronds are deltoid1 twice or three times pinnate1 and of two kinds4 ,the ultimate divisions of the barren fronds are wedge-shaped1 cut1 and toothed2 those of the fertile fronds are linear1 oblong1 and entire4 ,although the sori are at first circular1 and situated near the extremities of the lateral veins1 they become confluent in maturity1 and being covered by the reflexed margin of the pinnules of the contracted but scarcely altered fertile frond1 instead of by an indusium1 they bear some resemblance in fructification to ,pteris aquilina4 ,the ,adiantie form an exceedingly numerous and mostly tropical group of ferns1 in which the rhizome is creeping or globose4 ,their sori are linear or oblong1 straight or curved1 and growing on the under-side of the edges of the leaf1 which are folded over with them1 and thus serve as an indusium4 ,adiantum has a free venation1 but ,hewardia1 a related genus1 has a reticulated venation4 ,the ,adiantie have linear1 oblong or lunate sori1 seated on the margin of the leaf4 ,of the seventy species of ,adiantum1 only ,a4 pedatum and ,a4 ,capillus-,veneris1 the first ,american1 the latter ,british1 are inhabitants of a cold climate4 ,the ,a4 ,capillus-,veneris1 which is universally distributed in warm latitudes1 is believed to have migrated in ancient times to the mild and damp south-western counties of ,england and ,ireland4 ,the ,adiantum ,capillus-,veneris1 or ,maiden's ,hair1 has a slender1 black1 scaly1 creeping1 and branching rhizome1 from the extremities of which spring lax tufts of fronds growing from a few inches to a foot high4 ,the stems with their alternate branches and branchlets are slender1 hair-like1 and of a blackish purple tint4 ,the capillary branchlets bear at their extremities thin1 bright1 but glaucous green1 wedge-shaped leaves1 serrated at their edges4 ,the fibro-vascular bundles which traverse the stems and branches1 on reaching the leaves1 spread into a palmate venation1 which terminates at the margin in bifurcations2 and upon these1 in the fertile leaves1 roundish sori are placed1 and covered by the transverse oblong folds of the edge of the leaf1 as in fig4 #fg4 ,these delicately graceful ferns flourish almost exclusively in damp shady crevices of rocks under the spray of cascades1 and still more luxuriantly in deep tropical forests1 where the air is loaded with warm vapour4 ,illustration3 ,fig4 #fg4 ,adiantum ,capillus-,veneris4 ,the ,acrostiche are among the most remarkable of ferns in having the whole under-surface of the frond indiscriminately covered with naked sori1 and in a few species the upper-surface also4 ,they are situated on the veins and veinlets1 from whence they extend into the interstices of the fertile fronds1 which are sometimes much contracted4 ,the species are almost all tropical or subtropical4 ,a ,new ,zealand species of ,lomariopsis climbs high trees by means of its stout rooting caudex1 and has different leaves on different parts of the plant4 ,the ,cyatheine are chiefly arborescent ferns1 and1 with the exception of some fossil species1 contain the noblest representatives of the cryptogamic flora4 ,their fructification consists of dot-like sori1 in which the usually compressed oblique sporangia are placed on an elevated receptacle1 which forms a raised point on the surface of the fronds when the sporangia are removed4 ,of these the ,alsophile are without true indusia1 while the ,cyathe have a spherical indusium1 bursting above or below1 and forming a cup round the sorus4 ,the pulpy substance of the stem of ,cyathea medullaris was a common article of food with the ,new ,zealanders4 ,the ,gleichenine have a creeping or climbing rhizome1 and globose or trigonal sporangia1 few in number1 and disposed in a radiating manner1 so that the narrow end is internal4 ,they are often seated in a little cavity1 and are highly deciduous4 ,the fronds are generally forked or trifid1 the middle division being sometimes supplied with a little bulb-like body4 ,they are mostly tropical or subtropical plants1 but some species grow in ,chili1 ,new ,zealand1 and ,japan4 ,the ,trichomanine are pretty well distinguished from other ferns by their pellucid membranaceous texture4 ,as regards their technical characters1 they have an oblique and complete ring to the sporangia1 which are of a lenticular form1 and are collected about a more or less elongated receptacle1 which is free within either an urn-shaped cup or a two-valved indusium1 projecting from the edge of the frond4 ,they are chiefly inhabitants of the moist tropical forests1 or extra-tropical regions of damp and mild temperature4 ,great ,britain only owns one species of the genus ,trichomanes1 and two of the genus ,hymenophyllum1 while species of these two genera constitute one-fifth of the fern vegetation of our antipode islands of ,new ,zealand4 ,it is more than doubtful even that the ,trichomanes radicans1 or ,bristle fern1 is indigenous1 as it is found in no other part of ,great ,britain except the ,irish counties of ,cork and ,kerry1 growing on dripping rocks and waterfalls1 or depending from the walls and roofs of caverns2 and as it is also found in the ,west ,indies and the ,north ,atlantic islands its transit may be accounted for1 as in other cases4 ,illustration3 ,fig4 #fh4 ,trichomanes radicans4 ,the fronds of the ,bristle fern1 ,trichomanes radicans1 are somewhat deltoid1 or of a more elongated form1 flimsy1 and beautifully reticulated when viewed with a microscope4 ,they rise at intervals from a creeping rhizome1 bristly1 with narrow articulate scales1 which often covers the most precipitous rocks on which it grows with a dark-coloured network4 ,the rachis is branched and rebranched three or four times1 and the whole being distinctly winged on both sides in the plane of the frond1 the successive branches and branchlets running through the leafy part become the veins of those parts1 so that a segment of the frond is merely a winged vein1 the wings on the branches being however broader than those on the rachis4 ,the veins1 which divide alternately1 are hard1 woody1 and wire-like1 and1 when barren1 terminate before reaching the ends of the segments2 but1 when fertile1 they extend beyond the segment1 the tissue of which separates and distends in the form of a more or less elongated cup around the prolonged vein4 ,at the base of that vein the sporangia form a small globular cluster2 and1 as they advance towards maturity1 the vein extends in the form of a bristle1 far beyond the mouth of the cup 7fig4 #fh74 ,the cup is winged in the more luxuriant form of the plant1 in consequence of the double layer of tissue composing the segment to which it belongs not separating through its whole breadth4 ,the cup-like cylinder being slightly compressed in the plane of the frond is indicative of its origin4 ,illustration3 ,fig4 #fi4 ,hymenophyllum tunbridgense4 ,a slight difference in fructification separates the ,hymenophyllum tunbridgense1 or ,film fern 7fig4 #fi71 from the ,trichomanes1 for both have a creeping rhizome1 from which single fronds spring at short intervals4 ,the leafy parts of the fronds are merely winged veins1 and the wings consist of two layers of cellular tissue finely reticulated4 ,the ,hymenophyllum is distinguished from the ,trichomanes by a two-valved cup spinously serrated1 which completely conceals the fruit-bearing vein1 while1 in the ,trichomanes1 the cup is more cylindrical1 smooth-edged1 with the fertile vein projecting far beyond it 7fig4 #fh74 ,the beautiful little ,film fern1 with its semi-transparent fronds not more than two or three inches high1 grows on shady wet rocks1 among the moss on the branches and roots of old trees1 and on the ground near lakes and rivulets4 ,it is hardy enough to live in the ,highlands of ,scotland2 but the ,h4 unilaterale1 a far less beautiful plant1 has its limit in ,unst1 the most northern of the ,shetland ,islands4 ,the fructification in the latter plant1 though the same in position1 is stalked instead of being sessile4 ,the involucre is rounded and ovate1 instead of being cup-shaped1 with much swollen convex valves1 meeting by their edges but not compressed towards the apex4 ,the ,schizine are many of them climbing ferns1 and for the most part tropical4 ,lygodium articulatum climbs trees in ,new ,zealand to the height of fifty or one hundred feet1 and its tough wiry stems are used for cordage4 ,in one group of this order1 represented by ,lygodium1 the sporangia are disposed at the back of the frond in imbricated marginal spikes1 formed by a transformation of the ultimate pinn4 ,in the other division1 represented by ,schiza1 the fruitful spikes are really on the under-side of the frond1 but the frond being reversed they seem to be on the upper4 ,the ,ceratopteridine1 sometimes called ,parkeriace1 are tropical aquatic ferns1 whose sterile fronds1 which are membranaceous1 with a thick vascular footstalk1 float on the surface of the water1 and by the time these are nearly decayed the fertile fronds are perfected4 ,the latter are more erect1 repeatedly divided and forked1 the divisions being linear4 ,there is only a single genus1 ,ceratopteris1 which has continuous sori occupying the longitudinal veins at the edge of the frond1 and covered by the indusioid margin4 ,the sporangia have a very broad incomplete ring1 and connect the ringless ferns with the group which possess them4 ,the spores are triangular1 and marked with three sets of concentric ridges4 ,the order ,osmundine contains the ,osmunda regalis1 considered to be the finest of all ,european ferns1 which is common throughout ,great ,britain in wet spongy soils1 and appears to be the only species of the group that is ,european4 ,the fronds grow in tufts from a thick woody caudex1 which branches and extends widely by the formation of lateral crowns1 but1 if impeded1 it elongates and rises in an erect position to the height of two or even three feet above the soil4 ,the barren fronds of the large luxuriant tufts are highly developed1 and are from six to nine or even eleven feet high2 the fertile fronds are shorter and fewer in number4 ,the bipinnate character prevails throughout2 the primary divisions are opposite1 the secondary alternate1 and the pinnules are oblong and opposite4 ,the sculptured sporangia have a very rudimentary ring1 and1 in the fruit-bearing fronds1 four or five of the lower pairs of pinnules have the leafy character1 while the remainder develop clusters of sporangia in place of pinnules4 ,the sporangia on the fruitful branches are at first pale green1 but gradually become reddish brown1 hence the name of ,flowering fern4 ,the ,leptopteris section of the genus ,todea1 almost peculiar to ,new ,zealand1 has beautiful transparent fronds1 with naked sporangia placed upon the veins1 forming very much scattered sori4 ,the ,,marattiace may be partly known by their huge globose rhizome projecting above the ground1 and rough with the processes from which the leaf-stalks have fallen4 ,this sends out a few large fibrous roots1 and consists of cellular tissue abounding in starch1 with small bundles of fibro-vascular tissue regularly distributed through it4 ,the stipes have a pair of stipule-like organs at their base2 and the sori are either oblong fronds of a double row of sporangia1 which in some cases is concrete1 or they are circular with the sporangia annularly concrete1 or they are connate throughout the fertile portions4 ,these peculiarities respectively distinguish the smaller groups of ,marattine1 ,kaulfussine1 and ,danine1 while the group ,marattiace itself is distinguished from ,ophioglossace by having its sori dorsal1 that is1 set on the back1 or under-surface1 of flat leafy fronds4 ,the leaves of ,angiopteris evecta are used as a perfume in the ,sandwich ,islands1 and its rhizome serves for food1 as that of the ,marattia salicina does in ,new ,zealand4 ,the ,,ophioglossace1 or ,adder's ,tongue ferns1 are few in number1 and present comparatively little difference in structure4 ,they are known among the exannulate series1 from the ,marattiace1 by having their fertile fronds contracted1 bearing their sporangia at the margin1 so that being entirely occupied by sporangia1 the fertile fronds appear as if they were an inflorescence distinct from the foliaceous organs1 as indeed they are analogically4 ,in this group there is the further difference that the fronds are not circinate1 but straight1 in their stivation4 ,these ,adder's ,tongue ferns are dwarf herbaceous plants1 differing greatly in structure from the true ferns1 though there is some similarity to them in the fructification4 ,they are divided into four genera1 of which ,ophioglossum and ,botrychium are best known4 ,the base of the stem is thick and bulbiform1 and sends off spreading succulent roots4 ,the species of the genus ,ophioglossum are chiefly plants of a warm climate1 but ,ophioglossum vulgatum1 or common ,adder's ,tongue1 is distributed in almost every part of the globe4 ,in ,england it is exceedingly abundant in meadows and pastures1 and varies in height from a few inches to a foot1 in moist soil4 ,it has one barren ovate and one fertile linear frond4 ,the barren frond1 which is of a yellowish-green colour1 invests the stem of the fertile frond like a spathe2 its form is ovate1 varying to ovate lanceolate1 and more or less obtuse1 with a complicated network of anastomosing veins4 ,bivalved sporangia form two parallel series on the margins of the club-like terminations of the fertile frond4 ,soon after the fruit is shed the fronds die1 but one or two buds are previously formed at the base of the plant1 which remain dormant till the following spring4#gd ,the genus ,botrychium has few species1 about half of which grow in ,north ,america4 ,botrychium ,lunaria1 or ,moonwort1 is the only species indigenous in ,great ,britain4 ,this plant1 which is from five to six inches high1 has a rather long succulent stem1 invested at the base by the dark-coloured membranous remains of withered leaves4 ,it has one barren frond1 the base of whose stem is a sheath1 through which the tall1 fertile frond rises4 ,the barren frond has from three or four to seven pairs of opposite smooth pinn1 of a lunate shape and glaucous green colour1 overlapping each other2 they are smooth1 crenated on the margin1 and occasionally lobed1 which gives them a fan shape4 ,the fertile frond is longer than the barren one1 and ends in a panicle or thyrse4 ,the sporangia1 which are large and bivalved1 are disposed in two regular series upon the divisions of the panicle1 and directed towards the upper or inner face of the frond4 ,this fructification bears a strong resemblance to that of ,osmunda regalis1 the ,flowering fern4 ,the stem of this plant has been assumed to be solid and branched1 which is by no means the case2 for1 upon dissection1 it is found to be hollow1 and at its base the fronds of the following year may be detected more or less perfectly formed1 and the rudimentary bud of the succeeding year within the latter2 the position of the barren and fertile fronds being reversed in the successive developments4 ,,section ,,ix4 ,,equisetace1 ,,or ,,horsetails4 ,,the ,equiseta are leafless1 herbaceous plants1 annually renewed from a creeping rhizome1 and growing in marshy land1 in pools and ditches1 on the banks of rivulets1 and in rivers1 from ,lapland and ,siberia to within the tropics4 ,there is but one genus1 and few species4 ,the largest of the ten or eleven species1 which are indigenous in ,great ,britain1 is not more than five or six feet high1 but they are of greater size in warm climates4 ,the ,horsetails begin their lives precisely like the ,ferns2 for1 when a spore begins to germinate1 it forms a marchantioid leaf or prothallus lying flat on the ground1 upon which are produced antheridia1 full of cells1 in each of which there is a spermatozoid with numerous cilia4 ,archegonia are also formed on the prothallus4 ,these1 after fertilization1 give rise to the perfect plant1 which throws out a rhizome1 whence new shoots are produced4 #8,the structure of the rhizome is very different from that of ferns4 ,in an early stage it consists of a central column of cellular tissue1 sending off about eight radiating plates1 which connect it with an external cylinder of the same tissue1 and opposite to each of which there is1 in the central column1 a vascular bundle consisting of annular vessels passing into spiral4 ,at a later period1 tissue grows from the walls into the cavities1 in such wise that they are more or less perfectly obliterated4'#ge ,from the rhizome1 which often extends to a great length1 the stems of the ,equisetums rise in the form of rough1 rigid1 hollow cylinders1 striated longitudinally1 and articulated at intervals by separable joints4 ,each articulation is invested at its base by a toothed membranaceous sheath1 from beneath which1 in the greater number of the species1 whorls of branches spring1 jointed like the stem1 and similar to it even to the number of teeth in the sheaths and stri on the surface1 but unbranched4 ,illustration3 ,fig4 #gj4 ,equisetum giganteum3--a1 fragment of stem with branches2 b1 cone or spike of fructification2 c1 one of