,,agricultural ,,and ,,biological ,,publications ,,charles ,v4 ,,piper1 ,,consulting ,,editor ,,the ,,chemistry ,,of ,,plant ,,life ---------------------------------------- ---------------------- ,mc,graw-,hill ,book ,co4 ,inc4 ,,publishers ,,of ,,books ,,for ,coal ,age ,electrical ,railway ,journal ,electrical ,world ,engineering ,news-,record ,american ,machinist ,ingenieria ,internacional ,engineering ,mining ,journal ,power ,chemical ,metallurgical ,engineering ,electrical ,merchandising ---------------------------------------- ---------------------- ,,the ,,chemistry ,,of ,,plant ,,life ,,by ,,roscoe ,w4 ,,thatcher1 ,m4,a41 ,d4,,agr4 ,,dean ,,of ,,the ,,department ,,of ,,agriculture ,,and ,,director ,,of ,,the ,,agricultural ,,experiment ,,stations4 ,,university ,,of ,,minnesota 7,,formerly ,,professor ,,of ,,plant ,,chemistry4 ,,university ,,of ,,minnesota7 ,,first ,,edition ,,second ,,impression ,,mcgraw-,,hill ,,book ,,company1 ,,inc4 ,,new ,,york3 #cgj ,,seventh ,,avenue ,,london3 #f #h ,,bouverie ,,st41 ,e4 ,c4 #d #aiba ,,copyright #aiba2 ,,by ,,the ,mc,g,r,a,w-,,hill ,,book ,,company1 ,,inc4 ,,preface ,the author has had in mind a two-fold purpose in the preparation of this book4 ,first1 it is hoped that it may serve as a text or reference book for collegiate students of plant science who are seeking a proper foundation upon which to build a scientific knowledge of how plants grow4 ,the late ,dr4 ,charles ,e4 ,bessey1 to whom ,i owe the beginning of my interest in plant life1 once said to me3 ,the trouble with our present knowledge of plant science is that we have had very few chemists who knew any botany1 and no botanists who knew any chemistry4 ,this may have been a slightly exaggerated statement1 even when it was made1 several years ago4 ,but it indicated a very clear recognition by this eminent student of plants of the need for a better knowledge of the chemistry of plant cell activities as a proper foundation for a satisfactory knowledge of the course and results of plant protoplasmic activities4 ,it is hoped that the present work may contribute something toward this desired end4 ,second1 the purpose of the writer will not have been fully accomplished unless the book shall serve also as a stimulus to further study in a fascinating field4 ,even the most casual perusal of many of its chapters cannot fail to make clear how incomplete is our present knowledge of the chemical changes by which the plant cell performs many of the processes which result in the production of so many substances which are vital to the comfort and pleasure of human life4 ,studies of the chemistry of animal life have resulted in many discoveries of utmost importance to human life and health4 ,it requires no great stretch of the imagination to conceive that similar studies of plant life might result in similar or even greater benefit to human life1 or society1 since it is upon the results of plant growth that we are dependent for most of our food1 clothing1 and fuel1 as well as for many of the luxuries of life4 ,the material presented in the book has been developed from a series of lecture-notes which was used in connection with a course in ,phyto-chemistry which was offered for several years to the students of the ,plant ,science ,group of the ,university of ,minnesota4 ,in the preparation of these notes1 extensive use was made of the material presented in such general reference works as ,abderhalden's ,biochemische ,handlexicon and ,handbuch der ,biochemischen ,arbeitsmethoden1 ,oppenheimer's ,handbuch der ,biochemie des ,menschen und der ,tiere1 ,czapek's ,biochemie der ,pflanzen1 ,rohmann's ,biochemie1 ,frankel's ,descriptive ,biochemie1 and ,dynamische ,biochemie1 ,euler's ,pflanzenchemie1 and ,haas and ,hill's ,chemistry of ,plant ,products2 as well as of the most excellent series of ,monographs on ,biochemistry1 edited by ,plimmer1 several numbers of which appeared in print prior to and during the period covered by the preparation of these lectures4 ,frequent use was made also of the many special treatises on individual groups of compounds which are mentioned in the lists of references appended to each chapter1 as well as of articles which appeared from time to time in various scientific journals4 ,hence1 no claim is made of originality for the statements presented herein1 except in an insignificant number of studies of enzyme action1 and of the possible physiological functions of certain specific compounds4 ,the only contributions which the writer has felt qualified to make to this general subject are those of an intense personal interest in the chemistry of plant processes and a viewpoint with reference to the relation of chemical processes to vital phenomena which will be apparent as the various subjects are presented4 ,the text has been prepared upon the assumption that the students who will use it will have had some previous training in elementary inorganic and organic chemistry4 ,a systematic laboratory course in organic preparations1 such as is required of students who are preparing to become professional chemists1 is not at all a necessary requisite to the understanding of the chemistry of the different groups of plant compounds as here presented2 but it is assumed that the student will have had such previous training as is now commonly given in a one-year collegiate course in ,general ,chemistry1 or a year's work in general inorganic chemistry followed by a brief course in ,types of ,carbon ,compounds or ,elements of ,organic ,chemistry1 such as is usually required of students who are preparing for advanced work in agricultural science1 in animal or human nutrition1 etc4 ,an attempt has been made to arrange the material in such a way as to proceed from simpler chemical principles and substances to those of more complex structures4 ,this results in an arrangement of the groups to be studied in an order which is quite different than their biological significance might suggest4 ,it is believed1 however1 that in the end a more systematic understanding and a more orderly procedure is obtained in this way than would result from the treatment of the groups in the order of their relative biological importance4 ,,contents ,,introduction ,,page ,development of biological science2 characteristics of protoplasm2 plant and animal life1 similarities and differences2 protoplasmic activity essentially chemical changes2 objects of study of the chemistry of plant life xiii-xvi ,,chapter ,i--,,plant ,,nutrients ,definitions2 the plant food elements2 available and unavailable forms2 the value of the different soil elements as plant foods2 functions of the different plant food elements in plant growth2 inorganic plant toxins and stimulants2 references #a-ae ,,chapter ,,ii--,,organic ,,components ,,of ,,plants ,plants as synthetic agents2 types of changes involved in plant growth2 groups of organic compounds found in plants2 physiological use and biological significance defined2 physiological uses of organic groups #af-bj ,,chapter ,,iii--,,photosynthesis ,definitions2 physiological steps in photosynthesis2 formaldehyde1 the simplest carbohydrate structure2 the condensation of formaldehyde into sugars2 theories concerning photosynthesis2 the production of starches and sugars2 references #ba-bi ,,chapter ,,iv--,,carbohydrates ,importance1 nomenclature1 and classification2 groups of carbohydrates2 isomeric forms of monosaccharides2 chemical constitution of monosaccharides2 characteristic reactions of hexoses2 the occurrence and properties of monosaccharides2 disaccharides2 trisaccharides2 tetrasaccharides2 the relation of molecular configuration to biochemical properties2 polysaccharides1 dextrosans1 levulosans1 mannosans1 and galactosans2 physiological uses and biological significance of carbohydrates2 references #cj-ff ,,chapter ,v--,,gums1 ,,pectins1 ,,and ,,celluloses ,relation to carbohydrates2 groups2 the natural gums and pentosans2 mucilages2 pectins2 celluloses2 physiological uses of celluloses2 references #fg-ge ,,chapter ,,vi--,,glucosides ,definition2 general structure2 hydrolysis of the natural glucosides2 general properties2 the phenol glucosides2 the alcohol glucosides2 the aldehyde glucosides2 the oxycumarin glucosides2 the cyanophoric glucosides2 the mustard-oil glucosides2 the pigment glucosides2 the digitalis glucosides2 the saponins2 physiological uses2 biological significance2 references #gf-ic ,,chapter ,,vii--,,tannins ,general properties2 occurrence2 chemical constitution2 classes2 some common tannins2 physiological uses2 biological significance of tannins in fruits2 references #id-aja ,,chapter ,,viii--,,pigments ,types and classes2 the chlorophylls1 chemical constitution1 similarity of chlorophyll and hmoglobin1 properties of the chlorophylls2 the carotinoids1 carotin1 xanthophyll1 lycopersicin1 and fucoxanthin2 phycoerythrin and phycophin2 the anthocyans2 the anthoxanthins2 the production of ornamental pigments in flowers1 etc42 the functions of pigments2 references #ajb-abc ,,chapter ,,ix--,,organic ,,acids1 ,,acid ,,salts1 ,,and ,,esters ,chemical constitution2 some common organic acids2 physiological uses of organic acids2 biological significance of fruit acids and esters #abd-abh ,,chapter ,x--,,fats ,,and ,,oils1 ,,waxes1 ,,and ,,lipoids ,general composition2 fats and oils1 occurrence1 chemical constitution1 acids which occur in natural fats1 alcohols which occur in natural fats1 hydrolysis and synthesis of fats1 extraction of oils from plant tissues1 identification of fats and oils1 physiological use2 the waxes2 the lipoids1 lecithin1 other plant phosphatides1 plant cerebrosides1 physiological uses of lipoids2 references #abi-ade ,,chapter ,,xi--,,essential ,,oils ,,and ,,resins ,definitions1 classes1 occurrence2 the essential oils2 the resins2 physiological uses and biological significance of essential oils2 references #adf-aej ,,chapter ,,xii--,,the ,,vegetable ,,bases ,composition and groups2 the plant amines2 alkaloids2 the purine bases2 the pyrimidines2 the nucleic acids1 composition and uses2 references #aea-afc ,,chapter ,,xiii--,,proteins ,importance2 general composition2 amino-acids and peptid units2 individual amino-acids2 composition of the plant proteins2 general properties of proteins2 classification2 differences between plant and animal proteins2 extraction of proteins from plant tissues2 synthesis in plants2 physiological uses2 references #afd-ahj ,,chapter ,,xiv--,,enzymes ,reaction velocities2 enzymes as catalysts2 general properties2 extracellular and intracellular enzymes2 chemical nature2 nomenclature and classification2 occurrence and preparation2 general and individual enzymes2 nature of enzyme action2 accelerators and inhibitors2 coenzymes and antienzymes2 zymogens2 physiological uses2 further studies needed2 references #aha-bja ,,chapter ,,xv--,,the ,,colloidal ,,condition ,colloids and crystalloids2 the colloidal condition a dispersion phenomenon2 nomenclature and classification2 conditions necessary to the formation of sols2 gel-formation2 general properties of colloidal solutions2 suspensoids and emulsoids2 adsorption2 catalysis affected by the colloidal condition2 industrial applications of colloidal phenomena2 natural colloidal phenomena2 references #bjb-bbj ,,chapter ,,xvi--,,the ,,physical ,,chemistry ,,of ,,protoplasm ,heterogeneous structure of protoplasm2 protoplasm a colloidal gel2 water2 salts2 osmotic pressure2 surface boundary phenomena2 electrical phenomena2 acidity and alkalinity2 summary2 vital phenomena as chemical and physical changes2 references #bba-bch ,,chapter ,,xvii--,,hormones1 ,,auximones1 ,,vitamines1 ,,and ,,toxins ,external and internal stimulants2 hormones2 vitamines2 auximones1 toxins #bci-bdh ,,chapter ,,xviii--,,adaptations ,general discussion2 adaptations1 accommodations1 and adjustments2 chromatic adaptations2 morphological adaptations2 accommodations2 concluding statements #bdi-beh ,,index #bei-bfh ,,introduction ,the history of biological science shows that the conceptions which men have held concerning the nature of plant and animal growth have undergone a series of revolutionary changes as the technique of1 and facilities for1 scientific study have developed and improved4 ,for a long time1 it was thought that life processes were essentially different in character than those which take place in inanimate matter1 and that the physical sciences had nothing to do with living changes4 ,then1 too1 earlier students had only vague notions of the actual structure of a living organism4 ,beginning with the earliest idea that a plant or an animal exists as a unit organism1 to be studied as such1 biological science progressed1 first to the recognition and study of the individual organs which are contained within the organism2 then to the tissues which make up these organs2 then 7with the coming into use of the microscope as an aid to these investigations7 to the cells of which the tissues are composed2 then to the protoplasm which constitutes the cell contents2 and finally to the doctrine of organic evolution as the explanation of the genealogy of plants and animals1 and the study of the relation of the principles of the physical sciences to the evolutionary process4 ,the ultimate material into which organisms are resolved by this process of biological analysis is the cell protoplasm4 ,but protoplasm is itself made up of a complex system of definite chemical compounds1 which react and interact according to the laws of physical science4 ,hence1 any study of the chemistry of plant growth is essentially a study of the chemical and physical changes which take place in the cell protoplasm4 ,protoplasm differs from non-living matter in three respects4 ,these are 7#a7 its chemical composition2 7#b7 its power of waste and repair and of growth2 and 7#c7 its reproductive power4 ,from the standpoint of chemical composition1 protoplasm is the most complex material in the universe4 ,it not only contains a greater variety of chemical elements1 united into molecules of enormous size and complexity1 but also a greater variety of definite chemical compounds than exist in any other known mixture1 either mineral or organic in type4 ,one of the first problems in the study of protoplasm is1 therefore1 to bring this great variety of complex compounds into some orderly classification and to become familiar with their compositions and properties4 ,again1 living matter is continually undergoing a process of breaking down as a result of its energetic activities and of simultaneously making good this loss by the manufacture of new protoplasm out of simple food materials4 ,it also has the power of growth by the production of surplus protoplasm which fills new cells1 which in turn produce new tissues and so increase the size and weight of individual organs and of the organism as a whole4 ,hence1 a second field of study includes the chemical changes whereby new protoplasm and new tissue-building material are elaborated4 ,finally1 living material not only repairs its own waste and produces new material of like character to it1 but it also produces new masses of living matter1 which when detached from the parent mass1 eventually begin a separate existence and growth4 ,furthermore1 the plant organism has acquired1 by the process of evolution1 the ability not only to produce an embryo for a successive generation but also to store up1 in the tissues adjacent to it1 reserve food material for the use of the young seedling until it shall have developed the ability to absorb and make use of its own external sources of food material4 ,so that1 finally1 every study of plant chemistry must take into consideration the stored food material and the germinative process whereby this becomes available to the new organism of the next generation4 ,also1 the chemistry of fertilization of the ovum1 so that a new embryo will be produced1 and the other stimuli which serve to induce the growth phenomena1 must be brought under observation and study4 ,a further step in the development of biological science has been to separate the study of living things into the two sciences of botany and zoology4 ,from the standpoint of the chemistry of the processes involved this segregation is unfortunate4 ,it has resulted in the devotion of most of the study which has been given to life processes and living things to animal chemistry1 or physiological chemistry4 ,as a consequence1 biochemistry1 which deals with the living processes of both plants and animals1 is yet in its infancy2 while phytochemistry is almost a new science1 yet its relation to the study of plants can scarcely be less vital than is that of physiological chemistry to studies of animal life4 ,the common conception that plant life and animal life are antithetical or complementary to each other has much to justify it4 ,animals breathe in oxygen and exhale carbon dioxide2 while plants use the carbon dioxide of the air as a part of the raw material for photosynthesis and exhale oxygen4 ,plants absorb simple gases and mineral compounds as raw food materials and build these up into complex carbohydrates1 proteins1 fats1 etc42 while animals use these complex compounds of plant origin as food1 transforming parts of them into various other forms of structural material1 but in the end breaking them down again into the simple gases and mineral compounds1 which are expelled from the body through the excretory organs4 ,thus it would seem that the study of the chemistry of plant life and of animal life must necessarily deal with opposite types of phenomena4 ,but one cannot advance far into the study of the biochemistry of plants and animals before he discovers marked similarities in the chemical principles involved4 ,many of the compounds are identical in structure1 undergo similar changes1 and are acted upon by similar catalysts4 ,plant cells exhibit respiratory activities1 using oxygen and giving off carbon dioxide1 in exactly the same way that animal organisms do4 ,the constructive photosynthetic processes of green plants are regulated and controlled by a pigment1 chlorophyll1 which is almost identical with the blood pigment1 hmatin1 which regulates the vital activities in the animal organism1 differing from the latter only in the mineral element which links the characteristic structural units together in the molecule4 ,many other points of similarity in the chemistry of the life processes of plants and animals will become apparent as the study progresses4 ,it is sufficient now to call attention to the fact that these vital processes1 in either plants or animals1 are essentially chemical in character1 and subject to study by the usual methods of biochemical investigations4 ,the protoplasm of the cell is the laboratory in which all the changes which constitute the vital activities of the plant take place4 ,all of the processes which constitute these activities--assimilation1 translocation1 metabolism1 and respiration--involve definite chemical changes4 ,in so far as it is possible to study each of these activities independently of the others1 they have been found to obey the ordinary laws of chemical reactions4 ,thus1 the effect of the variations in intensity of light upon photosynthesis causes increase in the rate of this activity which may be represented by the ordinary responses of reaction velocities to external stimuli4 ,similarly1 the effect of rises in temperature upon the rate of assimilation and upon respiration are precisely the same as their effect upon the velocity of any ordinary chemical reaction4 ,within certain definite ranges of temperature1 the same statement holds true with reference to the rate of growth of the plant1 although the range of temperature within which protoplasm lives and maintains its delicate adjustment to the four vital processes of life is limited2 beyond a certain point1 further rise in temperature does not produce more growth but rather throws the protoplasmic adjustment out of balance and growth either slows up markedly or stops altogether4 ,hence1 we may say that the methods by which the plant machine 7protoplasm7 accomplishes its results are essentially and definitely chemical in character and may be studied purely from the standpoint of chemical reactions1 but the maintenance of the machine itself in proper working order is a vital phenomenon which is largely dependent upon the external environmental conditions under which the plant exists4 ,a study of the phenomena resulting from the colloidal condition of matter is throwing a flood of light upon the mechanism by which protoplasm accomplishes its control of vital activities4 ,but we are1 as yet1 a long way from a complete understanding of how colloidal protoplasm acquires and maintains its unique ability of self-regulation of the conditions necessary to preserve its colloidal properties and of how it elaborates the enzymes which control the velocity of the chemical reactions which take place within the protoplasm itself and which constitute the various processes of vital activity4 ,the object of this study of the chemistry of plant growth is to acquire a knowledge of the constitution of the compounds involved and of the conditions under which they will undergo the chemical changes which1 taken all together1 constitute the vital processes of cell protoplasm4 ,,chemistry ,,of ,,plant ,,life ,,chapter ,i ,,plant ,,nutrients ,there is some confusion in the use of the terms nutrient1 plant food1 etc41 as applied to the nutrition and growth of plants4 ,strictly speaking1 these terms ought probably to be limited in their application to the organized compounds within the plant which it uses as sources of energy and of metabolizable material for the development of new cells and organs during its growth4 ,botanists quite commonly use the terms in this way4 ,but students of the problems involved in the relation of soil elements to the growth of plants1 including such practical questions as are involved in the maintenance of soil productivity and the use of commercial fertilizers for the growing of economic plants1 or crops1 are accustomed to use the terms plant foods1 or mineral nutrients1 to designate the chemical elements and simple gaseous compounds which are supplied to the plant as the raw material from which its food and tissue-building materials are synthetized4 ,common usage limits these terms to the soil elements2 but there is no logical reason for segregating the raw materials derived from the soil from those derived from the atmosphere4 ,the essential difference between these raw materials for plant syntheses and the organic compounds which are produced within the plants and used by them1 and by animals1 as food1 is that the former are inorganic and can furnish only materials but no energy to the organism2 while the latter are organic and supply both materials and potential energy4 ,it would probably be the best practice to confine the use of the word food to materials of the latter type1 and several attempts have been made to limit its use in this way and to apply some such term as intake to the simple raw materials which are taken into the organism and utilized by it in its synthetic processes4 ,but the custom of using the words food1 or nutrient1 to represent anything that is taken into the organism and in any way utilized by it for its nourishment has been followed so long and the newer terms are themselves so subject to criticism that they have not yet generally supplanted the loosely used word food4 ,if such use is permitted1 however1 it is necessary to recognize that only the green parts of green plants can use this inorganic food1 and that the colorless plants must have organic food4 ,to avoid this confusion1 the suggestion has recently been made that all of the intake of plants and animals shall be considered as food1 but that those forms which supply both materials and potential energy to the organism shall be designated as synergic foods1 while those which contain no potential energy shall be known as anergic foods4 ,on this basis1 practically all of the food of animals1 excepting the mineral salts and water1 and all of the organic compounds which are synthetized by plants and later used by them for further metabolic changes1 are synergic foods2 while practically all of the intake of green plants is anergic food4 ,it is with the latter type of food materials that this chapter is to deal2 while the following and all subsequent chapters deal with the organic compounds which are synthetized by plants and contain potential energy and are1 therefore1 capable of use as synergic food by either the plants themselves or by animals4 ,it will be understood1 therefore1 that in this chapter the word food is used to mean the anergic food materials which are taken into and used by green plants as the raw materials for the synthesis of organic compounds1 with the aid of solar energy1 or that of previously produced synergic foods4 ,in all later chapters1 the term food will be used to mean the organic compounds which serve as the synergic food for the green parts of green plants and as the sole supply of nutrient material for the colorless parts of green plants and for parasitic or saprophytic forms 7see page #af74 ,,plant ,,food ,,elements ,the raw materials from which the food and tissue-building compounds of plants are synthetized include carbon dioxide1 oxygen1 water1 nitrogen1 phosphorus1 sulfur1 potassium1 calcium1 magnesium1 and iron4 ,the two gases first mentioned are derived directly from the air1 through the respiratory organs of the plant4 ,water is taken into the plant chiefly from the soil1 through its fibrous roots4 ,all the other elements in the list are taken from the soil1 nitrogen being derived from decaying organic matter 7the original source of the nitrogen is1 however1 the atmosphere1 from which the initial supply of nitrogen is obtained by direct assimilation by certain bacteria and perhaps other low forms of plant life71 and the remaining ones from the mineral compounds of the soil4 ,carbon dioxide and oxygen1 being derived from the air1 are always available to the leaves and stems of growing plants in unlimited supply2 but the supply available to a seed when germinating in the soil1 or to the roots of a growing farm crop1 may sometimes become inadequate1 especially in soils of a very compact texture1 or water-logged soils4 ,in such cases1 the deficiency of these gaseous food elements may become a limiting factor in plant growth4 ,water is often a limiting factor in plant growth4 ,experiments which have been repeated many times and under widely varying conditions show that when water is supplied to a plant in varying amounts1 by increasing the percentage of water in the soil in which the plant is growing by regular increments up to the saturation point1 the growth of the plant1 or yield of the crop1 increases up to a certain point and then falls off because the excess of water reduces the supply of air which is available to the plant roots4 ,hence1 abundance of water is1 in general1 a most essential factor in plant growth4 ,under normal conditions of air and moisture supply1 however1 the plant food elements which may be considered to be the limiting factors in the nutrition and growth of plants are the chemical elements mentioned in the list above4 ,,available ,,and ,,unavailable ,,forms ,the plant food materials which are taken from the soil by a growing plant must enter it by osmosis through the semi-permeable membranes which constitute the epidermis of the root-hairs1 and circulate through the plant either carried in solution in the sap or by osmosis from cell to cell4 ,hence1 they must be in water-soluble form before they can be utilized by plants4 ,obviously1 therefore1 only those compounds of these elements in the soil which are soluble in the soil water are available as plant food4 ,the greater proportion of the soil elements are present there in the form of compounds which are so slightly soluble in water as to be unavailable to plants4 ,the processes by which these practically insoluble compounds become gradually changed into soluble forms are chiefly the weathering action of air and water 7particularly if the latter contains carbonic acid7 and the action of the organic acids resulting from decaying animal or vegetable matter or secreted by living plants4 ,,the ,,value ,,of ,,the ,,soil ,,elements ,,as ,,plant ,,food ,analyses of the tissues of plants show that they contain all of the elements that are to be found in the soil on which they grew4 ,any of these elements which are present in the soil in soluble form are carried into the plants with the soil water in which they are dissolved1 whether they are needed by the plant for its nutrition or not4 ,but in the case of those elements which are not taken out of the sap to be used by the plant cells in their activities1 the total amount taken from the soil is much less than is that of the elements which are used in the synthetic processes of the plant4 ,hence1 much larger proportions of some elements than of others are taken from the soil by plants4 ,the proportions of the different elements which are used by plants as raw materials for the manufacture of the products needed for their growth varies with the different species2 but a certain amount of each of the so-called essential elements 7see below7 is necessary to every plant1 because each such element has a definite rle which it performs in the plant's growth4 ,a plant cannot grow to maturity unless a sufficient supply of each essential element comes to it from the soil4 ,from the standpoint of their relative value as raw materials for plant food1 the elements which are present in the soil may be divided into three classes2 namely1 the non-essential1 the essential and abundant1 and the critical elements4 ,the first class includes silicon1 aluminium1 sodium1 manganese1 and certain other rarer elements which sometimes are found in soils of some special type1 or unusual origin4 ,these elements seem to have no rle to play in the nutrition of plants2 although silicon is always present in plant ash and sodium salts are found in small quantities in all parts of practically all plants4 ,nearly all species of plants can be grown to full maturity in the entire absence of these elements from their culture medium4 ,occasional exceptions to this statement in the case of special types of plants are known1 and are of interest in special studies of plant adaptations1 but need not be considered here4 ,the second group includes iron1 calcium1 magnesium1 and1 generally1 sulfur4 ,all of these elements are essential for plant growth1 but are usually present in the soil in ample quantities to insure a sufficient supply in available form for all plant needs4 ,recent investigations have shown1 however1 that there are many soils in which sulfur is present in such limited quantities that many agricultural crops1 when grown on these soils1 respond favorably to the application of sulfur-containing fertilizers4 ,in such cases1 sulfur is a critical element4 ,the critical elements are those which are essential to the growth of all plants and which are present in most soils in relatively small proportions and any one may1 therefore1 be the limiting factor in plant growth so far as plant food is concerned4 ,these are nitrogen1 phosphorus1 potassium1 and 7possibly7 sulfur4 ,r,,le ,,of ,,plant ,,food ,,elements ,,in ,,plant ,,growth ,the use which a plant makes of the elements which come to it from the soil has been studied with great persistency and care by many plant physiologists and chemists4 ,many of the reactions which take place in a plant cell are extremely complicated1 and the relation of the different chemical elements to these is not easily ascertained4 ,it is probable that the same element may play a somewhat different rle in different species of plants1 in different organs of the same plant1 or at different stages of the plant's development4 ,but the usual and most important offices of each element are now fairly well understood1 and are briefly summarized in the following paragraphs4 ,it should be understood that a thorough and detailed discussion of these matters1 such as would be included in an advanced study of plant nutrition1 would reveal other functions than those which are presented here and would require a more careful and more exact method of statement than is suitable here4 ,however1 the general principles of the utilization of soil elements by plants for their nutrition and growth may be fairly well understood from the following statements4 ,nitrogen is a constituent of all proteins 7see ,chapter ,,xiii74 ,proteins are apparently the active chemical components of protoplasm4 ,since it is in the protoplasm of the green portions1 usually foliage1 of plants that the photosynthesis of carbohydrates and the synthesis of most1 or all1 of the other tissue-building materials and reserve food substances of the plant takes place1 the importance of nitrogen as a plant food can hardly be over-emphasized4 ,nitrogen starvation produces marked changes in the growth of a plant4 ,leaves are stunted in growth and a marked yellowing of the entire foliage takes place2 in fact1 the whole plant takes on a stunted or starved appearance4 ,abundance of nitrogen1 on the other hand1 produces a rank growth of foliage of a deep rich color and a luxuriant development of tissue1 and retards the ripening process4 ,in the early stages of growth1 the nitrogen is present most largely in the leaves2 but when the seeds develop1 rapid translocation of protein material into the seeds takes place1 until finally a large proportion of the total supply is deposited in them4 ,nitrates are the normal form of nitrogen in the soil which is available to plants4 ,during germination and early growth1 the young seedling uses amino-acids1 etc41 derived from the proteins stored in the seed1 as its source of nitrogen2 and experiments have shown that similar forms of soluble organic nitrogen compounds can be successfully fed to the seedling as an external food supply4 ,soluble ammonium salts can be utilized as sources of nitrogen by most plants during later periods of growth1 particularly by the legumes4 ,but for most1 if not all1 of the common farm crops whose possibilities in these respects have been studied1 it has been found that a unit of nitrogen taken up as a nitrate is very much more effective in promoting growth1 etc41 than is the same unit of nitrogen in the form of ammonium salts4 ,while the proteins are finally stored up largely in the seeds1 or other storage organs1 they are actively at work during the growing period in the cells of the foliage parts of the plant4 ,hence1 the popular statement that nitrogen makes foliage is a fairly accurate expression of its rle4 ,inordinate production of straw in cereal crops and of leaves in root crops often results from liberal supplies of available nitrogen in the soil early in the growing season4 ,if the crops develop to normal maturity1 this excessive foliage growth has no harmful results1 as the surplus material which has been elaborated is properly translocated into the desired storage organs2 but1 unfortunately1 the retarding effect of the surplus nitrogen supply upon the date of maturing of the crop is often associated with premature ripening of the plants from other causes1 with the consequence that too large a proportion of the valuable food material is left in the refuse foliage material of the crop4 ,crops which are grown solely for their leaves1 such as hay crops1 lettuce1 cabbage1 etc41 profit greatly by abundant supplies of available nitrogen2 although when foliage growth is stimulated in this way the tissue is likely to be thin-walled and soft rather than firm and solid4 ,phosphorus is likewise an extremely important element in plant nutrition4 ,but phosphorus starvation produces no such striking visible effects upon the growth of the plant as does lack of nitrogen4 ,abundance of available phosphorus early in the plant's life greatly stimulates root growth1 and later on it undoubtedly hastens the ripening process2 hence1 this element seems to act as the exact antithesis of nitrogen4 ,the rle of phosphorus1 or of phosphates1 in the physiological processes of the cell seems to be difficult to discover4 ,the element itself is a constituent of some protein complexes and of the lecithin-like bodies 7see page #ada7 which are supposed by some investigators to play an important part in determining the rate of chemical changes which take place in the cell and the movement of materials into and out of it4 ,it is an essential constituent of the nucleus1 and a meager supply of phosphorus retards1 or inhibits1 mitotic cell-division4 ,photosynthesis of sugars and the condensing of these into starch or cellulose takes place in plants in the absence of available phosphorus2 but the change of these insoluble carbohydrates back again into soluble and available sugar foods does not4 ,phosphorus is taken from the soil by plants in the form of phosphates4 ,much study has been given to the problem of the proper supply of available soil phosphates for economic crop production4 ,any discussion of soil fertility and fertilization which did not devote large attention to the conditions under which phosphates become available as plant food would be wholly inadequate2 but such a discussion would be out of place here4 ,the final result of an ample supply of phosphates in hastening the ripening process and stimulating seed production1 as contrasted with that of an over-supply of nitrogen1 has led to the popular statement that phosphates make seeds4 ,this statement1 while not strictly accurate1 is a fairly good summary of the combined results of the rle of phosphorus in the plant economy4 ,large amounts of phosphorus are stored in the seeds4 ,the two facts that large amounts of these compounds are thus available to the young seedling and that relatively large proportions of phosphates are taken from the soil by the plant during its early stages of growth are undoubtedly connected with the need for rapid cell-division at these periods in the plant's life4 ,potassium4--,the popular expression that potash makes sugars and starch is a surprisingly accurate description of the rle of this element in plant metabolism4 ,either the photosynthesis of starch1 or the changes necessary to its translocation 7it is not yet certain which7 is so dependent upon the presence of potassium in the cell sap that the whole process stops at once if an insufficient supply is present4 ,the production and storage of sugar1 or starch1 in such root crops as beets1 potatoes1 etc41 diminishes in direct proportion with a decreasing supply of potassium as plant food4 ,the grains of the cereal crops become shrunken as a result of potassium starvation2 and are plump and well filled with starch in the endosperm when sufficient potassium is available for the crop's needs4 ,the general tone and vigor of growth of the plant is largely dependent upon an ample potassium supply2 potash-hungry plants1 like those which have been weakened by any other unfavorable conditions1 have been found to be more susceptible to injury by disease1 than those which are well nourished with this food element4 ,but potassium-starvation does not produce any pathological condition of the cell contents2 its absence simply prevents the possibility of the development of the necessary carbohydrates for vigorous growth4 ,there is no known difference in the availability1 or effectiveness1 of potassium from the different forms of compounds containing it which may be present in the soil4 ,apparently1 the only essential is that the compound shall be soluble so that it can be absorbed into the plant through the root-hairs4 ,of course1 the acid radical to which the basic potassium ion is attached may1 in itself1 have some beneficial or deleterious influence which gives to the compound as a whole some important effect in one case1 which might not follow in the case of another type of compound2 but the relative efficiency as plant food of a given unit of potassium seems to be the same regardless of the nature of the compound in which it is present4 ,calcium is an essential plant food element but its physiological use has not yet been definitely established4 ,it seems to stimulate root-development1 and certainly gives vigor and tone to the whole plant4 ,it is commonly believed that calcium is in some way connected with the development of cell-wall material4 ,it has been reported that the stems of grasses and cereal plants become stiffer in the presence of ample calcium1 but this may be due to greater turgidity rather than to strengthened cell-walls4 ,calcium remains in the leaves or stem as the plant ripens1 but it is not clear that this has anything to do with the stiffness or weakness of the stem1 or straw1 of the plant4 ,experiments with alg have shown that in the absence of calcium salts mitotic cell division takes place1 showing that the nucleus functions properly1 but the formation of the new transverse cell-wall is retarded4 ,this is the only direct evidence that has been reported that calcium has any connection with cell-wall formation4 ,certain species of plants1 notably many legumes1 require such large amounts of calcium salts for their growth as to give to them the popular appellation of lime-loving plants4 ,other plants1 known as calciphiles1 while not actually showing abnormally large percentages of calcium in their ash1 flourish best on soils rich in lime4 ,on the other hand1 certain other species1 known as calcifuges1 will not grow on soils which are even moderately rich in lime2 in what respect these differ in their vital processes from others which demand large amounts of calcium1 or those which flourish on soils rich in lime1 has not been determined1 however4 ,the beneficial effect of alkaline calcium compounds in the soil1 in correcting injurious acidity1 in improving the texture of clay soils1 and in promoting the proper conditions for bacterial growth1 is well known2 but this has no direct connection with the rle of calcium as plant food4 ,furthermore1 calcium salts in the soil have a powerful influence in overcoming the harmful1 or toxic1 effects of excessive amounts of soluble salts of magnesium1 sodium1 or potassium1 in the so-called alkali soils 7i4e41 those which contain excessive amounts of water-soluble salts74 ,the probable explanation for this fact is pointed out in a later paragraph of this chapter 7see page #ad72 but this property of calcium probably has no connection with its physiological uses as plant food4 ,magnesium1 like phosphorus1 is finally stored up mostly in the seeds1 not remaining in the leaves and stems1 as do calcium and potassium4 ,this fact1 together with other evidence obtained from experiments in growing plants in culture solutions containing varying amounts of this element1 has led certain investigators to the conclusion that the rle of magnesium is to aid in the transport of phosphorus1 particularly from older to more rapidly growing parts of the plant4 ,more recent investigations have shown1 however1 that magnesium has other rles which are probably more specific and more important than this one4 ,it is now known that magnesium is a definite constituent of the chlorophyll molecule serving1 as will be shown 7see ,chapter ,,viii71 as the means of linkage between its essential component organic groups4 ,because of this fact1 magnesium-starvation produces etiolated plants1 which cannot function normally4 ,further1 magnesium seems to be necessary for the formation of fats1 apparently standing in a similar relation to fat-formation to that of potassium to carbohydrate-formation4 ,this view is supported by the observations that when alg are grown in magnesium-free solutions they contain no fat globules and that oily seeds are richer in magnesium than are those which store up starch as their reserve food material4 ,observers of the second of these phenomena have failed to note1 however1 that oily seeds are likewise richer in phosphorus than are starchy ones1 and that the presence of larger proportions of magnesium in such seeds may1 perhaps1 be related to phosphorus-translocation rather than to fat-formation4 ,whatever relation magnesium may have to fat-formation1 or to the translocation of phosphorus1 it is evident that these are rles quite apart from its use as a constituent element in chlorophyll4 ,as yet1 no explanation of how it aids in these other synthetic processes has been advanced4 ,on the other hand1 an excess of soluble magnesium salts in the soil produces definite toxic effects upon plants1 magnesium compounds being known to be among the most destructive of the alkali soil salts4 ,calcium salts are remarkably efficient in overcoming these harmful effects of magnesium salts4 ,on this account1 a large amount of experimental study has been given to the question of the calcium-magnesium ratio in plants4 ,numerous analyses of plant ashes have established the fact that there is a fairly definite ratio of this kind1 which ratio1 however1 varies with the species of plant and is not correlated with the ratio of these elements present in the soil on which the plant grows1 as was formerly believed4 ,cereal plants1 as a rule1 contain approximately twice as much lime as magnesia2 while leafy plants 7tobacco1 cabbage1 etc47 usually contain about four times as much calcium oxide as magnesium oxide4 ,iron is essential to chlorophyll-formation4 ,it is not a constituent of the chlorophyll molecule1 as is magnesium2 but in the absence of iron from the culture solution1 a plant fails to produce chlorophyll and a green plant which is deprived of a supply of iron rapidly becomes etiolated4 ,the way in which iron is related to chlorophyll-formation is not known4 ,iron is taken from the soil by plants in the smallest proportions of any of the essential elements4 ,only soluble ferric compounds seem to serve as a suitable source of supply of the element2 ferrous compounds being usually highly toxic to plants4 ,sulfur is an essential element of plant food4 ,the amounts required by plants were supposed1 until recently1 to be relatively small4 ,this was due to the fact that earlier studies took account only of the sulfur which1 on analysis1 appeared as sulfates in the ash4 ,improved methods of analysis1 which insure that the sulfur which is present in the plant tissue in organic combinations is oxidized under such conditions that it is not lost by volatilization during the combustion of the material1 have shown that the total sulfur which is present in many plants approaches the quantity of phosphorus which is present in the same tissue4 ,furthermore1 recent field and pot experiments have shown that at least a considerable part of the beneficial effects of many fertilizers1 which has previously been attributed to the calcium1 potassium1 or phosphorus which they contain1 is actually due to the sulfur present as sulfates in the fertilizers used4 ,sulfur occurs in the organic compounds of plants1 associated with phosphorus4 ,it seems probable that its physiological uses are similar to those of the latter element2 but there is as yet no experimental evidence to establish its exact rle in the economy of plant growth4 ,it appears to be needed in largest proportion by plants which contain high percentages of nitrogen in their foliage1 such as the legumes4 ,there is some evidence that sulfur has a particular rle in promoting the growth of bacteria1 and it may be that the percentages of total sulfur which are found in the tissues of legumes are due to the presence of the symbiotic nitrogen-gathering bacteria in the nodules on the roots of these plants4 ,this point has not yet been investigated1 however4 ,sodium is probably not essential to plant growth1 although it is present in small proportions in the ash from practically all plants4 ,in cases of insufficient supply of potassium1 sodium can apparently perform at least a part of the rle of the former element2 but this seems not to be a normal relationship or use4 ,chlorine is found in small amounts in the sap and in the ash of nearly all plants4 ,however1 it does not appear to be essential to the growth of a plant1 except possibly in the case of certain species1 such as asparagus1 buckwheat1 and1 perhaps1 turnips and some other root crops4 ,whether the benefit which these crops derive from the application of common salt to the soil in which they are growing is due to the direct food value of either the chlorine1 or the sodium1 or to some indirect effect1 is not yet known4 ,the presence of chlorine in the sap of plants is undoubtedly due to the inevitable absorption of soluble chlorides from the soil and apparently has no connection with the nutritional needs of the plant4 ,silicon is always considered as a non-essential element1 although it occurs in such large proportions in some plants as to indicate that it cannot be wholly useless4 ,it accumulates in the stems of plants1 chiefly in the cell-wall1 and has sometimes been supposed to aid in giving stiffness to the stems4 ,but large numbers of analyses have failed to show any direct correlation between the stiffness of straw of cereal plants and the percentage of silicon which they contain4 ,further1 plants will grow to full maturity and with erect stems when no silicon is present in the mineral nutrients which are furnished to them4 ,on the other hand1 certain experiments appear to indicate that silicon can perform some of the functions of phosphorus1 if soluble silicates are supplied to phosphorus-starved plants4 ,but under normal conditions of plant nutrition1 it seems to have no such function4 ,,inorganic ,,plant ,,toxins ,,and ,,stimulants ,much study has been given during recent years to the question of the supposed poisonous1 or toxic1 effects upon plants of various soil constituents4 ,there seems to be no doubt that certain organic compounds which are injurious to plant life are often present in the soil1 either as the normal excretions of plant roots or as products of the decomposition of preceding plant growths4 ,a consideration of these supposedly toxic organic substances would be out of place in this discussion of mineral soil nutrients4 ,but there seems to be no doubt that there may also be mineral substances in the soil which may sometimes exert deleterious influences upon plant growth4 ,in fact1 most metallic salts1 except those of the few metals which are required for plant nutrition1 appear to be toxic to plants4 ,the exact nature of the physiological effects which are produced by these mineral toxins is not clearly understood2 indeed1 it is probably different in the case of different metals4 ,further1 it is certain that both the stimulating and the toxic effect of metallic compounds upon low forms of plants is quite different from the effects of the same substances upon the more complex tissues of higher plants1 a fact which is utilized to advantage in the application of fungicides for the control of parasitic growths on common farm crops4 ,among the elements whose physiological effects upon higher plants1 such as the cereal crops1 etc41 when their soluble compounds are present in the soil1 have been carefully studied1 there are three fairly distinct types of injurious mineral elements4 ,the first of these1 represented by copper1 zinc1 and arsenic1 apparently exert their toxic effect regardless of the proportion in which they are present in the nutrient solution which is presented to the plant2 although the degree of injury varies with the amount of injurious substance present1 of course4 ,the second type1 of which boron and manganese are representatives1 apparently exerts a definite stimulating effect upon plants when supplied to them in concentrations below certain clearly defined limits2 but are toxic in concentrations above these4 ,the third includes many soluble salts of magnesium1 sodium1 potassium1 etc41 which while either innocuous or else definite sources of essential plant foods when in lower concentrations1 become highly toxic1 or corrosive1 when present in the soil solution in concentrations above the limits of toleration of individual plants for these soluble salts4 ,the tolerance shown by the different species of plants toward these soluble salts 7the so-called alkali in soils7 varies widely2 indeed1 there seems to be considerable variation in the resistance of different individual plants of the same species to injury from this cause4 ,with reference to the toxic effect of the third type of substances1 i4e41 the common soluble salts1 it is known that single salts of potassium1 magnesium1 sodium1 or calcium1 in certain concentrations1 are toxic to plants1 while mixtures of the same salts in the same concentrations are not4 ,thus1 solutions of sodium chloride1 magnesium sulfate1 potassium chloride1 and calcium chloride which1 when used singly1 killed plants whose roots were immersed in them for only a few minutes1 formed when mixed together a nutrient solution in which the same plants grew normally4 ,the remarkable remedial effect of calcium salts in overcoming the injurious effects of other soluble salts has already been mentioned4 ,one explanation of these relationships between mineral soil constituents and the living plant is that the life phenomena depend upon a balanced adjustment between the compounds of these different mineral elements with the proteins 7producing the so-called metal proteids7 which constitute the active material of the cell protoplasm4 ,according to this theory1 any excess or deficiency of any one or more of these elements in the plant juices which surround a given cell will1 of course1 cause an interchange with the mineral components of the supposed metal proteids which upsets the assumed essential balance between them1 with disastrous results4 ,a more recent1 and much more satisfactory1 explanation of the antagonism between mineral elements in their toxic effects upon plants1 which has both theoretical and experimental confirmation1 is that single salts disturb the colloidal condition 7see ,chapter ,,xv7 of the protoplasm of the plant cells in such a way as to destroy its permeability to nutrient substances1 while mixtures of salts restore the proper state of colloidal dispersion and permit the normal functioning of the protoplasm4 ,it is apparent from the above brief discussions that the rle of the different soil elements as plant food1 and their relations to the complex processes which constitute plant growth1 afford an interesting and promising field for further study4 ,references ,,brenchley1 ,,winifred ,e4--,inorganic ,plant ,poisons and ,stimulants1 #ajf pages1 #ah figs41 ,cambridge1 #aiad4 ,,hall1 ,a4 ,d4--,fertilizers and ,manures1 #chd pages1 #g plates1 ,london1 #aiji4 ,,hall1 ,a4 ,d4--,the ,book of the ,rothamsted ,experiments1 #bid pages1 #di figs41 #h plates1 ,london1 #aije4 ,,hopkins1 ,c4 ,g4--,soil ,fertility and ,permanent ,agriculture1 #fec pages1 ,chicago1 #aiaj4 ,,hilgard1 ,e4 ,w4--,soils1 #eic pages1 #hi figs41 ,new ,york1 #aijf4 ,,loew1 ,o4--,the ,physiological ,rle of ,mineral ,nutrients1 ,u4 ,s4 ,department of ,agriculture1 ,bureau of ,plant ,industry1 ,bulletin ,no4 #de1 #gj pages1 ,washington1 ,d4 ,c41 #aijc4 ,,russell1 ,e4 ,j4--,soil ,conditions and ,plant ,growth1 #bdc pages1 #ac figs41 ,monographs on ,biochemistry1 ,london1 #aiag4 7#c;d ed47 ,,whitney1 ,m4--,a ,study of ,crop ,yields and ,soil ,composition in ,relation to ,soil ,productivity1 ,u4 ,s4 ,department of ,agriculture1 ,bureau of ,soils1 ,bulletin ,no4 #eg1 #abg pages1 #bd figs41 ,washington1 ,d4 ,c41 #aiji4 ,,chapter ,,ii ,,the ,,organic ,,components ,,of ,,plants ,from the standpoint of their ability to synthetize synergic foods 7see page #b7 from inorganic raw materials1 plants may be divided into two types2 namely1 the autotrophic1 or self-nourishing1 plants1 and the heterotrophic plants4 ,strictly speaking1 only those plants whose every cell contains chlorophyll are entirely self-nourishing2 and some parts1 or organs1 of almost any autotrophic plant are dependent upon the active green cells of other parts of the plant for their synergic food4 ,furthermore1 if the term is used in a very wide sense1 green plants are more than self-nourishing1 they really nourish all living things4 ,but the general significance of the term autotrophic plants is apparent4 ,heterotrophic plants must1 of necessity1 get food1 either directly or indirectly1 from some other plant which can synthetize synergic foods or1 in a few cases1 from animal organic matter4 ,if they do this by feeding upon the organic compounds of other living organisms1 they are known as parasites2 while if they secure their organic food from the tissues or debris of dead organisms1 they are called saprophytes4 ,the heterotrophic plants are chiefly the bacteria and fungi2 although a few seed-plants are devoid of chlorophyll or have nutritive habits similar to those of the non-green plants1 and a few species are semi-parasitic or semi-saprophytic4 ,it is obvious that the metabolic processes of the autotrophic plants are very different from those of the heterotrophic type of plants4 ,these differences constitute a most interesting field of study for plant physiologists4 ,but the nature of the chemical compounds themselves and of the chemical changes involved in their transformations is not radically different in the two types of plants1 the essential difference being in the preponderance of one kind of activities1 or chemical reactions1 over another in bringing about the metabolic processes which are characteristic of each particular species4 ,hence1 it does not seem necessary1 or desirable1 in this study of the chemistry of plant growth1 to present as detailed a consideration of the differences in metabolic activity of the different types of plants as complete accuracy of statement in all cases might demand4 ,we will1 instead1 discuss the organic chemical components of plant tissues and the reactions which they undergo1 using the more common type of autotrophic plants as the illustrative material in most cases4 ,hence1 it will be understood that in all the following discussions of plant activities1 except where specific exceptions are definitely mentioned1 it is the green1 or autotrophic1 plants to which reference is made in each case4 ,from the standpoint of the sum total of its activities1 a green plant is essentially an absorber of solar energy and a synthetizer of organic substances4 ,each individual autotrophic plant takes up certain amounts of the anergic foods which are discussed in the preceding chapter and manufactures from them a great variety of complex organic compounds1 using the energy of the sun's rays1 absorbed by chlorophyll1 as the source for the energy necessary to accomplish these synthetic reactions4 ,the ultimate object of these processes is to produce seeds1 each containing an embryo and a sufficient supply of food for the young plant of the next generation to use until it has developed its own synthetic organs2 or 7in the case of perennials7 to store up reserve food materials with which to start off new growth after a period of rest and often of defoliation4 ,to be sure1 animals and men often interfere with the completion of the life cycle of the plant1 and utilize the seeds or stored food material for their own nutrition1 but this is a biological relation which has no influence upon the nature of the plant's own activities4 ,since all of these synthetic reactions must go on at ordinary temperatures1 active catalyzers are necessary4 ,these the plant provides in the form of enzymes 7see ,chapter ,,xiv7 which are always present in active plant protoplasm4 ,proper conditions for rapid chemical action are further assured by the colloidal nature 7see ,chapter ,,xv7 of the protoplasm itself4 ,,types ,,of ,,chemical ,,changes ,,involved ,,in ,,plant ,,growth ,the whole cycle of chemical changes which is involved in plant growth represents the net result of two opposite processes2 the first of these is a constructive one which has at least three different phases3 namely1 a synthesis of complex organic compounds1 the translocation of this synthetized material to the centers of growth1 and the building up of this food material into tissues or reserve supplies2 and the second is a destructive process of respiration whereby carbohydrate material is broken down1 potential energy is released1 and carbon dioxide is excreted4 ,the synthetic processes which take place in plants are of two types2 namely1 photosynthesis1 in which sugars are produced1 and another1 which has no specific name1 whereby proteins are elaborated4 ,the translocation of the synthetized material involves the change of insoluble compounds into soluble ones1 effected by the aid of enzymes4 ,for storage purposes1 the soluble forms are usually1 though not always1 condensed again into more complex forms1 these latter changes requiring much less energy than do the original syntheses from raw materials4 ,the destructive process1 respiration1 is characteristic of all living matter1 either plant or animal organisms4 ,it takes place continuously throughout the whole life of a plant4 ,during rapid growth it is overshadowed by the results of the synthetic process1 but during the ripening period in which the seed is matured1 and during the germination of the seed itself1 growth is practically at a standstill and the respiratory1 destructive action predominates1 so that the plant