the scales of the cone2 d1 spore with its elastic filaments4 ,the fructification is occasionally on separate stems1 which make their appearance before the barren ones1 and are in general unbranched and succulent1 bearing a cone on their apex4 ,the surface of the cone is at first smooth or indistinctly reticulated1 but it eventually splits into numerous octagonal1 brown1 shield-like discs1 spirally arranged1 which1 separated from the stem1 are found to have a stalk1 and to bear on the under-side four or eight pendent sac-like bodies of a whitish hue4 ,these are the sporangia1 which open on the inside by a slit for the discharge of the spores4 ,the inner coat of the cells of the sporangium is composed of beautifully spiral tissue4 ,the spores arise by cell division1 each being covered by a separate membrane1 which ultimately forms a pair of elastic fibres attached by their middle1 closely coiled round the spore1 as it is formed within the cell2 but1 when the spore is liberated1 they extend2 the least moisture1 however1 even the breath1 makes them contract4 ,the ,equisetace differ from the ,ferns in having spiral instead of scalariform vessels in their structure2 but they agree in having only one period of fertilization1 after which they produce a crop of spores year after year1 and these1 when sown1 give rise to the primary leaf with its antheridia and archegonia--a perpetual cycle4 ,the whole substance of the stems of the ,equisetums is so completely penetrated with silex1 that a silicious skeleton remains after the herbaceous part is destroyed1 and in some species as much as thirteen per cent4 of the whole plant1 and fifty per cent4 of its ashes are found to be pure silex4 ,on account of the crystallization of the silex1 the ,horsetails form some of the most beautiful of microscopic objects4 ,if a fragment of the cuticle is magnified and viewed by polarized light1 the colours are seen to be intense and vivid1 and the arrangement of the silicious particles so elaborate and symmetrical as to resemble necklaces of diamonds and coloured gems4 ,the rows of crystals run in lines parallel to the axis of the stem1 the greater number being so disposed1 but the rest are grouped so as to form ovals joined together by a chain of particles forming a sort of curvilinear quadrangle1 these rows of oval combinations being arranged in pairs4 ,the effect is brilliant when they are seen in polarized light4 ,according to ,sir ,david ,brewster every particle has a regular axis of double refraction2 but ,professor ,bailey1 of the ,united ,states of ,america1 states that the effect under polarized light is not produced by the silicious particles1 but by the organized tissues1 since1 after these have been destroyed1 the silex shows no double refraction4 ,the vascular tissue of the ,equisetums shows them to be of a higher class than the ,ferns4 ,the recent forms vary much in size1 but even the ,equisetum giganteum of ,brazil1 which is eighteen feet high and three-quarters of an inch in diameter1 is incomparably less than the ,calamites and other fossil ,equiseta1 which appear in the coal measures and new red sandstone4 ,recent species are found in ,iceland and the high northern latitudes of ,america1 in the tropics1 and in most parts of the world1 except ,australia and ,new ,zealand4 ,,section ,x4 ,,marsileace1 ,,or ,,rhizosperm4 ,illustration3 ,fig4 #ga4 ,pilularia minuta3--a1 mature plant1 natural size2 b1 receptacle1 slightly magnified4 ,,the ,marsileace1 a natural tribe of small perennial aquatic herbs1 have a filiform creeping rhizome with alternate erect leaves1 curled in vernation like those of the ferns4 ,the sporangia are enclosed in oval or spherical leathery capsules1 or receptacles1 which contain two dissimilar forms of reproductive organs--sporangia and antheridia1 and are sessile1 or nearly so1 on the rhizome at the base of the leaves1 whence the general name of ,rhizosperm4 ,the ,pilularia globulifera1 or ,pillwort1 the only ,british species of its genus1 may be taken as a type4 ,its rhizome creeps over sand or mud1 at the margins of lakes and pools1 where it is always submerged1 or in sandy or gravelly places1 which are only occasionally overflowed4 ,at regular intervals the rhizome sends off a tuft of roots and a tuft of leaves opposite to them2 the leaves are smooth1 erect1 and very slender1 in deep water almost hair like1 varying from four to five inches in height4 ,the solitary globular receptacles1 brown1 hairy1 and about the size of a small peppercorn1 spring from the axils of the leaves1 supported on so short a stem that they appear to be sessile4 ,fig4 #ga shows an ,algerian species of its natural size4 ,the receptacles are divided by cross partitions into two or more cells1 and separate at maturity into four equal valves4 ,each cell has a sort of placenta to which the sporangium and antheridia are attached2 and its upper half is lined with three minute1 sessile1 obovate1 yellowish bodies1 which are the antheridia2 the other half is occupied by a larger1 roundish1 or oblong sessile sporangium1 containing one spore1 which has a firm outer coat1 tapering to a point1 and leaving a cavity at the top of the nucleus4 ,according to ,hofmeister1 this cavity becomes filled with cellular tissue1 constituting a conical prothallus confluent with the nucleus4 ,a single archegonium is formed in the centre1 the orifice of which corresponds with the apex of the prothallus4 ,the antheridia contain numerous granules1 from which long spiral delicate spermatozoids are ultimately developed4#gf ,the embryos of the young plants push forth their radicle in one direction to fix them to the soil1 and a frond or leaf in the opposite direction4 ,thus these minute plants1 approaching so nearly to a monocotyledon1 exhibit a high organization1 only inferior to that of the ,lycopods4 ,the group contains the genera ,marsilea1 which has leaves made up of cuneiform lobes1 and resembling those of some leguminous plant2 and ,salvinia and ,azolla1 both of which consist of small floating plants1 which mostly occur in tropical or subtropical countries4 ,,section ,,xi4 ,,lycopodiace1 ,,or ,,club ,,mosses4 ,,the ,club ,mosses are mostly perennial plants1 with slender creeping stems1 often several feet or yards in length1 occasionally erect1 and clothed by small1 sessile1 closely set1 often imbricated leaves without veins4 ,they have in some instances a habit resembling that of ,conifers4 ,the stems consist of a mass of thick-walled1 often dotted cells1 enclosing one or many bunches of scalariform tissue1 which sends off branches to every leaf and bud4 ,the scalariform tissue is accompanied by fine1 elongated1 and sometimes rather coarser cells1 which are occasionally reticulated4 ,the stem approaches to that of ferns1 but the bundles of vascular tissue are confined to the centre4 ,the branches of the stems are often bifurcate1 and terminate in one or a pair of cone-like spikes1 which are either sessile or stalked4 ,the sporangia are sessile in the axils of the imbricated leaves or bracts that cover the cones4 ,two kinds grow on the same plant1 one of them bivalved1 containing a powdery substance1 whose particles a high magnifying power shows to be globular spermatozoids3 these do not germinate2 and the other three-valved1 enclosing comparatively large1 nearly spherical granules1 marked with three prominent ridges1 radiating from one extremity4 ,these certainly germinate1 forming by cell-division a prothallus of hexagonal cellular tissue1 adherent to and confluent with the spores1 as in ,marsileace1 or penetrating their cavity1 but without the protrusion of threads1 as in ferns or mosses4 ,on this prothallus1 archegonia are soon produced1 the embryo being formed from a cell at its base2 this sends down roots on one side1 and a minute stem with the two primary leaves of the young plant at the other4 ,the plant thus bears a close resemblance to a young plant of the dicotyledons1 and exhibits1 with regard to fructification1 the highest organization of which the ,cryptogams are capable1 although in their tissues the ,lycopods are inferior to the ,equisetace and ,marsileace4 ,there are four genera of this order1 very widely dispersed1 most abundant and larger in the hot moist parts of ,india and the ,indian islands1 but large tracts are covered with them within the arctic circles and in temperate latitudes4 ,there are #bjj species of the genus ,lycopodium1 or ,wolfs-claw1 and of these1 six only are indigenous in ,britain2 they grow in very exposed situations1 as in the case of ,l4 clavatum1 which lives on upland heaths and pastures1 and which has a procumbent stem1 creeping for many feet or yards1 sending out branches in all directions1 with a pair of cones at their extremities1 and strong roots at intervals to fix it to the ground4 ,lycopodium inundatum forms large patches on the marshes in the south of ,england4 ,new ,zealand has many more species of this genus than ,britain1 and some of the noblest specimens4 ,the dried spores of the ,l4 clavatum are so inflammable1 that they have been used on the stage to produce the effect of lightning4 ,some ,club ,mosses yield a blue dye1 a colour which is now obtained of a better quality from coal tar4 ,others possess cathartic properties1 but although they have been used as medicine1 they are very dangerous from the violence of their effects4 ,the genus ,selaginella has a moss-like habit4 ,the stem is generally creeping1 and flat-looking from being clothed with distichous leaves2 but sometimes it is tall and erect1 having feathery branches clad with leaves4 ,the sporangia are sacs1 with two or three valves containing large spores and sub-globose antheridia1 containing orange-coloured or minute scarlet bodies1 ultimately developed into spermatozoids4 ,the species are very numerous and greatly varied1 and mostly tropical4 ,from a comparison of the structure of the stems of the fossil plants1 ,sigillaria and ,lepidodendron1 ,dr4 ,hooker concludes that they are highly developed ,lycopods1 approaching closely in structure to the highest class of plants4 ,the stems of the former differ chiefly in size from those of the ,lycopodium1 and the cones of the ,lepidostrobus differ in their greater development and in the thickness of their scales from those of the ,conifers4 ,the spores of the ,lepidostrobus ornatus too are sphericotetrahedral1 like those of the ,lycopodium4 ,but inferior as the existing ,lycopods are to their fossil ancestors1 their analogy to the ,conifers gives them a more exalted position in the vegetable world than their tall and graceful allies1 #8the tree ferns4' ,the gradual change of structure from the lowest to the highest cryptogamic form is accompanied by a singular variety in the mode of reproduction1 and a degree of vital energy scarcely to be expected1 at least in beings of such low organization as the yeast plant1 which produces gemm in vast and rapid profusion1 each gem or bud being only a facsimile of the parent cell4 ,in like manner the mother plant is reproduced by the germination of the green zoospores1 the green globular cells in the fronds of the lichens1 the motile gonidia1 and the discs in the baskets of the ,marchantia1 especially those of the ,marchantia polymorpha1 which have such vigorous vegetation that they form stomates on whichever side is turned to the light1 and roots on the other4 ,the result of all these is an individual perfectly similar to its parent1 like that produced by a bud and cutting of a tree1 or the axillary fruit buds of the ,begonia4 ,the leaves of that flowering plant1 as well as those of the ,achimenes and ,gloxinia1 possess the property of reproducing the parent plant1 for1 when laid on moist earth and slit in different places1 a young plant rises from the upper side of the fracture1 and roots shoot down from the under4 ,although this manner of growth resembles the germination of the embryo of an archegonium1 it is widely different1 for the embryonic cell is fertilized by the spermatozoids1 so there is a certain analogy but not the smallest affinity4 ,the highest vegetable classes can reproduce the mother plant in many ways1 but they have nothing akin to the alternation of generations exhibited by many of the lower tribes1 nor yet to conjugation like the ,desmidiace and ,diatoms4 ,possibly the spores resulting from these two modes of reproduction1 as well as the resting spores1 may produce new species2 certainly those resulting from fructification do occasionally yield new varieties4 ,many spores produce the plant directly1 others indirectly1 as most of the fungi2 but if the definition of a perfect plant be that which bears the fructification1 the mycelium of a mushroom constitutes the plant1 for the mushroom itself is only a kind of sporangium or spore-case4 ,nevertheless1 the spores of the ,puccinia and other microscopic fungi1 which are the cause of the rust and mildew in wheat1 give rise to a kind of prothallus1 #8a slight fore-shadowing' of the prothallus of the ,marchantia and ,mosses1 which only produce sporangia1 and those of the ,ferns1 ,horsetails1 and ,club ,mosses1 whose archegonia contain the embryo of the plant itself4 ,the fructification of the ,lycopods is the highest of which the ,cryptogamia are capable1 and brings them into a singular analogy with the flowering class4 ,for in the ovule1 or seed-vessel of the flower-bearing race1 a large cell is formed1 containing mucilaginous matter1 which1 soon after fructification1 is converted into a mass of cellular tissue1 which gives rise to the cell containing the embryo1 just as the prothallus of a ,lycopod gives rise to the archegonium containing the embryo of the plant4 ,the linear leaves of existing ,lycopods and the cones of their fossil allies1 are similar to the leaves and cones of the ,conifer3 there is no affinity1 but an analogy existing between these two groups sufficient to make them form links between the two great divisions of the vegetable kingdom4 ,the ,lycopodiace probably may be regarded as the highest of the ,cryptogamia1 and ,conifer as the lowest of the flower-bearing class4 ,,section ,,xii4 ,,general ,,structure ,,of ,,flowering ,,plants4 ,,in some of the ,cryptogamic families fertilization takes place before the plant itself is developed4 ,in the two highest classes1 those containing the great groups of ,flowering ,plants1 on the contrary1 it is the ultimate result of the inflorescence1 which consists of calyx1 corolla1 stamens1 and pistils1 all which are the later expansions of the cellular tissues and groups of vessels which have in earlier stages of development formed the leaves4 ,they contain the same materials1 and in fact they are leaves modified in form1 structure1 and function4 ,although the almost innumerable diversities in the form of leaves must produce corresponding diversities in the inflorescence1 yet the general characteristics are the same or similar in both of the great botanical classes4 ,the structure of the calyx and corolla which form the floral envelope of the fructification1 is similar to that of leaves4 ,the calyx consists1 in its early stage1 of several parts called sepals1 which have all the characters of leaves2 subsequently they are sometimes united by their edges1 so as to form a tube1 or are otherwise modified4 ,the corolla only differs from a leaf by greater delicacy of organization2 it has fewer stomates or breathing pores1 and the veins have less woody fibre and sometimes many spiral vessels2 the veins in the petals of chickweed and some other plants are entirely composed of spiral vessels4 ,the calyx and corolla protect the fructifying organs consisting of stamens with their anthers1 and the pistil or pistils4 ,the stamens are formed of very fine filaments1 and the anthers1 when young and still enclosed in the unexpanded flower1 are full of a liquid which is afterwards changed into a delicate homogeneous1 cellular tissue4 ,then the internal part of that tissue becomes divided into two kinds of cells1 one of which goes to form the walls of two lateral and parallel chambers or loculi1 separated by a part more or less continuous with the filament4 ,the other kind of cells are developed into pollen grains within the chambers4 ,they gradually form a cylindrical assemblage of mother cells4 ,within each of these1 four cells are ultimately formed1 each containing a single pollen cell4 ,in all plants1 except the aquatic1 the pollen cells are soon clothed by the deposition of one or more layers of cells1 which form the outer membrane1 on which are impressed figures or markings peculiar to each species of plant1 such as slits1 points1 papill1 sharply defined circles1 pores1 c4 ,the colour of the external layer is generally yellow1 rarely green1 blue1 or red2 the thread is usually white1 except in the fuchsia and some others4 ,when the pollen is ripe the chambers dehisce to emit it4 ,the opening is usually a slit between the valves which close the chambers4 ,the length of the slit is variable1 and the form of the pollen grains is equally so2 they are commonly ellipsoidal1 and attenuated at the extremities2 but in all cases they are beautiful microscopic objects4 ,the