actually loses weight4 ,,groups ,,of ,,organic ,,compounds ,,found ,,in ,,plants ,as a result of their various synthetic and metabolic activities1 a great variety of organic compounds is produced by plants4 ,certain types of these compounds1 such as the carbohydrates and proteins1 are necessary to all plants and are elaborated by all species of autotrophic plants4 ,other types of compounds are produced by many1 but not all1 species of plants2 while still others are found in only a few species4 ,it is fairly easy to classify all of these compounds into a few1 well-defined groups1 based upon similarity of chemical composition4 ,these groups are known1 respectively1 as the carbohydrates and their derivatives1 the glucosides and tannins2 the fats and waxes2 the essential oils and resins2 organic acids and their salts2 the proteins2 the vegetable bases and alkaloids2 and the pigments4 ,a consideration of these groups of compounds1 as they are synthetized by plants1 constitutes the major portion of the study of the chemistry of plant life as presented in this book4 ,following the discussion of the compounds themselves1 the chapters dealing with enzymes1 with the colloidal nature of protoplasm1 and with the supposed accessory stimulating agencies1 aim to show how the manufacturing machine known as the plant cell accomplishes its remarkable results1 so far as the process is now understood4 ,,physiological ,,uses ,,and ,,biological ,,significance ,in connection with the discussion of each of the above-mentioned groups of organic components of plants1 an attempt will be made to point out what significance these particular compounds have in the plant's life and growth4 ,certain terms will be used to designate different rles1 which it is probably necessary to define4 ,there may be two possible explanations of1 or reasons for1 the presence of any given type of compound in the tissues of any particular species of plant4 ,first1 it may be supposed that this particular type of compounds is elaborated by the plant to satisfy its own physiological needs1 or for the purpose of storing it up in the seeds as synergic food for the growth of the embryo1 in order to reproduce the species4 ,for this rle of the various organic food materials1 etc41 we will employ the term physiological use4 ,on the other hand1 it is often conceivable that certain types of compounds1 which have properties that make them markedly attractive 7or repellent7 as a food for animals and men1 or which are strongly antiseptic in character1 or which have some other definite relationship to other living organisms1 have had much to do with the survival of the particular species which elaborates them1 in the competitive struggle for existence2 or have been developed in the plant by the evolutionary process of natural selection4 ,for this relation of the compound to the plant's vital needs1 we will use the term biological significance4 ,such a segregation of the rles which the different compounds play in the plant's economy may be more or less arbitrary in many cases2 but it will be clear that when physiological uses are discussed1 reference is being made to the plant's own internal needs2 while the phrase biological significance will be understood to refer to the relation of the plant to other living organisms4 ,,physiological ,,uses ,,of ,,the ,,organic ,,component ,,groups ,from the standpoint of the rle which each plays in the plant economy1 the several groups of organic compounds may be roughly divided into three classes4 ,these are3 7a7 the framework materials1 including gums1 pectins1 and celluloses2 7b7 synergic foods1 including carbohydrates1 fats1 and proteins2 and 7c7 the secretions1 including the glucosides1 volatile oils1 alkaloids1 pigments1 and enzymes4 ,the framework material1 as the name indicates1 constitutes the cell-wall and other skeleton substances of the plant4 ,it is made up of carbohydrate complexes1 produced by the cell protoplasm from the simpler carbohydrates4 ,the synergic foods1 or reserve foods as they are sometimes called1 produced by the excess of synthetized material over that needed for the immediate use of the plant1 are accumulated either in the various storage organs1 to be available for future use by the plant itself or by its vegetative offspring1 or in the seed1 to be available to the young seedling of the next generation4 ,proteins not only serve as reserve food materials but also make up the body of the living organism itself4 ,carbohydrates and fats serve as synergic and reserve foods4 ,the secretions may be produced either in ordinary cells and found in their vacuoles1 or in special secretory cells and stored in cavities in the secreting glands 7as in the leaves of mints1 skin of oranges1 etc471 or in special ducts 7as in pines1 milkweeds1 etc47 or on the epidermis 7as the bloom of plums1 cabbages1 etc41 the resinous coating of many leaves1 etc474 ,as a general rule1 the glucosides1 pigments1 and enzymes are the products of unspecialized cells and have some definite connection with the metabolic processes of the plant2 while the volatile oils and the alkaloids are usually secreted by special cells and have no known rle in metabolism4 ,,chapter ,,iii ,,photosynthesis ,photosynthesis is the process whereby chlorophyll-containing plants1 in the presence of sunlight1 synthetize organic compounds from water and carbon dioxide4 ,the end-product of photosynthesis is always a carbohydrate4 ,chemical compounds belonging to other groups1 mentioned in the preceding chapter1 are synthetized by plants from the carbohydrates and simple raw materials2 but in such cases the energy used is not solar energy and the process is not photosynthesis4 ,under the ordinary conditions of temperature1 moisture supply1 etc41 necessary to plant growth1 photosynthesis will take place if the three essential factors1 chlorophyll1 light1 and carbon dioxide are available4 ,,physiological ,,steps ,,in ,,photosynthesis ,there are five successive and mutually dependent steps in the process of photosynthesis1 as follows3 7#a7 ,there must be a gas exchange between the plant tissue and the surrounding air1 by means of which the carbon dioxide of the air may reach the protoplasm of the chlorophyll-containing cells4 7#b7 ,radiant energy must be absorbed1 normally that of sunlight1 although photosynthesis can be brought about by the energy from certain forms of artificial light4 7#c7 ,carbon dioxide and water must be decomposed by the energy thus absorbed1 and the nascent gases thus produced combined into some synthetic organic compound1 with a resultant storage of potential energy4 7#d7 ,this first organic synthate must be condensed into some carbohydrate suitable for translocation and storage as reserve food4 7#e7 ,the oxygen1 which is a by-product from the decomposition of the water and carbon dioxide and the resultant synthetic process1 must be returned to the air by a gas exchange4 ,of the five steps in this process1 the first two and the last are essentially purely physical phenomena1 the chemical changes involved being those of the third and fourth steps4 ,hence1 it is only these two parts of the process which need be taken into account in a consideration of the chemistry of photosynthesis4 ,,formaldehyde1 ,,the ,,simplest ,,carbohydrate ,,structure ,the simplest carbohydrates known to occur commonly in plant tissues are the hexoses 7see ,chapter ,,iv7 having the formula ,c#f;,h#ab,o#f1 which is just six times that of formaldehyde1 ,,ch#b,o4 ,also1 it is known that formaldehyde easily1 and even spontaneously1 polymerizes into more complex forms having the general formula 7,,ch#b,o7n2 trioxymethylene1 ,c#c;,h#f,o#c1 being a well-known example4 ,further1 both trioxymethylene and formaldehyde itself can easily be condensed into hexoses1 by simple treatment with lime water as a catalytic agent4 ,hence1 it is commonly believed that formaldehyde is the first synthetic product resulting from photosynthesis1 that this is immediately condensed into hexose sugars1 and that these in turn are united into the more complex carbohydrate groups which are commonly found in plants 7see ,chapter ,,iv74 ,there is considerable experimental confirmation of the soundness of this view4 ,the whole photosynthetic process takes place in chlorophyll-containing plant tissues with astonishing rapidity1 sugars1 and even starch1 appearing in the tissues almost immediately after their exposure to light in the presence of carbon dioxide4 ,hence1 any intermediate product1 such as formaldehyde1 is present in the cell for only very brief periods and in very small amounts4 ,but small amounts of formaldehyde can often be detected in fresh green plant tissues and1 as will be pointed out below1 the whole process of photosynthesis1 proceeding through formaldehyde as an intermediate product1 can be successfully duplicated in vitro in the laboratory4 ,assuming1 then1 that formaldehyde is the first photosynthetic product in the process of the production of carbohydrates from water and carbon dioxide1 the simple empirical equation for this transformation would be ,h#b,o ,,co#b ,,ch#b,o ,o#b4 ,it is apparent1 however1 that the process is not so simple as this hypothetical reaction would indicate1 as water and carbon dioxide can hardly be conceived to react together in any such simple way as this4 ,various theories as to the exact nature of the steps through which the chemical combinations proceed have been advanced4 ,a discussion of the experimental evidence upon which these are based and of the conclusions which seem to be justified from these experimental studies is presented below4 ,the only value which may be attached to the empirical equation just presented is that it does accurately represent the facts that a volume of oxygen1 equal to that of the carbon dioxide consumed in the process1 is liberated and that formaldehyde is the synthetical product of the reactions involved4 ,it should be noted1 in this connection1 that formaldehyde is a powerful plant poison and that few1 if any1 plant tissues can withstand the toxic effect of this substance when it is present in any considerable concentration4 ,hence1 it is necessary to this whole conception of the relation of formaldehyde to the photosynthetic process1 to assume that1 however rapidly the formaldehyde may be produced in the cell1 it is immediately converted into harmless carbohydrate forms4 ,,the ,,condensation ,,of ,,formaldehyde ,,into ,,sugars ,as has been mentioned1 it is easily possible to cause either formaldehyde1 or trioxymethylene1 to condense into ,c#f;,h#ab,o#f1 using milk of lime as a catalyst4 ,of course1 no such condition as this prevails in the plant cell1 and the mechanics of the protoplasmic process may be altogether different from those of the artificial syntheses4 ,furthermore1 the hexose produced by the artificial condensation of these simpler compounds is1 in every case1 a non-optically active compound1 while all natural sugars are optically active 7see ,chapter ,,iv74 ,emil ,fischer has succeeded1 however1 by a long and round-about process which need not be discussed in detail here1 in converting the artificial hexose into glucose and fructose1 the optically-active sugars which occur naturally in plant tissues4 ,the condensation of formaldehyde directly into glucose and fructose in the plant cell is brought about by some process the nature of which is not yet understood4 ,probably synthetic enzymes 7see ,chapter ,,xiv71 whose nature and action have not yet been discovered1 come into play4 ,it is a noteworthy fact1 however1 that the mechanics of this apparently simple chemical change1 upon which the whole nutrition of the plant depends1 and which furnishes the whole animal kingdom1 including the human race1 with so large a proportion of its food supplies1 is as yet wholly unknown4 ,it is the common practice to represent the whole results of the photosynthetic action by the empirical equation #f;,h#b,o #f;,,co#b ,c#f;,h#ab,o#f #f,o#b2 but here again the only value to be attached to such an algebraic expression is that it accurately represents the gaseous exchange of carbon dioxide and oxygen involved in the process4 ,certainly1 it throws no light upon the nature of the process itself4 ,,theories ,,concerning ,,photosynthesis ,the many theories which have been advanced concerning the nature of the chemical changes which are involved in photosynthesis have served as the basis for much experimental study of the problem4 ,the following brief summary will serve to point out the general trend of these investigations and the present state of knowledge concerning the chemistry of photosynthesis4 ,von ,baeyer1 in #ahgj1 advanced the hypothesis that the first step in the process is the breaking down of carbon dioxide into carbon monoxide and oxygen and of water into hydrogen and oxygen2 that the carbon monoxide and hydrogen then unite to produce formaldehyde1 which is immediately polymerized to form a hexose4 ,these theoretical changes may be represented by the following equations3 ,,co#b ,,co ,o #a4 ,h#b,o ,h#b ,o #b4 ,h#b ,,co ,,ch#b,o #c4 #f7;,,ch#b,o7 ,c#f;,h#ab,o#f ,in the investigations and discussions of this hypothesis1 it has been ascertained3 first1 that carbon monoxide has never been found in the free form in plant tissues2 second1 that when ,tropaeolum plants were surrounded with an atmosphere in which there was no carbon dioxide1 but which contained sufficient carbon monoxide to give a concentration of this gas in the cell-sap equivalent to that in which ,,co#b is normally present1 the plants grew normally and apparently elaborated starch2 third1 other and more extensive experiments indicated1 however1 that green plants in general cannot make use of carbon monoxide gas for photosynthesis1 although this does not prove that von ,baeyer's idea that ,,co is a step in the process is necessarily erroneous2 and finally it was shown that carbon monoxide1 in sufficient concentration to produce the results with ,tropaeolum mentioned above1 usually acts as a powerful ansthetic towards most other plants4 ,while these considerations do not positively prove that von ,baeyer's hypothesis is incorrect1 they render it so improbable that it has generally been abandoned in favor of others which are described below4 ,erlenmeyer1 even before the experimental work mentioned in the preceding paragraph had been reported1 suggested that instead of assuming a separate breaking down of the carbon dioxide and water1 it is easier to conceive that they are united in the cell-sap into carbonic acid and that this is reduced by the chlorophyll-containing protoplasm into formic acid and then to formaldehyde1 as indicated by the following equations3 #a4 ,h#b;,,co#c ,h#b;,,co#b ,o #b4 ,h#b;,,co#b ,,ch#b,o ,o ,like von ,baeyer's hypothesis1 this assumes that formaldehyde and oxygen are the first products of photosynthesis4 ,proceeding upon this assumption1 many investigators have studied the question as to whether formaldehyde actually is present in green leaves4 ,several workers have reported successful identification of formaldehyde in the distillate from green leaves2 while others have criticized these results and have maintained that formaldehyde can likewise be obtained by distilling decoctions of dry hay1 etc41 in which the photosynthetic process could not possibly be conceived to be at work4 ,other investigators1 notably ,bach and ,palacci1 reported that they had succeeded in artificially producing formaldehyde from water and carbon dioxide1 in the presence of a suitable catalyzer or sensitizer4 ,euler1 however1 later showed conclusively that under the conditions described by these investigators1 formaldehyde can be obtained even if no carbon dioxide is present1 being apparently produced by the action of water upon the organic sensitizer which was used4 ,these conflicting reports led ,usher and ,priestley1 in a series of studies reported between #aijf and #aiaa1 to submit the whole matter to a critical review4 ,briefly1 these investigators showed that the photolysis of carbon dioxide and water results in the formation of formaldehyde and hydrogen peroxide1 as represented by the equation ,,co#b #c;,h#b,o ,,ch#b,o #b;,h#b,o#b4 ,the formaldehyde is then condensed by the protoplasm into sugars1 while the hydrogen peroxide is decomposed1 by an enzyme in the plant cell1 into water and oxygen4 ,if the formaldehyde is not used up rapidly enough by the protoplasm1 it kills the enzyme and the undecomposed hydrogen peroxide destroys the chlorophyll1 which stops the whole photosynthetic process4 ,usher and ,priestley were able to cause the photolysis of carbon dioxide and water into formaldehyde outside of a green plant1 in the presence of a suitable catalyzing agent which continually destroys the hydrogen peroxide as fast as it is formed2 to show the actual bleaching effect of an excess of hydrogen peroxide in plant tissues which had been treated in such a way as to prevent the enzyme from decomposing it2 and1 finally1 to demonstrate the condensation of formaldehyde into starch by the action of protoplasm which contained no chlorophyll4 ,in the meantime1 ,fenton1 in #aijg1 found that in the presence of magnesium as a catalyst 7it will be shown in ,chapter ,,viii that magnesium is a constituent of the chlorophyll molecule7 formaldehyde may be obtained from a solution of carbon dioxide in water1 especially if weak bases are present4 ,further1 ,usher and ,priestley's later results showed that radium emanations1 acting upon a solution of carbon dioxide in water1 produce hydrogen peroxide and formaldehyde1 and the latter polymerizes but not up to the point represented by the hexose sugars2 also1 that the ultra-violet rays from a mercury vapor lamp are very effective in bringing about the production of hydrogen peroxide and formaldehyde from a saturated aqueous solution of carbon dioxide1 the reaction taking place even in the absence of any sensitizer1 but much more readily if some optical or chemical sensitizer is present4 ,finally1 these investigators were able to duplicate all their results1 using green plant tissues1 and to show that the temperature changes which take place in a film of chlorophyll when it is exposed to an atmosphere of moist carbon dioxide in the sunlight are such as would be required by the formation of formaldehyde and hydrogen peroxide from carbonic acid4 ,more recently1 ,ewart has showed that formaldehyde can combine chemically with chlorophyll2 from which fact1 ,schryver deduces the theory that if for any reason the condensation of formaldehyde into carbohydrates by the cell protoplasm does not proceed as rapidly as the formaldehyde is produced by photosynthesis1 the excess of the latter enters into combination with the chlorophyll1 and that if condensation into sugar uses up all the free formaldehyde which is present in the active protoplasm1 the compound of formaldehyde with chlorophyll is broken down setting free an additional supply for further sugar manufacture4 ,according to this conception there are1 in the chlorophyll-bearing protoplasm1 not only the agencies for the production of formaldehyde from carbon dioxide and water and for the condensation of this into carbohydrates1 but also a chemical mechanism by means of which the amount of free formaldehyde in the reacting mass may be regulated so that at no time will it reach the concentration which would be injurious to the cell protoplasm or fall below the proper proportions for sugar-formation4 ,this explanation affords a satisfactory solution of the difficulty which formerly confronted the students of photosynthesis1 namely1 the fact that free formaldehyde is powerfully toxic to cell protoplasm4 ,without some such conception1 it was difficult to imagine how the presence of formaldehyde in the cell contents1 even as a transitory intermediate product1 could be otherwise than injurious4 ,as a result of these studies1 the nature of the chemical changes which result in the production of formaldehyde as the first product of photosynthesis1 with the liberation of a volume of oxygen equal to that of the carbon dioxide consumed1 seems to be fairly well established4 ,,the ,,production ,,of ,,sugars ,,and ,,starches ,the next step in the process1 the conversion of formaldehyde into sugars and starches1 is not necessarily a photosynthetic one1 as it can be brought about by protoplasm which contains no chlorophyll or other energy-absorbing pigment4 ,it is1 however1 a characteristic synthetic activity of living protoplasm4 ,there is little definite knowledge as to how the cell protoplasm accomplishes this important task4 ,as has been pointed out1 the polymerization of formaldehyde into a sugar-like hexose1 known as acrose1 can be easily accomplished by ordinary laboratory reactions1 and acrose can be converted into glucose or fructose by a long and difficult series of transformations4 ,but such processes as are employed in the laboratory to accomplish these artificial synthesis of optically-active sugars from formaldehyde can have no relation whatever to the methods of condensation which are used by cell protoplasm in its easy1 almost instantaneous1 and nearly continuous accomplishment of this transformation4 ,furthermore1 these simple hexoses are by no means the final products of cell synthesis1 even of carbohydrates alone4 ,in many plants1 starch appears as the final1 if not the first1 product of formaldehyde condensation4 ,at least1 the transformation of the simple sugars1 which may be supposed to be the first products1 into starch is effected so nearly instantaneously that it is impossible to detect measurable quantities of these sugars in the photosynthetically active cells of such plants4 ,other species of plants always show considerable quantities of simple sugars in the vegetative tissues1 and some even store up their reserve carbohydrate food material in the form of glucose or sucrose4 ,attempts have been made to associate the type of carbohydrate formed in cell synthesis with the botanical families to which the plants belong1 but with no very great success4 ,for each individual species1 however1 the form of carbohydrate produced is always the same1 at least under normal conditions of growth4 ,for example1 the sugar beet always stores up sucrose in its roots1 although under abnormal conditions considerable quantities of raffinose are developed4 ,similarly1 potatoes always store up starch1 but with abnormally low temperatures considerable quantities of this may be converted into sugar1 which becomes starch again with the return to normal conditions4 ,while it is impossible1 with our present knowledge1 to even guess at the mechanism by which protoplasm condenses formaldehyde into sugars and these1 in turn1 into more complex carbohydrates1 the structure and relationships to each other of the final products of photosynthesis are well known1 and are discussed at length in the following chapter4 ,references ,,barnes1 ,c4 ,r4--,physiology 7,part ,,ii of ,coulter1 ,barnes and ,cowles' ,textbook of ,botany71 #ahg pages1 #ah figs41 ,chicago1 #aiaj4 ,,ganong1 ,w4 ,f4--,plant ,physiology1 #bfe pages1 #fe figs41 ,new ,york1 #aijh 7#b;d ed474 ,,jost1 ,l41 trans4 by ,,gibson1 ,r4 ,j4 ,h4--,plant ,physiology1 #efd pages1 #agb figs41 ,oxford1 #aijg4 ,,marchlewski1 ,l4--,die ,chemie des ,chlorophylls1 #ahg pages1 #e figs41 #g plates1 ,berlin1 #aiji4 ,,parkin1 ,,john4--,the ,carbohydrates of the ,foliage ,leaf of the ,snowdrop 7,galanthus nivalis ,l47 and their ,bearing on the ,first ,sugar of ,photosynthesis1 in ,biochemical ,journal1 ,vol4 #f1 pages #a to #dg1 #aiab4 ,,pfeffer1 ,w41 trans4 by ,,ewart1 ,a4 ,j4--,physiology of ,plants4 ,vol4 ,i1 #fcb pages1 #gj figs41 ,oxford1 #aijj4 ,,chapter ,,iv ,,carbohydrates ,these substances comprise an exceedingly important group of compounds1 the members of which constitute the major proportion of the dry matter of plants4 ,the name carbohydrate indicates the fact that these compounds contain only carbon1 hydrogen1 and oxygen1 the last two elements usually being present in the same proportions as in water4 ,as a rule1 natural carbohydrates contain six1 or some multiple of six1 carbon atoms and the same number of oxygen atoms less one for each additional group of six carbons above the first one2 e4g41 ,c#f;,h#ab,o#f1 ,c#ab;,h#bb,o#aa1 ,c#ah;,h#cb,o#af1 etc4 ,carbohydrates are classed as open-chain compounds1 that is1 they may be regarded as derivatives of the aliphatic hydrocarbons4 ,from the standpoint of the characteristic groups which they contain1 they are aldehyde-alcohols4 ,in common with many other polyatomic open-chain alcohols1 they generally possess a characteristic sweet1 or mildly sweetish1 taste4 ,in the case of the more complex and less soluble forms1 this sweetish taste is scarcely noticeable and these compounds are commonly called the starches1 as contrasted with the more soluble and sweeter forms1 known as sugars4 ,the characteristic ending ose is added to the names of the members of this group4 ,as systematic names1 the ,latin numeral indicating the number of carbon atoms in the molecule is combined with this ending2 e4g41 ,c#e;,h#aj,o#e1 pentose1 ,c#f;,h#ab,o#f1 hexose1 etc4 ,in recent years1 as a matter of scientific interest1 many sugarlike substances which contain from two to nine carbon atoms combined with the proper number of hydrogen and oxygen atoms to be equivalent to the same number of molecules of water in each case1 have been artificially prepared in the laboratory and designated as dioses1 trioses1 tetroses1 pentoses1 hexoses1 heptoses1 octoses1 and nonoses1 respectively4 ,substances corresponding in composition and properties with the artificial tetroses and one or two derivatives of heptoses are occasionally found in plant tissues1 and a considerable number of pentoses and their condensation products are common constituents of plant gums1 etc42 but the great majority of the natural carbohydrates are hexoses and their derivatives4 ,,groups ,,of ,,carbohydrates ,since the simpler carbohydrates are sugars1 i4e41 they possess the characteristic sweet taste1 the name saccharide is used as a basis for the classification of the entire group4 ,the simplest natural sugars1 the hexoses1 ,c#f;,h#ab,o#f1 are known as mono-saccharides4 ,the group of next greater complexity1 those which have the formula ,c#ab;,h#bb,o#aa and may be regarded as derived from the combination of two molecules of a hexose with the dropping out of one molecule of water at the point of union1 are known as di-saccharides4 ,compounds having the formula ,c#ah;,h#cb,o#af 7i4e41 three molecules of ,c#f;,h#ab,o#f minus two molecules of ,h#b,o7 are tri-saccharides2 and the still more complex groups1 having the general formula 7,c#f;,h#aj,o#e7n1 are called the poly-saccharides4 ,the mono-1 di-1 and tri-saccharides are generally easily soluble in water1 have a more or less pronouncedly sweet taste1 and are known as the sugars2 while the polysaccharides are generally insoluble in water and of a neutral taste1 and are called starches4 ,as will be seen later1 there are many natural plant carbohydrates belonging to each of these groups4 ,in addition to these saccharide groups1 there are other types1 or groups1 of compounds which resemble the true carbohydrates in their chemical composition and properties and are often considered as a part of this general group4 ,these are the pentoses1 ,c#e;,h#aj,o#e1 and their condensation products1 the pentosans 7,c#e;,h#h,o#d7n1 and their methyl derivatives1 ,c#f;,h#ab,o#e2 certain polyhydric alcohols having the formula ,c#f;,h#h7,,oh7#f2 pectose and its derivatives1 pectin and pectic acid2 and lignose substances of complex composition4 ,it is doubtful whether these compounds are actual products of photosynthesis in plants1 or have the same physiological uses as the carbohydrates and it has seemed wise to consider them in a separate and later chapter4 ,,isomeric ,,forms ,,of ,,monosaccharides ,four sugars having the formula ,c#f;,h#ab,o#f1 namely1 glucose1 fructose1 mannose1 and galactose1 occur very commonly and widely distributed in plants4 ,in addition to these1 thirteen others having the same percentage composition have been artificially prepared1 while seven additional forms are theoretically possible4 ,in other words1 twenty-four different compounds1 all having the same empirical formula and similar sugar-like properties are theoretically possible4 ,in order to arrive at a conception of this multiplicity of isomeric forms1 it is necessary to understand the two types of isomerism which are involved4 ,one of these is structural isomerism1 and the other is space- or stereo-isomerism4 ,structural ,isomerism4--,this refers to an actual difference in the characteristic groups which are present in the molecule4 ,as has been said1 all carbohydrates1 from the standpoint of the characteristic groups which they contain1 are aldehyde-alcohols4 ,the hexoses all contain five alcoholic groups and one primary aldehyde1 or one secondary aldehyde 7ketone71 group4 ,if the aldehyde oxygen is attached to the carbon atom which is at the end of the six-membered chain1 the structural arrangement is that of an aldehyde1 ,c,o and the sugar is of the type known ,h as aldoses2 whereas1 if the oxygen is attached to any other carbon in the chain1 the ketone arrangement1 ,c,o results and the sugar is a ketose4 ,this difference is illustrated in the ,fischer open-chain formulas for glucose 7an aldose7 and fructose 7a ketose7 as follows3 ,glucose ,fructose ,,ch#b,,oh ,,ch#b,,oh ,,choh ,,choh ,,choh ,,choh ,,choh ,,choh ,,choh ,c,o ,,cho ,,ch#b,,oh ,stereo-isomerism1 or space isomerism1 as its name indicates1 depends upon the different arrangement of the atoms or groups in the molecule in space1 and not upon any difference in the character of the constituent groups4 ,this possibility depends upon the existence in the molecule of the substance in question of one or more asymmetric carbon atoms and manifests itself in differences in the optical activity of the compound4#a ,thus1 in the formula for glucose shown above there appear four asymmetric carbon atoms1 namely1 those of the four secondary alcohol groups 7in the terminal1 or primary alcohol1 group1 carbon is united to hydrogen by two bonds1 and in the aldehyde group it is united to oxygen by two bonds74 ,similarly1 fructose contains three asymmetric carbon atoms4 ,as an example of how the presence of these asymmetric carbon atoms results in the possibility of many different space relationships1 the following graphic illustrations of the supposed differences between dextro-glucose and levo-glucose1 and between dextro- and levo-galactose1 may be cited4#b d-glucose l-glucose d-galactose l-galactose ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c--,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,,cho ,,cho ,,cho ,,cho ,comparisons of the above formulas will show that the difference between the formulas for d- and l-glucose lies in the arrangement of the ,h atoms and the ,,oh groups around the two asymmetric carbon atoms next the aldehyde end of the chain2 while the d- and l-galactoses differ in that this arrangement is in the reverse order around all four of the asymmetric carbons4 ,by similar variations in the grouping around the four asymmetric atoms1 it is possible to produce the sixteen different space arrangements shown on page #cg for the groups of an aldohexose4 ,sugars corresponding to fourteen of these different forms have been discovered1 three of which are of common occurrence in plants1 either as single mono-saccharides or as constituent groups in the more complex carbohydrates2 the remaining two forms have only theoretical interest4 ,similarly1 for a ketohexose1 which contains three asymmetric carbon atoms1 there are eight possible arrangements4 ,three sugars of this type are known1 only one 7fructose7 being common in plants2 the others are of only theoretical interest4 ,,footnotes3 #a ,it is assumed that the reader1 or student1 is familiar with the theoretical and experimental evidence in support of the existence of the so-called asymmetric carbon atom and its relation to the effect of the compound which contains it1 when in solution1 in rotating the plane of polarized light4 ,for purposes of review1 or of study of this most interesting and important phenomenon1 the reader is referred to any standard text-book on ,organic ,chemistry4 #b ,attention should be called1 at this point1 to the fact that such formulas as these cannot possibly accurately represent the actual arrangement of the constituent groups of a carbohydrate molecule around an asymmetric carbon atom4 ,the limitations of a plane-surface formula prevent any illustration of the three-dimension relationships in space4 ,furthermore1 there are certain facts in connection with the birotation phenomenon and the relation of the molecular configuration to biochemical properties 7which see7 that cannot be explained on the basis of the open-chain arrangement represented by the ,fischer formulas used here4 ,a closed-ring arrangement1 showing the aldehyde oxygen as linked by its two bonds to the first and the fourth carbon atoms of the chain1 thus forming a closed-ring of four carbon and one oxygen atoms1 instead of being attached by both bonds to a single carbon atom1 as in the above formulas1 is undoubtedly a more nearly accurate representation of the actual linkage in the molecule than are the open-chain formulas used above4 ,the differences in conception embodied by these two types of formulas may be shown by the following formulas for glucose3 ,,ch#b,,oh ,,ch#b,,oh ,,choh ,,choh ,,choh ,,ch-,,choh ------,o------- ,,choh ,o or ,,ch#b,,oh,,choh,,ch,,choh,,choh,,choh ,,choh ,,ch-,,choh ,,cho ,,oh ,fischer's ,closed-ring formulas formula ,it will be observed that in the closed-ring formula there are five asymmetric carbon atoms1 and the asymmetry of the terminal one forms the basis for the explanation of the existence of the so-called alpha and beta modification of d-glucose 7see page #df74 ,however1 the ordinary aldehyde reactions of the sugars are more clearly indicated by the open-chain formula4 ,some investigators are inclined to be that sugars actually exist in the open-chain arrangement when in aqueous solution1 and in the closed-ring arrangement when in alcoholic solution4 ,the closed-ring formulas will be used in this text in the discussions of the birotation phenomena and of biochemical properties1 but for the explanations of the stereo-isomeric forms and similar phenomena1 the open-chain formulas are just as useful in conveying an idea of the possibilities of different space relationships1 and are so much simpler in appearance and in mechanical preparation1 that it seems desirable to use these rather than the more accurate closed-ring formulas4 ,,chemical ,,constitution ,,of ,,monosaccharides ,the term monosaccharides1 as commonly used1 refers to hexoses4 ,it applies equally well1 however1 to any other sugar-like substance which either occurs naturally or results from the decomposition of more complex carbohydrates1 and which cannot be further broken down without destroying its characteristic aldehyde-alcohol groups and sugar-like properties4 ,all such monosaccharides1 being alcohol-aldehydes1 can easily be reduced to the corresponding polyatomic alcohols1 containing the same number of carbon atoms as the original monosaccharides1 each with one ,,oh group attached to it4 ,all aldose monosaccharides are converted1 by gentle oxidation1 into the corresponding monobasic acid1 having a ,,cooh group in the place of the original ,,cho group4 ,further oxidation either changes the alcoholic groups into ,,cooh groups1 producing polybasic acids1 or breaks up the chain4 ,when ketose monosaccharides are submitted to similar oxidation processes1 they are broken down into shorter chain compounds4 ,the various monosaccharides which have thus far been found as constituents of plant tissues1 or as parts of other more complex compounds which occur in plants1 are shown in the following table3 ,trioses 7,c#c;,h#f,o#c7 ,tetroses 7,c#d;,h#h,o#d7 ,aldose--,glyceric aldehyde1 ,aldoses--d- and l-,erythrose1 or glycerose l-,threose ,ketose--,dioxyacetone ,pentoses 7,c#e;,h#aj,o#e7 ,methyl ,pentoses 7,c#f;,h#ab,o#e7 ,aldoses--d- and l-,arabinose ,aldoses--,rhamnose d- and l-,xylose ,fucose l-,ribose ,rhodeose l-,lyxose ,chinovose ,hexoses 7,c#f;,h#ab,o#f7 ,mannitol series ,dulcitol series ,aldoses--d- and l-,glucose d- and l-,galactose d- and l-,mannose d- and l-,talose d- and l-,gulose d- and l-,idose d-,altrose d-,allose ,ketoses-- d-,fructose d-,tagatose d-,sorbose ,heptoses ,octoses ,nonoses 7,c#g;,h#ad,o#g7 7,c#h;,h#af,o#h7 7,c#i;,h#ah,o#i7 ,glucoheptose ,gluco-octose ,glucononose ,mannoheptose ,manno-octose ,mannononose ,galactoheptose ,galacto-octose ,persuelose ,sedoheptose ,the hexoses are by far the most important group of monosaccharides4 ,they are undoubtedly the first products of photosynthesis1 and all the other carbohydrates may be considered to be derived from them by condensation4 ,because of their biochemical significance and their immense importance as the fundamental substances for all plant and animal energy-producing materials1 the following detailed studies of their chemical composition and molecular configuration are fully warranted4 ,that all the hexoses contain five alcoholic groups is proved by the experimental evidence that each one forms a penta-ester1 by uniting with five acid radicals1 when treated with mineral or organic acids under proper conditions4 ,thus1 glucose penta-acetate1 penta-nitrate1 penta-benzoate1 etc41 have all been prepared4 ,the presence of the aldehyde group is proved by the fact that all aldohexoses have been converted1 by gentle oxidation1 into pentaoxy-monobasic acids1 and the ketohexoses broken down into shorter chain compounds by similar gentle oxidations2 these reactions being characteristic of compounds containing an aldehyde and a ketone group respectively4 ,this experimental evidence establishes the nature of the characteristic groups in the molecule1 in each case4 ,the molecular configurations illustrated in the following table are those suggested by ,emil ,fischer1 as a result of his exhaustive studies of the chemical constitution of the various carbohydrates4 ,there is1 of course1 no thought that the printed formulas here presented accurately represent the actual relationships in space of the different groups2 but there is fairly conclusive evidence that the variations in special groupings in the different sugars are properly referable to the particular asymmetric carbon atoms as indicated in the several formulas as presented4 #a4 ,aldohexoses of the mannitol series3 d-,glucose l-,glucose d-,mannose l-,mannose ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,,cho ,,cho ,,cho ,,cho d-,gulose l-,gulose d-,idose l-,idose ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,,cho ,,cho ,,cho ,,cho d-,altrose l-,altrose d-,allose l-,allose 7unknown7 7unknown7 ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,,cho ,,cho ,,cho ,,cho #b4 ,aldohexoses of the dulcitol series3 d-,galactose l-,galactose d-,talose l-,talose ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,,cho ,,cho ,,cho ,,cho #c4 ,ketohexoses3 d-,fructose d-,sorbose d-,tagatose ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,h-,c-,,oh ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,c,o ,c,o ,c,o ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,reference will be made in subsequent paragraphs to the probable chemical constitution of the monosaccharides other than hexoses2 but the above discussion of the structure of the hexoses will serve as a sufficient introduction to the study of the composition of the common carbohydrates4 ,,characteristic ,,reactions ,,of ,,hexoses ,specific ,rotatory ,power4--,all soluble carbohydrates1 since they contain asymmetric carbon atoms1 with the consequent larger groups on one side of the molecule than the other1 rotate the plane of polarized light when it passes through a solution of the carbohydrate in question4 ,the amount of the rotation depends upon the nature of the carbohydrate1 the concentration of the solution1 and the length of the column of solution through which the ray of polarized light passes4 ,but the same definite amount of the same sugar1 dissolved in the same volume of water1 and placed in a tube of the same length1 will always cause the same angular deviation1 or rotation1 of the plane in which the polarized light which passes through it is vibrated4 ,in other words1 the same number of molecules of the optically active substance in solution will always produce the same rotatory effect4 ,this is called the specific rotatory power of the substance in question4 ,it is expressed as the number of degrees of angular deviation of the plane of polarized light caused by a column of the solution exactly #bjj mm4 in length1 the concentration of the solution being #ajj grams of substance in #ajj cc4 at a temperature of #bj ,c4 ,actual determinations of specific rotatory power are usually made with solutions more dilute than this standard1 and the observed deviation multiplied by the proper factor to determine the effect which would be produced by the solution of standard concentration4 ,if the direction of the deviation is to the right 7i4e41 in the direction in which the hands of the clock move7 it is spoken of as dextro rotation and is indicated by the sign 1 or the letter d2 while if in the opposite direction1 it is called levo rotation and indicated by the sign -1 or the letter l4 ,for example1 the specific rotation of ordinary glucose is #eb4g2 of fructose1 -#ib2 of sucrose1 #ff4e4 ,reducing ,action4--,all of the hexose sugars are active reducing agents4 ,this is because of the aldehyde group which they contain4 ,many of the common heavy metals1 when in alkaline solutions1 are strongly reduced when boiled with solutions of the hexose sugars4 ,alkaline copper solutions yield a precipitate of red cuprous oxide2 ammoniacal silver solutions give silver mirrors2 alkaline solutions of mercury salts are reduced to metallic mercury1 etc4 ,any sugar which contains a potentially active aldehyde group will exhibit this reducing effect and is known as a reducing sugar4 ,in some of the di- and tri-saccharides1 the linkage of the hexose components together is through the aldehyde group1 in such a way that it loses its reducing effect2 such sugars are known as non-reducing4 ,advantage is taken of this property for both the detection and quantitative determination of the reducing sugars4 ,a standard alkaline copper solution of definite strength1 known as ,fehling's solution1 is added to the solution of the sugar to be tested and the mixture boiled1 when the characteristic brick-red precipitate appears4 ,if certain standard conditions of volume of solutions used1 length of time of boiling1 etc41 are observed1 the quantity of cuprous oxide precipitated bears a definite ratio to the amount of sugar which is present1 so that if the precipitate be filtered off and weighed under proper conditions1 the weight of sugar present in the original solution can be calculated4 ,the proper conditions for carrying on such a determination and tables showing the amounts of the various reducing sugars which correspond to the weight of cuprous oxide found1 are given in all standard text-books dealing with the analysis of organic compounds4 ,fermentability4--,the common hexoses are all easily fermented by yeast1 forming alcohol and carbon dioxide1 according to the equation ,c#f;,h#ab,o#f #b;,c#b;,h#e,,oh #b;,,co#b4 ,the importance and biochemical significance of this reaction will be considered in detail in connection with the discussions of the relation of molecular configuration to biochemical properties 7see page #ef7 and the nature of enzyme action 7see page #aid74 ,formation of ,hydrazones and ,osazones4--,another property of the hexoses which is due to the presence of an aldehyde group in the molecule1 is that of forming addition products with phenyl hydrazine1 known as hydrazones and osazones4 ,for example1 glucose reacts with phenyl hydrazine in acetic acid solution1 in two stages4 ,the first1 which takes place even in a cold solution may be represented by the equation ,c#f;,h#ab,o#f;,c#f;,h#e,,nh,,nh#b ,c#f;,h#ab,o#e3,n,,nh,c#f;,h#e ,glucose ,phenyl-hydrazine ,glucose-hydrazone ,h#b,o4 ,the structural relationships involved may be represented as follows3 ,,cho ,h#b,n,,nh ,,ch,n-------,,nh _/ _/ 7,,choh7#d 7,,choh7#d ,,ch#b,,oh _/ ,,ch#b,,oh _/ ,the hydrazones of the common sugars1 with the exception of the one from mannose1 are colorless compounds1 easily soluble in water4 ,hence1 they do not serve for the separation or identification of the individual sugars4 ,but if the solution in which they are formed contains an excess of phenyl hydrazine and is heated to the temperature of boiling water for some time1 the alcoholic group next to the aldehyde group 7the terminal alcohol group in ketoses7 is first oxidized to an aldehyde and then a second molecule of phenyl hydrazine is added on1 as illustrated above1 forming a di-addition-product1 known as an osazone4 ,the osazones are generally more or less soluble in hot water1 but on cooling they crystallize out in yellow crystalline masses each with definite melting point and crystalline form4 ,all sugars which have active aldehyde groups in the molecule form osazones4 ,these afford excellent means of identification of unknown sugars1 or of distinguishing between sugars of different origin and type4 ,glucose1 mannose1 and fructose all form identical osazones4 ,this is because the structure of these three sugars is identical except for the arrangement within the two groups at the aldehyde end of the molecule 7see formulas on page #dd74 ,since it is to these two groups that the phenyl hydrazine residue attaches itself1 it follows that the resulting osazones must be identical in structure and properties4 ,all other reducing sugars yield osazones of different physical properties4 ,when an osazone is decomposed by boiling with strong acids1 the phenyl hydrazine groups break off1 leaving a compound containing both an aldehyde and a ketone group4 ,such compounds are known as osones4 ,the osones from glucose1 mannose1 and fructose are identical4 ,by carefully controlled reduction1 either one of the ,c,o groups of the osone may be changed to an alcoholic group1 producing thereby one of the original sugars again4 ,hence1 it is possible to start with one of these sugars1 convert it into the osone and then reduce this to another sugar1 thereby accomplishing the transformation of one sugar into another isomeric sugar4 ,formation of ,glucosides4--,by treatment with a considerable variety of different types of compounds1 under proper conditions1 it is possible to replace one of the hydrogen atoms of the terminal alcoholic group of the hexose sugars with the characteristic group of the other substance1 forming compounds known1 respectively1 as glucosides1 fructosides1 galactosides1 etc4 ,the structural relation of methyl glucoside to glucose1 for example1 may be illustrated as follows3 ,glucose 7,c#f;,h#ab,o#f7 ,methyl ,glucoside 7,c#g;,h#ad,o#f7 ,,cho ,,cho 7,,choh7#d 7,,choh7#d ,,ch#b,,oh ,,choh ,,ch#c ,a general formula for glucosides is ,r7,,choh7#e;,,cho2 and the ,r may represent a great variety of different organic radicals 7see the chapters dealing with ,glucosides and with ,tannins74 ,when the glucosides are hydrolyzed1 they yield glucose and the hydroxyl compound of the radical with which it is united4 ,all the statements which have been made with reference to glucosides1 apply equally well with reference to fructosides1 galactosides1 mannosides1 etc4 ,it is possible1 by various laboratory processes1 to replace additional hydrogen atoms in the glucose molecule with the same or other organic radicals1 thus producing glucosides containing two or more ,r groups2 but most of the natural glucosides contain only one other characteristic group4 ,oxidations4--,when the hexoses are oxidized they give rise to three different types of acids1 depending upon the conditions of the oxidation and the kind of oxidizing agent used4 ,with glucose1 for example1 the relationships involved may be illustrated as follows3 ,,cho ,,cooh ,,cho ,,cooh 7,,choh7#d 7,,choh7#d 7,,choh7#d 7,,choh7#d ,,ch#b,,oh ,,ch#b,,oh ,,cooh ,,cooh ,glucose ,gluconic acid ,glucuronic acid ,saccharic acid ,an important property of the acids of the gluconic type is that when heated with pyridine or quinoline to #acj-aej they undergo a molecular rearrangement whereby the acid corresponding to an isomeric sugar is produced4 ,for example1 gluconic acid1 under these conditions1 becomes mannonic acid1 which can be reduced to mannose4 ,the process is reversible2 mannose can be converted to mannonic acid1 thence to gluconic acid1 thence to glucose4 ,similarly1 galactonic acid can be converted into talonic acid1 and this to talose1 and this process is reversible4 ,these facts afford another means of conversion of one sugar into another4 ,from the standpoint of physiological processes1 glucuronic acid is the most interesting and important oxidation product of glucose4 ,it is often found in the urine of animals1 as the result of the partial oxidation of glucose in the animal tissues4 ,normally1 glucose is oxidized in the body to its final oxidation products1 carbon dioxide and water4 ,but when many difficultly oxidizable substances1 such as chloral1 camphor1 turpentine oil1 aniline1 etc41 are introduced into the body1 the organism has the power of combining these with glucose to form glucosides4 ,these so-called paired compounds are then oxidized to the corresponding glucuronic acid derivatives and eliminated from the body in the urine4 ,no phenomenon similar to this occurs in plants1 however1 and glucuronic acid has never been found in plant tissues4 ,synthesis and ,degradation of ,hexoses4--,monosaccharides of any desired number of carbon atoms can be produced from aldoses having one less carbon atoms1 by way of the familiar nitrile reaction4 ,aldoses1 like all other aldehydes1 combine directly with hydrocyanic acid1 forming compounds known as nitriles1 which contain one more carbon atom than was present in the original aldehyde2 the cyanogen group can easily be converted into a ,,cooh group2 and this1 in turn1 reduced to an aldehyde1 thus producing an aldose with one more carbon atom than was present in the initial sugar4 ,these changes may be illustrated by the following equations3 7#a7 ,,cho ,,hcn ,,choh,,cn ,,cn 7,,choh7#c 7,,choh7#c or 7,,choh7#d ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,aldopentose ,nitrile 7#b7 ,,cn ,h#b,o ,,cooh ,,nh#c 7,,choh7#d 7,,choh7#d ,,ch#b,,oh ,,ch#b,,oh ,nitrile ,acid 7#c7 ,,cooh - ,o ,,cho 7,,choh7#d 7,,choh7#d ,,ch#b,,oh ,,ch#b,,oh ,acid ,aldohexose ,it is possible1 by this process1 to advance step by step from formaldehyde to higher sugars1 ,emil ,fischer and his students having carried the process as far as the production of glucodecose 7,c#aj;,h#bj,o#aj74 ,it usually happens1 however1 that two stereo-isomers result from the step-up by way of the nitrile reaction2 thus1 arabinose yields a mixture of glucose and mannose1 glucose yields glucoheptose and mannoheptose1 etc4 ,the reverse process1 or the so-called degradation of a sugar into another containing fewer carbon atoms1 may be readily accomplished in either one or two ways4 ,in ,wohl's process1 the aldehyde group of the sugar is first converted into an oxime1 by treatment with hydroxylamine2 the oxime1 on being heated with concentrated sodium hydroxide solution1 splits off water and becomes the corresponding nitrile2 this1 on further heating1 splits off ,,hcn and yields an aldose having one less carbon atom than the original sugar4 ,this process is the exact reverse of the nitrile synthesis1 described above4 ,the second method of degradation1 suggested by ,ruff1 makes use of ,fenton's method of oxidizing aldehyde sugars to the corresponding monobasic acid1 using hydrogen peroxide and ferrous sulfate as the oxidizing mixture2 the aldonic acid thus formed is then converted into its calcium salt1 which1 when further oxidized1 splits off its carboxyl group and one of the hydrogens of the adjacent alcoholic group1 leaving an aldose having one less carbon atom than the original aldose sugar4 ,enolic ,forms4--,a final avenue for the interconversion of glucose1 mannose1 and fructose into one another1 is through the spontaneous transformations which these undergo when dissolved in water containing sodium hydroxide or potassium hydroxide4 ,this change is due to the conversion of the sugar1 in the alkaline solution1 into an enol1 which is identical for all three sugars1 and which may subsequently be reconverted into any one of the three isomeric hexoses4 ,the relationships involved are illustrated in the following formulas3 ,,cho ,,cho ,,ch#b,,oh ,,choh ,h-,c-,,oh ,,ho-,c-,h ,c,o ,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,glucose ,mannose ,fructose ,enolic ,form ,the preceding technical discussion of the chemical constitution and reactions of the hexoses has been presented1 not because it has any direct connection with the occurrence or functions of these compounds in plant tissues1 but for the purpose of giving to the student a graphic conception of the structure and properties of these simple carbohydrates1 as a basis for the understanding of the nature1 properties1 possible chemical reactions1 syntheses1 etc41 of the more complex types of carbohydrates1 which1 along with these simple monosaccharides1 constitute the most important single group of organic components of plants4 ,,the ,,occurrence ,,and ,,properties ,,of ,,monosaccharides ,only two monosaccharides occur as such in plants4 ,these are glucose and fructose4 ,all the other hexoses1 whose structure is shown on pages #cg and #ch1 occur in plants only as constituents of the more complex saccharides1 in glucoside-formations1 or as the corresponding polyatomic alcohols4 ,the aldo-hexoses which occur most commonly in plants1 either free or in combination1 are d-glucose1 d-mannose1 and d-galactose2 while d-fructose and d-sorbose are the common keto-hexoses4 ,glucose 7often called also dextrose1 fruit sugar1 or grape sugar7 occurs widely distributed in plants1 most commonly in the juices of ripening fruits1 where it is usually associated with fructose and sucrose1 the two hexoses being easily derived from sucrose by hydrolysis4 ,glucose is also produced by the hydrolysis of many of the more complex carbohydrates1 by the action either of enzymes or of dilute acids2 lactose1 maltose1 raffinose1 starch1 and cellulose1 as well as many glucosides all yielding glucose as one of the products of their hydrolysis4 ,in all such cases1 it is d-glucose which is obtained4 ,glucose is a crystalline solid 7although it does not form such sharply defined crystals as does sucrose1 or granulated sugar71 which is easily soluble in water4 ,it usually appears on the market in the form of thick syrups1 which are produced commercially by the hydrolysis of starch with dilute sulfuric acid1 removal of the acid after the hydrolysis is complete1 and evaporation of the resulting solution to the desired syrupy consistency4 7,since corn starch is commonly used as the raw material for this process1 these syrups are often spoken of as corn syrup47 ,the sweetness of glucose is about three-fifths that of ordinary cane sugar4 ,glucose exhibits all the properties of hexoses which have been described in general terms above4 ,it is a reducing-sugar1 and is easily fermented4 ,the specific rotatory power of d-glucose is #eb4g4 ,but when glucose is dissolved in water1 it exhibits in a marked degree the phenomenon known as mutarotation2 that is1 freshly made solutions exhibit a certain definite rotatory power1 but this changes rapidly until it finally reaches another definite specific rotation4 ,in other words1 glucose is birotatory1 or possesses two distinct specific rotatory powers1 and the changing rotation effect in aqueous solutions is due to the change from one form to the other4 ,when dissolved in alcohol1 it does not exhibit this change in rotatory power4 ,in order to explain this phenomenon1 it is necessary to assume that there are two modifications of d-glucose1 which have been designated respectively as the alpha and beta forms4 ,the possibility of the existence of these two forms is explained by the assumption of the closed-ring arrangement of the glucose molecule1 as indicated in the following formulas which represent the two possible isomeric arrangements3 ,,ho-,c-,h ,h-,c-,,oh _/ _/ _/ _/ ,h-,c-,,oh ,h-,c-,,oh ,o ,o ,,ho-,c-,h _/ ,,ho-,c-,h _/ _/ _/ _/ _/ ,c-,h ,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ch#b,,oh ,,ch#b,,oh alpha-,glucose beta-,glucose ,it is assumed that the alpha modification 7with its specific rotatory power of #aje7 is the normal form for crystalline glucose1 but that when dissolved in water it is changed into an aldehydrol1 i4e41 a compound containing two additional ,,oh groups1 which later breaks down again1 into the beta modification 7with its specific rotatory power of #bb74 ,when dissolved in alcohol1 this change does not take place because of the absence of the excess of water necessary to produce the intermediate aldehydrol form4 ,there are other examples of the existence of the alpha and beta modification of glucose4 ,for example1 alpha-methyl-glucoside and beta-methyl-glucoside 7specific rotatory powers1 #aeg and -#cc1 respectively7 are both known1 as well as several other similar glucoside arrangements4 ,mannose4--,this sugar does not occur as such in plants2 but complex compounds which yield d-mannose when hydrolyzed1 known as mannosans1 are found in a number of tropical plant forms4 ,the mannose which is obtained from these by hydrolysis is very similar to glucose in its properties1 forms the same osazones as do glucose and fructose1 exhibits mutarotation1 etc4 ,mannose may also be obtained by oxidizing mannitol1 a hexatomic alcohol1 known as mannite1 which occurs in many plants1 especially in the manna-ash 7,fraxinus ornus71 the dried sap from which is known as manna4 ,galactose occurs in the animal kingdom as one of the constituents of lactose1 or milk-sugar4 ,it is also one of the constituents of raffinose1 a trisaccharide sugar found in plants1 and occurs as galactans in many gums and sea-weeds4 ,the d-galactose1 obtained by the hydrolysis of any of these compounds1 is a faintly sweet substance which resembles glucose in many of its properties2 having one characteristic difference1 however1 in that it forms mucic acid instead of saccharic acid when oxidized by concentrated nitric acid4 ,these oxidation products are very different in their physical properties and this difference serves to distinguish between the two sugars from which they are derived4 ,fructose 7levulose1 honey sugar1 or diabetic sugar7 occurs along with glucose in the juices of many fruits1 etc4 ,it is a constituent of sucrose1 of raffinose1 and of the polysaccharide inulin1 from which it may be obtained by hydrolysis4 ,it is a ketose sugar1 reduces ,fehling's solution1 forms the same osazone as glucose1 and is easily fermentable by yeast4 ,its sweetness is slightly greater than that of ordinary cane sugar4 d-fructose 7the ordinary form7 is easily soluble in water1 and is strongly levorotatory1 its specific rotatory power at #bj ,c4 being -#ib4e2 it is unique in the very large effect which is produced in its rotatory power by increasing the temperature of the solution2 at #hg its specific rotatory power is reduced to -#eb4g1 exactly equal to but in the opposite direction of the effect of glucose2 hence1 invert sugar1 which is a mixture of an equal number of molecules of glucose and fructose1 and which has a specific rotatory power of -#ai4d at #bj ,c41 becomes optically inactive at #hb ,c4 ,sorbose is the only other ketohexose which has any importance in plant chemistry4 ,it does not occur free in plants1 but is the first oxidation product from the hexatomic alcohol1 sorbitol1 which is present in the juice of the berries of the mountain-ash4 ,sorbose is a crystalline solid1 which is not fermentable by yeast1 but which otherwise closely resembles fructose4 ,,disaccharides ,the disaccharides1 having the formula ,c#ab;,h#bb,o#aa1 may be regarded as derived from the monosaccharides by the linking together of two hexose groups with the dropping out of a molecule of water1 in the same way that many other organic compounds form such linkages4 ,that this is a perfectly correct conception1 is shown by the fact that1 when hydrolyzed1 the disaccharides break down into two hexose sugars1 thus ,c#ab;,h#bb,o#aa ,h#b,o ,c#f;,h#ab,o#f ,c#f;,h#ab,o#f4 ,with all known disaccharides1 at least one of the hexoses obtained by hydrolysis is glucose2 hence all disaccharides may be regarded as glucosides 7,c#f;,h#ab,o#e,r7 in which the ,r is another hexose group4 ,since hexoses have both alcoholic and aldehyde groups1 and since either of these types of groups may function in the linkage of the two hexoses to form a disaccharide1 it is possible for two hexoses1 both of which are reducing sugars to be linked together in three different ways3 7#a7 through an alcoholic group of each hexose1 7#b7 through an alcoholic group of one and the aldehyde group of the other1 and 7#c7 through the aldehyde group of each hexose4 ,disaccharides linked in either of the first two ways will be reducing sugars1 since they still contain a potentially active aldehyde group2 but those of the third type will not be reducing sugars1 since the linkage through the aldehyde groups destroys their power of acting as reducing agents4 ,examples of each of these three types of linkage are found among the common disaccharides1 as will be pointed out below4 ,the following table shows the general characteristics of the common disaccharides4 ,type #a4--;,aldehyde group potentially active1 reducing sugars3 ,sugar ,components ,maltose ,glucose and glucose ,gentiobiose ,glucose and glucose ,lactose ,glucose and galactose ,melibiose ,glucose and galactose ,turanose ,glucose and fructose ,type #b4--,non-reducing sugars3 ,sucrose ,glucose and fructose ,trehalose ,glucose and glucose ,the disaccharides of ,type #a reduce ,fehling's solution and form hydrazones and osazones1 although somewhat less readily than do the hexoses4 ,they all show mutarotation and exist in two modifications1 indicating that the component groups have the closed-ring arrangement4 ,the disaccharides of ,type #b1 since they contain no potentially active aldehyde group1 do not reduce ,fehling's solution1 nor form osazones2 neither do they exhibit mutarotation4 ,the only disaccharides which occur as such in plants are of this type4 ,disaccharides of ,type #a may be obtained by the hydrolysis of other1 more complex1 carbohydrates4 ,all disaccharides are easily hydrolyzed into mixtures of their component hexoses1 by boiling with dilute mineral acids1 or by treatment with certain specific enzymes which are adapted to the particular disaccharide in each case 7see page #ee1 also ,chapter ,,xiv74 ,sucrose 7cane sugar1 beet sugar1 maple sugar7 is the ordinary granulated sugar of commerce4 ,it occurs widely distributed in plants1 where it serves as reserve food material4 ,it is found in largest proportions in the stalks of sugar cane1 in the roots of certain varieties of beets1 and in the spring sap of maple trees1 all of which serve as industrial sources for the sugar4 ,in the sugar cane1 and beet-roots1 it constitutes from #ab to #bj per cent of the green weight of the tissue and from #ge to #ij per cent of the soluble solids in the juice which can be expressed from it4 ,its universal use as a sweetening agent is due to the combined facts that it crystallizes readily out of concentrated solutions and1 hence1 can be easily manufactured in solid form1 and that it is sweeter than any other of the common sugars except fructose4 ,sucrose is a non-reducing sugar1 forms no osazone1 and is not directly fermentable by yeast1 although most species of yeasts contain an enzyme which will hydrolyze sucrose into its component hexoses1 which then readily ferment4 ,when hydrolyzed by acids1 or by the enzyme invertase1 it yields a mixture of equal quantities of glucose and fructose4 ,sucrose is dextrorotatory1 but since fructose has a greater specific rotatory action to the left than glucose has to the right1 the mixture resulting from the hydrolysis of sucrose is levorotatory4 ,since the hydrolysis of sucrose changes the rotatory effect of the solution from the right to the left1 the process is usually called the inversion of sucrose1 and the resultant mixture of equal parts of glucose and fructose is called invert sugar4 ,as has been pointed out1 solutions of invert sugar become optically inactive when heated to #hb ,c41 because of the reduction in the rotatory power of fructose due to the higher temperature4 ,the probable linkage of the two hexoses to form sucrose1 in such a way as to produce a non-reducing sugar1 is illustrated in the following formula3 ------,o------- ,,ch#b,,oh,,choh,,ch,,choh,,choh,,ch ,o ,,ch#b,,oh,,choh,,choh,,ch,c,,ch#b,,oh _/ ,o ,trehalose seems to serve as the reserve food for fungi in much the same way that sucrose does for higher plants4 ,it is composed of two molecules of glucose linked together through the aldehyde group of each1 as trehalose is a non-reducing sugar4 ,this linkage is illustrated in the following formula3 ------,o------- ,,ch#b,,oh,,choh,,ch,,choh,,choh,,ch ,o ,,ch#b,,oh,,choh,,ch,,choh,,choh,,ch ------,o------- ,trehalose may be hydrolyzed into glucose by dilute acids and by the enzyme trehalase1 which is contained in many yeasts and in several species of fungi4 ,it is strongly dextrorotatory 7specific rotatory power1 #aii74 ,it is not fermentable by yeast4 ,trehalose appears to replace sucrose in those plants which contain no chlorophyll and do not elaborate starch4 ,the quantity of trehalose in such plants reaches a maximum just before spore formation begins4 ,since it is manufactured in the absence of chlorophyll1 its formation must be accomplished by some other means than photosynthesis1 yet it is composed wholly of glucose--a natural photosynthetic product4 ,maltose rarely occurs as such in plants1 although its presence in the cell-sap of leaves has sometimes been reported4 ,it is produced in large quantities by the hydrolysis of starch during the germination of barley and other grains4 ,this hydrolysis is brought about by the enzyme diastase1 which is present in the sprouting grain4 ,maltose is easily soluble in water1 and crystallizes in masses of slender needles4 ,it is a reducing sugar2 readily forms a characteristic osazone2 is strongly dextrorotatory 7specific rotatory power #acg72 and is readily fermented by ordinary brewer's yeast1 which contains both maltase 7the enzyme which hydrolyzes maltose to glucose7 and zymase 7the alcohol-producing enzyme74 ,when hydrolyzed1 either by dilute acids or by maltase1 one molecule of maltose yields two molecules of glucose4 ,its component hexoses are1 therefore1 the same as those of trehalose1 a non-reducing sugar1 this difference in properties being due to the difference in the point of linkage between the two glucose molecules1 that for maltose being such as to leave one of the aldehyde groups potentially active1 as shown in the following formula1 -------,o------ ,,ch#b,,oh,,choh,,ch,,choh,,choh,,ch ,o ,,choh,,choh,,choh,,ch,,choh,,ch#b ----------,o----- ,isomaltose is a synthetic sugar1 obtained by ,fischer1 by condensing two molecules of glucose4 ,its properties are quite similar to those of maltose1 but it yields a slightly different osazone and is not fermentable by yeast4 ,these differences are explained by the assumption that this sugar is a glucose-beta-glucoside1 while normal maltose is a glucose-alpha-glucoside4 ,gentiobiose is a disaccharide which results from the partial hydrolysis of the trisaccharide gentianose 7see page #ec74 ,it is very similar in its general properties to isomaltose4 ,cellobiose is a disaccharide which results from the hydrolysis of cellulose4 ,it is a reducing sugar1 forms an osazone1 and resembles maltose4 ,maltose1 isomaltose1 gentiobiose1 and cellobiose1 are all glucose-glucosides1 the difference between them being undoubtedly due to linkage being between different alcoholic groups in the glucose molecules4 ,the disaccharide lactose is a glucose-galactoside4 ,it is the sugar which is present in the milk of all mammals4 ,it has never been found in plants4 ,melibiose1 which is the corresponding vegetable glucose-galactoside1 may be obtained by the partial hydrolysis of the trisaccharide raffinose 7see below74 ,it is a reducing sugar2 forms a characteristic osazone2 and exhibits mutarotation4 ,it is not fermented by ordinary top-yeasts1 but is first hydrolyzed and then fermented by the enzymes present in bottom-yeasts4 ,,trisaccharides ,trisaccharides1 as the name indicates1 consist of three hexoses 7or monosaccharides7 linked together by the dropping out of two molecules of water4 ,their formula is ,c#ah;,h#cb,o#af4 ,when completely hydrolyzed1 they yield three molecules of monosaccharides2 when partially hydrolyzed1 one each of a disaccharide and a monosaccharide4 ,one trisaccharide of the reducing sugar type1 namely rhamnose1 exists in plants as a constituent of the glucoside xanthorhamnin4 ,it is composed of one molecule of glucose united to two molecules of rhamnose 7methyl pentose1 ,c#f;,h#ab,o#e74 ,it is of interest only in connection with the properties of the glucoside in which it is present 7see page #hd74 ,three trisaccharides which are non-reducing sugars are found in plants2 namely1 raffinose1 gentianose1 and melizitose4 ,raffinose occurs normally in cotton seeds1 in barley grains1 and in manna2 also1 in small quantities in the beet root1 associated with sucrose4 ,it is more soluble in water than is sucrose and hence remains in solution in the molasses from beet-sugar manufacture1 which constitutes the commercial source for this sugar4 ,raffinose crystallizes out of concentrated solutions1 with five molecules of water of crystallization1 in clusters of glistening prisms4 ,it is strongly dextrorotatory1 the anhydrous sugar having a specific rotatory power of #ahe1 and the crystalline form1 ,c#ah;,h#cb,o#af1 showing a specific rotation of #ajd4e4 ,it does not reduce ,fehling's solution1 nor form an osazone1 and in its other properties it closely resembles sucrose4 ,the hydrolysis of raffinose presents several interesting possibilities4 ,if its structure is represented as follows3 ,c#f;,h#aa,o#e-;,c#f;,h#aj,o#d-;,c#f;,h# aa,o#e ,fructose ,glucose ,galactose _/ _/ _/ _/ ,sucrose ,melibiose it is apparent that it may break down by hydrolysis in three different ways3 7#a7 into sucrose and galactose1 7#b7 into fructose and melibiose1 and 7#c7 into fructose1 glucose1 and galactose4 ,as a matter of fact1 it does actually break down in these three different ways1 under the influence of different catalysts2 invertase or dilute acids break it down into fructose and melibiose1 emulsin hydrolyzes it to sucrose and galactose1 while strong acids or the enzymes of bottom-yeasts break it down into the three hexoses4 ,gentianose1 a trisaccharide found in the roots of yellow gentian 7,gentiana lutea71 is a non-reducing sugar1 which when hydrolyzed yields either fructose and gentiobiose1 or fructose and two molecules of glucose4 ,melizitose1 a trisaccharide which1 in crystallized form1 has the formula1 ,c#ah;,h#cb,o#afb;,h#b,o1 occurs in the sap of ,larix europea and in ,persian manna1 and has recently been found in considerable quantities in the manna which collects on the twigs of ,douglas fir and other conifers4 ,when hydrolyzed1 it yields one molecule of fructose and one of turanose1 a disaccharide containing fructose and glucose linked together in a slightly different way than they are in sucrose4 ,turanose itself is a reducing sugar1 but when linked with fructose to form melizitose its reducing properties are destroyed4 ,melizitose is a very sweet sugar4 ,,tetrasaccharides ,a complex saccharide1 known as stachyose1 which is found in the tubers of ,stachys tuberifera1 is said by some investigators to be a tetrasaccharide and by others to have the formula ,c#cf;,h#fb,o#cag;,h#b,o 7i4e41 a hexasaccharide74 ,it is a crystalline solid1 with a faintly sweetish taste1 and a specific rotatory power of #adh4 ,when hydrolyzed it yields glucose1 fructose1 and two 7or more7 molecules of galactose4 ,,the ,,relation ,,of ,,the ,,molecular ,,configuration ,,of ,,sugars ,,to ,,their ,,biochemical ,,properties ,as will be pointed out later 7see ,chapter ,,xiv71 all chemical reactions which are involved in vital phenomena1 including those of plant growth and metabolism1 are controlled by enzymes4 ,the biochemical reactions which the soluble carbohydrates undergo afford such excellent illustrations of the relation of the molecular configuration of an organic compound to the possibility of the action of an enzyme upon it1 that it seems desirable to discuss this relationship at this point1 rather than to postpone it until after the nature of enzyme action has been considered4 ,undoubtedly1 the student1 after he has studied the nature of enzymes and their mode of action1 as presented in ,chapter ,,xiv1 will find it profitable to return to this section and review the facts here presented1 as illustrating the principles and mechanism of enzyme action4 ,but a consideration1 at this time1 of the relation of the molecular configuration of the sugars to their biochemical reactions cannot fail to add interest to the study of these matters from the chemical and biological standpoints4 ,it has been known for a long time that the dextro- and levo-isomers of a compound which contains one or more asymmetric carbon atoms are affected differently by biological agents1 such as yeasts1 moulds1 bacteria1 etc4 ,pasteur1 as early as #ahej1 showed that the green mould1 ,penicillium glaucum1 when growing in solutions of racemic acid 7a mixture of equal molecules of d- and l-tartaric acids7 uses up only the d-acid1 leaving the l-form absolutely untouched4 ,later1 it was found that the same green mould attacks l-mandelic acid in preference to the d- form2 whereas the yeast1 ,saccharomyces ellipsoideus1 exhibits the opposite preference for these acids4 ,these observations upon some of the earlier known forms of optically active organic acids led the way to a general study of this phenomenon as exhibited by the optically active soluble carbohydrates4 ,the results of these studies may be considered in connection with the several different types of reactions which these sugars undergo1 as follows3 ,glucoside ,hydrolysis4--,as was pointed out in connection with the discussion of the mutarotation of glucose1 this sugar may exist in either the alpha or the beta modification4 ,glucosides of both alpha and beta glucose are of common occurrence4 ,the difference in molecular configuration1 in such cases1 may be represented by the following formulas3 ,r-,o-,c-,h ,h-,c-,o-,r _/ _/ _/ _/ ,h-,c-,,oh ,h-,c-,,oh ,o ,o ,,ho-,c-,h _/ ,,ho-,c-,h _/ _/ _/ _/ _/ ,c-,h ,c-,h ,h-,c-,,oh ,h-,c-,,oh ,,ch#b,,oh ,,ch#b,,oh alpha-,glucoside beta-,glucoside ,the radical represented by the ,r may be either a common alkyl radical 7as ,,ch#c1 ,c#b;,h#e1 etc471 another saccharide group 7as in the case of the disaccharides1 trisaccharides1 etc471 or some other complex organic group 7as in the case of the natural glucosides described in ,chapter ,,vi74 ,but1 in every case1 the glucoside is easily hydrolyzed by the enzyme maltase 7or alpha-glucase7 if the molecular arrangement is that represented by the alpha-attachment1 or by the enzyme emulsin 7or beta-glucase7 if the glucoside is of the beta type2 but emulsin is absolutely without effect upon alpha-glucosides1 and maltase does not produce the slightest change in beta-glucosides4 ,these statements hold true regardless of the nature of the group which is represented by the ,r in the formulas above4 ,hence1 the biochemical properties of the glucosides1 so far as their hydrolysis by the enzymes which are present in many biological agents is concerned1 depends wholly upon the molecular configuration of the glucose itself4 ,furthermore1 neither the mannosides1 which differ from glucosides only in the arrangement of the ,h and ,,oh groups attached to one of the asymmetric carbon atoms in the hexose1 nor galactosides in which two such arrangements are different 7see configuration formulas on page #eg71 are attacked by either maltase or emulsin4 ,but other enzymes specifically attack other disaccharides1 or polysaccharides1 or glucoside-like complexes4 ,for example1 lactase acts energetically upon ordinary lactose and all other beta-galactosides2 but not upon any glucoside1 mannoside1 etc4 ,again1 neither alpha- nor beta-xylosides1 which correspond with the above-described glucosides in every particular except that the ,,hcoh group next the terminal ,,ch#b,,oh group is missing1 are hydrolyzed by either emulsin or maltase4 ,these instances1 selected from among many similar observations1 clearly prove that not only the number and kind of groups in the molecule1 but also the arrangement of the constituent groups in space1 must be identical in order that the compound may be acted upon by any given enzyme acting as a biological hydrolytic agent4 ,fermentability4--,the enzyme zymase1 present in all yeasts1 promotes the fermentation of the natural d- forms of the three hexoses1 glucose1 mannose1 and fructose1 but is without effect upon the artificial l- forms of the same sugars4 ,the uniform action of zymase upon these hexoses is easily explained upon the basis of the same assumption which was used to account for the formation of identical osazones from these sugars and their easy transformation into each other2 namely1 their easy transformation into an enolic form which is identical for all three4 ,further1 galactose is fermented by some yeasts 7although not by all71 but much less readily than are the other sugars1 and the temperature reaction is quite different with galactose than with the others4 ,talose and tagatose are entirely unfermentable4 ,a study of the configuration formulas for these several sugars shows the explanation for these observed facts4 ,these formulas are as follows3 ,,cho ,,cho ,,ch#b,,oh ,,choh ,h-,c-,,oh ,,ho-,c-,h ,c,o ,c-,,oh ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,glucose ,mannose ,fructose ,enol ,,cho ,,cho ,,ch#b,,oh ,h-,c-,,oh ,,ho-,c-,h ,c,o ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,,ho-,c-,h ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,,ch#b,,oh ,,ch#b,,oh ,,ch#b,,oh ,galactose ,talose ,tagatose ,it will be noted that in the case of glucose1 mannose1 and fructose1 the configuration is identical at every point except at the aldehyde end of the chain1 and that here the two groups readily arrange themselves into the same enolic form for the three sugars4 ,galactose differs from these three sugars only in the arrangement of the ,h and ,,oh groups attached to one of the other carbon atoms 7the third from the alcoholic end72 the difficulty of its fermentation indicates that some molecular rearrangement to bring this group into its proper configuration must precede the fermentation process4 ,the fact that it is the third ,,hcoh group which thus undergoes rearrangement is significant because of the participation of these parts of molecules in groups of threes in many biological processes1 as will be mentioned elsewhere4 ,talose is unfermentable1 even though the arrangement of its upper three groups is the same as in the galactose and the lower three the same as in mannose4 ,if further proof that fermentability depends upon molecular configuration were needed1 it is furnished by the fact that no pentose is fermentible1 even though the stereo-arrangement of each of the four alcoholic groups in the molecule is identical with the corresponding groups in a fermentible hexose4 ,oxidation by ,bacteria4--,the bacillus ,bacterium xylinum contains an enzyme1 or enzymes1 which promote the oxidation of the aldehyde group of an aldose sugar to ,,cooh1 or of one alcoholic ,,choh group next the terminal ,,ch#b,,oh group of a hexatomic alcohol to ,c,o4 ,but these oxidizing enzymes affect only those compounds in which the ,,oh groups are on the same side of the two asymmetric carbon atoms next the end of the molecule where the oxidation takes place1 as indicated in the following groupings4 ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh ,h-,c-,,oh or ,h-,c-,,oh but not ,,ho-,c-,h or ,,ho-,c-,h ,,cho ,,ch#b,,oh ,,ch#b,,oh ,,cho ,the configuration of the remainder of the molecule is immaterial to action by these oxidizing bacteria2 hence1 the enzymes in this case are apparently concerned only with the configuration arrangement of a portion of the molecule1 instead of with the whole hexose grouping1 as in the cases of the other reactions which have been thus far considered4 ,it is apparent from these illustrations1 and from many more which might be cited1 that there is a very definite relation between the molecular configuration of a carbohydrate and its biochemical properties1 as represented by the possibilities of the action of enzymes upon it4 ,the probable nature of this relationship will be better understood after the general questions involved in the mode of enzyme action have been considered 7see chapter ,,xiv74 ,but for the present1 it will be sufficient to note that it seems to be necessary that the enzyme shall actually fit the molecular arrangement of the compound at all points1 in the same way that a key fits its appropriate lock2 or a still better illustration is that of the fitting of a glove to the hand4 ,on the basis of the latter illustration1 it is just as impossible for a dextro-enzyme to affect a levo-sugar1 or for alpha-glucase to affect a beta-glucoside1 as it is to fit a right-hand glove upon a left hand4 ,further attention will be given to these matters in later chapters4 ,,polysaccharides ,the polysaccharides which1 like the simpler saccharides1 or sugars1 which have thus far been studied1 undoubtedly serve as reserve food for plants1 are known under the general name of starches4 ,they are substances of high molecular weight1 whose constitution is represented by the general formula 7,c#f;,h#aj,o#e7n4 ,it should be noted that an exactly accurate formula should be 7,c#f7n7,h#ab,o#f7n-#a2 but since the value of n is very high1 the simpler formula is approximately correct4 ,the value of n has not been accurately determined for any of the individual members of the group1 but is probably never less than #cj and may often be #bjj or more4 ,the fact that these compounds are insoluble in most of the solvents which can be used for molecular weight determinations makes it difficult to determine their actual molecular constitution4 ,when completely hydrolyzed1 the polysaccharides yield only hexoses4 ,they are1 therefore1 technically known as hexosans4 ,each individual polysaccharide which has been studied thus far yields only a single hexose1 although the particular hexose obtained varies in different cases4 ,in fact1 the polysaccharides are often classified according to the hexoses which they yield on hydrolysis1 into the following groups3 the dextrosans1 which yield glucose1 and include starch1 dextrin1 glycogen1 lichenin1 etc42 the levulosans1 which yield fructose1 and include inulin1 graminin1 triticin1 etc42 the mannans2 and the galactans4 ,the more common representatives of each of these groups are discussed below4 7,a7 ,,the ,,dextrosans ,these are by far the most common type of polysaccharides to be found in plants4 ,starch4--,it is probable that no other single organic compound is so widely distributed in plants as is ordinary starch4 ,it is produced in large quantities in green leaves as the temporary storage form of photosynthetic products4 ,as a permanent reserve food material1 it occurs in seeds1 in fruits1 in tubers1 in the pith1 medullary rays and cortex of the stems of perennials1 etc4 ,it constitutes from #ej to #fe per cent of the dry weight of seeds of cereals1 and as high as #hj per cent of the dry matter of potato tubers4 ,starch occurs in plant tissues in the form of microscopic granules1 composed of concentric layers1 there being apparently alternate layers of two types of carbohydrate material1 which have been distinguished from each other by several different pairs of names used by different authors3 thus1 ,ngeli uses the terms granulose and amylocellulose2 ,meyer1 alpha and beta amylose2 ,wolff1 amylo-cellulose and amylo-pectin2 while ,kramer asserts that the layers are alternate lamella of crystalline and colloidal starch4 ,many theories as to the nature of these concentric layers and their mode of deposition have been advanced1 but it would not be profitable to discuss them in detail here4 ,for purposes of study1 starch may be prepared from the ground meal of cereals1 potatoes1 etc41 by kneading the meal in a bag or sieve of fine-meshed muslin or silk1 under a slow stream of water4 ,the starch granules1 being microscopic in size1 readily pass through the cloth with the water1 and may be caught in any suitable container4 ,the starch is then allowed to settle to the bottom1 the water poured off and the starch collected and dried4 ,starch is insoluble in water2 but if boiled in water1 the granules burst and a slimy opalescent mass1 known as starch paste1 is obtained4 ,this is undoubtedly a colloidal suspension of the starch in water4 ,by various processes1 such as boiling with very dilute acids1 treatment with acetone1 etc41 starch is converted into soluble starch which dissolves in water to a clear solution4 ,soluble starch is precipitated out of solution by alcohol1 or by lead subacetate solution4 ,air-dried starch contains from #ae to #bj per cent of water2 but this can be completely removed1 without altering the starch in any way1 by heating for some time at #ajj ,c4 ,the starch granules from different sources vary considerably in size and shape1 and can generally be identified by observation under the microscope4 ,the most characteristic reaction of starch is the blue color which it gives with iodine4 ,the reaction is most marked with starch paste or soluble starch1 but even dry starch granules are colored blue when moistened with a solution of iodine in water containing potassium iodide1 or with tincture of iodine4 ,when hydrolyzed1 either by boiling with dilute acids or under the influence of enzymes1 starch undergoes a series of decompositions1 yielding first dextrins1 then maltose1 and finally glucose4 ,these transformations can be traced by the iodine color reaction1 as starch will show its characteristic blue1 dextrins purple or rose-red1 and maltose and glucose no color with iodine4 ,dextrins may occur in plants as transition products in the transformation of starch into sugars1 or vice versa4 ,most commonly1 however1 they are artificial products resulting from the partial hydrolysis of starch in the laboratory or factory4 ,they are amorphous substances1 which are readily soluble in water1 forming sticky solutions which are often used as adhesives 7library paste is a common example of a very concentrated preparation of this kind74 ,they are precipitated from solution by alcohol1 but not by lead subacetate 7distinction from starch74 ,they are strongly dextrorotatory 7specific rotatory power #aib to #aif72 are not fermented by yeast alone1 but readily undergo hydrolysis to glucose which does ferment4 ,there are several different modifications1 or forms1 of dextrins1 depending upon the extent to which the simplification of the starch molecule by hydrolysis is carried4 ,three fairly definite forms are generally recognized1 as follows3 amylo-dextrin1 or soluble starch1 slightly soluble in cold water1 readily so in hot water1 giving a blue color with iodine2 erythro-dextrin easily soluble in water1 neutral taste1 red color with iodine2 and achroo-dextrin1 easily soluble in water1 sweetish taste1 no color with iodine4 ,commercial dextrin1 which is much used in the preparation of mucilages and adhesive pastes1 is prepared by heating dry starch to about #bej ,c4 ,it is composed chiefly of achroo-dextrin1 mixed with varying quantities of erythro-dextrin and glucose4 ,glycogen1 or animal starch1 is one of the most widely distributed reserve foods of the animal body2 in fact1 it is the only known form of carbohydrate-reserve in animal tissues4 ,but it is present only rarely in plants4 ,it occurs in certain fungi1 particularly in yeasts4 ,in the animal body1 glycogen is found in all growing cells2 also in the muscles and blood2 but most largely in the liver1 where it is stored in large quantities4 ,the glycogen found in yeasts is identical with that found in animal tissues4 ,the quantity of glycogen in a yeast cell increases rapidly as the yeast grows during the fermentation process4 ,glycogen is a white1 amorphous compound1 readily soluble in hot water1 forming an opalescent solution similar in appearance to the solutions of soluble starch4 ,it is strongly dextrorotatory 7specific rotatory power #aij71 is colored brown by iodine1 and is hydrolyzed to dextrin and maltose1 and finally to glucose4 ,lichenin1 para dextran1 and para isodextran are dextrosans which have been isolated from various lower plants4 ,they all yield glucose when completely hydrolyzed4 ,they resemble starch in chemical properties1 but differ from it in physical form1 etc4 7,b7 ,,levulosans ,inulin replaces starch as the reserve food carbohydrate in a considerable number of natural orders of plants1 particularly in the ,compositae4 ,it is the carbohydrate of the tubers of the dahlia and artichoke and of the fleshy roots of chicory4 ,it is often found associated with starch in monocotyledonous plants1 such as many species of ,iris1 ,hyacinthus1 and ,muscari4 ,among the monocotyledons1 starch seems to be the characteristic carbohydrate reserve of aquatic1 or moisture-loving1 species1 while inulin is more common among those which prefer dry situations4 ,inulin may be prepared from the tubers of dahlias or artichokes1 by boiling the crushed tubers with water containing a little chalk 7to precipitate mineral salts1 albumins1 etc47 filtering and cooling the filtrate practically to the freezing point1 which precipitates the inulin4 ,inulin is a white1 tasteless1 semi-crystalline powder1 which is soluble in hot water1 from which it may be precipitated by alcohol or by freezing4 ,it forms no paste like that of starch or dextrin1 and gives no color with iodine4 ,it is levorotatory1 and when hydrolyzed by acids or by the enzyme inulinase yields fructose2 in fact1 inulin bears the same relation to fructose that starch does to glucose4 ,graminin1 irisin1 phlein1 sinistrin1 and triticin are all inulin-like polysaccharides1 which have been found in the plants after which they are named4 ,their solutions are1 as a rule1 sticky or gummy in consistency1 which suggests that these compounds bear the same relation to inulin that dextrins do to starch4 7,c7 ,,mannosans1 ,,or ,,mannans ,mannan bears the same relation to mannose that starch does to glucose and inulin to fructose4 ,it occurs as a reserve food substance in many plants4 ,it has been reported as present in moulds1 and in ergot2 in the roots of asparagus1 chicory1 etc42 in the leaves and wood of many trees1 such as the chestnut1 apple1 mulberry1 and many conifers2 also as a part of the so-called hemi-celluloses which are present in the seeds of many plants1 notably the palms1 the elders1 cedar1 larch1 etc4 ,it is a white1 amorphous powder1 which is difficultly soluble in water1 is strongly dextrorotatory 7specific rotatory power #bhe71 and when hydrolyzed yields mannose4 ,secalin 7or carubin7 is a substance which is found in the seeds of barley1 rye1 etc41 which is similar to mannan1 but is optically inactive4 7,d7 ,,galactans ,these bear the same relation to galactose that the preceding dextrosans do to their constituent hexoses4 ,four