contents of the pollen grains consist of a liquid containing mucilaginous granules1 which is in circulation4 ,the granules increase in number towards the period of maturation1 mingled with oil globules1 and frequently starch4 ,the circulation of the fluid ceases long before maturation in all cases1 except the ,zostera2 but the granules of the contents exhibit an active molecular motion often within the pollen cell1 and always after expulsion even in pollen taken from dried specimens4 ,after the liquid ceases to circulate1 it becomes concentrated and contracted2 and when the pollen is only enclosed in one delicate membrane1 it simply bursts the vesicle2 but1 as most pollen grains have a double coat1 they burst open at the slits1 or pores1 on their surface1 and through these the internal membrane1 in the form of a tube1 is protruded1 and emits its contents2 but it may be projected to a considerable distance without bursting4 ,the pistil in a very young state is a greenish concave body scarcely to be distinguished from a nascent leaf2 it becomes more concave2 and finally the borders meet and unite1 so that a hollow body is formed1 which ultimately becomes a perfect pistil consisting of three parts1 the apex or stigma1 the style1 and the ovary1 in which the ovules1 or unripe seeds1 are formed and fertilized1 the latter afterwards becoming the fruit4 ,the ovary is composed of an outward skin containing cellular tissue and vascular bundles of spiral vessels1 which1 running upwards1 converge towards the style2 they vary in number1 and are sometimes ramified4 ,a single ovule1 which is an unripe seed1 may be produced within the ovary1 or the ovary may be divided into two or more compartments1 in each of which an ovule may be formed and attached to the ovary by a mass of cellular tissue1 and not unfrequently by a single thread4 ,the style1 when examined with a microscope1 is a hollow tube1 or canal1 extending from the cavity of the ovary to the stigma4 ,it consists of cellular tissue with vascular bundles near the circumference1 which pass upwards in straight lines1 and end below the summit4 ,in certain cases the canal is open2 in others it is obstructed by lax cellular tissue having many gaps4 ,the stigma is an expansion of that lax tissue at the point where the canal opens externally4 ,at the time of fructification1 the canal of the style is occupied by soft humid elongated cells mixed with a viscous fluid1 which exudes upon the surface of the stigma1 rendering it moist and glutinous4 ,when the pollen grains adhere to that humid substance1 the tubular extension of their inner lining1 with its contents1 passes down the style and fertilizes the unripe seeds4 ,after fructification the anthers1 stigma1 and conducting tissues wither1 yet1 in many fruits1 additions are made to the ovary and its contents by the remains of some of the other parts of the inflorescence4 ,in the apple1 which is a simple fruit1 the skin of the calyx forms the skin of the apple1 and the flesh or edible part is developed out of the ovary and the remainder of the calyx1 while the inner layer of the ovary forms the horny cells containing the ripe seeds4 ,in the strawberry1 which is a compound fruit1 the pulp is the enlarged fleshy receptacle bearing the simple fruit on its surface4 ,in the orange1 the membranous partitions of its segments are the linings of the ovary1 and the pulp is formed of lax large-celled cellular tissue developed within it4#gg ,all fruits have the mark of the style2 it is very evident in the apple and orange4 ,simple fruits are formed by a single flower2 multiple fruits1 like the ananas1 or pine-apple1 and fir cone1 are formed of masses of inflorescence in a state of adhesion4 ,spiral vessels are frequently found passing from the fleshy part of fruits into the seeds2 they are very numerous in the seeds of the ,collomia grandiflora and others1 coiled up and compressed by the outer skin2 but they start to their full length as soon as released4 ,the coats of the seeds of various plants1 when seen through a microscope1 are beautifully marked4 ,that of the ,bignonia is surrounded by a fringe of elongated spiral vessels1 the seed of the poppy has a reticulated surface1 and many have wings like those of the ash tree1 or down like the thistle1 that they may be dispersed by the wind4 ,the tendency of roots to strike downwards is so great1 that seeds right themselves whichever way they may fall4 ,,section ,,xiii4 ,,monocotyledonous1 ,,or ,,endogenous ,,plants4 ,,the structure1 growth1 and reproduction of the flower-bearing vegetation offer objects of the highest interest1 though very different from those furnished by the flowerless class4 ,the plants whose seeds have but one lobe form a transition from the lowest to the highest class of vegetables1 and include those which furnish the principal articles of food to man and animals4 ,they are all flower-bearing1 and consist of numerous families of land and water plants4 ,the most important are the palms1 which serve for food in tropical countries1 the grasses1 which are cosmopolite and social1 covering extensive tracts of country with rich verdure1 and including the ,cerealia1 which have been cultivated from such remote antiquity1 that the grasses from whence they were derived are unknown4 ,this monocotyledonous class includes1 besides the palms and cereals already mentioned1 the sugar-cane1 the bamboo and other canes1 together with reeds1 rushes1 screw pines1 most garden bulbs1 the singular and beautiful race of ,orchids1 and a multitude of other ornamental and useful plants4 ,the seeds of this class consist of a thin skin covering a mass of white or green matter1 which1 when ripe1 constitutes the starch and flour in the ,cerealia4 ,within that matter lies a fleshy lobe with the infant plant imbedded in one corner4 ,the same general structure may be traced throughout the class1 though the lobe with its embryo in the surrounding matter may be covered with a hard coat1 as in the cocoa-nut1 or inclosed in a shell covered with a rich fruit1 as in the date4 ,the infant plant1 as it lies in its seed lobe1 has a stem with a leaf bud or plumule at one end1 and an embryo root at the other2 and1 as soon as the seed begins to germinate1 it is nourished by the conversion of the starch of the surrounding matter into sugar4 ,at first the whole young plant is of cellular tissue1 but1 as soon as the seed leaf appears above the soil1 it decomposes the carbonic acid of the atmosphere1 absorbs the oxygen1 and consolidates the carbon4 ,then cords of fibro-vascular tissue are formed within it1 which converge at its base1 and unite with the radicle of the young plant to form the solid centre of the underground stem1 from whence the real roots descend1 like slender white cords1 which supply the plant with food4 ,the seed lobe having set the current of the cell sap in motion disappears1 and the arial or above-ground stem1 which now consists of pith1 sap1 wood1 and skin or bark1 grows rapidly in length to its first node1 or thickened part1 where the first leaf or leaves appear1 for the first leaves generally appear at the top of the stem in this class1 and are annually succeeded by others rising above them from the top of the elongated stem1 as in the palms and grasses4 ,the stem or axis of a palm is a cylinder with a graceful plume of leaves at its summit1 and a cone of white roots at its base4 ,a section of the stem perpendicular to its axis exhibits a mass of cellular tissue with a number of dark-coloured spots irregularly scattered throughout the whole with the exception of an envelope of dense cellular tissue1 which forms a kind of bark4 ,the dark spots are the sections of bundles consisting of two or three very wide and large vascular ducts enclosed in extremely fine woody fibre and spiral vessels closely pressed together4 ,these bundles after having formed the ribs and footstalks of the leaves1 enter the upper part of the stem1 approach towards its centre1 bend down for a short distance1 then turn towards the exterior1 interlace with the bundles of the previous year1 which have followed a similar course1 and make a circle of rough marks on the surface of the stem4 ,the stem then increases in length1 and a new plume of leaves crowns its top2 the same process is repeated2 and1 as this goes on indefinitely1 the lower part of the stem is rough1 and sometimes even rugged1 as that of the ,palmyra palm4 ,in consequence of this manner of growth1 a perpendicular section of a stem shows a series of curves intersecting each other and originating in points gradually ascending as the palm grows in height4 ,these curves proceed from every point of the circumference of the stem1 present their convexities to the centre1 and bend round1 and enter the leaves1 which are long1 lanceolate1 and often pinnate with veins running through them longitudinally4 ,in some palms the greater part of the centre of the trunk is altogether cellular tissue1 but each species has an arrangement of its own4 ,some palms1 as the date palm1 are dicious1 one plant bearing male1 the other female flowers4 ,in these cases1 the pollen is carried from one tree to the other by the wind or by insects1 and1 as much is lost in the transit1 there is always more produced than is required to fertilize the female flowers4 ,the ,graminace are very numerous1 but the general structure is virtually the same1 whether it be a simple herbaceous grass1 a sugar cane1 or a bamboo4 ,the stem of the grasses is jointed1 and furnished with long lanceolate leaves1 springing alternately to the right and left of each successive joint1 and the parts of the stem between the joints are embraced and nearly surrounded1 as by a sheath1 with the expanded bases of the leaves2 for1 in this class of plants1 one growth always springs from the interior of that which precedes it4 ,in youth the stems of the grasses are solid1 and the bundles of woody tissue which surround the pith are parallel to one another and to the axis of the stem2 but1 at the joints1 they are turned aside and are condensed into a node or joint1 where they enter into a new arrangement1 and pass into the lanceolate leaf1 to form its longitudinal ribs4 ,the compression of the fibro-vascular tissue is so great as to form a septum across the interior of the stem as the node4 ,this is the case in all the grasses2 for the pith1 which is of moist green cellular tissue when they are young1 soon disappears1 so that a full grown grass is a hollow stem articulated at intervals by solid joints1 from whence the long narrow leaves spring alternately1 and as the bases of the leaves are continuous with the stem1 they do not fall off when they wither4 ,in the majority of cases1 the inflorescence of the ,graminace consists of a pistil and three anthers2 but in the ,anthoxanthum odoratum1 or sweet-scented vernal grass1 and some others1 there are but two anthers1 while some few species have more than three4 ,in general1 the flowers are hermaphrodite2 but in certain genera they are moncious1 as in ,zea and ,zizania2 and in others they are polygamous1 as in ,andropogon and ,sorghum4 ,the grasses are1 for the most part1 low and herbaceous2 but the ,arundo ,donax of ,southern ,europe1 and the sugar cane and bamboo of the tropics are lofty strong-growing plants1 the latter reaching as much as #ej or #fj feet in height4 ,the stems and leaves of the grass family are strengthened by silex2 many of them are so entirely coated with it1 that their leaves are as sharp as the edge of a knife4 ,it gives hardness to the beards of wheat and barley1 and is often found in concrete masses1 called tabasheer1 in the joints of bamboos1 which in the ,indian jungles have been set on fire by the friction of their silicious coats during a gale of wind4 ,as no solid matter can enter the roots of a plant1 the silex must be absorbed in a state of solution2 and1 as it coats the surface1 which is full of pores1 the liquid is removed by perspiration1 and the silex is consolidated4 ,the whole of this family abounds in sugar1 and its farinaceous products are too well known to require any notice4 ,the grasses seem to have been the means of revealing the earliest dawn of plant life1 for the ,hon4 ,sidney ,osborne discovered that the colourless protoplasm1 or organizable liquid extracted from the roots of young wheat1 produced spontaneously and simultaneously double ovate vesicles1 or cells1 such as are found in the roots themselves2 and in that liquid1 though hermetically sealed in glass tubes1 the formation of these vesicles or cells was as active after six months as in the liquid freshly taken from the young plant4 ,mr4 ,osborne believed these vesicles to be the earliest organisms of plant life1 and that this is the direct and prevailing mode of production of the embryo4 ,this accords with the observations of ,messrs4 ,wenham and ,devey4 ,many other very remarkable plants belonging to the ,monocotyledons might be mentioned1 as the ,dracna ,draco1 or ,dragon tree of ,teneriffe1 one of the most ancient trees existing2 the ,pandanus1 or screw pine1 with its arial roots1 indigenous in the islands of ,oceania2 and the ,zostera1 or sea wrack1 the only flower-bearing plant except one that inhabits the ocean2 their flowers are minute and bisexual1 are rarely produced1 but they cover large areas with long grassy leaves4 ,bulbous plants1 and the ,orchidace1 the most splendid ornaments of our gardens and hothouses1 are members of this class4 ,of the former1 the snowdrop1 crocus1 colchicum1 arum1 hyacinth1 narcissus1 tulip1 and lily form a group of singular beauty4 ,a bulb is merely a subterranean stem remaining permanently in the condition of a bud4 ,it consists of a disc1 or conical plate1 which is the point of growth whence the flower-bearing stem and the leaves spring4 ,these are surrounded by leafy scales of a fleshy character overlapping one another4 ,the ,liliace and the ,amaryllidace contain many of the most remarkable and beautiful bulbous plants known in gardens4 ,to the former order belong the hyacinth1 tulip1 and onion1 in which the growing point is surrounded by a series of fleshy tunics1 each of which encloses its predecessor2 as also the lily itself1 in the bulb of which the growing point is enclosed in fleshy scales imbricated in rows one above the other4 ,one or two circles of roots descend from the circumference of the disc in the form of slender1 soft1 white cords or threads1 with a spongy termination of cellular tissue to imbibe water and other liquids for the nourishment of the plant4 ,these bulbs are reproduced by buds1 or offsets1 developed in the axils of the fleshy scales1 which fall off either the first or second year of growth4 ,offsets are also produced by the arum1 crocus1 and meadow saffron or colchicum1 whose bulbs form a solid mass1 and are called corms4 ,these offsets merely reproduce a facsimile of the parent4 ,in these and all flowering plants fructification must take place before a new form or variety can be expected4 ,the ,orchids surpass every plant in the vegetable world1 for the variety of means employed by nature to continue the race4 ,the blossoms are1 for the most part1 at once both male and female1 though some plants are dicious1 but1 except in rare instances1 as in that of the ,bee ,orchis1 not a blossom can be fertilized without the aid of insects4 ,the flowers of the ,orchide are constructed upon a fixed plan1 which can be traced through the innumerable variety of beautiful1 singular1 and often grotesque forms which they assume4 ,a corresponding variety is exhibited in the admirable contrivances and adaptations which enable insects to detach the pollen from one blossom1 and carry it to fertilize another blossom4 ,illustration3 ,fig4 #gb4 ,orchis mascula3--,a1 side view of flower1 with a portion cut away2 ,b1 section through one side of rostellum1 with included disc and caudicle of pollinium2 a1 anther2 r1 rostellum2 d1 disc4 ,the ,british ,orchide belong mainly to three natural groups3 the ,ophre1 which comprise the ,orchis1 ,ophrys1 and other common ,orchids2 the ,neotte1 comprising ,epipactis1 ,neottia1 ,spiranthes1 c42 and the ,malaxe1 represented by ,malaxis4 ,orchids have white1 fibrous roots1 and many of them a pair of fleshy tubercles4 ,from thence a straight stem springs up1 ending in a spike of blossoms1 each of which is attached to the stem by a twisted stalk1 containing the ovarium1 as represented in fig4 #gb4 ,ribbed lanceolate leaves rise from the roots1 and some are attached sparingly to alternate sides of the stem4 ,the calyx is formed of three pointed sepals1 one perpendicular1 the others horizontal4 ,instead of being green they are usually coloured4 ,sometimes the whole plant is green4 ,one petal 7fig4 #gb7 is much larger than the others1 occasionally assuming the most extraordinary forms4 ,it is called the labellum1 or lower lip2 it secretes nectar1 a sweet juice1 to attract insects1 and is often produced into a long1 hollow1 spur-like nectary1 as in fig4 #gb n4 ,on that side of the spur which is opposite to the labellum1 the organs of reproduction are so placed1 that an insect alighting upon the labellum cannot insert its proboscis into