different galactans have been isolated from plant tissues2 they are all white1 amorphous solids which dissolve with difficulty in water1 forming gummy solutions4 ,both galactans and mannans commonly occur associated with cellulose and hemi-celluloses in the seeds or other storage organs of plants4 ,they are practically indigestible by animals1 as the proper enzymes to hydrolyze them are not present in the digestive tract2 hence1 they are commonly classed with the indigestible cellulose as the crude fiber of plants which are to be used as food by animals4 ,,physiological ,,use ,,and ,,biological ,,significance ,,of ,,carbohydrates ,if the organic compounds produced by plants be classified with reference to their uses in metabolism into the three groups known1 respectively1 as temporary foods1 storage products1 and permanent structures1 it is clear that the carbohydrates which have been discussed in this chapter may fall into either one of the first two of these classes4 ,there can be no doubt that the first products of photosynthesis1 whichever ones they may be in different plants1 may be directly used as temporary foods1 to furnish the energy and material for the building up of permanent structures4 ,also1 there can be no doubt that these same carbohydrates are translocated to the storage organs and accumulated for later use by the same plant 7as1 for example1 in the case of the perennials71 or by the next generation of the plant 7when the storage is in the endosperm adjoining the embryo of the seed74 ,there is no known explanation as to why different species of plants make use of different carbohydrates for these purposes2 or why certain species elaborate starch out of the same raw materials from which other species produce sugars1 inulin1 or glycogen1 etc4 ,in general1 starch is the final product of photosynthesis in most green plants2 but there are many exceptions to this4 ,the polysaccharides1 which are generally insoluble1 must be broken down into the simpler soluble sugars before they can be translocated to other organs of the plant for immediate1 or future1 use4 ,when they reach the storage organs1 they may be recondensed into insoluble polysaccharides1 or stored as soluble sugars4 ,examples of the latter type of storage are1 sucrose in beet roots1 glucose in onion bulbs1 etc4 ,sometimes1 this habit of storage seems to be a species characteristic2 as potatoes store starch1 while beets1 growing in the same soil and under exactly the same environment1 store sugar4 ,but in other cases1 the nature of the carbohydrate stored undoubtedly is correlated with the external temperatures at the time of storage4 ,it has been shown that cold1 which tends to physiological dryness1 very frequently favors the storage of sugars instead of starches4 ,thus1 in temperate zones1 among aquatic1 or moisture-loving plants1 those species which hibernate during the winter at the bottom of lakes or ponds and are killed by temperatures below freezing1 store starch and no sugar2 while in the same ponds1 the species whose storage organs pass the winter above the level of the water and can withstand temperatures as low as -#g ,c4 contain sugar during the winter months1 even if they contain starch during warmer periods4 ,similarly1 sugars often appear in the leaves and stems of conifers during the winter months1 only to disappear1 or be replaced by starch1 when spring approaches4 ,this same phenomenon is noticeable in arctic plants1 which generally contain but small proportions of starch and relatively large amounts of sugars4 ,similarly1 the phenomenon of the turning sweet of potatoes when exposed to low temperatures has often been noted4 ,the change of the starch in potato tubers to sugar is most rapid at the temperature of #j ,c41 and ceases at #g1 or above4 ,also1 if potatoes in which the maximum amount of sugar is present 7not over one-sixth of the total starch can be converted into sugar7 are exposed to a higher temperature the sugar soon disappears4 ,in general1 however1 it may be said that each particular species of plant has its own particular preference for a specific carbohydrate as its reserve food material1 and elaborates the proper enzymes to make it possible to utilize this particular carbohydrate for its metabolic needs4 ,again1 the question as to whether the storage of energy-producing materials for the use of the next generation shall be in the form of carbohydrates or of fats seems to be definitely connected with the size of the seed1 and the consequent available storage space 7see page #ach74 ,animals habitually use the space-conserving form of fats for their energy-storage1 while plants more commonly use carbohydrates for this purpose1 except in the case of those small seeds in which sufficient energy cannot be stored in carbohydrate form to develop the young seedling to the point where it can manufacture its own food4 ,as a general rule1 nuts1 which contain the embryo of slow-growing seedlings1 and need large proportions of energy reserve1 are characteristically oily instead of starchy in type4 ,but1 aside from temperature reactions and space requirements1 there is no law which has yet been discovered which determines the character of the energy-storage compound which any given species of plant will elaborate4 ,the process of photosynthesis would seem to be identical in all cases1 at least up to the point of the production of the first hexose sugar2 but the transformation of glucose into other monosaccharides1 disaccharides1 and polysaccharides seems to be a matter which obeys no rule or law4 ,finally1 there remains to be considered the occurrence and uses of sugars in the fleshy tissues of fruits4 ,these tissues have1 of course1 no direct function in the life history of the plant4 ,they surround the seed1 but they must decay or be destroyed before the seed can come into the proper environment for germination and growth4 ,in most fruits1 starch is the form in which the carbohydrate material is first deposited in the green tissue1 but as the fruit ripens the starch rapidly changes into sugars1 with the result that the fruit takes on a flavor which makes it much more attractive as a food for men and animals4 ,this purely biological significance of the presence of sugars 7and of the other substances which give desirable flavors to fruits1 vegetables1 etc471 can have no possible relation to the physiological needs of the individual plant1 however4 ,it is apparent that the production of these immense stores of reserve food by plants makes them useful as food for animals1 and it is1 of course1 the storage parts of the plants which are most useful for this purpose4 ,this biological relationship needs no further emphasis4 ,,references ,,abderhalden1 ,e4--,biochemisches ,handlexikon1 ,band #b 444 ,die ,einfachen ,zuckerarten1 ,inuline1 ,cellulosen1 4441 #gbi pages1 ,berlin1 #aiaa1 and ,band #h--a ,ergnzungsband 7same title as ,band #b7-- #ejg pages2 ,berlin1 #aiad4 ,,armstrong1 ,e4 ,f4--,the ,simple ,carbohydrates and ,glucosides1 #bcc pages4 ,monographs on ,biochemistry1 ,london1 #aiai 7#c;d ed474 ,,fischer1 ,e4--,untersuchung ueber ,kohlenhydrate und ,fermente1 #ahhd-aijh1 #iab pages1 ,berlin1 #aiji4 ,,mackensie1 ,j4 ,e4--,the ,sugars and their ,simple ,derivatives1 #bdb pages1 #ag figs41 ,london1 #aiac4 ,,tollens1 ,b4--,kurzes ,handbuch der ,kohlenhydrate1 #haf pages1 #bi figs41 ,leipzig1 #aiad 7#c;d ed474 ,,chapter ,v ,,gums1 ,,pectins1 ,,and ,,celluloses ,these substances constitute a group of compounds which are very similar to the polysaccharide carbohydrates in composition and constitution1 but which serve entirely different purposes in the plant4 ,as a class1 they are condensation products of pentoses1 known as pentosans and having the formula 7,c#e;,h#h,o#d7n1 or hexosans having the formula 7,c#f;,h#aj,o#e7n1 or combined pentosan-hexosans4 ,in general1 these compounds make up the skeleton1 or structural framework material1 of the plant1 in contrast with the protoplasmic materials or food substances for which most of the other types of organic compounds 7discussed in other chapters of this book7 serve4 ,they are the principal constituents of woody fiber1 of cell-walls1 and of the middle lamella which fills up the spaces between the plant cells4 ,they are1 therefore1 found in largest proportions in the stems of woody plants2 but they are also present in every other organ of plants1 as the cell-wall or other structural material4 ,for purposes of study1 these compounds may conveniently be divided into three groups2 namely1 the natural gums and pentosans1 the pectins and mucilages1 and the celluloses4 ,the segregation into these three groups is not sharply defined4 ,the distinction between the groups is based upon the solubility of the compounds in water4 ,the gums and pentosans readily dissolve in water2 the pectins form colloidal solutions which are easily converted into jellies2 the mucilages do not dissolve but form slimy masses2 while the celluloses are insoluble in and unaltered by water4 ,some authors add a fourth group1 known as humins2 but as these are the products of decay 7usually in the soil7 of these structural compounds1 rather than of growth and development1 they need not be taken into consideration in a study of the chemistry of plant growth4 ,,the ,,natural ,,gums ,,and ,,pentosans ,the natural gums1 when hydrolyzed1 yield large proportions of sugars1 but most of them also contain a complex organic acid nucleus1 by means of which they form salts with calcium1 magnesium1 etc4 ,some of them1 such as cherry gum and those which are found in the woody stems of plants 7wood gum1 and those found in corn stalks1 the straw of cereals1 etc47 yield practically pure pentoses4 ,these are known as pentosans4 ,they bear the same relation to the pentose sugars as do the dextrosans to glucose1 etc4 ,the wound gums1 for example1 yield arabinose1 and the wood gums yield xylose4 ,but most of the natural gums yield a mixture of galactose1 some pentose1 and some complex organic acid4 ,the gums are translucent1 amorphous substances1 whose solutions in water are levorotatory4 ,they are precipitated out of solution by alcohol and by lead subacetate solution4 ,gums are extremely difficult to hydrolyze1 the laboratory process of hydrolysis usually requiring from eighteen to twenty-four hours of continuous boiling with acids for its completion4 ,because of this difficulty of hydrolysis1 gums are practically indigestible by animals and of little use as food4 ,the following common examples will serve to illustrate the general nature of these compounds4 ,gum arabic1 found in the exudate from the stems of various species of ,acacia1 is a mixture of the calcium1 magnesium1 and potassium salts of a diaraban-tetragalactan-arabic acid4 ,arabic acid has the formula ,c#bc;,h#ch,o#bb1 and one molecule of this acid serves as the nucleus for the union of eight galactose and four arabinose groups1 linked together in some unknown way4 ,the formula for the compound1 exclusive of the metallic elements with which it is loosely united is ,c#ia;,h#aej,o#gh4 ,this gives some idea of its complexity4 ,when boiled with nitric acid1 it is oxidized to mucic1 saccharic1 and oxalic acids4 ,it gives characteristic reactions with alum1 basic lead acetate1 and other common reagents4 ,gum arabic comes on the market as a brittle1 glassy mass1 which is used in the preparation of mucilages1 and as a carrier for essential oils1 etc41 in certain toilet preparations4 ,recent investigations have shown that the so-called meta-pectic acid1 which is often found in sugar beets and interferes with the process of sugar manufacture1 is identical with gum arabic in composition and properties4 ,gum tragacanth is the soluble portion of the natural gum which is found in several species of ,astragalus4 ,it constitutes only #h to #aj per cent of the total gum-like material which is present1 the remainder being composed of insoluble gummy substances of unknown composition4 ,the soluble gum consists of calcium1 potassium1 and magnesium salts of an acid which1 when hydrolyzed1 yields several molecules of arabinose1 six of galactose1 and one of geddic acid 7an isomer of arabic acid74 ,it is said to be produced by the metamorphosis of the medullary rays under unfavorable conditions of growth4 ,it comes on the market in globular masses of amorphous material1 and is used in the manufacture of cosmetics1 etc4 ,wound gum is frequently found in the trache of plants1 and near surface wounds1 which it stanches4 ,it is secreted by the cells surrounding the injured part4 ,it responds to the reactions of other gums and to some of those of woody fiber4 ,its exact composition is not known1 but probably lies between that of the true gums and that of cellulose4 ,these gums are generally considered to be decomposition products of celluloses1 resulting from the action of some hydrolytic ferment1 usually stimulated by some unfavorable condition of growth1 some injury1 or some morbid condition4 ,the pentosans1 araban and xylan1 occur normally in the stems and outer seed coats of many common plants4 ,they constitute a considerable proportion of these tissues1 as indicated by the following results of typical analyses3 ,wheat bran1 #bb to #be per cent2 clover hay1 #h to #aj per cent2 oat straw1 #af to #bj per cent2 wheat straw1 #bf to #bg per cent2 corn bran1 #ch to #dc per cent2 jute fiber1 #ac to #ae per cent2 various wood gums1 #fj to #ib per cent4 ,they are white1 fluffy solids1 which are difficultly soluble in cold water1 more readily in hot water4 ,they are very difficult to hydrolyze1 and indigestible by animals4 ,when finally hydrolyzed1 they yield arabinose and xylose1 respectively4 ,the pith of dry corn stalks is a good illustration of their general character4 ,,mucilages ,these are characterized by forming slimy masses when moistened with water4 ,they are secreted by hairs on the skin of many plants1 so that the external walls of the leaves1 fruit1 and seeds are often mucilaginous when damp4 ,this is particularly true of aquatic plants4 ,the chemical composition of the mucilages is unknown4 ,when hydrolyzed1 they yield arabinose and a hexose2 the latter is sometimes galactose and sometimes mannose4 ,when present on the surface of plant tissues1 the mucilages probably serve to prevent the too rapid diffusion of materials through the skin1 in the case of the aquatic plants1 and too rapid transpiration1 in the case of young vegetative tissues or in other plants when growing under extremely dry conditions4 ,when found in tubers1 or other storage organs1 it has been supposed that they may serve as reserve food materials1 but it seems that such difficultly hydrolyzable compounds as these can hardly function as normal reserve foods4 ,,pectins ,many fruits1 such as currants1 gooseberries1 apples1 pears1 etc41 and many fleshy roots of vegetables1 such as carrots1 parsnips1 etc41 contain substances known as pectins4 ,these are readily soluble in water1 and when dissolved in concentrated solutions in hot water1 they set into jellies when the solution is cooled4 ,these jellies carry with them the soluble sugars and flavors which are present in the fruits1 and constitute a familiar article of diet4 ,there are undoubtedly several different modifications of the pectins1 to which the names meta-pectin1 para-pectin1 pectic acid1 meta-pectic acid1 and para-pectic acid1 have been applied4 ,these all seem to be products of hydrolysis of a mother substance known as pectose1 which constitutes the middle lamella of unripe fruit1 etc4 ,as the fruit ripens1 the pectose is hydrolyzed into the various semi-acid1 or acid1 bodies mentioned above4 ,the intermediate products of the hydrolysis are the pectins1 which swell up in water and readily form jellies2 while the final meta-pectic acid is easily soluble in water and resembles the true gums in its properties4 ,when the middle lamella reaches the pectic acid stage1 the fruit becomes soft and mushy in texture4 ,the pectins more nearly approach to the composition1 properties1 and functions of the celluloses than do any of the other groups of organic compounds4 ,they have been extensively studied in connection with the parasitism of certain fungous diseases which cause the soft rots of fruits and vegetables4 ,these parasites usually penetrate the tissues of the host plant by dissolving out the middle lamella material1 which may sometimes serve as food material for the fungus2 but more often the parasite secures its food supply from the protoplasm of the cell contents4 ,in such cases1 the parasite secretes both a pectose-dissolving enzyme1 known as pectase and a cellulase which attacks the cell-wall material in order to provide for the entry of the fungus into the cells4 ,other enzymes1 known as pectinases1 which coagulate the soluble pectins or pectic acids into insoluble jellies in the tissues of the plants seem to aid the plant in resisting the penetration by the parasite4 ,,celluloses ,used in its general sense1 this term includes all those substances which are elaborated by protoplasm to constitute the cell-wall material4 ,cellulose proper is a definite chemical compound1 whose properties are well established4 ,in plants1 however1 this true cellulose is nearly always contaminated by various encrusting materials2 and in the process of wood-formation1 the cell-wall material continually thickens by the conversion of the cellulose into ligno-cellulose and the protoplasm of the cell as continuously diminishes in volume4 ,thus the protoplasm of the cell produces a number of different kinds of material which are deposited in the walls of the cell4 ,all of these1 taken together1 constitute the general group known as the celluloses4 ,these may be divided into three classes3 namely1 7#a7 the hemi-celluloses1 7#b7 the normal celluloses1 and 7#c7 the compound celluloses4 ,the hemi-celluloses 7pseudo-1 or reserve celluloses7 include a series of complex polysaccharides which occur in the cell-walls of the seeds of various plants4 ,they are found in the shells of nuts1 rinds of cocoanuts1 shells of stony fruits1 etc41 and in the seedcoats of beans1 peas and other legumes4 ,they are much more easily hydrolyzed than the other members of this group1 and when hydrolyzed yield various sugars1 chiefly galactose1 mannose1 and the pentoses4 ,they bear the same relation to these sugars that starch does to glucose1 and are generally supposed to serve as reserve food material1 although it is difficult to conceive how the shells1 etc41 in which they appear can be utilized by a growing seedling4 ,they differ in structure from the fibrous celluloses and are probably not cell-wall building material4 ,they appear to be a form of reserve carbohydrates1 which differ from the glucose-polysaccharides in being condensed in1 or as a part of1 the external structural material rather than in the internal storage organs4 ,they are soluble in water and exhibit the properties of gums1 and are often classified with the gums and described under the names galactans1 mannosans1 pentosans1 etc4 ,the normal celluloses1 of which the fibers obtained from cotton1 flax1 hemp1 etc41 are typical examples1 are widely distributed in plants and form the commercial sources for all textile fibers of vegetable origin4 ,ordinary cotton fiber contains #ia per cent of cellulose1 about #g4e per cent of water1 #j4d per cent of wax and fat1 #j4ee per cent of pectose derivatives1 and #j4be per cent of mineral matter2 or a total of only #a4b per cent of non-cellulose solids4 ,filter paper is practically pure cellulose4 ,pure cellulose is a white1 hygroscopic substance1 which is insoluble in water and in most other solvents4 ,if heated with water under pressure to about #bfj ,c41 it dissolves completely without decomposition4 ,if boiled with a strong solution of zinc chloride1 or treated in the cold with zinc chloride and concentrated hydrochloric acid1 or with an ammoniacal solution of copper hydroxide 7,schweitzer's reagent71 it dissolves to a clear solution from which it may be reprecipitated without chemical change by neutralizing or diluting the solution4 ,cellulose has the formula 7,c#f;,h#ab,o#e7n4 ,when hydrolyzed under the influence of the enzyme cytase1 it breaks down1 first into cellobiose1 an isomer of maltose1 and then into glucose4 ,it is1 therefore1 chemically like1 but not identical with1 starch2 and structurally it is arranged in fibrous form instead of in granules4 ,under the action of fermentative enzymes1 as when vegetable matter decays under stagnant water1 in swamps1 etc41 cellulose breaks down into carbon dioxide and marsh gas1 according to the equation 7,c#f;,h#ab,o#e7n n,h#b,o #cn,,co#bcn,,ch#d4 ,cellulose is acted upon by caustic alkalies in a variety of ways4 ,when fused with a mixture of dry sodium and potassium hydroxides1 it is decomposed into oxalic and acetic acids4 ,when heated with a #aj to #ae per cent solution of caustic soda1 cellulose fibers thicken and become translucent1 thus resembling silk fibers4 ,this process1 known as ,mercerizing1 is largely used for the production of commercial fabrics4 ,acids also act on cellulose in a variety of ways4 ,when heated with nitric acid 7sp4 gr4 #a4be71 it is converted into oxycellulose2 while dilute sulfuric acid1 under similar conditions1 yields hydro-cellulose1 a substance having the formula ,c#ab;,h#bb,o#aa1 which retains the fibrous structure of the original cellulose but which1 when dry1 may be rubbed up into a fine powder4 ,concentrated nitric acid1 or better1 a mixture of concentrated nitric and sulfuric acids1 acts upon cellulose1 converting it into various nitro-derivatives1 several of which have great industrial value4 ,the number of ,,no#c groups which unite with the cellulose molecule under these conditions depends upon the temperature1 pressure1 etc41 employed during the nitration process2 di-1 tri-1 tetra-1 penta-1 and hexanitrates are all known4 ,pyroxylin1 or collodion1 is a mixture of the tetra- and penta-nitrates1 which is soluble in alcohol and is used in surgery1 in photography1 and in the manufacture of celluloid1 which is a mixture of collodion and camphor4 ,the hexanitrate1 ,c#ab;,h#ad7,,no#c7f,o#d1 is the violent explosive known as gun-cotton4 ,gentler oxidizing agents1 such as bleaching powder1 etc41 have no effect upon cellulose1 and hence are extensively used in the treatment of cotton and other vegetable fibers1 in preparation for their use in the manufacture of textiles1 paper1 etc4 ,cellulose is indigestible in the alimentary tract of animals1 but the putrefactive bacteria which are generally present there ferment it1 with the production of acids of the fatty acid series1 carbon dioxide1 methane1 and hydrogen4 ,excessive fermentations of this kind are responsible for the distressing phenomenon known as bloat4 ,the compound celluloses comprise the larger proportion of the material of the woody stems of plants4 ,they consist of a base of true cellulose1 which is either encrusted with or chemically combined with some non-cellulose constituent4 ,depending upon the nature of the non-cellulose component1 the compound celluloses are divided into three main groups1 known respectively as 7#a7 ligno-celluloses1 7#b7 pecto-celluloses1 and 7#c7 adipo-1 or cuto-celluloses4 ,as the names indicate1 the non-cellulose component in the first group is lignin2 in the second1 pectic substances2 and in the third1 fats or waxes4 ,ligno-celluloses4--,in the young plant cell1 the cell-walls consist of practically pure cellulose2 but as the plant grows older1 this becomes permeated with lignin1 or woody fiber1 until in the stem of a tree1 for example1 the proportion of cellulose in the tissue is only #ej to #fj per cent4 ,in the preparation of wood pulp for the manufacture of paper1 the lignin materials are dissolved off by means of various chemical reagents1 leaving the cellulose fibers in nearly pure form for use as paper4 ,the lignin material generally consists of two types of substances1 one of which contains a closed-ring nucleus of unknown composition and the other is probably a pentosan4 ,these materials are so extremely difficult to hydrolyze that their composition has not yet been definitely determined4 ,pecto-celluloses are found in various species of flowering plants2 those which are present in the stems and roots being true pecto-celluloses1 while those which are found in fruits and seeds contain mucilages rather than pectose derivatives1 and are generally designated as muco-celluloses4 ,the exceedingly inert character of these compounds makes their study difficult and their functions uncertain4 ,the term cuto-celluloses is applied to the group of substances1 including suberin and cutin1 which constitute waterproof cell-walls4 ,these were formerly supposed to consist of true cellulose impregnated with fatty or wax-like materials4 ,recent investigations seem to indicate1 however1 that there is really no cellulose nucleus in such walls as these1 but that they are compound glyceryl esters resembling the true fats 7see chapter ,x7 in composition4 ,if this view should finally be established as a fact1 this sub-group of supposed compound celluloses should be dropped from consideration as such4 ,,physiological ,,use ,,of ,,celluloses ,there seems to be no question that the sole use of celluloses is to serve as structure-building materials4 ,they are undoubtedly elaborated from the carbohydrates as the cell grows4 ,in only rare cases1 however1 is there any evidence that they can be reconverted into carbohydrates to serve as food material4 ,certain bacteria can make use of cellulose as food1 and secrete an enzyme1 cytase1 which aids in the hydrolysis of cellulose to sugars for this purpose4 ,but this enzyme seems rarely1 if at all1 to be present in the tissues of higher plants4 ,it has been reported that some cellulose is hydrolyzed during the malting of barley1 indicating that this might have some food use for the growing seedling2 but this observation has not been confirmed and later investigations seem to throw doubt upon its accuracy4 ,bacteria of decay also act upon cellulose materials1 converting them chiefly into gaseous products2 but this seems to be a provision of nature for the destruction of the cell-wall material of dead plants1 rather than an arrangement for the constructive use of it as food for the bacterium4 ,when fibrous plant residues decay in the soil1 the cellulose compounds are first converted into a series of complex organic acids1 known as humins1 which undoubtedly have a significant effect upon the chemical and physical properties of the soil1 but these have little interest or significance in a study of the chemistry of plant growth4 ,,references ,,abderhalden1 ,e4--,biochemisches ,handlexikon1 ,band #b1 ,gummisubstanzen1 ,hemicellulosen1 ,pflanzenschleimen 444 #gbi pages1 ,berlin1 #aiaa2 and ,band #h--a ,ergnzungsband 7same title as ,band #b7--1 #ejg pages1 ,berlin1 #aiad4 ,,schwalbe1 ,c4 ,g4--,die ,chemie der ,cellulose1 #ffe pages1 ,berlin1 #aiaa4 ,,chapter ,,vi ,,glucosides ,strictly speaking1 the term glucoside should be applied only to such compounds as contain glucose as the characteristic basic group4 ,but in common usage1 it refers to any compound which1 when hydrolyzed1 yields a sugar as one of the products of the hydrolysis4 ,in all the natural glucosides which occur in plant tissues1 the other organic constituent1 which is represented by the ,r in the formula for glucosides 7,r,c#f;,h#aa,o#e1 or ,r7,,choh7#e;,,cho7 is some aromatic group1 or closed-ring benzene derivative4#c ,the different organic constituents of glucosides are of a great variety of types1 such as phenols1 alcohols1 aldehydes1 acids1 oxyflavone derivatives1 mustard oils1 etc4 ,it is noteworthy1 however1 that no nitrogenous groups of the protein type have been found combined with sugars in glucosides4 ,some glucosides contain more than one saccharide group1 possibly as di- or trisaccharides4 ,under proper conditions of hydrolysis1 one or more of the saccharide groups can be removed from such compounds1 resulting in glucosides of simpler structure4 ,most of the common glucosides are derived from d-glucose4 ,some are known1 however1 which are derivatives of galactose or rhamnose2 while in some cases the exact nature of the sugar which is present has not yet been determined4 ,,footnotes3 #c ,,hc _/_/ ,,hc ,,ch ,the structural formula for benzene1 ,c#f;,h#f1 is one which it is ,,hc ,,ch _/ ,,ch difficult and inconvenient to reproduce in type4 ,on that account1 it is _/ customary to indicate this formula by a plane hexagon1 thus 4 _/ ,it is understood1 in all such cases1 that the figure represents six carbon atoms arranged in a closed ring1 with alternate double and single bonds1 and with a hydrogen atom attached to each carbon4 ,the printing of some other group as ,,oh1 ,,ch#c1 adjacent to an angle of the hexagon means that this group replaces the ,h atom in the compound which is being illustrated4 ,,hydrolysis ,,of ,,the ,,natural ,,glucosides ,all natural glucosides are hydrolyzed into a sugar and another organic residue by boiling with mineral acids2 although they vary widely in the ease with which this hydrolysis is brought about4 ,in most cases1 the glucoside is easily hydrolyzed by an enzyme which occurs in the same plant tissue1 but in different cells than those which contain the glucoside4 ,injury to the tissues1 germination processes1 and perhaps other physiological activities of the cells1 result in bringing the enzyme in contact with the glucoside and the hydrolysis of the latter takes place4 ,a large number of such enzymes have been found in plants1 many of which hydrolyze only a single glucoside4 ,however1 two enzymes1 namely1 the emulsin of almond kernels1 and myrosin of black mustard seeds1 each hydrolyze a considerable number of glucosides4 ,in general1 emulsin will aid in the hydrolysis of any glucoside which is a derivative of beta-glucose1 and myrosin will help to split up any sulfur-containing glucoside4 ,glucosides which are derivatives of rhamnose require a special enzyme1 known as rhamnase1 for their hydrolysis4 ,the following reactions for the hydrolysis of arbutin and of amygdalin are typical of this action1 and will serve to illustrate the general structure of these compounds3 ------,o------- ,,ch#b,,oh,,choh,,ch,,choh,,choh,,ch,o,c #f;,h#d,,oh ,h#b,o ,arbutin ,c#f;,h#ab,o#f ,,hoc#f;,h#d,,oh ,glucose ,hydroquinone ,c#f;,h#e 7a7 ,c#f;,h#aa,o#e,o,c#f;,h#aj,o#d,o,,ch ,h#b,o ,amygdalin ,,cn ,c#f;,h#e ,c#f;,h#aa,o#e,o,,ch ,c#f;,h#ab,o#f ,mandelo-nitrile ,glucose glucoside ,,cn ,c#f;,h#e 7b7 ,c#f;,h#aa,o#e,o,,ch,h#b,o ,c#f;,h#e;,,choh,,cn,c#f;,h#ab,o#f ,mandelo-nitrile ,mandelo-nitrile ,glucose glucoside ,,cn 7c7 ,c#f;,h#e;,,choh,,cn ,h#b,o ,c#f;,h#e;,,cho ,,hcn ,mandelo-nitrile ,benzaldehyde ,hydrocyanic acid ,,general ,,properties ,,of ,,glucosides ,as a rule1 glucosides are easily soluble in water4 ,they are generally extracted from plant tissues by digestion with water or alcohol4 ,in most cases1 the enzyme which is present in other cells of the same tissue must be killed by heating the material1 in a moist condition1 to the temperature of boiling water1 before the extraction is begun1 as otherwise the glucoside will be hydrolyzed as rapidly as it is extracted from its parent cell4 ,maceration or otherwise bruising the tissue1 after the enzyme has been destroyed1 facilitates the extraction4 ,the glucosides1 after extraction and purification by recrystallization1 are generally colorless1 crystalline solids1 having a bitter taste and levorotatory optical activity4 ,this latter property is remarkable1 as most of them are compounds of the strongly dextrorotatory d-glucose4 ,many of the natural glucosides have marked therapeutic properties and are largely used as medicines2 others are the mother-substances for brilliant dyes2 for example1 indican1 from which indigo is obtained1 and the alizarin glucosides4 ,several hundred different glucosides have been isolated from plant tissues1 and their properties described1 and this number is being added to constantly1 as the methods of isolation and study are improved4 ,they may be classified into groups1 according to the nature of the organic compound other than sugars which they yield when hydrolyzed4 ,the following descriptions of the occurrence1 constitution1 products of hydrolysis1 and special properties of typical members of each of the several different classes of glucosides will serve to illustrate their general relationship to plant growth4 ,,the ,,phenol ,,glucosides ,arbutin1 ,c#ab;,h#af,o#g1 is obtained from the leaves of the bear berry 7,arctostaphylos uva-ursi71 a small evergreen shrub4 ,when hydrolyzed by mineral acids or emulsin1 it yields glucose and hydroquinone4 ,c#ab;,h#af,o#g;,h#b,o ,c#f;,h#ab,o#f;,c#f;,h#d7,,oh7#b4 ,hydroquinone has strongly antiseptic properties4 ,arbutin is both an antiseptic and a diuretic1 and is used in medicine4 ,phloridzin1 ,c#ba;,h#bd,o#aj1 is found in the bark of apple1 pear1 cherry1 plum1 and similar trees4 ,mineral acids 7but not emulsin7 hydrolyze it to glucose and phloretin 7,c#ae;,h#ad,o#e71 according to the equation ,,ch#c ,c#ba;,h#bd,o#aj ,h#b,o ,c#f;,h#ab,o#f 7,,oh7#c;,c#f;,h#b;,,co,,ch,c#f;,h#d,,oh 4 ,it is used in medicine as a remedy for malaria1 having marked anti-periodic properties4 ,glycyphyllin1 ,c#ba;,h#bd,o#i1 found in leaves of ,smilax1 yields rhamnose and phloretin1 when hydrolyzed4 ,iridin1 ,c#bd;,h#bf,o#ac 7glucose and irigenin71 found in rootstocks of ,iris1 is used in medicine as a cathartic and diuretic4 ,baptisin1 ,c#bf;,h#cb,o#adi;,h#b,o 7two rhamnose and baptigenin71 found in roots of wild indigo 7,baptisia71 has strong purgative properties4 ,hesperidin1 ,c#ej;,h#fj,o#bg 7one rhamnosetwo glucosehesperitin71 is found in the pulp of lemons and oranges4 ,the characteristic phenol group which is present in these glucosides has the following structural formula1 in each case1 the ,x indicating the ,h atom which is replaced by the sugar molecule to form the glucoside3 ,phloretin _/ _/ _/ ----,c----,,ch------_/ ,,ox ,,ho ,,oh ,o ,,ch#c ,,oh _/ _/ _/ _/ ,irigenin ,o _/ -,,ch#b-;,c-,o--_/ _/ _/ ,o,,ch#c _/ ,o- ,,ox ,,ch#c,o- _/ _/ _/ ,o ,,ch#c ,hesperitin _/ _/ _/ _/ ,,ho -,,ch,,ch-,c- ,,ox ,,ch#c,o _/ ,o _/ _/ _/ ,,the ,,alcohol ,,glucosides ,salicin1 ,c#ac;,h#ah,o#g 7glucosesaligenin1 or o-oxy benzyl alcohol7 is found in the bark1 leaves1 and flowers of most species of willow1 the proportion present depending upon the season of the year1 and the sex of the tree4 ,it is used as a remedy against fevers and rheumatism1 causing less digestive disturbances than the salicylic acid which is the oxidation product of saligenin and which is sometimes used as a remedy for rheumatism4 ,coniferin1 ,c#af;,h#bb,o#h 7glucose and coniferyl alcohol71 is found in the bark of fir trees4 ,the coniferyl alcohol obtained from coniferin by hydrolysis can be easily oxidized to vanillin1 and is1 therefore1 the source for the artificial flavoring extract used as a substitute for the true extract of the vanilla bean4 ,populin1 ,c#bj;,h#bb,o#h 7glucosesaligeninbenzoic acid71 found in the bark of poplar trees1 is used in medicine as an antipyretic4 ,it can be hydrolyzed1 by a special enzyme1 into salicin and benzoic acid4 ,the structure of the two typical closed-ring alcohols which are present in these glucosides is indicated by the following formulas2 ,coniferyl alcohol ,saligenin ,,ch,,ch,,ch#b,,oh _/ _/ _/ _/ ,,ch#b,,oh ,,ox ,,och#c _/ _/ _/ _/ ,,ox ,,the ,,aldehyde ,,glucosides ,salinigrin1 ,c#ac;,h#af,o#g 7glucose and m-oxy benzaldehyde71 is found in the bark of one species of willow 7,salix discolor74 ,its isomer1 known as helicin 7glucose and o-oxy benzaldehyde1 or salicylic aldehyde71 does not occur naturally in any plant1 but is easily produced artificially by the gentle oxidation of salicin4 ,their relationships are shown on the following formulas2 ,salicin ,helicin ,salinigrin _/ _/ _/ _/ _/ _/ ,,ch#b,,oh ,,cho ,,cho ,,ox ,,ox _/ _/ _/ _/ _/ _/ ,,ox ,amygdalin1 also contains a benzaldehyde group1 but there is linked with it a hydrocyanic acid group2 hence1 this glucoside is usually classed with the cyanophoric glucosides 7see page #hf74 ,,the ,,acid ,,glucosides ,the most common example of this group is gaultherin1 ,c#ad;,h#ah,o#h1 which is found in the bark of the black birch and is a combination of glucose with methyl salicylate4 ,both the glucoside itself and the methyl salicylate 7oil of wintergreen7 which is derived from it are used as remedies for rheumatism4 ,jalapin1 ,c#dd;,h#ef,o#af 7glucose and jalapinic acid71 and convolvulin1 ,c#ed;,h#if,o#bg 7glucoserhodeoseconvolvulinic acid71 are glucosides of very complex organic acids1 found in jalap resin1 which are used in medicine as cathartics or purgatives4 ,,the ,,oxy-,,cumarin ,,glucosides ,cumarin itself is widely distributed in plants4 ,no glucoside containing cumarin as such has yet been isolated2 but several glucosides of its oxy-derivatives are known4 ,the following are common ones3 ,skimmin1 ,c#ae;,h#af,o#h 7glucose and skimmetin71 is found in ,skimmia japonica2 sculin1 ,c#ae;,h#af,o#i 7glucose and sculetin71 is found in the bark of the horse-chestnut1 sculus hippocastanum1 and its isomer1 daphnin 7glucose and daphnetin71 in several species of ,daphne2 and fraxin1 ,c#af;,h#ah,o#aj 7glucose and fraxetin71 is found in the bark of several species of ash4 ,the structural arrangement of the oxy-cumarin groups which are found in these glucosides is shown in the following formulas4 ,it is not known to which ,,oh group the sugar is attached1 in each case4 ,skimmetin sculetin ,,ch,,ch,,co ,,ch,,ch,,co _/ _/ _/ ,o _/ ,o ,,ho _/ _/ _/ _/ ,,oh ,,oh ,daphnetin ,fraxetin ,,ch,,ch,,co ,,ch,,ch,,co _/ _/ _/ ,o _/ ,o ,,ho ,,oh ,,ho _/ _/ _/ _/ ,,oh ,,och#c ,scopolin1 ,c#bb;,h#bh,o#ad1 found in ,scopolia japonica1 contains two glucose molecules united to a monomethyl ether of sculin2 while limettin1 found in certain citrus trees1 is the dimethyl ether of sculin4 ,,the ,,pigment ,,glucosides ,many1 if not all1 of the red1 yellow1 violet1 and blue pigments of plants either exist as1 or are derived from1 glucosides4 ,these are of three types3 the madder1 or alizarin1 reds are derivatives of various oxy-anthraquinones2 most of the soluble yellow pigments are glucosides derived from flavones or xanthones2 and the soluble red1 blue1 and violet pigments of the cell-sap of plants are mostly anthocyan derivatives4 ,the four basic groups1 or nuclei1 which are present in these different types of compounds are complex groups consisting essentially of two benzene rings linked together through a third ring in which there are either two oxygen atoms in the ring1 or one oxygen in the ring and a second attached to the opposite carbon in the 7,c,o7 arrangement1 as shown by the following diagrammatic formulas3 ,xanthone ,anthraquinone ,o ,o #a #a #a' _/ ,c _/ _/ ,c _/ _/ _/ _/ _/ _/ _/ #b #b #b' #c #c #c' _/ _/ _/ _/ _/ _/ _/ ,o _/ _/ ,c _/ #d #d #d' ,o ,flavone ,anthocyan #a #a _/ ,o #e'd' _/ ,o #e'd' _/ _/ _/ _/ _/ _/ #b _/#c' #b _/#c' #c #e #a' #b' #c #f #a' #b' _/ _/ _/ _/ _/ ,c _/ #e #d #d ,o ,the red dyes which were formerly obtained from madder1 the powdered roots of ,rubia tinctoria1 but are now almost wholly artificially synthetized1 consist of at least four different glucosides1 the organic group of which1 in each case1 is an hydroxy-derivative of anthraquinone4 ,the most important of these is ruberythric acid1 composed of two molecules of glucose linked with one of alizarin 7#a1b1 dioxyanthraquinone74 ,xanthopurpurin contains #a1c1 dioxyanthraquinone1 which is isomeric with alizarin2 and rubiadin is a monomethyl 7the ,,ch#c being in the #d position71 derivative of this compound4 ,purpurin is a glucoside of #a1b1d1 trioxyanthraquinone4 ,the soluble yellow pigments are generally glucosides of hydroxy-derivatives of xanthone or flavone1 known as oxyxanthones or oxyflavones4 ,the sugars which are united to these nuclei vary greatly1 so that there are a great variety of yellow1 white1 or colorless flavone or xanthone pigment compounds4 ,these compounds are almost universally present in plants4 ,for example1 one typical set of examinations of the wood1 bark1 leaves1 and flowers of over #bdj different species of tropical plants showed that flavone derivatives were present in every sample which was tested1 the pigments being usually located in the powdery coating of the epidermis of the tissues4 ,the following typical examples will serve to illustrate the composition and properties of the glucosides of this type4 ,quercitrin1 ,c#ba;,h#bj,o#aa1 is found in oak bark1 in the leaves of horse-chestnut1 and in many other plants1 often associated with other pigments4 ,it is a brilliant yellow crystalline powder4 ,industrially1 it ranks next to indigo and alizarin in importance as a natural dye stuff4 ,it is a glucoside of rhamnose with #a1c1c'1d'1 tetraoxyflavonol 7i4e41 the flavone nucleus with five ,,oh groups replacing the hydrogens in the #a1 #c1 #e1 #c'1 and #d' positions74 ,quercetin1 ,c#ae;,h#aj,o#g1 which is the tetraoxyflavonol itself1 without any sugar in combination with it1 is found in the leaves of several species of tropical plants and in the bark of others4 ,isoquercitrin1 ,c#ba;,h#bj,o#ab1 is derived from the same flavone1 but contains glucose instead of rhamnose1 as the sugar constituent of the glucoside4 ,apiin1 ,c#bf;,h#bj,o#i1 the yellow glucoside found in the leaves of parsley1 celery1 etc41 contains apiose 7a pentose sugar of very unusual structure1 represented by the formula1 ,,ch#b,,oh ,,coh,,choh,,cho71 and apigenin1 which is a #a1c1d'1trioxyflavone4 _/ ,,ch#b,,oh ,xanthorhamnin1 ,c#cd;,h#db,o#bj1 is a very complex glucoside containing two rhamnose and one galactose groups1 united with rhamnetin1 which is quercitin with the ,h of the ,,oh in either the #a1 or #c1 position replaced by a methyl group4 ,there are several similar pigments which differ from xanthorhamnin only in the number or position of the methoxy groups 7i4e41 the ,,oh groups with a ,,ch#c replacing the ,h71 or in the nature of the sugar which is present in the compound4 ,rhamnetin itself is found in the fruits of certain species of ,rhamnus1 and is used in dyeing cotton4 ,the structural arrangement of the characteristic groups of these flavone pigments will be dealt with more in detail in the chapter dealing with ,pigments 7,chapter ,,viii74 ,the best-known yellow pigment which is a xanthone derivative is euxanthic acid1 known as ,indian yellow1 which is a paired compound of glucuronic acid 7see page #db7 and euxanthone4 ,the latter is a #b1 #c'1 dioxyxanthone4 ,the pigment is found in the urine of cattle which have been fed on mango leaves4 ,the soluble red1 blue1 and violet pigments are glucosides of various hydroxy-derivatives of the anthocyan nucleus4 ,their constitution and properties will be discussed in detail in the chapter dealing with the ,pigments4 ,these compounds are isomeric with similar flavone and xanthone derivatives1 and the transition from one color to the other in plants takes place very easily under the action of oxidizing or reducing enzymes4 ,this accounts for the change of reds and blues to yellows and browns1 and vice versa1 under changing temperature conditions4 ,the following red or blue plant pigments1 which are anthocyan glucosides1 have been isolated and studied 7for the structural arrangement of the characteristic groups1 see pages #aaf73 from cornflower and roses1 cyanin1 ,c#bh;,h#ca,o#af;,cl 7#b molecules glucose cyanidin72 from cranberries1 idain1 ,c#ba;,h#ba,o#aj;,cl 7galactose cyanidin72 from geranium1 pelargonin1 ,c#bg;,h#cj,o#ae;,cl 7#b molecules glucose pelargonidin72 from pony1 ponin1 ,c#bh;,h#cc,o#af;,cl 7#b molecules glucose ponidin1 a monomethyl cyanidin72 from blue grapes1 oenin1 ,c#bc;,h#be,o#ab;,cl 7glucose oenidin72 from whortle berry1 myrtillin1 ,c#bb;,h#bc,o#ab;,cl 7glucose myrtillidin72 from larkspur1 delphinin1 ,c#da;,h#ci,o#ba;,cl 7#b molecules glucose #b molecules p-oxybenzoic acid delphinidin72 and from mallow1 malvin1 ,c#bi;,h#ce,o#ag;,cl 7#b molecules glucose malvidin74 ,the blue dye1 indigo1 is derived from a glucoside of an entirely different type1 known as indican4 ,indican is readily extracted from the leaves of various species of indigo plants4 ,when hydrolyzed1 it yields glucose and indoxyl 7colorless74 ,indoxyl is easily oxidized to indigotin 7the deep blue dye known as indigo74 ,the equations illustrating these changes are as follows3 7a7 ,c#ad;,h#ag,o#f,n ,h#b,o ,c#f;,h#ab,o#f ,c#h;,h#g,,on ,indican ,glucose ,indoxyl 7b7 #b;,c#h;,h#g,,on ,o#b ,c#af;,h#aj,o#b,n #b;,h#b,o ,indoxyl ,indigotin ,the structural relationships of indoxyl and indigotin may be illustrated by the following formulas3 ,o ,o _/ _/ _/ _/ ,,coh _/ ,c ,c_/ ,c-,h ,c,c _/ _/ _/ _/ _/ _/ _/ ,n _/ ,n ,n _/ ,h ,h ,h ,indoxyl ,indigotin ,natural indigo dye is prepared by fermentation of indigo leaves1 the decay of the cell-walls liberating the enzymes in the tissues1 which bring about the chemical changes illustrated in the above equations4 ,,the ,,cyanophore ,,glucosides ,several glucosides which yield hydrocyanic acid as one of the products of their hydrolysis are of common occurrence in plants4 ,these are generally spoken of as the cyanogenetic glucosides2 but as they do not actually produce cyanogen compounds1 but only liberate them when hydrolyzed1 the recently suggested term cyanophore undoubtedly more correctly indicates their properties4 ,the best known and most widely distributed of these is amygdalin4 ,amygdalin was first discovered in #ahcj1 and was one of the first substances to be recognized as a glucoside4 ,it is found in large quantities in bitter almonds and in the kernels of apricots1 peaches1 and plums2 also in the seeds of apples1 etc41 in fact in practically all the seeds of plants of the ,rose family4 ,it is the mother substance for oil of bitter almonds1 which is widely used as a flavoring extract4 ,amygdalin has been the object of very extensive studies1 and even yet the exact nature of the linkage between its constituent groups is not certainly known4 ,when completely hydrolyzed1 it yields two molecules of glucose and one each of benzaldehyde and hydrocyanic acid4 ,recent studies indicate that the two sugar molecules are separately united to the other constituents1 rather than united with each other in the disaccharide relationship4 ,in other words1 amygdalin is a true glucoside rather than a maltoside4 ,this is indicated by the fact that when submitted to the action of all known hydrolyzing agents which affect it1 it has never been found to yield maltose as one of the products of hydrolysis4 ,furthermore1 the rate of hydrolysis of amygdalin is not affected by the presence of maltose2 and the segregation of the two glucose molecules is accomplished by enzymes other than maltase1 which is the only enzyme which is known to break up a maltose molecule4 ,since the exact nature of the linkage is not known1 it is customary and convenient to indicate the unit groups as linked together in the following order3 ,c#f;,h#aa,o#e-,o-,c#f;,h#aj,o#d-,o-,c#f ;,h#e;,,ch-,ctrb,n 7#a7 7#b7 7#c77d7 ,a study of the hydrolysis reactions of amygdalin shows that there are three different linkages in the molecule which may be broken by the simple interpolation of a single molecule of water and a fourth which may be split by a different type of hydrolysis1 namely1 the ,ctrb,n linkage4 ,these are indicated by the numbers below the corresponding portion of the formula above4 ,most hydrolyzing agents break the molecule first at 7#a71 yielding one molecule of glucose and one of mandelo nitrile glucoside 7see page #gg74 ,the next step usually breaks the latter at the point indicated by 7#b71 yielding glucose and benzaldehyde cyanhydrin1 or mandelo nitrile4 ,the latter in turn breaks down at 7#c7 into benzaldehyde and ,,hcn4 ,but when amygdalin is boiled with concentrated hydrochloric acid1 the first change is the splitting off at 7#d7 of the nitrogen in the form of ammonia and the consequent conversion of the ,,cn group into a ,,cooh group1 producing amygdalinic acid4 ,on further hydrolysis1 this breaks up in the same order as before4 ,similarly1 it is possible to convert mandelo nitrile into mandelic acid by splitting off the nitrogen to form a ,,cooh group1 instead of splitting off the ,,hcn group leaving benzaldehyde4 ,the mandelo nitrile glucoside contains an asymmetric carbon atom which is wholly outside its glucose group1 thus ,c#f;,h#aj,o#e-,o-,c#f;,h#e;,,ch,,cn4 ,hence1 it may exist in dextro1 levo1 and racemic forms4 ,in the amygdalin molecule1 it exists in the dextro form1 which has been named prunasin4 ,the levo form1 known as sambunigrin1 has been obtained by hydrolysis of a compound isomeric with amygdalin1 whose composition has not been definitely worked out2 while the racemic form1 known as prulaurasin1 has been prepared from isoamygdalin1 by the action of alkalies4 ,hence1 all the possible compounds indicated by the presence of the asymmetric carbon have been found and identified4 ,the crude enzyme preparation which is obtained from almond seeds1 known as emulsin1 contains two enzymes1 amygdalase1 which breaks the amygdalin molecule at linkage 7#a71 and prunase1 which breaks it at 7#b74 ,the action of amygdalase must always precede that of prunase4 ,in other words1 it is never possible to break off a disaccharide sugar from the molecule1 either by the action of prunase alone1 or by means of any other hydrolytic agent4 ,dhurrin1 ,c#ad;,h#ag,o#g,n1 is another glucoside of fairly general occurrence in plants1 which yields ,,hcn as one of the products of its hydrolysis4 ,it is found in the leaves and stems of several species of millets and sorghums4 ,frequent cases of poisoning of cattle from eating of these plants as forage have been reported4 ,on hydrolysis1 dhurrin first yields glucose and paraoxy-mandelo nitrile2 the latter then breaks down into paraoxy-benzaldehyde and ,,hcn4 ,vicianin1 ,c#ai;,h#be,o#aj,n1 is a cyanophoric glucoside1 found in the seeds of wild vetch1 etc4 ,on hydrolysis1 it yields glucose1 arabinose1 and d-mandelo nitrile4 ,it is1 therefore1 similar to amygdalin1 except that one glucose molecule is replaced by arabinose4 ,,the ,,mustard ,,oil ,,glucosides ,the seeds of several species of plants of the ,crucifer or mustard family contain glucosides in which the other characteristic group is a sulfur-containing compound4 ,these glucosides yield mustard oils when they are hydrolyzed by the enzyme myrosin1 which accompanies them in the plant4 ,the following glucosides1 found in the seeds of white and black mustard1 are the best-known representatives of this class4 ,sinigrin1 ,c#aj;,h#af,o#i,,ns#b,k1 found in black mustard seeds1 when hydrolyzed yields glucose1 acid potassium sulfate1 and allyl isosulfocyanide 7mustard oil71 as indicated by the equation4 ,c#aj;,h#af,o#i,,ns#b,k,h#b,o ,c#f;,h#ab,o#f ,c#c;,h#e,ntrb,c,s,,khso#d4 ,the acid potassium sulfate group separates first and most readily1 leaving a compound known as merosinigrin1 for which the following formula has been suggested3 -----,o------ ,,ch#b,,oh,,choh,,ch,,choh,,ch,,ch ,o ,s _/ _/ ,c,ntrb,c#c;,h#e ,this compound usually breaks down into glucose and mustard oil2 but by special treatment it is possible to obtain from it thioglucose1 ,c#f;,h#aa,o#e,,sh4 ,this indicates that in the original glucoside the glucose is linked with the mustard oil through the sulfur atom4 ,sinalbin1 ,c#cj;,h#db,o#ae,n#b,s#b1 from white mustard seeds1 when hydrolyzed by myrosin1 yields glucose1 sinalbin mustard oil 7a paraoxybenzyl derivative of allyl isosulfocyanide7 and sinapin acid sulfate2 according to the equation ,c#cj;,h#db,o#ae,n#b,s#b;,h#b,o ,c#f;,h#ab,o#f;,c#g;,h#g,o,,ncs ,sinalbin ,glucose ,sinalbin mustard oil ,c#af;,h#bd,o#e,n,,hso#d4 ,sinapin acid sulfate ,the sinalbin mustard oil may be represented by the formula _/ ,,ho-,,ch ,,ch-,,ch#b,,ncs4 ,hydrolysis of the sinapin acid sulfate converts _/ it into sinapinic acid1 ,c#f;,h#b,,oh7,,och#c7b;,,ch,,ch,,cooh1 choline1 ,n7,,ch#c7d;,c#b;,h#d,,oh 7see page #aeb71 and ,h#b,,so#d4 ,it is1 therefore1 a very complex glucoside4 ,,tee ,,digitalis ,,glucosides ,the five1 or more1 glucosides which are present in the leaves and seeds of the foxglove 7,digitalis purpurea7 have been extensively studied1 as they are the active principles in the various digitalis extracts which are used in medicine as a heart stimulant4 ,digitoxin1 ,c#cd;,h#ed,o#aa1 which is the most active of these glucosides in its physiological effects1 when hydrolyzed1 yields digitoxigenin1 ,c#bb;,h#cb,o#d1 and a sugar having the formula ,c#f;,h#ab,o#d1 which is known as digitoxose and is supposed to be a dimethyl tetrose4 ,digitalin1 ,c#ce;,h#ef,o#ad1 is also strongly active4 ,when hydrolyzed1 it yields digitaligenin1 ,c#bb;,h#aj,o#c1 glucose1 and digitoxose4 ,digitonin1 ,c#ed;,h#ib,o#bh1 constitutes about one-half of the total glucosides in the extract which is obtained from most species of the digitalis plants4 ,it is much less active than the others4 ,it is a saponin 7see page #ij7 in type4 ,on hydrolysis1 it yields #b molecules of glucose1 #b of galactose1 and one of digitogenin4 ,gitonin1 ,c#di;,h#hj,o#bc1 containing #c molecules of galactose1 one of a pentose sugar1 and one of gitogenin2 and gitalin1 ,c#bh;,h#dh,o#aj1 containing digitoxose and gitaligenin1 have also been isolated from digitalis extracts4 ,the structural arrangement of the characteristic groups in these glucosides has not yet been definitely worked out4 ,cymarin1 the active principle of ,indian hemp 7,apocynum cannabinum71 is similar in type to the digitalis glucosides4 ,when hydrolyzed1 it yields a sugar known as cymarose1 ,c#g;,h#ad,o#g1 which seems to be a monomethyl derivative of digitoxose1 and cymarigenin1 ,c#bc;,h#cj,o#e1 a compound which is either identical or isomeric with the organic residue obtained from other members of this group4 ,,the ,,saponins ,the saponins constitute a group of glucosides which are widely distributed in plants1 whose properties have been known since early ,grecian times4 ,they have been found in over four hundred different species of plants1 belonging to more than forty different orders4 ,the most characteristic property of saponins is that they form colloidal solutions in water which produce a soapy foam when agitated1 and are peculiarly toxic1 especially to frogs and fishes4 ,in dry form1 they have a very bitter1 acrid taste1 and their dust is very irritating to the mucous membranes of the eye1 nose1 and throat4 ,on hydrolysis1 the saponins yield a variety of sugars1--glucose1 galactose1 arabinose1 and sometimes fructose1 and even other pentoses--and a group of physiologically active substances1 known as sapogenins4 ,the more toxic forms of these glucosides are known as sapotoxins4 ,the chemical composition of the saponins varies so widely that it is scarcely possible to cite typical individuals4 ,sarsaparilla1 the dried root of smilax plants1 contains a mixture of non-poisonous saponins1 from which at least four individual glucosides have been isolated and studied4 ,corn cockle contains a highly poisonous sapotoxin which1 on hydrolysis1 yields four molecules of a sugar and one of sapogenin1 ,c#aj;,h#af,o#b4 ,other sapotoxins are obtained from the roots of soapwort and from several species of ,gypsophila4 ,digitonin and digito-saponin are glucosides of this type which are found in the extracts from various species of ,digitalis4 ,,the ,,physiological ,,uses ,,of ,,glucosides ,it is scarcely conceivable that substances which vary so widely in composition as do the different types of glucosides can possibly all have similar physiological uses in plants4 ,the cyanophoric glucosides1 the pigment glucosides1 the mustard oil glucosides1 and the saponins1 for example1 can hardly be assumed to have the same definite relationships to the metabolism and growth of the plant4 ,to be sure1 they are alike in that they all contain one or more sugar molecules1 and it is probable that the carbohydrates which are held in this form may serve as reserve food material1 especially when the glucoside is stored in the seeds2 but it is obvious that the simpler and more normal form of such stored food is that of the polysaccharides which contain no other groups than those of the carbohydrates4 ,it seems much more probable that the physiological uses of glucosides depend upon their ability to form temporarily inactive pairs with a great variety of different types of organic compounds which are elaborated by plants for a variety of purposes4 ,it has been noted that in most1 if not all1 instances1 the glucosides are accompanied in the same plant tissue 7although in separate cells7 by the appropriate enzyme to bring about their hydrolysis and so set free both the sugar and the other characteristic component whenever the conditions are such as to permit the enzyme to come in contact with the glucoside4 ,this occurs whenever the tissue is injured by wound or disease1 and also during the germination process4 ,injury to the plant tissue seems to be a necessary preliminary to the functioning of the active components of the glucoside1 except in the case of the seeds4 ,this leads naturally to the supposition that at least some of these glucosides are protective or curative agents in the plant tissues4 ,this conception is further supported by the facts that many of the non-sugar components of glucosides are bactericidal in character and that the glucosides commonly occur in parts of the plant organism which are otherwise best suited to serve as media for the growth of bacteria4 ,thus1 it is known that in the almond1 as soon as the tissue is punctured1 amygdalin is hydrolyzed and all bacterial action is inhibited4 ,similarly1 the almost universal presence of glucosides containing bactericidal constituents in the bark of trees insures natural antiseptic conditions for all wounds of the outer surfaces of the stem of the plant4 ,in fact1 it is easily conceivable that at least one of the reasons for the failure of the processes of decay of plant tissues to set in until after the death of the cells1 is that during living1 respiratory activity these antiseptic glucosides are so generally present in the tissues4 ,further1 it has been fairly well established that the chromogens1 or mother-substances of the pigments1 which1 under the influence of oxidase enzymes1 serve to regulate the respiratory activities of the plant are essentially glucosidic in character4 ,this1 and other1 functions of the pigments1 most of which are glucosides1 will be discussed at some length in the chapter dealing with the ,pigments 7,chapter ,,viii74 ,many gaseous ansthetics are known to have a marked effect in stimulating plant growth4 ,in a number of cases1 it has been shown that the contact of plant tissues with these ansthetics brings about an interaction of the enzyme and glucoside which are present in the tissue1 with the consequent hydrolysis of the latter1 setting free its characteristic components4 ,this observation has led to the supposition that many of the organic constituents of glucosides are definite plant stimulants1 to which the name hormones has been applied4 ,there is considerable experimental evidence to support this conception that glucosides may be the source of stimulating hormone substances1 which will be discussed more in detail in the chapter dealing with these plant stimulants 7,chapter ,,xvii74 ,glucosides may also serve as the mechanism for putting out of action of harmful products which may appear in the tissues as the result of abnormal conditions4 ,these harmful substances may be rendered soluble by combination with sugars and so transposed by osmosis to some other part of the plant4 ,the abnormally large percentages of glucosides which are present in certain species of plants during unfavorable climatic conditions lends some support to this view4 ,finally1 it may be assumed that easily oxidizable substances1 such as aldehydes and acids1 are possibly protected against too rapid1 or premature1 oxidation by being transformed into glucosides4 ,in general1 it may be said that the glucosides seem to serve as the regulatory1 protective1 and sanatory agencies of the plant mechanism4 ,,biological ,,significance ,,of ,,glucosides ,the bitter taste of glucosides and their almost universal presence in the bark of plants undoubtedly helps to prevent the destructive gnawing of the bark by animals4 ,glucosides having either a strong bitter taste1 or pronouncedly poisonous properties1 likewise undoubtedly serve to protect such important organs of plants as the seeds and fruits from being prematurely eaten by birds and animals4 ,the common disappearance of these bitter substances as the seed or fruit ripens adds to the attractiveness of the material for food for animals at the proper stage of ripeness to provide for wider distribution of the seeds for further propagation4 ,further1 the very general occurrence of these protective glucosides in many of the vegetative parts of plants during the early stages of growth1 followed by their disappearance after the seeds of the plant have been formed1 certainly serves to protect these plants from consumption as forage by animals before they have been able to develop their reproductive bodies4 ,the lack of palatability1 and even the production of digestive disorders resulting from the eating of unripe fruit may be due1 in part at least1 to the presence of