the nectary tube to eat the honey1 without touching them4 ,illustration3 ,fig4 #gc4 ,orchis mascula3--,front view of flower1 with sepals and petals removed2 a1 anther2 r1 rostellum2 s1 stigma2 l1 labellum4 ,mr4 ,darwin1 in his admirable work on the #8,fertilization of ,orchids1' assumes the ,orchis mascula as a type for explaining the mechanism of the reproductive organs of the ,orchidace generally4 ,fig4 #gc represents a front view of the flower with all the sepals and petals cut off1 except the labellum1 or lip2 and fig4 #gb is a side view of the same1 with the near half of the labellum cut away1 as well as the upper portion of the near side of the nectary1 or spur4 ,in all common ,orchids there is only one stamen1 which is confluent with the three pistils1 to form what is called the column4 ,the edges of the labellum are attached to the sides of the column1 leaving a space known as the chamber or mouth of the nectary1 and thus the mouth has the column on one side1 and the labellum on the other4 ,although the three pistils are united into one1 the three stigmas are not2 for the stigma of the upper pistil is transformed into a pouch-shaped viscous mass 7r1 fig4 #gc71 called the rostellum1 bearing no resemblance whatever to a stigma1 while the other two stigmas form a bi-lobed confluent mass or stigma below it1 through which the pollen grains fertilize the ovary1 which latter forms the apparently twisted stalk1 by which the blossom is attached to the stem4 ,in fact1 the rostellum 7r7 projects into the mouth of the nectary1 and overhangs the confluent stigmas 7s s74 ,the lowest and narrowest part of a hood-shaped anther 7fig4 #gc a a17 is attached to the back of the rostellum1 and consists of two rather widely separated oblong cells1 which open longitudinally in front4 ,each cell contains a pollen-mass1 or pollinium4 ,fig4 #gd represents one with its club-shaped mass of pollen grains1 its stalk1 and viscid disc4 ,these objects are seen in situ in fig4 #gc4 ,a pollinium consists of a number of wedge-shaped packets of pollen grains held together by exceedingly elastic fine threads1 as in fig4 #ge2 the packets unite into the club-shaped head1 and the threads form the stem2 the viscid discs are formed by the rostellum4 ,illustration3 ,fig4 #gd4 ,pollinium of ,orchis mascula3--p1 pollinium2 c1 caudicle2 d1 disc4 ,illustration3 ,fig4 #ge4 ,pollen grains of ,orchis mascula4 ,at an early period of growth the rostellum consists of a mass of polygonal cells full of brownish matter1 which soon resolve themselves into two balls of an extremely viscid semifluid substance void of structure4 ,these two discs are flat on the top1 and rounded below4 ,they lie quite free within the rostellum1 except at the back1 where each viscid disc firmly adheres to a small portion of the exterior membrane of the rostellum4 ,the ends of the two stalks of the pollinia1 or granular masses1 are strongly attached to these little discs1 or balls4 ,illustration3 ,fig4 #gf4 ,pollinia of ,orchis mascula1 showing front view of the discs and caudicles within the rostellum3--r1 rostellum2 c1 caudicle2 d1 disc4 ,at first the membrane forming the exterior surface of the rostellum is continuous2 but as soon as the flower opens1 the slightest touch causes it to rupture in such a manner as to set free from it1 and from one another1 the little discs1 while at the same time the anther cells themselves split in a longitudinal direction from top to bottom4 ,in this state none of the organs are changed2 they are merely set free1 and ready for change1 yet maintaining their normal positions4 ,the labellum1 which is the largest petal of the flower1 lies on one side of the nectary tube1 and the rostellum projects into it on the other2 hence1 if an insect alights on the labellum1 and pushes its head into the tube1 in order to reach the honey in the nectary with its proboscis1 it cannot fail to touch and depress the rostellum 7see fig4 #gf71 so that one or both of the viscid discs carrying the pollinia will stick to it1 and as the anther cells are open in front1 when the insect withdraws its head1 one or both of the pollinia are drawn out of their cells1 and stick upright on it like horns4 ,in that position they never could fertilize any blossom which the insect might afterwards visit2 but ,mr4 ,darwin has shown that their position is changed by a contrivance that is not surpassed in beauty in the whole vegetable world4 ,while a pollinium is upright on the head of the insect1 the little viscid disc which supports it contracts on being exposed to the air1 so as to cause the pollinium to sweep through ninety degrees towards the apex of the insect's proboscis1 and this is accomplished in about thirty seconds1 the time an insect would take to fly to another flower4 ,the pollinium in this position would exactly strike the surface of the stigma when the insect inserts its proboscis into the nectary of a flower4 ,it was long ago noticed by ,robert ,brown1 that the stigma is very viscid1 but not so viscid as when touched to pull the whole pollinium off the insect's head1 yet sufficiently viscid to break the elastic threads by which the packets of pollen grains are tied together1 and leave some of them on the stigma4 ,hence a pollinium attached to an insect can be applied to many stigmas1 and fertilize them all4 ,mr4 ,darwin mentions having seen the pollinium of ,orchis pyramidalis adhering to the proboscis of a moth with the stalks alone left1 all the packets of pollen having been left glued to the stigma of the flowers successively visited4 ,it appears that insects1 for the most part1 only remove one pollinium at a time1 and that the rostellum returns to its normal position to prevent the viscid matter of the discs of the remaining pollinia from being exposed to the air4 ,illustration3 ,fig4 #gg4 ,orchis pyramidalis3--,front view of flower with upper sepal and petals removed2 a1 anther2 s1 stigma2 r1 rostellum2 l1 labellum4 ,the ,orchis pyramidalis is considered by ,mr4 ,darwin to be the most highly organized species of the ,british ,orchids he has examined4 ,it has sharp leaves1 and a close pyramid of white or rose-coloured blossoms4 ,the upper sepal and the two upper petals form a hood1 protecting the anther and stigmatic surfaces from the weather4 ,in fig4 #gg1 a front view of a blossom1 these are cut off as well as in fig4 #gh a1 which represents a side view of the same blossom deprived of half the labellum1 and the upper part of the nectary1 or spur4 ,the labellum is long1 with three equal entire lobes1 and is produced into an awl-shaped spur1 or nectary4 ,it has a small ridge on each side of its narrow base to guide the proboscides of insects to the mouth of the nectary1 which1 besides being small1 is partially closed by the pouch-shaped rostellum1 which is placed very low in this species1 and is flanked on each side by a distinct stigmatic rounded surface 7fig4 #gg s s74 ,the rostellum 7r7 is hollowed out on its under-side in the middle1 and is filled with a fluid4 ,instead of two little viscid discs or balls1 as in the ,orchis mascula1 there is but one which is saddle-shaped 7figs4 #gh1 #gi71 carrying on its nearly flat top or seat1 the two stalks of the pollinia1 of which the two truncated ends firmly adhere to its upper-surface4 ,before the membrane of the rostellum ruptures1 the saddle-shaped disc forms part of its continuous surface4 ,the upper membrane of the disc is rather thick2 it is lined with a layer of highly adhesive matter formed within the rostellum4 ,illustration3 ,fig4 #gh4 ,orchis pyramidalis3--,side view of flower1 with a portion cut away2 a1 anther2 r1 rostellum2 l1 labellum2 n1 nectary4 ,illustration3 ,fig4 #gi4 ,disc of ,orchis pyramidalis seen from above1 with one pollinium1 flattened by force4 ,illustration3 ,fig4 #hj4 ,pollinia of ,orchis pyramidalis1 attached to saddle-shaped disc4 ,illustration3 ,fig4 #ha4 ,pollinia of ,orchis pyramidalis with the disc contracted4 ,illustration3 ,fig4 #hb4 ,pollinia of ,orchis pyramidalis3--a1 as withdrawn by the insertion of a needle2 b1 as after the second contraction4 ,when the flower opens1 the saddle-shaped disc is set free by the rupture of the membrane of the rostellum4 ,then the rostellum1 which projects into the minute round orifice of the nectary1 is easily depressed by the proboscis of a moth1 and as the now naked and sticky under-surface of the saddle-shaped disc is uncovered1 it adheres to the proboscis1 and is withdrawn with it into the air1 carrying the two pollinia 7fig4 #hj7 on its exterior surface4 ,almost instantly the saddle is exposed to the air1 a rapid movement takes place4 ,the two flaps curl inwards 7fig4 #ha71 and embrace the proboscis1 and the pollinia1 at first parallel1 become divergent4 ,a second movement now takes place1 which causes the divergent pollinia 7fig4 #ha71 which are at right angles to the proboscis1 to sweep through ninety degrees towards the tip of the proboscis1 so as to become depressed1 and lie on each side of it4 ,hence1 when a moth pushes its proboscis between the guiding ridges of the labellum into the nectary of another flower1 the two thick ends of the pollinia will exactly strike against the two stigmas4 ,these stigmas are so viscid that they hold and rupture the elastic threads which bind the packets of pollen grains together1 and some dark green grains are seen even with the naked eye remaining on the two white stigmatic surfaces4 ,in the ,orchids1 as in all other flowering plants1 tubes sent out by the pollen grains penetrate through the stigmas1 and fertilize the ovules in the twisted ovary4 ,the double movement of the pollinia1 while on the moth's proboscis1 is owing to the rapidity with which the viscid matter contracts and dries4 ,both butterflies and moths frequent this ,orchis4 ,mr4 ,darwin enumerates twenty-three species of these insects which he had seen with the pollinia of the ,orchis pyramidalis attached to their proboscides4 ,many had two or three pairs2 the proboscis of the ,acherontia had seven1 and that of the ,caradium had no less than eleven of these saddles attached at regular distances from top to bottom of its proboscis4 ,few of the species of ,orchis are visited by bees4 ,on account of some resemblance in form1 the ,ophre are named after insects4 ,the ,fly ,ophrys differs in no material respect from the other ,orchids4 ,the stem or caudicle of the pollinium1 instead of being straight1 as in the ,orchis mascula1 is doubly and almost rectangularly bent4 ,the upper membrane of the disc to which the stalk of the pollinium is fixed1 being the summit of the rostellum1 is exposed to the air1 and becomes dry when the flower opens1 consequently the disc1 though viscid enough on its under-side to stick to an insect's head1 is incapable of shrinking1 and causing that depression of the pollinium1 characteristic of all the species of ,orchis4 ,the labellum has no spur1 but at its base1 just below the stigma1 there is a deep depression representing the nectary2 and as the pollinia1 which cannot be shaken out of their cells1 or pouches1 are certainly1 though rarely1 extracted1 ,mr4 ,darwin conceives that small insects crawl along the labellum to its base1 strike against one of the pouches1 extract a pollinium1 and fly with it sticking on their head to another blossom1 and that while bending their heads into the hollow at the base of the labellum1 the pollinium1 owing to its doubly bent stalk1 strikes the sticky stigmatic surface1 and leaves pollen grains on it4 ,there can be no doubt that this plant is visited occasionally by insects1 as it cannot be fructified without them2 but it is scentless1 and as no nectar has as yet been found in it1 their motive for visiting it is unknown4 ,illustration3 ,fig4 #hc4 ,epipactis palustris3--,side views of flower1 with lower sepals cut away3 ,a1 with lip in natural position2 ,b1 with lip depressed as by an insect4 ,the fructification of the ,ophrys apifera1 or ,bee ,ophrys1 is independent of insects1 for the stalks of the pollinia are extremely long1 thin1 and flexible2 and although their viscid discs still remain in their pouches1 as soon as the flower expands1 and the anther cells or pouches open1 the heavy thick ends of the pollinia fall out of their cells1 and hang freely down in the air exactly opposite to the stigmatic surface4 ,a breath of air is sufficient to make them vibrate1 strike the stigma with their pollen mass1 and leave pollen grains on its sticky surface4 ,illustration3 ,fig4 #hd4 ,epipactis palustris3--,c1 side view of flower1 with sepals and petals and half the labellum removed3 ,d1 front view of column3 a1 anther2 r1 rostellum2 s1 stigma2 l1 labellum4 ,the great tribe of ,british ,neotte is characterized by a free anther standing like a hood behind the stigma2 the pollen grains are tied together with threads1 and attached to a viscous cap lying on the top of the rostellum4 ,the ,epipactis palustris is a type of this group of orchids4 ,its spike is short1 and the pink blossoms stand out horizontally from the stem on long ribbed footstalks1 which contain the ovaries4 ,fig4 #hc ,a is a side view of the flower in its natural position1 with the lower sepals alone removed4 ,the labellum1 or lowest petal1 is interrupted in the middle by a kind of flexible hinge3 the basal part is a cup-shaped trough1 at times abounding in nectar2 the extreme part is a wavy leaf 7fig4 #hc ,b74 ,the entrance to the nectary cup is nearly closed by the hood and the large anther2 but1 on account of the elasticity of the hinge1 the weight of an insect is sufficient to give access to the nectar2 but no sooner is the labellum relieved of the weight1 than it springs up into its natural position1 and the insect creeps backwards and comes out at the top of the flower with the viscous cap clasped round its proboscis1 and the pollen grains attached to it ready to fertilize another blossom4 ,in fig4 #hd1 ,c represents a section of the ,epipactis1 and ,d is a front view of the column4 ,illustration3 ,fig4 #he4 ,listera ovata3--,side view of flower1 with sepals and petals cut away3 a1 anther2 col1 summit of column2 p1 pollen2 r1 rostellum2 s1 stigma2 l1 labellum2 n1 nectar-secreting furrow4 ,of all the ,british ,orchids1 the ,listera ovata1 or ,twayblade 7fig4 #he71 has the most curious structure4 ,it grows in woods and pastures1 has a creeping root1 oval leaves1 a downy stem1 and yellowish green flowers4 ,fig4 #he represents a lateral view of a blossom1 with all the sepals and petals removed1 except the labellum4 ,in this plant the rostellum 7r7 is large1 thin1 convex in front1 concave behind1 and arches over 7s7 the stigmatic surface4 ,when the flower is full blown1 the anther cells 7a7 are already open1 and the naked and friable pollen grains united by a few threads1 which form the pointed tips of the pollinia1 rest upon the concave back of the rostellum4 ,the labellum1 which is contracted at the base1 is exceedingly long1 hanging down like a narrow ribbon4 ,it is divided half-way up1 and furrowed along the middle1 from the bifurcation close up to the base of the stigmatic surface 7s74 ,the borders of the furrow are globular1 and secrete much nectar4 ,the rostellum is internally divided into a series of longitudinal cells1 or chambers1 which contain and expel viscid matter with violence on the slightest touch1 and the viscid matter sets hard in two or three seconds1 and soon assumes a purplish brown tint4 ,so exquisitely sensitive is the rostellum1 that a touch from the thinnest human hair suffices to cause the explosion4 ,as the pointed tops of the loose pollinia lie on the crest of the rostellum1 they are always caught by the exploded drop4 ,this never fails4 ,so rapid is the explosion1 and so viscid the fluid1 that it is difficult to touch the rostellum with a needle quick enough not to catch the pollinia already attached to the partially hardened drop1 and consequently the slightest touch of any small insect which enters the flower1 suffices to explode the rostellum1 and the pollinia which attach themselves to its proboscis are carried by it to the next flower to adhere to the viscid stigma and fertilize it4 ,mr4 ,darwin has seen two ,hymenopterous insects retreat from one of these plants with bright yellow pollinia on their heads1 and ,mr4 ,c4 ,k4 ,sprengel saw an insect of that kind leave pollen upon a stigma4 ,the action and structure of ,neottia ,nidus-avis is almost identically the same as that of ,listera ovata4 ,the ,malaxis paludosa1 or ,bog ,malaxis1 the smallest of ,british ,orchids1 is a rare plant1 and differs from all of them in having its labellum turned upwards instead of downwards4 ,its lower margin clasps the column1 making the entrance into the flower tubular4 ,in this orchis the upper sepal and two upper petals are reflexed1 to allow insects freely to visit the flower4 ,in many orchids the labellum is properly directed upwards1 but assumes its usual position as the lower lip by the twisting of the ovarium1 or pedicel1 of the flower4 ,in the ,malaxis paludosa1 however1 the twisting has been carried to such an excess1 that the flower occupies the same position it would have held if the ovarium had not been twisted at all1 and which the stalk ultimately assumes when ripe by the process of gradual untwisting4 ,this little plant belongs to a genus distinguished by having a movable and deciduous anther1 and is one of the ,british orchids that have allied forms among the exotic genera4 ,all ,dr4 ,lindley's vast tribes of ,epidendre1 and the still more numerous and splendid ,vande1 have not a single ,british representative4 ,the structure of the exotic orchids is often very complicated1 and they possess many properties unknown in the ,british genera4 ,their labellum1 or lower lip1 is so varied1 and sometimes so singular1 that it baffles description2 besides1 it often possesses peculiar motions1 sometimes from structure1 at other times from irritation4 ,in the ,bolbophyllum ,rhizophor1 the labellum is attached to the column by a very narrow thin strap1 elastic as india rubber1 which oscillates in a singular manner2 while that of the ,b4 barbigerum has a beard of fine hairs in almost constant agitation4 ,the irritability of the labellum in many of the allied forms of the orchids is one of their remarkable properties2 the slightest touch sets them into motion4 ,the ,australian genus ,caleana possesses it in the highest degree2 for when an insect settles on its labellum1 it suddenly shuts up against the column1 and encloses it1 as it were1 in a box4 ,some of the exotic orchids have a pseudo-dicious character4 ,thus some species of ,catasetum have two long horns1 or antenn1 attached to the rostellum1 which stand over the labellum1 and the pedicels of the anthers are fastened down in a curved position2 so1 when an insect alights upon the labellum and touches the antenn1 the excitement is conveyed by them to the rostellum1 the attached edge of the disc of the anthers is ruptured1 and they straighten themselves with such force1 that not only do they drag the balls of pollen and anther cells from their places of attachment1 but the whole pollinium is jerked forward over and beyond the tips of the horns1 to the distance of two or three feet4 ,the insect1 disturbed by so sharp a blow1 or after having eaten its fill1 flies with the pollen adhering to it to fertilize the female plant1 which differs from the male in having no antenn4 ,thus the agency of insects is as requisite to fertilize these semi-dicious as hermaphrodite orchids4 ,the ,vanilla1 which is cultivated for its aromatic pods in ,tahiti1 ,bourbon1 and the ,east ,indies1 does not bear fruit without artificial aid1 which shows that the ,american insect1 which fertilizes it in its own native home1 is not indigenous in the places mentioned4 ,it appears that many exotic orchids require a less elevated temperature than has hitherto been supposed4 ,the form and position of the nectary are exceedingly varied4 ,in certain species1 both of the native and tropical orchids1 they are always dry2 but ,mr4 ,darwin has discovered that1 in these cases1 the walls of the nectaries are thick and formed of two coats1 and that a liquid is contained between them1 to which the insect penetrates by piercing the inner wall4 ,the exotic orchids are1 for the most part1 larger1 and require larger insects to fertilize them than our small ones1 whose organs are generally microscopic4 ,a curious instance1 both of this and of the extraordinary form of the nectary1 is found in the ,angrcum sesquipedale1 a ,madagascar orchid1 with large six-rayed flowers1 like stars formed of snow-white wax4 ,it has a green whip-like nectary1 sometimes as much as a foot long1 and1 from the structure of the plant1 it appears that the pollinia never could be withdrawn1 until a large moth1 with a wonderfully long proboscis1 attempts to drain the last drop of nectar from the bottom of the nectary4 ,notwithstanding the vast diversity in the form of the orchids1 they are homologous in their general structure4 ,mr4 ,robert ,brown was the first to observe1 that an orchid flower consists of fifteen organs1 arranged alternately1 three within three1 in five whorls4 ,this accords perfectly with a system of spiral vessels developed at an early age in all orchids4 ,mr4 ,brown and three of the greatest living botanists#gh have each traced the spirals from six bundles surrounding the ovary in the footstalk to the different organs of the flower1 and have found that they consist of fifteen bundles corresponding to the fifteen organs of the flower2 namely1 three sepals1 three petals1 six anthers in two whorls 7three of which are rudimentary71 and three pistils1 with their stigmas3 these are arranged in alternate whorls1 and undergo many modifications4 ,the pistils and anthers are confluent1 and form the column2 the uppermost stigma becomes the rostellum2 the three inner anthers are rudimentary1 one forming the front of the column1 and the other two forming the membranous sides of the hood which protects the pollen2 and1 lastly1 the two lower anthers are united to the sides of the lowest petal1 and form the labellum1 which accounts for its great size1 frequent tripartite form1 and peculiar manner of attachment4 ,this system has been wonderfully modified to produce the varied groups of extra-tropical and brilliant forms of exotic orchids1 yet it can be traced in all4 ,,section ,,xiv4 ,,dicotyledonous1 ,,or ,,exogenous ,,plants4 ,,in ,endogenous plants the seeds have but one lobe1 and the growth is invariably from the interior4 ,in the ,exogenous class1 on the contrary1 the seeds have two lobes1 and the increase in growth is external3 hence the botanical distinction of ,exogenous plants4 ,although the distinctive character of the highest class of vegetables is to have seeds with two lobes1 yet the structure and position of the seeds are extremely diversified4 ,many have horny coats1 such as the pips of apples and oranges2 or hard ones1 as nuts1 and the stones of plums and cherries4 ,they are sometimes on the outside of the fruit1 as in strawberries1 but oftener within it1 as in the melon1 the pear1 and a variety of others4 ,these succulent substances nourish the young seeds for a time1 but1 when they are matured1 the light and heat which ripened the fruits now combine to accelerate their decay and decomposition1 in order to set the seeds free4 ,whatever be the size or form of the seeds1 whether large or microscopic1 they invariably contain two seed lobes or primary leaves1 consisting of cellular tissue1 between which the miniature plant1 with its radicle1 stem1 and terminal bud lies concealed4 ,at the end of the first year there is little difference in the structure of a young woody plant1 whether from a one or two lobed seed2 the distinction begins the second year4 ,in herbaceous plants1 the stem1 which is in general annual1 is of loose cellular tissue1 with separate bundles of fibro-vascular tissue running from the roots upwards1 and passing at last into the leaves1 where they form the ribs or veins4 ,many of the higher forms of plants have fleshy underground stems1 as instances of which may be named the ,corm1 as seen in the crocus and colchicum1 the ,tuber1 as in the potato1 the ,rhizome1 as in the fleshy rootstock of ,iris florentina1 which yields the violet powder of the shops1 and indeed most bulbs may be considered as modifications of stems1 though they are more strictly analogous to buds4 ,the edible parts of the carrot1 turnip1 parsnip1 and radish are not stems1 but highly developed succulent roots1 the unusual development of which is a direct result of cultivation4 ,a young tree1 at the end of the first year of its growth1 has subterranean roots1 with their branches and fibrils1 and an arial stem1 often more or less branched1 formed of bark1 wood1 and pith1 with a few leaves at its extremity1 all exceedingly tender4 ,every succeeding year a new cylinder of woody fibre and vascular tissue is formed between the wood and the bark1 both in the stem and branches4 ,it follows from this manner of growth1 that the stem of a tree1 consisting of bark1 wood1 and pith1 is formed of a series of cylinders or extremely elongated concentric cones closely united1 so that a transverse section exhibits a series of concentric circles or zones from the surface of the bark to the central pith4 ,the structure of the branches is similar1 but the number of zones depends upon the age4 ,since all the tissues that have been described are combined to form the organs of nutrition and reproduction in a full-grown tree1 it affords the best general illustration of the organization of the highest class of vegetables4 ,every part of a tree or plant1 except the top of the stigma and extremity of the roots1 is covered by an extremely delicate film of cellulose1 closely pressed down upon one1 two1 or three layers of transparent colourless cellular tissue compressed into a tubular form1 which constitutes the cuticle4 ,these flattened cells1 which are firmly united to one another by their edges1 differ in shape in almost every tribe of plants4 ,in the monocotyledons they are elongated in the direction of the parallel ribs of the leaves2 in the highest class they differ little from circular discs1 but they have large sinuosities in their edges1 which make their junction very irregular4 ,the upper cells of the cuticle are lined with a waxy substance1 which protects the plant from damp2 and in many cases it contains more or less silex4 ,this general covering1 or cuticle1 is perforated by numerous pores1 especially on the under-side of the leaves1 and the green tender parts of the branches2 they are the organs of respiration4 ,these pores1 or stomata1 are usually formed of two crescent-shaped cells1 joined together by their points or horns1 so as to leave an open space like a mouth1 through which the plant breathes4 ,these1 however1 are only the guardians3 the opening between them leads into a cavity full of air1 which is the antechamber to an interior cavity4 ,the valves of the stomata open and shut according to the humidity or dryness of the atmosphere4 ,all plants of both classes1 woody or herbaceous1 have stomates1 except water plants1 fungi1 fuci1 and others of the lowest class4 ,they are generally very abundant on the under-surface of leaves4 ,they are sometimes in vast numbers on both sides of the leaves1 and are essential to the life of the plant4 ,according to ,,mm4 ,payen and ,liepner1 silex and azote1 together with calcareous and alkaline salts1 are invariably found in the cells forming the skin of the roots1 stems1 leaves1 fruits1 hairs1 and spines4 ,the strong cohesion of the skin1 together with the presence of these substances1 becomes a defence against the wearing effect of the weather1 without diminishing the transparency of the tissues4 ,the bark is divided into three regions1 or zones4 ,the external coat1 lying immediately under the skin1 is formed of one or many layers of cubical or oblong cells1 elongated horizontally4 ,they are transparent and colourless at first1 but become brown and opaque with the colouring matter of cork as they grow older4 ,on that account it is called the suberous zone1 and sometimes acquires great thickness1 as in the ,quercus ,suber1 or cork tree4 ,the green cellular envelope comes next to the corky layer1 and consists of prismatic cells and laticiferous tubes1 which form an irregular wide-meshed network1 elongated in the direction of the axis of the tree1 and sometimes constituting the chief thickness of the bark4 ,this zone1 as well as the succeeding1 increases imperceptibly by new layers added to its interior1 while the exterior coats of the bark perish annually4 ,in some trees they are annually cast off in plates and large flakes1 as in the ,oriental plane1 whose stem and branches look as if they had been peeled in autumn4 ,the liber1 which is the third and innermost zone of the bark1 generally consists of several layers of cellular tissue1 traversed longitudinally by bundles of woody fibre and laticiferous tubes4 ,the generating layer of cambium1 in which all the phenomena of growth takes place1 is a semi-fluid mucilaginous substance1 which comes between the liber and the wood4 ,it is most abundant in the spring1 and is the origin of all horizontal growth4 ,this mucilage is really made up of a vast multitude of cells1 with cell-walls as delicate as those of a soap bubble1 which gradually undergo transformation into woody fibre1 laticiferous ducts1 spirals1 c41 thence called the cambium zone4 ,the whole of this matter spontaneously divides into two parts3 one forms a new layer of liber on the interior of all those which precede it1 and the other a new ring of young sap-wood1 exterior to all its predecessors4 ,a portion of the cambium1 in its unchanged or liquid state1 always remains between the wood and the bark1 which are never in absolute contact4 ,as a new cylinder of wood enclosing all its predecessors is annually formed1 the section of a stem perpendicular to its axis exhibits a ring of woody fibre1 alternating with a ring of spotted and rayed vascular tubes1 which constitute the silver grain of the wood4 ,the rings are more and more crowded1 and narrower towards the centre1 and at last become impervious to the sap1 which only rises through the younger part of the sap wood4 ,in fact1 a large portion of the solid fibres of most plants have ceased to take any active share in the performance of vital functions1 and1 like the solid heart of an oak1 retain their integrity simply because they are not exposed to influences which would cause their decomposition4 ,a vegetable tissue exposed to ordinary chemical action1 can only remain entire so long as it is performing vital functions4 ,the arrangement of the woody fibre and ducts in the different orders and genera is much varied4 ,the breadth of the rings of wood shows the effect of good and bad seasons2 and in extra-tropical latitudes1 where there is alternately a period of growth and repose1 their number frequently indicates the number of years' growth2 so that the age of a tree may be approximately1 if not exactly1 learned from a critical examination of a section of its stem4 ,the innermost cylinder of wood is lined by the medullary canal or tube containing the pith4 ,it is a delicate membrane1 entirely formed of hollow spiral tubes4 ,the pith1 which fills the canal1 is of greenish cellular tissue when young1 full of sap1 and occasionally1 though rarely1 mixed with vascular and spiral tissue4 ,it passes uninterruptedly to the end of every branch1 leaf bud1 and flower4 ,perpendicular plates1 called medullary rays1 radiate from the medullary sheath and end at the bark1 dividing the whole mass of the wood into triangular or wedge-shaped sections4 ,they are thin plates of cellular tissue1 stretched horizontally between the central pith and the bark4 ,in each family of trees and shrubs they have a different arrangement1 but in all they keep up a horizontal communication between the centre and the circumference1 though they do not all extend throughout the whole length of the stem2 some do1 others do not4 ,thus the cellular tissue forms a horizontal system1 while the fibro-vascular ducts constitute a perpendicular system of tissues4 ,in some trees the pith is scarcely perceptible1 and in others it diminishes or vanishes with age1 as in the oak4 ,in the alder and other plants it dries up1 breaks into pieces1 and the canal is filled with air4 ,in the stem and branches of the ,conifer1 there is scarcely any mixture of vessels amongst the woody fibre1 the vascular system generally consisting exclusively of glandular woody tissue1 except in the medullary sheath1 where spiral vessels are found in small numbers4 ,the subterranean growth1 or descending axis of trees consists of large branches1 sometimes tending downwards1 but more frequently spreading in extensive ramifications1 not far from the surface of the earth4 ,their growth and structure are similar to those of the stem1 but the cylinders of wood are less apparent2 they have medullary rays1 but no pith2 they merely connect the active roots with the stem1 and fix the plant firmly in the ground1 for they have few or no pores1 and contribute little to the nourishment of the plant1 except by conveying liquids from the fibrous roots to the upper growth4 ,the active feeding roots spring from them in the form of bunches of white fibres1 like cords or threads1 which sink straight down into the ground4 ,these real roots are of cellular tissue enclosed in vascular tubes and spiral vessels1 which terminate at a little distance from the extremity1 leaving a point of loose spongy cellular tissue1 called the spongiole1 which absorbs from the ground the liquids that nourish the plant4 ,these root fibrils are temporary organs2 they die on the older parts of the subterranean branches1 and are succeeded by others on the new4 ,the various tissues which form the stem of a tree form1 in the same manner1 though in diminished numbers1 the complicated ramifications of the branches and the leaf-stalks1 and terminate in the leaves themselves4 ,under the transparent film which forms the skin on the upper-surface of a leaf1 there is a layer of soft thin-walled cylindrical or prismatic cells1 closely pressed together1 and full of green vegetable matter1 or chlorophyll4 ,several layers of thick-walled cells follow1 each more loosely aggregated than that which precedes it1 and fuller of void spaces1 till in the last green layer on the under-side of the leaf the cells are globular1 with numerous large irregular void spaces1 united in a reticulated system filled with air1 and in direct communication with the atmosphere by means of the innumerable stomata1 which are to be found in the under-surface of the leaves of all land plants of the higher classes1 and which are their organs of respiration4 ,the form of the leaf is determined by the arrangement of the vascular bundles1 which are in communication with those in the interior of the stem1 and branch out in various directions through the green layers3 these branches unite again1 and form the skeleton of the leaf1 which is often a delicate maze of the finest lacework of nerves4 ,the vascular system is double1 consisting of an ascending and descending portion4 ,the ascending portion1 which is continuous with the medullary sheath1 becomes continuous at the apex of each nerve of the leaf with the descending portion1 which is beneath and in contact with it throughout its ramifications4 ,this descending portion at the base of the leaf-stalk1 or petiole1 becomes continuous with the bundles of the liber4 ,in the upper part of the nerves of the leaf there are spotted vascular ducts1 in the lower part there are laticiferous vessels4 ,those on the upper side carry the rising sap to the green matter1 where it is elaborated and matured1 and then it passes into the vessels on the under-side of the nerves or veins1 which carry it down the liber4 ,buds are generally formed of scales closely imbricated round the young leaves1 which are variously folded and firmly packed2 they contain the rudiments of the whole plant1 and as in a large tree they are renewed every year1 the sources of life are all but infinite4 ,the spines with which many plants are armed are of two kinds2 one is permanent1 being an excrescence from the wood1 as in the blackthorn2 the other proceeds from the bark1 and may be stripped off1 as in the rose2 both contain silex1 and are covered by the skin common to the whole plant4 ,few plants of any kind are without hairs1 which are chiefly found on the young shoots1 and on the under surface of the leaves4 ,they are either formed of a transparent elongated hollow cell1 or consist of a number of transparent colourless superimposed cells1 sometimes jointed1 but more frequently rectilinear4 ,when they sting1 as in the nettle1 they are set upon a kind of bulb composed of cells which secrete the acrid colourless liquid which causes the irritation1 and when slightly pressed send it through the hair1 the point of which breaks off as it enters the skin of the hand4 ,the hairs are so transparent that the gyration of the azotized liquid1 called protoplasm they contain1 has been distinctly traced1 a motion so universal in some part of the structure of plants that according to the observations of ,mr4 ,wenham1 the difficulty is to find a plant1 aquatic or terrestrial1 in which it does not take place at some period of its growth4 ,the gyration in any given cell preserves a uniform direction2 in different cells the direction is different4 ,it will persist in a detached part of a plant for several days or even several weeks4 ,it is arrested by cold1 and recommences its gyration when the temperature is raised4 ,it has been mentioned that in the primordial cell the solid coloured particles often form a nucleus in the centre of the viscid liquid called protoplasm1 which is continually diminished by the increase of the watery vegetable sap4 ,at length the protoplasm in the hairs is reduced to mere threads extending from the cell wall to the nucleus1 so that the latter looks like a spider in the middle of its web4 ,these threads are really streams of the viscid protoplasm flowing through the more liquid cell sap from the nucleus to the cell wall1 where they turn and flow back again in another thread4 ,when there are several currents in the same cell1 the nucleus1 which is the common point of departure and return1 is the centre of the vital activity of the cell1 though it does not always maintain a central position2 in the cells of the leaves of the ,vallisneria spiralis the nucleus even follows the protoplasm1 which flows in a broad stream up one side of the cell and down the other1 as in the ,chara4 ,in most plants the gyration is transitory1 for the nucleus which always exists in young cells is dissolved as the cell advances in age1 and the protoplasm is so much diminished in quantity1 that its motion is imperceptible4 ,there are exceptions1 however1 as in the hairs of the nettles and some other plants1 where it is persistent4 ,the motion is in general very slow4 ,the thinness and minuteness of the currents may be imagined1 since they and the cells containing them are microscopic objects1 and the solid particles carried by the liquid1 which afford the means of tracing its course1 are not more than between the three and the five thousandth part of an inch in diameter4 ,m4 ,schleiden ascribes the motion to changes in the form of the cells produced by an internal vital action1 while ,professor ,karsten believes1 from observations he made on the rotation of liquids in the hairs of the common nettle1 that it is a phenomenon of diffusion1 depending upon the chemical changes taking place in the cells of the hairs independent of any contractibility1 not referable to them4 ,the whole of the tissues that exist in a well-grown tree are not to be met with in each of the numerous woody and herbaceous plants of the first class2 some may be wanting1 and those that do exist may be1 and generally are1 much modified both in form and size4 ,all the trees in the temperate zone1 and most of those in the tropics1 belong to the class of ,exogens2 but the annual rings of wood are less distinct in the latter1 the periods of repose and activity depending upon the dry and wet seasons not being so decided as our winter and summer4 ,the leaves of tropical plants have a thicker skin than in colder climates1 to defend them from an ardent sun4 ,the structure of herbaceous plants in all countries is lax and juicy1 they have abundance of pith1 large medullary rays1 and zones of fibro-vascular tubes1 which separate the pith from the bark4 ,in fact1 each herbaceous and ligneous family has a structure and properties peculiar to itself2 but although there is almost an infinite diversity of form and character1 the general type of the class may be traced in all4 ,vegetable matter consists of carbon1 hydrogen1 oxygen1 and nitrogen1 yet no plant can combine these simple elements into organic substances2 they imbibe them by their roots and leaves under the form of carbonic acid1 water and ammonia3 these they have the power of decomposing1 and recombining their simple elements into new compounds4 ,carbon forms the hard part of plants1 and enters extensively into their most delicate structure2 but it is never found free4 ,combined with hydrogen and oxygen it not only constitutes the cell wall cellulose1 which may be regarded as the skeleton of the vegetable world1 but hundreds of compounds differing decidedly in their properties1 yet consisting only of these three elements united with one another in different quantities and proportions4 ,proteine1 a compound of all the four simple elements1 is a mucilaginous substance1 which lines the primordial cell1 is homogeneous at first1 and afterwards more or less granulated4 ,it is present wherever the vital energy is in activity4 ,although these four primary elements form the basis of vegetation1 plants require other substances which they absorb from the ground in a state of solution1 such as silex1 or rather silicious salts having a base of potash or soda1 the carbonates1 sulphates1 and phosphates of lime1 the phosphate of manganese1 and the oxides of manganese and iron1 with various other metals and substances in a state of combination and solution4 ,a few are universal constituents1 as the earths and alkalies2 in general each race of plants only absorbs such as are peculiar to itself4 ,soda abounds in the ,alg and is found in the ,liliace1 ,crucifer1 and other plants that are indigenous on the sea-coast1 or in brackish marshes4 ,potash exists in land plants1 and cannot be replaced by soda1 for however rich the soil may be in soda1 they do not thrive in it4 ,the ashes of land plants consequently contain the metal potassium1 while most of the ,alg yield sodium2 they also yield chlorine1 iodine1 and bromine in a state of combination4 ,it is proved by spectrum analysis1 that every plant1 with the exception of the very lowest1 contains a variety of metals in infinitesimal quantities1 as lithium1 rhodium1 and others2 but they are not essential to the welfare of the plants4 ,iron is the most frequent constituent in very small quantities2 there are also occasional deposits of soda1 lime1 and a little manganese4 ,all the various substances which enter the vegetable system1 are combined in definite proportions into an infinite variety of organic compounds in different plants1 and in different parts of the same plant1 for the decomposed matter is carried by the ascending sap to every part even of the highest trees4 ,throughout the whole process the law of the division of labour prevails2 to each part of a plant1 and to each group of cells1 its own duty is allotted4 ,the vegetable sap1 consisting of water1 carbonic acid1 ammonia1 and other substances1 which enter the spongy extremities of the roots in a liquid state1 rises in the form of a crude fluid through the whole loose texture of herbaceous plants1 through both the wood and pith of trees under two years' growth1 and in older trees and shrubs it rises through the sap-wood of the stem into the branches1 and thence into the leaves1 the limit of ascent in all plants1 so that in spring1 all the cells are full of sap4 ,the vascular ducts are capillary tubes1 and the cellular tissue is an assemblage of closed cells or sacs1 whose wall or cell-membrane is permeable by liquids2 hence the imbibition of the roots and the rise of sap in the plant are essentially due to capillary attraction acting contrary to gravitation4 ,the ascension of the liquid is inversely as the diameter of the capillary tubes and cells in the stem and branches2 the quantity raised is the same at all heights1 and the velocity of ascent is inversely as the height4#gi ,as soon as the leaves are expanded1 they evaporate a quantity of water through their stomata during the day1 so that in a tree or any plant1 an enormous extent of evaporating surface aids in raising the sap by creating a vacuum in all the upper cells and vessels1 by which the force of suction and the rapidity of ascent are increased4 ,it appears that the water evaporated by the leaves is in exact proportion to that taken up by the roots to supply its place2 but as soon as the young branches are formed1 the buds for the following year produced1 and when the leaves are full of the chlorophyll which they have consolidated during the summer1 the evaporation is less1 the sap ceases to rise1 the spirals and vascular ducts in the medullary canal and sap-wood are left dry1 and fill with air1 which they convey to every part of the plant except the bark1 to assist in assimilation1 that is1 in the formation of organic compounds4 ,during the whole of this process the leaves and other green parts1 which are the organs of vegetable respiration1 are most active4 ,they absorb carbonic acid gas from the atmosphere by day1 and exhale oxygen4 ,for by the direct action of solar light the carbonic acid gas and ammonia in the crude sap are decomposed1 part of the oxygen is set free and exhaled1 and the rest1 with part of the remaining elements1 combine to form chlorophyll1 which is a compound of starch and a little nitrogen4 ,the oxygen inhaled by plants during the night1 combined with other elements in the sap1 forms oxidized vegetable compounds4 ,m4 ,kosmann1 of ,strasburg1 observed that both the leaves of plants and their corollas give out a ponderable quantity of ozonized oxygen1 much more than that which exists in the air1 and that the quantity is less in the night4 ,all parts of plants that are not green exhale carbonic acid gas1 and inhale oxygen1 like animals1 night and day2 if prevented from inhaling oxygen they lose their vital power1 are soon suffocated1 and the plant dies4 ,the expiration of oxygen by the leaves is connected with the nourishment of a plant1 the inspiration of that gas is connected with its life4 ,when the sap is completely organized by respiration1 evaporation1 and the chemico-vital agency of light1 it descends chiefly through the cambium1 lying between the liber and the wood4 ,from this layer the sap distributes to each organ capable of increase1 the requisite nutritious liquids1 deposits various organic compounds1 and annually renews the cambium4 ,part of the sap in its descent runs into the wood through the horizontal medullary rays1 in the cells of which it deposits starch4 ,the descent of the sap is no doubt due to gravitation4 ,the latex is a general name for those white or coloured juices peculiar to some plants4 ,it is separated in the leaves from the descending sap1 which is always colourless1 and consists of a clear liquid1 thickened and coloured by white1 yellow1 reddish-brown1 or green globules floating in it2 it does not turn blue under the action of iodine1 therefore it does not contain starch4 ,these proper juices differ as much in quality as in colour2 some contain fatty matters1 others substances of a totally different nature1 as caoutchouc2 a few are bland and nutritious1 many acrid and poisonous2 some contain alkaloids1 others have none4 ,these juices are by no means essential to the life of the plant1 for sometimes they are wanting in their most essential parts1 and they are found in certain species and not in others most nearly allied4 ,certain it is1 that tropical lactescent plants which do not produce their proper juices when brought to a cold climate1 still produce their milk vessels4 ,these vessels follow the ramifications of the veins of the leaves in the highest class1 and also in some of the monocotyledons4 ,in the stem the milk vessels belong especially to the layers of the bark1 where they take the form of long reticulated perpendicular ducts1 through which the proper juices descend towards the roots4 ,each plant has its own system of milk vessels1 and ,m4 ,lestiboudois has found that the coloured liquids have a rapid motion2 the movements are very complicated1 not from point to point1 but in such a manner that the granules are carried by the liquid into all the ramifications of a complicated network4 ,the septa1 or divisions between the primordial cells1 exert a powerful influence upon the substances contained in the sap as it permeates through them1 no doubt acting as a dialysing membrane1 which separates the gelatinous from the crystalloid matter4 ,the latex is probably separated from the sap by the septa in the cells of the leaves1 and sent into the vessels peculiar to it1 and then1 while the sap is descending and passing through the cambium1 it is likely to be dialysed by the septa between the cells of that layer1 arresting the protein1 and other gelatinous substances1 and allowing sugar1 starch1 and other crystalloid matter to pass freely1 and form deposits of organic compounds for the following year4 ,for perennial plants in extra-tropical countries remain in a dormant state during the winter2 their cells are then full of organic compounds under the form of protein1 as well as sugar1 gum1 c41 but especially starch1 which is converted into sugar or dextrine1 when spring awakens the plants to renewed life and activity4 ,the composition of inorganic matter is very simple2 there are comparatively few radicals1 and the substances are compounded of few equivalent atoms1 at most eight or ten1 sometimes only two or three4 ,carbonic oxide is formed of one atom of carbon and one of oxygen2 carbonic acid is formed of one atom of carbon and two of oxygen2 and acetylene1 ,m4 ,bertholet's base of synthetic compounds1 contains two atoms of carbon and two of hydrogen1 chemically united2 but no organic compound contains less than three equivalent atoms1 generally a great many more4 ,for example1 citric acid1 which is lemon juice1 contains #ab atoms of carbon1 #e of hydrogen1 and #aa of oxygen2 while strychnine contains #dd atoms of carbon1 #bc of hydrogen1 #d of oxygen1 and #b of nitrogen4 ,experiment has proved that the powers which maintain stability among the numerous and complex constituents of organic substances decrease in energy as the number of the equivalent atoms augments2 hence such compounds are in less stable equilibrium than those of inorganic bodies1 and are more liable to be disturbed and changed into new and more stable forms4 ,as the chemical functions are not the same in all the cells1 situated as they are in different parts of a plant1 they elaborate different substances from the same materials4 ,besides1 new substances are introduced with the growth of the plant1 to be acted upon by the light and heat of the different seasons1 so that numerous compounds may be formed out of a given number of the primary elements4 ,for example1 the ultimate elements of wheaten flour1 or a grain of ripe wheat1 are carbon1 the three elementary gases1 sulphur1 phosphorus1 calcium1 magnesium1 and silex2 but during the germination and growth of the plant1 its flowering1 forming the seed1 and ripening the grain1 certain portions of these elements chemically combine in definite proportions to form cellulose1 starch1 sugar1 gum1 gluten1 fibrin1 albumen1 casein1 and fat1 all of which are found in wheaten flour4 ,however much plants may differ in their organic products1 they all agree in producing protein1 which takes an active part in the formation of cells2 and all produce neutral hydrates of carbon1 such as cellulose1 starch1 sugar1 gum1 c41 which consist of carbon1 combined with hydrogen and oxygen in the exact proportion that forms water4 ,many of them have precisely the same quantity of carbon1 and only differ in the quantity of the aquatic element1 as for example1 lignin1 starch1 and cane-sugar1 which consist of #ab parts of carbon1 in a state of combination with #h1 #aj1 and #aa parts of water respectively2 indeed the affinity between many of these neutral hydrates is of a most intimate character4 ,some of their varieties are isomeric1 that is to say1 they contain the same ingredients in the same proportions1 and yet they differ essentially in regard to their properties4 ,next to cellulose1 starch is the most universal and distinctive of vegetable productions1 being a constituent of all plants1 except the fungi4 ,it abounds in the grains and other seeds1 and supplies the young plant with food till it can feed itself4 ,in both of the flowering classes it occurs in small colourless transparent grains1 either floating in the sap1 attached to the walls of the cells1 or accumulated within them4 ,starch globules of very small size are imbedded1 either singly or in groups1 in the granules of chlorophyll1 or leaf green2 the manner in which the green coating takes place is unknown4 ,starch is an organic substance1 varying from grains of inappreciable minuteness to such as are visible to the naked eye1 and of such a variety of forms that it can be ascertained with tolerable certainty by what plant a grain of starch has been produced4 ,the small grains are generally globular1 but whatever the form may be1 each consists of a series of superimposed layers of different densities1 which exhibit coloured rings and a black cross in polarized light4 ,starch is an early and transient product of young plants1 which is destined to be changed into nutritious substances at a later period1 but being insoluble in cold water it is unfit to travel with the sap4 ,however a ferment called diastase produced during the incipient germination of the grains and seeds1 in the tubers of potatoes1 c41 being in a state of change1 imparts that state to the starch1 and converts it into a sweet soluble matter known as dextrine or starch-gum which is capable of being carried throughout the plant with the sap1 and which is itself ultimately changed into sugar4 ,dextrine is an ingredient in the primordial cell4 ,starch1 dextrine1 and cellulose are isomeric3 consisting of the same elements with different characters4 ,the woody part of trees and shrubs1 the fibres of hemp1 flax1 of the ,agave1 and many other plants1 are formed of cellulose1 the purest form of that substance being bleached flax and linen4 ,during the progress of vegetation1 the cells of the ligneous tissue of trees1 also those of woody and fibrous plants1 which are transparent and colourless when young1 become internally coated or filled with sclerogen1 the colouring matter of wood1 a substance of various hues4 ,in extra-tropical countries it is generally some shade of brown1 sometimes dark1 sometimes so pale as to be almost white with a yellowish or reddish tinge2 and occasionally it is beautifully marked as in the wood of the olive4 ,in tropical countries the colours are more vivid and varied1 deeper and even black1 as in ebony4 ,this colouring matter has the same quantity of oxygen as cellulose1 but it contains hydrogen and more carbon1 hence wood is combustible in proportion to the quantity of sclerogen it contains4 ,in beech it forms half of the wood1 in oak two thirds1 and in ebony nine tenths1 so it is the most highly combustible of the three4 ,the additional carbon is obtained by increased respiration1 the hydrogen by decomposition of water in the sap4 ,sugar is almost as universal a constituent of the higher classes of plants as cellulose and starch1 for besides the saccharine juice of innumerable plants1 starch1 the acids of unripe plants1 and even the acrid juice of the fig and other plants1 is turned into sugar as the plant advances to maturity1 and the fruits ripen4 ,manna and other saccharine exudations from the leaves or stems of trees1 as the lime tree1 are probably intercepted by the dialysing septa of the cells1 and exude to the exterior through the pores of the skin4 ,the sweet juice found in the nectaries of flowers is formed in other parts of the plant1 and rarely flows to the flower before it is full blown2 the quantity is at its maximum during the emission of the pollen1 and ceases when the fruit is formed4 ,in dicious plants and that singular and beautiful race the ,orchide1 it is evidently intended to attract insects for their aid in fertilization4 ,vegetable oils1 resins1 and wax1 consisting of the same simple elements as the hydrates1 form a large class of inflammable organic substances in which hydrogen predominates4 ,olive oil is a rare instance of a fixed oil being obtained from a fruit2 some laurels have that property also1 but the fixed oils are chiefly found in seeds1 as the walnut1 hazel nut1 and the almond1 in which the principle of oil is in its greatest purity4 ,it is particularly abundant in hemp seed1 and in a great variety of plants the starch in the seed is changed into oil to nourish the embryo1 till the seed lobes are above the ground1 and the true lobes appear4 ,resins1 gums1 and wax1 being colloid substances1 are dialysed and ejected from the system either through the fissures in the bark1 or by pores in the leaves4 ,the resins exude through the bark from canals that run between the cells of the plant1 in solution1 and are consolidated by the oxygen on coming into the air4 ,the herbaceous zone in the bark of the fir and pine family furnish an abundant supply of resins and balsams2 the camphor tribe and the ,amyrids are rich in them1 as frankincense1 myrrh1 balm of ,mecca1 and the ,olibanum1 supposed to be the frankincense of scripture4 ,wax is a frequent vegetable production1 especially in the torrid zone1 where many of the wax-bearing plants supply the natives with light4 ,an exudation through the pores of many plants coats their surfaces with resin or wax4 ,young buds are often covered with resin to protect them from cold and wet during the winter and early spring1 as those of the horse-chestnut and balsam poplar4 ,it is wax that gives the bloom to the plum1 cherry1 and grape1 and the rain drops lie on the waxy surface of the cabbage leaf1 like balls of diamond1 from the total reflection of light at their point of contact4 ,wax protects plants from damp in a rainy climate1 and prevents too strong perspiration from the fleshy leaves of the aloe1 cactus1 and other inhabitants of the parched and hot regions in the tropics4 ,the vegetable substances hitherto under consideration are neutral1 but the remarkable compounds albumen1 fibrin1 and casein1 already mentioned as constituents of wheaten flour1 not only contain carbon and hydrogen with a little oxygen1 but azote and small quantities of sulphur and phosphorus4 ,each of these three organic compounds is the same1 whether derived from animal or vegetable matter4 ,thus albumen is chemically the same1 whether obtained from wheat and other grains1 from arrowroot1 dahlia roots1 the serum of blood1 or the white of an egg4 ,as it constitutes the film or thin coating of the primordial cell1 and combines with dextrine in its internal viscid lining1 it not only forms an ingredient in all vegetable organisms1 but plays an important part in the growth of the whole vegetable world4 ,fibrin is chemically the same in the juice of plants and in blood1 in which it exists as a liquid during the life of the animal1 and as a fibre after death4 ,it forms the basis of the muscular system in animals1 and that extracted from the juice of plants coagulates spontaneously like blood4 ,casein is chemically identical1 whether derived from the curd of milk1 or from peas and beans4 ,azote is a very important principle in these substances as well as in the gelatinous substance gluten4 ,it forms an essential part of the animal structure1 and is either highly nutritious or deleterious in the vegetable1 being at once one of the most valuable1 contradictory and powerful agents in nature4 ,chemists have formed by synthesis compounds identical with all the fixed and essential oils1 for confectioners can now give the flavour of the pear1 orange1 quince1 pine apple and other fruits by means of artificial chemical compounds4 ,all the saccharine substances have not yet been artificially obtained1 nor the albuminous substances1 albumen1 fibrin1 and casein4 ,it cannot be a matter of surprise1 when chemists form organic substances out of inorganic elements1 that they should succeed in transforming compounds produced by living plants into new compounds1 as that of changing the vegetable acids into alcohols1 which is now done4 ,but some of the acids themselves are synthetically formed out of inorganic elements2 as for example the oxalic1 the most common of all the vegetable acids1 which is found most abundantly in the ,oxalis or wood sorrel1 and is a frequent constituent of the highest and lowest plants4 ,the formic acid1 which is the acrid stinging principle in ants1 is also synthetically formed2 it is found in the juice of the stinging nettle and in decaying pine leaves1 and contains hydrogen like all the other vegetable acids4 ,these acids result from an augmentation of oxygen during nocturnal respiration1 which penetrates deeply into the vegetable structure4 ,octahedral1 prismatic1 and stellar microscopic crystals formed by the chemical combination of the natural acids with bases imbibed by the roots1 are deposited in the cells under the skin1 and in all parts of plants4 ,however1 they appear most frequently as bundles of needle-shaped crystals of carbonate of lime1 lying side by side in the hollow of a cell4 ,they are known as raphides1 from raphis a needle1 and may be easily seen under the skin of the medicinal squill4 ,large single crystals of oxalate of lime1 octahedral or prismatic1 are found in the cells under the skin of the onion and other plants2 and stellar crystals of the same substance abound so much in the common rhubarb that the best specimens of the dry medicinal root contain as much as thirty-five per cent4 of them2 while certain aged plants of the cactus tribe have their tissues so loaded with them as to become quite brittle4 ,the calcareous base in some instances is combined with tartaric1 citric1 or malic acid4 ,the crystals of some raphides are #a_/djth of an inch long1 others are not more than the hundredth2 they are brought into view by polarized light4#hj ,spherical raphides between the #a_/bjjjth and #a_/djjjth of an inch in diameter have been discovered scattered profusely through the tissues of the leaves1 and those parts of plants which are modifications of the leaves2 they may be seen under the skin of ,pelargoniums and other plants1 and it is supposed that few if any orders of plants are without them4#ha ,although azote forms #ghh thousandth parts of the atmosphere1 none1 or at least no appreciable quantity of it1 is absorbed by the vegetable world2 that great principle of nourishment is entirely supplied by ammonia and nitric acid1 imbibed by the roots1 and decomposed by the chemico-vital power4 ,here it shows its capricious character by combining with other simple elements in the bark1 to produce the most precious medicines in some plants1 and in others the most deadly poisons1 while no vegetable substance is perfectly nutritious without it4 ,the milk sap1 when exposed to the air1 coagulates into a tenacious viscid solid4 ,the white juice is generally acrid1 or narcotic1 or both1 and for the most part extremely poisonous1 though exhibiting strong contrasts even in nearly allied species4 ,in the order ,euphorbiace or ,spurgeworts1 comprising nearly #a1ejj species1 a large proportion are hurtful2 but there is a gradation from mere stimulants to the most formidable poisons4 ,this order furnishes the ,ethiope and the native ,brazilian with poison for their arrows4 ,it contains the ,manchineel1 and ,exccaria ,agallocha1 the most poisonous of plants2 even the smoke from the burning branches of the ,exccaria affects the eyes with insufferable pain4 ,the white juice of the ,fig1 one of the ,morad order1 is violently poisonous2 in many1 as in the common fig1 it is acrid and irritating4 ,the ,antiaris toxicaria1 the celebrated ,upas-tree of ,java1 which is of the ,artocarpe or ,bread-fruit order1 owes its virulence to its milky juice1 which contains strychnia1 the most fatal of drugs4 ,dangerous and acrid as these orders are1 the ,bread-fruit1 abounding in starch1 supplies the inhabitants of the ,east ,indian islands with excellent food2 the milky juice of the ,cow-trees1 chiefly of the ,bread-fruit and ,fig orders1 furnishes a wholesome beverage to the ,south ,americans2 and the ,manihot or ,cassava1 a poisonous spurgewort when raw1 yields when roasted nutritious food to whole nations1 the heat driving off the dangerous principle4 ,caoutchouc1 a most harmless substance1 is the solid produce of many of the most acrid and virulent juices of plants belonging to the preceding orders2 the poison is probably left in the liquid4 ,the chemico-vital power is strikingly illustrated by the number of safe and excellent fruits produced by trees full of the most deleterious juices1 whether milky or not4 ,some of the finest fruits in the ,indian ,archipelago are products of eminently dangerous species of the ,sapindace or ,soapworts4 ,the acrid juices of the leaves and branches1 are so much diluted with water in the fruits1 that they become innocuous1 or they may be changed into sugar1 as in the common fig4 ,nothing can surpass the virulence of the juice of the ,upas-tree1 yet its nuts are eaten with impunity1 and the pulpy contents of the fruit of the ,strychnos nux vomica is food for birds4 ,the leaves and berries of the potato are so strongly narcotic1 that an extract from them is intermediate in power between that from deadly nightshade and hemlock1 yet the potato itself1 like the cassava1 is rendered wholesome by being boiled or roasted4 ,the alkaloids are alkaline substances formed in the bark and milky juices of plants1 always combined with an acid during the life of the plant4 ,the chemical structure of this class of substances is very much alike1 and chemists have succeeded in forming many of them synthetically2 they all contain azote1 and have a great affinity for acids4 ,the bark of the different species of ,cinchone1 especially the ,cinchona cordifolia and ,c4 ,condaminea1 yield three alkaloids--namely1 cinchonine1 quinine1 and cusconine--they are all formed of carbon1 hydrogen1 and azote in the same proportions2 but the first has one atom of oxygen in addition1 the second has two atoms in addition1 and the third has three2 so that in these alkaloids the carbon1 hydrogen1 and azote combine to form an organic radical1 which is oxidized in three different degrees4 ,six of the alkaloids have been obtained from opium1 which is the solid portion of the milk juice of the poppy2 of these1 morphine seems to be the narcotic principle2 and the orange-coloured milk sap of the ,chelidonium1 a very poisonous and acrid plant of the poppy order1 has furnished chelidonine4 ,the ,colchicum order1 containing the meadow saffron or autumnal crocus1 and ,veratrum album or white hellebore1 as well as many other plants1 yield alkaloids1 all of which are medicinal or poisonous1 according to the dose4 ,there is scarcely a people1 however savage1 that has not discovered some exciting narcotic4 ,opium is almost universally smoked or eaten among ,eastern nations2 and bhang1 a strong narcotic1 obtained from the leaves of ,indian hemp1 is in equally universal use among the ,brazilian savages and ,hottentots1 but especially among the ,malays1 who are excited to madness when they smoke it too freely4 ,the same intoxicating effect is produced by a strong liquor prepared from the ,datura sanguinea1 a species of stramonium2 and its congener tobacco1 now all but a necessary of life among civilized mankind1 was smoked by the natives of the ,american continent1 before the arrival of the ,europeans1 as a relief from hunger4 ,coffee has been long in use on account of its stimulating principle caffeine1 which is now discovered to be the same with theine1 the latter1 however1 being less exciting1 unless the tea plant grows in a very hot climate4 ,in countries where nature furnishes few narcotic principles1 wine1 beer1 and spirits supply their place1 especially in the far north1 where animal heat is rapidly carried off by the cold1 and carbon must be furnished to satisfy the all-devouring oxygen which we draw in at every breath4 ,caffeine1 the highly azotized principle of coffee1 obtained from tea leaves and coffee beans1 is one of the substances known as neutral crystallisable principles4 ,similar substances are found in asparagus1 pepper1 almonds1 the bark on the roots of the apple1 pear1 plum1 and cherry trees1 as well as in the bark of the willow4 ,the two last are especially analogous1 and contain no azote1 as the others do4 ,the colouring matter of flowers is a fluid contained in cells1 situated immediately under the skin1 which itself is perfectly transparent and colourless4 ,the whiteness of the white ,camellia1 rose1 lily1 and other flowers1 is supposed to be owing to the total reflection of light from the cells immediately below the skin1 which are either full of air1 or of a colourless liquid4 ,the predominating colours are yellow1 red1 and blue1 with the various intermediate tints4 ,sometimes these colours are converted one into another in the petal after fertilization1 at which period the colours are brightest4 ,the chemical nature of these liquids1 the cause of their variety1 and their definite arrangement in one and the same petal1 do not seem as yet to be ascertained4 ,the parts of plants that are not green inhale oxygen from the atmosphere1 and exhale carbonic acid gas exactly like animals4 ,during the chemical combinations of the oxygen with the carbon derived from the nutriment to form the carbonic acid gas1 heat is necessarily evolved1 especially in the flower1 the point of maximum heat varying with its expansion4 ,the blossoms of the ,aroide1 or ,arums1 are remarkable for the evolution of heat4 ,according to ,saussure1 a blossom of the common ,arum maculatum consumes five times its volume of oxygen in twenty-four hours previous to its evolution of fruit1 so it is not wonderful that the chemical combination of such a quantity of oxygen should produce a strong development of specific temperature4 ,by ,m4 ,dutrochet's observations1 the heat evolved by the ,arum maculatum has a maximum in the day and a minimum in the night1 and he found that it exceeded the heat of the surrounding air by between #be and #bg4 ,the heat of the ,colocasia odorata1 another ,arad1 was determined by several observers to be even #ej above the warmth of the air4 ,the heat evolved by germinating seeds when in a heap is not from fermentation2 it is owing to their consumption of oxygen and expiration of carbonic acid gas4 ,the temperature of all vegetating parts of plants1 the roots1 leaves1 young juicy shoots1 c41 is far superior to that of their flowers4 ,it arises from the nutritive process1 and has a maximum at noon1 and a minimum at midnight1 like that of the flower4 ,the growth of plants is most vigorous at noon2 consequently there is then a greater evolution of heat4 ,water in small quantities is secreted night and morning from the points of the leaves of many plants1 probably to relieve them from a superabundance of liquid1 which evaporation is insufficient to carry off4 ,the arums are remarkable for the quantity they eject4 ,it falls in drops from the points of the leaves4 ,about half a pint is given out every night by the enormous leaves of the ,caladium distillatorium1 a species of ,arad4 ,in that plant1 and in the ,colocasia1 the water flows in canals along each rib into a general duct1 which runs along the border of the leaf1 and terminates in an orifice upon the surface4 ,since electricity is developed by chemical action in unorganized matter1 it may be inferred that it is also developed within the vegetable cell where so many organic compounds are formed2 but it is probably given off from the points of the leaves or by evaporation from their surfaces4 ,professor ,fleming ascertained by actual experiment1 that the sap of a leaf1 and its surface1 are in different electric states2 he also found that the surface of the spongioles of the roots of plants and the ascending sap have opposite electricities4 ,both of the preceding cases the ,professor ascribes1 in part at least1 to organic changes which take place during vegetation4 ,slight currents of electricity were obtained from the petioles of flowers1 but fruits and tubers give powerful electrical currents due to the reaction of different vegetable juices upon one another4 ,the tuberose is said to emit scintillations and dart small sparks of light in a hot electric evening1 and gardeners have long been aware that mushroom spawn is most prolific in stormy weather4 ,the irritability of the tissues of plants which renders them liable to be acted upon by external causes1 has occupied the attention of many celebrated botanists4 ,from experiments by ,professor ,ferdinand ,cohn and his pupil ,m4 ,krabsch upon the irritability of the stamens in the florets on the discs of composite flowers1 more especially the ,centaureas1 they have come to the conclusion that susceptibility to the excitement of light1 as well as to that of mechanical and probably electrical impulse1 is possessed by all young vigorous tissues1 and upon comparing the phenomena of these with those of animal irritability1 they further conclude that the faculty of responding to external irritation by internal movements and change of form1 belongs to cells1 and holds good in the vegetable as in the animal kingdom4 ,to be irritable1 to change its normal form as a vessel of excitation1 and to revert to the normal form after a while by its internal elasticity1 are characteristics of the living cell4 ,in plants these properties are met with only when the vital processes are in full activity1 and therefore are particularly noticed during the period of flowering1 when the processes are at the maximum4 ,and it may be remarked that the stamens1 in which irritability is most frequently noticed1 are the only organs in which an elevation of temperature measurable by the thermometer occurs1 although a certain degree of heat is generated in all plant cells by the chemical process going on within them4 ,it is to be supposed that irritable properties belong to all parts of plants1 but that they exist in an intensified degree1 and for a certain epoch1 in those parts where their results arrest attention1 as in the stamens of the ,centaurea1 berberry1 cactus1 ,cistus1 nettle1 c41 and in the anthers of the ,stylide1 the leaves of ,diona muscipula1 and many others1 all of which are more or less affected by the external action of mechanical force and electricity2 for it is scarcely possible that plants should not be under the influence of atmospheric electricity1 since every shower of rain forms a perfect conductor between the clouds and the earth4 ,the motion does not always immediately follow the excitement2 plants often require to be rudely shaken before the movement begins4 ,m4 ,hofmeister has observed that all young shoots and leaves become curved by mechanical shaking4 ,light is the most universal and important exciting cause in the vegetable world4 ,the mouths of the stomata are opened by the influence of light4 ,the leaves1 young shoots1 and tendrils turn to the light2 it regulates the sleep of plants1 as well as the diurnal motions of the daisy and sunflower4 ,the opening of blossoms and of folded leaves which had been closed in sleep during the night1 shows the susceptibility of their tissues to the influence of light1 an influence beautifully exhibited by the orange-coloured ,eschscholtzia1 which shuts its golden blossoms under every passing cloud4 ,all ,m4 ,cohn's experiments prove that in the ,mimosa pudica1 which is highly sensible to the action of light1 heat1 electricity1 and touch1 #8the propagation of the external excitement1 proceeds in the same mode as in animals1 and there is little doubt that the vascular tissue 7which contain spiral vessels7 constitute the special bundles adapted for the purpose1 and that the phenomena of contractibility depend upon a muscular tissue4'#hb ,from ,professor ,franklin's experiments it appears that #8the motions resulting from external causes are owing to vital contractibility1 and that they are governed by the same laws which regulate similar action in the animal kingdom4 ,their energies vary with the vigour of the plant2 they are exhausted by over exercise1 and require rest2 and like animals they are lulled and put to sleep by chloroform and narcotics4' ,,end ,,of ,,the ,,first ,,volume4 ,,london3 ,,printed ,,by ,,spottiswoode ,,and ,,co41 ,,new-,,street ,,square ,,and ,,parliament ,,street ,footnote #a3 ,professor ,faraday4 ,footnote #b3 ,professor ,helmholtz4 ,footnote #c3 ,the address of the president1 ,sir ,william ,armstrong1 ,c4,b41 to the ,british ,association at ,newcastle-on-,tyne1 #bfth ,august1 #ahfc4 ,footnote #d3 ,j4 ,tyndall1 ,esq41 on ,force4 ,footnote #e3 ,the ,law of ,exchange was independently proved by ,messrs4 ,tyndall1 ,kirchhoff1 ,angstrm1 and ,balfour ,stewart4 ,footnote #f3 ,tyndall on ,heat4 ,footnote #g3 ,analogous to transparent media which receive their colour by stopping or absorbing some of the colours of white light and transmitting others4 ,footnote #h3 #8,connection of the ,physical ,sciences4' ,footnote #i3 #8,connection of the ,physical ,sciences4' ,footnote #aj3 ,they are called vacuum tubes1 and are filled while open by putting one end in communication with the vessel in which the gas is generated1 and the other end in communication with an air pump4 ,as soon as the atmospheric air is pumped out1 the gas rushes in and fills the tube1 the communication with the vessel containing the gas is cut off by fusing up that end of the tube1 and as soon as the gas is sufficiently rarefied the other end is fused up also4 ,an electrical discharge that will not pass through one inch of air1 will pass through thirty or forty inches in a vacuum tube4 ,footnote #aa3 #8,connection of the ,physical ,sciences4' ,footnote #ab3 ,lectures of much interest by ,dr4 ,william ,odling in the ,chemical ,news of #ahfb4 ,footnote #ac3 ,m4 ,h4 ,kopp4 ,footnote #ad3 ,lectures by ,dr4 ,crace ,calvert on improvement and progress of calico printing and dyeing since #ahea4 ,footnote #ae3 ,this prediction1 made in his ,treatise on ,light published in #ahbf1 has been completely fulfilled by the discovery of four new metals by spectrum analysis4 ,footnote #af3 ,phil4 ,mag4 vol4 iv4 #ahcd1 p4 #aad4 ,footnote #ag3 #8,on the ,spectrum of the ,electric ,spark in ,compound ,gases1' by ,mr4 ,j4 ,m4 ,seguin4 ,comptes ,rendus4 ,footnote #ah3 ,the light of the electric lamp is produced by an apparatus which successively makes and breaks an electric current1 whereby the terminal charcoal points become red-hot4 ,footnote #ai3 #8,on the ,means of ,increasing the ,intensity of ,metallic ,spectra4' ,by ,mr4 ,w4 ,crookes4 ,footnote #bj3 ,the ,chemical ,news and ,journal of ,physical ,science for ,july #d1 #ahfc4 ,footnote #ba3 ,dr4 ,w4 ,a4 ,miller has shown that these invisible highly refrangible rays exist in the vapours of all metals1 and has obtained photographs of their spectra 7see ,phil4 ,trans4 #ahfb1 p4 #hgf71 which correspond to the spectra of fluorescence4 ,footnote #bb3 ,in ,cassiopei1 ,mr4 ,huggins has detected a second bright line in the red part of the spectrum4 ,he has also found that these two bright lines agree in position with the two brightest lines of the spectrum of hydrogen1 and may therefore be considered due to luminous hydrogen4 ,footnote #bc3 ,sir ,john ,herschel1 who is of the highest authority with regard to the nebul in both hemispheres4 ,footnote #bd3 ,since this observation1 ,mr4 ,huggins discovered that two small comets give an analogous spectrum4 ,footnote #be3 ,from further observations ,mr4 ,huggins is of opinion that the red colour of this planet is not due to its atmosphere1 but is peculiar to certain parts of its surface4 ,footnote #bf3 #8,quarterly ,journal of ,science1' ,april #ahfd4 ,footnote #bg3 ,jan4 #g1 #ahfe4 ,footnote #bh3 ,on the latest discoveries concerning the sun's surface1 by ,balfour ,stewart1 ,esq41 in the #8,chemical ,news and ,journal of ,physical ,science' of ,april #ahfe4 ,footnote #bi3 ,according to ,payen4 ,like starch1 it is stained blue by iodine4 ,footnote #cj3 #8,on the ,functions of the ,nitrogenous ,matter of ,plants4' ,by ,m4 ,l4 ,garreau1 #8,annales des ,sciences naturelles1' t4 xiii4 #ahfj4 ,footnote #ca3 #8,remarks on the ,vessels of the ,latex1 the ,vasa ,propria1 and the ,receptacles of the elaborated ,juices of ,plants4' ,by ,m4 ,lestiboudois1 #8,comptes rendus1' #ahfc4 ,footnote #cb3 ,the author is indebted throughout many parts of this section to the excellent work of ,dr4 ,carpenter1 and to the #8,cryptogamic ,botany' of the ,rev4 ,m4 ,j4 ,berkeley1 from which also many of the cuts are derived4 ,footnote #cc3 ,mr4 ,berkeley's #8,cryptogamic ,botany4' ,footnote #cd3 #8,dr4 ,carpenter's ,microscope4' ,footnote #ce3 ,these motions were discovered1 and are described by ,dr4 ,harvey1 in his #8,manual of ,british ,marine ,alg4' ,footnote #cf3 #8,cryptogamic ,botany4' ,by the ,rev4 ,m4 ,j4 ,berkeley4 ,footnote #cg3 #8,cryptogamic ,botany4' ,by the ,rev4 ,m4 ,j4 ,berkeley4 ,footnote #ch3 #8,the ,microscope4' ,by ,dr4 ,carpenter4 ,footnote #ci3 #8,cryptogamic ,botany4' ,by the ,rev4 ,m4 ,j4 ,berkeley4 ,footnote #dj3 #8,british ,seaweeds4' ,by ,mrs4 ,alfred ,gatty4 ,footnote #da3 #8,flora ,italica ,crypta4' ,footnote #db3 ,mr4 ,berkeley's #8,cryptogamic ,botany4' ,footnote #dc3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #dd3 ,mrs4 ,gatty's #8,british ,sea ,weeds4' ,footnote #de3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #df3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #dg3 #8,voyage of the ,adventurer and ,beagle1' by ,mr4 ,darwin4 ,footnote #dh3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #di3 ,in the ,fuci each kind of fruit is discharged on the surface of the receptacle before fructification4 ,footnote #ej3 ,hooker's #8,flora ,antarctica4' ,footnote #ea3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #eb3 ,berkeley's #8,introduction to ,cryptogamic ,botany4' ,footnote #ec3 #8,des ,myxomycetes1' par ,m4 ,antoine de ,bary2 et ,mmoires par ,,mm4 ,tulasne et ,hermann ,hoffman1 #8,annales des ,sciences ,naturalles1' #dme sries4 ,footnote #ed3 #8,introduction to ,cryptogamic ,botany1' by the ,rev4 ,m4 ,j4 ,berkeley4 ,footnote #ee3 #8,sur des ,isaria et ,sphria ,entomogens1' par ,,mm4 ,l4 et ,h4 ,tulasne1 de l',institut1 #8,annales des ,sciences ,naturelles1' #dme srie1 #aheg4 ,footnote #ef3 #8,on the ,geographical ,distribution of ,fungi1' by ,m4 ,e4 ,p4 ,fries1 of ,upsala1 ,sweden4 ,footnote #eg3 ,memoir by ,m4 ,hermann ,hoffmann1 upon ,fermentation1 in the #8,ann4 des ,sciences ,naturelles1' #dme srie1 #ahfj4 ,footnote #eh3 #8,the ,microscope1' by ,dr4 ,carpenter4 ,footnote #ei3 ,m4 ,hoffmann4 ,footnote #fj3 #8,comptes rendus1' ,nov4 #ab1 #ahfj4 ,footnote #fa3 #8,geographical ,distribution of ,fungi1' by ,m4 ,fries4 ,footnote #fb3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #fc3 ,berkeley's #8,introduction to ,cryptogamic ,botany4' ,footnote #fd3 ,berkeley's #8,introduction to ,cryptogamic ,botany4' ,footnote #fe3 ,dr4 ,carpenter's #8,microscope4' ,footnote #ff3 ,dr4 ,carpenter's #8,microscope' ,footnote #fg3 #8,anatomy and ,physiology of the ,vegetable ,cell1' by ,m4 ,hugo von ,mohl4 ,footnote #fh3 ,m4 von ,mohl1 on the #8,vegetable ,cell4' ,footnote #fi3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #gj3 ,dr4 ,j4 ,d4 ,hooker on the #8,distribution of ,ferns1' in ,berkeley's #8,cryptogamic ,botany4' ,footnote #ga3 #8,index ,filicum1' by ,thomas ,moore1 ,f4,l4,s4 ,footnote #gb3 ,moore1 in #8,treasury of ,botany4' ,footnote #gc3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #gd3 ,charles ,johnson1 ,esq4 ,footnote #ge3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #gf3 ,berkeley's #8,cryptogamic ,botany4' ,footnote #gg3 ,inflorescence and fructification are fully explained1 and applied to a vast number of plants1 in #8,structural and ,physiological ,botany1' by ,arthur ,henfrey1 ,esq41--a work of great research and merit4 ,footnote #gh3 ,messrs4 ,hooker1 ,darwin1 and ,brongniart4 ,footnote #gi3 ,professor ,matteucci4 ,footnote #hj3 ,dr4 ,carpenter1 #8,microscope4' ,footnote #ha3 ,annals of ,natural ,history for #ahfc4 ,footnote #hb3 ,annals and ,magazines of ,natural ,history for #ahfc4 ,transcriber's ,note ,this book uses inconsistent spelling and hyphenation1 which were retained in the ebook version4 ,some corrections have been made to the text1 including correcting the errata and normalizing punctuation4 ,further corrections are noted below3 p4 #bi heat indedendent matter - heat independent matter p4 #aff next the visual center- next to the visual center p4 #agi in dependently - independently p4 #bea isr eproduced - is reproduced p4 #cdc ig #ef - ,fig #ef p4 #cea the fonds are articuled - the fonds are articulated