protective glucosides in unripe fruits and vegetables4 ,on the other hand1 the almost universal presence of the brilliant pigment glucosides in the external parts of flowers undoubtedly serves to attract the insects which are biologically adapted to provide for the transportation of pollen from one blossom to another and so to insure the cross-fertilization which is so important in maintaining the vigor of many species of plants4 ,it is apparent that this important group of compounds1 with its exceedingly varied and complex constituent groups1 may play a variety of significant rles in plant growth4 ,,references4 ,,armstrong1 ,e4 ,f4--,the ,simple ,carbohydrates and ,glucosides1 #bci pages1 ,monographs on ,biochemistry1 ,london1 #aiai 7#c;d ed474 ,,van ,,rijn1 ,j4 ,j4 ,l4--,die ,glykoside1 #eaa pages1 ,berlin1 #aijj4 ,,chapter ,,vii ,,tannins ,using the term in its general application to a group of substances having similar chemical and physical properties1 rather than in its limited application to a single definite chemical compound known commercially as tannin1 the tannins are a special group of plant substances1 mostly glucosides1 which have the following characteristic properties4 ,first1 they are non-crystalline#d substances1 which form colloidal solutions with water1 which have an acid reaction and a sharp astringent taste4 ,second1 they form insoluble compounds with gelatine-containing tissues1 as shown by the conversion of hide into leather4 ,third1 they form soluble1 dark-blue or greenish-black compounds with ferric salts1 the common inks4 ,fourth1 they are precipitated from their solutions by many metallic salts1 such as lead acetate1 stannous chloride1 potassium bichromate1 etc4 ,fifth1 they precipitate out of solution albumins1 alkaloids1 and basic organic coloring matters4 ,finally1 most tannins1 in alkaline solutions1 absorb oxygen from the air and become dark brown or black in color4 ,,footnotes3 #d ,the needle-like forms1 in which commercial tannin comes on the market1 are not true crystals1 but are broken fragments of the threads into which the colloidal tannin is spun-out from the syrupy extracts of nutgalls1 etc4 ,,occurrence ,tannins occur widely distributed in plants4 ,practically every group of plants1 from the fungi up to the flowering plants1 contains many species of plants which show tannin in some of their tissues4 ,among the higher plants1 tannins occur in a great variety of organs4 ,thus1 they are found in the roots of several species of tropical plants2 in the sterns1 both bark and wood1 of oaks1 pines1 hemlock1 etc42 in the leaves of sumac1 rhododendron1 etc42 in many fruits1 especially in the green1 or immature1 stages2 and in the seeds of several species1 either before or after germination4 ,tannins are also found in certain special structures1 such as gland cells1 cells of the pulvini1 laticiferous tissues1 etc4 ,further1 they are especially abundant in the pathological growths known as galls1 which often contain from #dj to #ge per cent of tannin and constitute the most important commercial source for these materials4 ,the principal commercial sources of tannin1 which is used in the manufacture of inks1 in the tanning of leather1 in certain dyeing operations1 etc41 are oak-galls1 the bark and wood of oak1 hemlock1 acacia1 and eucalyptus1 the bark of the mangrove1 the roots of canaigre1 and the leaves of several species of sumac4 ,,chemical ,,constitution ,tannins are either free phenol-acids or1 more commonly1 glucosides of these acids4 ,common tannin1 when hydrolyzed1 yields from #g to #h per cent of glucose1 which indicates that it is a penta-acid ester of glucose1 i4e41 each glucose molecule has five acid groups attached to it4 ,the formula for such a tannin is1 therefore1 as follows1 ------,o------- ,,ch#b,,or,,chor,,ch,,chor,,chor,,chor in which the ,r represents a complex phenol-acid like tannic acid1 or digallic acid4 ,these acids are derivatives of the common phenols1 whose constitution will be brought to mind by the following series of formulas3 ,ordinary phenol ,pyrocatechol ,resorcinol ,hydroquinone _/ _/ _/ _/ _/ _/ _/ _/ ,,oh ,,oh ,,oh ,,oh ,,oh ,,ho _/ _/ _/ _/ _/ _/ _/ _/ ,,oh ,pyrogallol ,oxyhydroquinone ,phloroglucinol ,,oh ,,oh ,,oh _/ _/ _/ _/ _/ _/ ,,oh ,,oh ,,oh ,,ho ,,oh _/ _/ _/ _/ _/ _/ ,,oh ,these phenols themselves do not occur as constituents of tannins1 although they are often found in other glucosides1 gums1 etc4 ,the following mono-carboxyl acid derivatives of these phenols are1 however1 found both free and in glucoside formation as constituents of many of the common tannins4 ,pyrocatechuic acid1 derived from pyrocatechol1 represented by the formula1 ,,oh _/ _/ ,,oh _/ _/ ,,cooh ,gallic acid1 derived from pyrogallol1 and represented by the formula1 ,,oh _/ _/ ,,ho ,,ho ,,cooh _/ _/ ,,cooh ,in most of the common tannins1 however1 the characteristic acids are oxy-derivatives of the so-called tannon group1 represented by the formula1 ,c#f;,h#e;,,co,o,c#f;,h#e4 ,for example1 digallic acid1 which is a constituent of many common tannins1 is a tetra-oxy1 mono-carboxyl derivative of this group1 having the structural formula1 _/ _/ _/ _/ ,,ho --,,co,o-- ,,cooh ,,ho ,,ho _/ _/ _/ _/ ,,oh ,,oh ,ellagic acid1 which is an hydrolysis product of many of the pyrogallol tannins 7see below7 and which produces the characteristic bloom on leather tanned by this type of tannins1 has the following formula1 -----,,co,o----- _/ _/ _/ _/ ,,ho ,,oh ,,ho ,,co,o ,,oh _/ _/ _/ _/ ,,classes ,,of ,,tannins ,the tannins are divided into two general classes1 known respectively as the pyrogallol tannins and the catechol tannins4 ,these differ in their characteristic reactions as follows3 ,pyrogallol variety ,catechol variety ,ferric salts ,dark blue ,greenish black ,bromine water ,no precipitate ,yellow or brown precipitate ,leather ,produce a bloom ,no bloom ,conc4 sulfuric acid ,yellow or brown ,red or pink ,lime water ,gray or blue ppte4 ,pink to brown ppte4 ,pyrogallol tannins contain approximately #eb per cent of carbon2 while the catechol tannins usually contain #ei per cent to #fj per cent1 the difference being due to the absence of glucose from the molecule in the latter types4 ,the two types are distributed in plants as follows3 pyrogallol tannins in oak-galls1 oak wood1 sumac1 chestnut1 divi-divi1 and algaro billa2 catechol tannins in the barks of pines1 hemlocks1 oaks1 acacias1 mimosas1 cassia1 and mangrove1 in quebracho wood1 canaigre roots1 cutch and gambier4 ,the so-called pseudo-tannins 7i4e41 compounds which do not tan leather but possess other properties like tannins7 are found in hops1 tea1 wine1 fruits1 etc4 ,,some ,,common ,,tannins ,ordinary commercial tannin1 or tannic acid1 is a compound of one molecule of glucose with five of digallic acid4 ,it is found in many plants1 and is prepared commercially from the ,turkish oak-galls and the ,chinese sumac-galls4 ,it exhibits all the characteristic properties which have been listed above for tannins in general and responds to all the characteristic reactions of a pyrogallol tannin4 ,it is extensively used for the manufacture of blue-black ink1 and in many technical processes4 ,catechu tannin and catechin are compounds of the catechol tannin type4 ,the latter is obtained from acacia wood1 mahogany wood1 mimosa wood1 etc4 ,it is not a true tannin1 since it does not convert hide into leather2 but when heated to #abj or above1 it is easily dehydrated1 forming catechu tannin which is identical with that which is obtained directly from gambier and ,bombay cutch 7products made by evaporating water extracts from the bark of various tropical trees74 ,this latter is a true tannin1 which is much used in dyeing and other technical processes4 ,quercitannic acid1 obtained from oak bark1 etc41 is likewise a catechol tannin4 ,it yields no glucose on hydrolysis4 ,a great many other tannins are known1 and their possibilities for technical use in tanning1 dyeing1 etc41 have generally been investigated2 but so little has been learned about their composition and relation to the plant's own needs1 that it seems unnecessary to discuss them in detail here4 ,,physiological ,,uses ,,of ,,tannins ,tannins are probably not direct products of photosynthesis4 ,they are1 however1 elaborated in the green leaves of plants and translocated from there to the stems1 roots1 etc4 ,their close association with the photosynthetic carbohydrates has led many investigators to seek to establish for them some significant function as food materials1 or as plastic substances in cell metabolism4 ,many conflicting views have been advanced1 but a careful review of these leads inevitably to the conclusion that tannins probably do not serve in any significant way as food material4 ,the glucose which is generally present in the tannin molecule may1 of course1 serve as reserve food material1 but it seems probable that it functions as a constituent of the tannins only to assist in making them more soluble and hence more easily translocated through the plant tissues4 ,some fungi1 and perhaps other plants as well1 can actually utilize tannins as food material under suitable conditions and in the absence of a proper supply of carbohydrates4 ,but this does not prove that tannins can normally replace carbohydrates as food material for these species of plants4 ,there seems to be ample evidence that tannins are elaborated where intense metabolism is in progress1 such as occurs in green leaves during the early growing season2 in the rapid tissue formation which takes place after the stings of certain insects1 producing galls1 etc42 during germination1 and as a result of any other unusual stimulation of metabolism4 ,it may be1 therefore1 that tannins serve as safety accumulations of excessive condensations of formaldehyde1 or other photosynthetic products1 under such conditions4 ,it seems certain that in all such cases tannins are the result of1 and not 7as some investigators have supposed7 the causative agents for1 the abnormally rapid metabolism4 ,it seems to be fairly well demonstrated that tannins are intermediate products for the formation of cork tissue4 ,this may account for their common occurrence in the wood and bark of trees4 ,indeed1 it has been shown that gallic and tannic acids are present in considerable proportions in those parts of the plant where cork is being formed4 ,further1 that they bear direct relation to cork-formation has been demonstrated in two different ways4 ,first1 cork-like substances have been artificially produced by passing a stream of carbon dioxide through mixtures of formaldehyde with various tannic acids4 ,second1 by various treatments of cork1 decomposition compounds showing tannin-like properties may be obtained4 ,some investigators have held that not only cork tissue but also other lignose1 or cell-wall material1 may be developed from tannins4 ,certain observations with ,spirogyra seem to indicate that tannin may play an important part in the formation of new cell walls during conjugation1 as cells which are ready to conjugate are rich in tannin1 which gradually diminishes in quantity until it is practically absent at the time of spore-formation4 ,there seems to be no evidence that tannins perform any such function as this in higher plants1 however4 ,again1 tannins may play a very important part in pigment-formation4 ,they are very similar in structure to the anthocyanin pigments1 both being made up of practically identical decomposition units1 the phenolic bodies4 ,the disappearance of tannins during the process of ripening of fruits may be connected1 in part at least1 with the development of the brilliant red1 blue1 and yellow pigments which give such rich colors to the thoroughly ripe fruits4 ,finally1 certain of the tannins undoubtedly serve as protective agents to prevent the growth of parasitic fungi in fruits1 etc4 ,recent investigations show that at least some of the varieties of fruits which are resistant to the attacks of certain parasitic diseases utilize tannins for this purpose4 ,this protective effect may be accomplished in two different ways4 ,either the tannin actually serves as an antiseptic to prevent the growth of the parasitic fungus within the tissues of the host plant1 or it assists in the development of a corky layer which walls-off the infected area and so prevents further spread of the disease through the tissue4 ,examples of both types of protective action have recently been reported4 ,it is obvious that the different forms of tannins may play different rles in plant life1 and the same tannin substance may possibly serve different purposes under different conditions4 ,,biological ,,significance ,,of ,,tannins ,,in ,,fruits ,the presence of tannins in fruits and the changes which they undergo during the ripening process cannot fail to attract attention to their biological significance in serving to protect the fruit from premature consumption as food by animals4 ,tannins are of frequent occurrence in green fruits1 imparting to them their characteristic astringent taste4 ,they nearly always disappear as the fruit ripens4 ,the fact that during the ripening process both sugars and fruit esters1 as well as attractive surface pigments1 are developed has led certain investigators to the conclusion that tannins serve as mother-substances for these materials in the green fruits and are converted into these attractive agencies during ripening4 ,there is nothing in the chemical composition of tannins which indicates1 however1 that they are precursors of sugars or fruit esters1 although 7as has been pointed out7 they may give rise to anthocyan pigments4 ,further1 recent researches concerning the tannin of persimmons 7the best-known and most striking example of the phenomena under discussion7 clearly show that the tannin is not actually used up during the ripening process2 that instead it remains in the ripe fruit in practically undiminished quantity2 but that when the fruit is ripe1 the tannin is enclosed in certain special large cells or sacs1 which are surrounded by an insoluble membrane1 so that when the fruit is eaten by animals the astringent tannin1 enveloped in these insoluble sacs1 passes by the organs of taste of the animal without causing any disagreeable effects4 ,this walling-off of the astringent tannins can be stimulated in partially ripe fruits by treating them with several different chemical agents1 the simplest method being that of placing the unripe fruit in an atmosphere of carbon dioxide gas for a short period4 ,the artificial processing of persimmons to render them edible for a longer period before they become naturally fully ripe and subject to decay is now a commercial enterprise4 ,this process is of interest because of its possible connection with the conversion of tannins into cork1 under the influence of carbon dioxide gas1 as mentioned in a preceding paragraph4 ,from these facts1 it is apparent that in persimmons1 and probably in other tannin-containing fruits1 the process of natural selection has developed a mechanism for the secretion of tannin in green fruits1 followed by a process for walling it off in harmless condition when the fruit is ripe1 which serves most admirably to protect the fruit from consumption by animals before the enclosed seeds have fully developed their reproductive powers4 ,,references4 ,,abderhalden1 ,e4--,biochemisches ,handlexikon1 ,band #g1 ,gerbstoffe1 ,flechtenstoffe1 ,saponine1 ,bitterstoffe1 ,terpene1 ,aetherische ,oele1 ,harze1 ,kautschuk1 #hbb pages1 ,berlin1 #aiab4 ,,allen',s ,commercial ,organic ,analysis1 ,vol4 #e1 ,tannins1 ,dyes and ,coloring ,matters1 ,inks1 #gjd pages1 #f figs41 ,philadelphia1 #aiaa 7#dth ed474 ,,cook1 ,m4 ,t4 and ,,taubenhaus1 ,j4 ,j4--,the ,toxicity of ,tannin1 ,delaware ,college ,agricultural ,experiment ,station ,bulletin ,no4 #ia1 #gg pages1 #dc figs41 ,newark1 ,del41 #aiaa4 ,,dekker1 ,j4--,die ,gerbstoffe1 #fcf pages1 #c figs41 ,berlin1 #aiac4 ,,gore1 ,h4 ,c4--,experiments on the ,processing of ,persimmons to ,render them ,nonastringent1 ,u4 ,s4 ,department of ,agriculture1 ,bureau of ,chemistry ,bulletin ,no4 #ada1 #ca pages1 #c plates1 #aiaa2 and ,no4 #aee1 #bj pages1 #aiab4 ,,lloyd1 ,f4 ,e4--,the ,tannin-,colloid ,complexes in the ,fruit of the ,persimmon1 ,diospyros1 in ,biochemical ,bulletin1 ,vol4 #a1 ,no4 #a1 pages #g to #da1 #cd figs41 ,new ,york1 #aiaa4 ,,chapter ,,viii ,,pigments ,practically all plant structures contain pigments4 ,these may be considered as of two types3 7a7 the vegetative pigments1 which have a definite energy-absorbing rle in the metabolic processes of the tissues which contain them1 and 7b7 the ornamental pigments4 ,it is probable that the same chemical compound may serve in either one of these capacities under different conditions1 but1 in general1 it is possible to assign either a definite vegetative1 or physiological1 use1 or else a simple ornamental1 or biological1 significance to each of the common pigments4 ,the first type is found widely distributed through the protoplasm1 or cell-sap1 of the plant structures2 while the ornamental pigments are located chiefly in the epidermal cells1 especially of flowers4 ,with respect to their colors1 the plant pigments may be grouped as follows3 ,green--the chlorophylls4 ,yellow--the carotinoids1 flavones1 and xanthones4 ,red--phycoerythrin1 lycopersicin1 anthocyanin4 ,blue--anthocyan derivatives4 ,brown--phycophin1 fucoxanthin4 ,of these1 the chlorophylls1 the carotinoids1 phycoerythrin 7in red sea-weeds7 and phycophin 7in brown sea-weeds7 are generally vegetative pigments2 while the others form the basis for most of the ornamental pigments1 although they may have a definite energy-absorbing effect1 in some cases4 ,,the ,,chlorophylls ,the importance of the green coloring matter in plants has been understood for more than a century1 its connection with photosynthesis having been known as far back as #ahai4 ,but definite knowledge as to its chemical constitution is of very recent origin4 ,as recently as #aijh1 it was asserted that chlorophyll is a lecithin-like body1 yielding choline and glycero-phosphoric acid on hydrolysis4 ,it is now known1 however1 that chlorophyll contains neither choline nor phosphorus1 the earlier observations being due to mixtures of various other materials with the true chlorophyll in the extracts which were examined4 ,beginning with #aiab1 ,willsttter and his collaborators1 in a series of classic papers which were finally collected in book form1 clearly demonstrated the chemical constitution of the green pigments of plants1 which had been previously designated under the single name chlorophyll4 ,in #aiab1 ,willsttter and ,isler first showed that the green coloring matter which is extracted from plants by alcohol1 ether1 etc41 is made up of two definite chemical compounds1 to which they assigned the names chlorophyll a and chlorophyll b1 associated with two yellow pigments1 carotin and xanthophyll1 and1 in some cases1 with the reddish-brown fucoxanthin4 ,the percentages of total pigment materials1 and the relative proportions of the five different pigments1 in several types of plants1 are as follows3 ---------------------------------------- --------------------------------- ,land ,brown ,green ,plants1 ,seaweeds1 ,alg1 ,per ,cent4 ,per ,cent4 ,per ,cent4 ---------------------------------------- --------------------------------- ,total pigment in the dry matter #j4ii #j4bi #j4ba ,proportion of3 ,chlorophyll a #fc #ee #dd ,chlorophyll b #bb #d #ca ,carotin #f #aa #g ,xanthophyll #i #aj #ah ,fucoxanthin #bj ,the two chlorophylls have the following formulas3 chlorophyll a1 ,c#ee;,h#gb,o#e,n#d,mg1 and chlorophyll b1 ,c#ee;,h#gj,o#f,n#d,mg4 ,hence1 they differ only in having two hydrogen atoms in the one replaced by one oxygen atom in the other4 ,both are amorphous powders1 from which crystalline chlorophyll 7see below7 can be obtained by hydrolysis4 ,chlorophyll a is blue-black1 is easily soluble in most organic solvents1 and when saponified by alcoholic potash gives a transient pure yellow color4 ,chlorophyll b is dark green1 is somewhat less soluble than the other form1 and when saponified by potash gives a transient brilliant red4 ,amorphous and ,crystalline ,chlorophyll4--,when the chlorophyll of plants is extracted by alcohol and the alcoholic extract evaporated nearly to dryness1 beautiful dark green crystals are obtained4 ,willsttter has shown1 however1 that in these crystallized forms the ethyl group 7from the ethyl alcohol used7 has replaced the phytyl group 7see below7 which is present in the pigments as they exist in the plant tissues2 and that1 when extracted by other solvents than alcohol1 the pigments may be obtained in the amorphous forms in which they exist in the plant4 ,this change from amorphous to crystalline compounds may be understood from the preliminary statement that the chlorophylls are esters of tri-basic acids1 in which one acid hydrogen is replaced by the methyl 7,,ch#c7 group and a second by the phytyl 7,c#bj;,h#ci1 from phytol1 or phytyl alcohol1 ,c#bj;,h#ci,,oh7 group4 ,when treated with ethyl alcohol 7,c#b;,h#e,,oh7 for the purpose of extracting the pigments1 the ethyl 7,c#b;,h#e7 group replaces the phytyl group1 thus yielding a methyl-ethyl ester1 and these esters are the crystalline forms of the chlorophylls4 ,this replacement is made possible through the action on the original pigment in the tissues of an enzyme1 chlorophyllase1 which is also present in the tissues1 which splits off the phytyl group1 forming phytyl alcohol1 and leaving a free ,,cooh group in the pigment1 with which the alcohol used in the extraction forms the ethyl ester 7see ,chapter ,,ix for a discussion of the formation and hydrolysis of esters74 ,while the chlorophylls are tri-basic acids1 only two of the acid ,,cooh groups actually function in ester-formation4 ,the third acid group seems not to exist as a free acid group2 but in chlorophyll a1 it is in what is known as the lactam arrangement1 represented by the --,,conh-- group1 and in chlorophyll b1 it is probably in the lactone arrangement1 represented by the --,,coo-- group2 the two bonds in each case being attached to different structural units in the molecule 7see page #ajf74 ,the change from amorphous to crystalline forms may be represented by the following formulas1 in which the ,r represents the whole of the complex group to which the acid ester groups are united3 ,,coo,,ch#c ,,coo,,ch#c ,,cooh _/ _/ _/ ,r ,r ,r ,,coo,c#bj;,h#ci ,,coo,c#b;,h#e ,,cooh ,amorphous chlorophyll ,crystalline chlorophyll ,chlorophyllin or or methyl-phytyl methyl-ethyl chlorophyllide chlorophyllide ,chlorophyllin1 the compound in which the ester groups have been converted into free acid groups1 as indicated above1 may be obtained from either amorphous or crystalline chlorophyll by treatment with caustic potash dissolved in methyl alcohol4 ,phytol4--,this alcohol1 which furnishes the characteristic ester group in the chlorophyll of plants1 is a compound of very unusual composition1 which has never been found in any other form or in any other type of compound which is present in either plant or animal tissues4 ,careful studies of its addition and oxidation products prove that it has the following structural arrangement3 ,h ,h ,h ,h ,h ,h ,h ,h ,h ,h ,h-,c-----,c-----,c-----,c-----,c-----,c -----,c-----,c-----,c,c-----,c--,,ch#b,, oh ,,ch#c;,,ch#c;,,ch#c;,,ch#c;,,ch#c;,,ch# c;,,ch#c;,,ch#c;,,ch#c;,,ch#c;,,ch#c ,as this formula indicates1 the compound contains one unsaturated1 double-bond linkage1 one primary alcohol group1 and eleven methyl groups4 ,as has been said1 this alcohol occurs nowhere else in nature1 and its presence and function in the chlorophyll molecule are1 as yet1 wholly unexplainable4 ,phytol itself is a colorless1 oily liquid1 with a high boiling point 7#ade in vacuo1 #bjd at #aj mm4 pressure74 ,,the ,,constitution ,,of ,,the ,,chlorophylls ,as has been mentioned1 chlorophyll a differs from chlorophyll b by having one more oxygen and two less hydrogen atoms in the molecule1 and in having one of its nitrogen atoms in the lactam arrangement4 ,these differences in structure are represented by the following formulas which are commonly used to represent the two compounds1 but which do not show the arrangements of the major groups of the complex molecules3 ,,coo,c#bj;,h#ci ,,coo,c#bj;,h#ci _/ _/ ,mg,c#ca;,h#bi,n#c-;,,coo,,ch#c ,mg,c#cb;,h#bh,o#b,n#d-;,,coo,,ch#c ,chlorophyll b ,,nh-,,co ,chlorophyll a ,the chlorophylls are unstable compounds1 readily acted upon by acids or alkalies1 and by the enzyme chlorophyllase1 which splits off the phytyl alcohol group4 ,the progressive action of acids and of alkalies in breaking down the molecule1 and the products of its oxidation and reduction1 have served to establish the chemical composition of the compound in each case4 ,because of the importance of these pigments in the whole metabolic processes of the plant1 it seems to be desirable to consider the nature of these reactions in some detail1 as follows3 ,decomposition of the ,chlorophylls by ,alkalies4--,the first action of dilute alkalies on the chlorophylls is to split off1 by hydrolysis1 the alcoholic groups of the esters1 producing the crystalline tri-basic acids1 or chlorophyllins a and b4 ,each of these chlorophyllins exists in two forms1 the normal and the iso1 in which the attachment of the ,,cooh groups to the other groups in the molecule is in different positions4 ,hence1 chlorophyll a yields chlorophyllin a and isochlorophyllin a1 and chlorophyll b yields chlorophyllin b and isochlorophyllin b1 all four of which are tri-basic acids4 ,these compounds1 when heated with alkalies1 split off carbon dioxide in successive stages1 losing one ,,cooh group at each step1 thus yielding a series of simpler compounds of the following types3 ,first1 di-basic acids2 second1 monobasic acids2 and finally1 tiophyllin1 a compound in which no ,,cooh group is present4 ,in all of these compounds1 derived from chlorophylls by the action of alkalies1 the ,mg remains in the molecule1 and all the ,mg-containing derivatives from the chlorophylls are known as phyllins4 ,at the stage at which only one ,,cooh group remains in the molecule1 only one group arrangement is possible1 and the derivatives from chlorophyllin a and isochlorophyllin b1 and those from chlorophyllin b and isochlorophyllin a1 are identical4 ,at the final stage1 the derivatives from all four forms are identical4 ,this may be graphically illustrated by the following diagram indicating the progressive decomposition of the two chlorophylls under the action of alkalies3 ,illustration3 ,decomposition of ,chlorophyll a and ,chlorophyll b ,decomposition of ,chlorophylls by ,acids4--,the first action of dilute acids upon chlorophylls is to remove the magnesium1 without otherwise changing the molecule4 ,two hydrogens go in in the place of the magnesium4 ,dilute acids act in precisely the same way upon each of the phyllins shown in the above scheme4 ,in this way1 a whole series of compounds1 corresponding to each of the chlorophylls and their alkali-decomposition products1 but with the magnesium lacking in each case1 has been prepared4 ,thus1 ,,coo,c#bj;,h#ci _/ ,chlorophyll a1 ,mg,c#ca;,h#bi,n#c-;,,coo,,ch#c1 7,,nhco7 ,,coo,c#bj;,h#ci _/ becomes ,phophytin a1 ,c#ca;,h#ca,n#c-;,,coo,,ch#c1 7,,nhco7 ,,coo,c#bj;,h#ci _/ ,chlorophyll b1 ,mg,c#ca;,h#bi,o#b,n#d ,,coo,,ch#c ,,coo,c#bj;,h#ci _/ becomes ,phophytin b1 ,c#cb;,h#cj,o#b,n#d ,,coo,,ch#c ,similarly1 ,isochlorophyllin a1 becomes ,phytochlorin e1 ,chlorophyllin a1 becomes ,phytochlorin f1 and g1 ,,cooh _/ ,c#cb;,h#cb,,on#d ,,cooh ,isochlorophyllin b1 becomes ,phytorhodin g ,chlorophyllin b1 becomes ,phytorhodin i and k1 ,,cooh _/ ,c#cb;,h#cj,o#b,n#d ,,cooh ,and bodies known as porphyrins are similarly derived from all the other known phyllins4 ,for example3 cyanophyllin1 ,mg,c#ca;,h#cb,n#d7;,,cooh7#b1 becomes cyanoporphyrin1 ,c#ca;,h#cd,n#d7;,,cooh7#b2 tiophyllin1 ,mg,c#ca;,h#cd,n#d1 becomes tioporphyrin1 ,c#ca;,h#cf,n#d1 etc4 ,phytochlorin e and phytorhodin g are the chief products of the decomposition by acids of the chlorophylls4 ,indeed1 it was the production of these compounds which led to the discovery of the existence of the two chlorophylls4 ,when treated with alkalies1 they lose their carboxyl groups and become tioporphyrin4 ,decomposition of the ,chlorophylls by ,oxidation and ,reduction4--,when acted upon by oxidizing agents1 such as chromic acid1 the porphyrins yield two chief oxidation products1 which are pyrrole derivatives having the following formulas1 ,,ch#c-;,c-,,co ,,ch#c-;,c-,,co ,,nh ,,nh _/ _/ ,,ch#c-;,,ch#b-;,c-,,co ,,hooc-,,ch#b-;,,ch#b-;,c-,,co ,methylethylmalein imide ,hmatinic acid imide ,by reduction1 there have been obtained from the chlorophylls and the various porphyrins1 three isomeric pyrrole derivatives having the following formulas1 ,,ch#c ,h ,,ch#c ,c#b;,h#e-;,c,c ,c#b;,h#e-;,c,c ,c#b;,h#e-;,c,c ,,nh ,,nh ,,nh _/ _/ _/ ,,ch#c-;,c,c ,,ch#c-;,c,c ,,ch#c-;,c,c ,,ch#c ,,ch#c ,h ,phyllopyrrole ,hmopyrrole ,isohmopyrrole ,as a result of the study of these decomposition units1 ,willsttter has suggested the following formulas for the structural arrangement of tiophyllin and tioporphyrin1 the compounds which result from the removal of all of the acid groups and finally of the magnesium from the chlorophylls1 ,h ,,hc,,ch ,,ch#c-;,c--,c ,c---,c _/_/ ,n ,n _/ ,c#b;,h#e-;,c--,c ,c---,,ch _/_/ ,c------------,c _/ ,c#b;,h#e-;,c,c ,c,c-,c#b;,h#e _/ ,n-----,mg-----,n _/ ,,ch#c-;,c,c ,c,c-,c#b;,h#e ,,ch#c ,,ch#c tiophyllin ,h ,,hc,,ch ,,ch#c-;,c--,c ,c---,c _/_/ ,n ,n _/ ,c#b;,h#e-;,c--,c ,c---,,ch _/_/ ,c------------,c _/ ,c#b;,h#e-;,c,c ,c,c-,c#b;,h#e _/ ,n ,n _/ ,,ch#c-;,c,c ,c,c-,,ch#c ,,ch#c ,,ch#c tioporphyrin ,the ,,cooh groups which are attached to these compounds to form the various phyllins and porphyrins1 as well as the original chlorophylls1 are supposed to be attached to the ,c#b;,h#e groups in the above formulas1 the different modifications1 or compounds1 depending upon the position in which one or more of these attachments are made4 ,,similarity ,,of ,,chlorophyll ,,and ,h,,moglobin ,it seems to be desirable1 at this point1 to call attention to the remarkable similarity in the chemical composition of chlorophyll1 the most important pigment of plants1 and hmoglobin1 the all-important respiration-regulating pigment in the blood of animals4 ,hmoglobin is a complex compound1 consisting of about #if per cent of albumin 7a protein1 see ,chapter ,,xiii7 united with about #d per cent of hmatin1 a brilliant red pigment which has the formula ,fe,cl,c#cb;,h#cb,o#d,n#d4 ,when treated with acids1 the iron 7and its accompanying ,cl7 is removed1 and hmatoporphyrin1 ,c#cb;,h#cf,o#d,n#d1 is obtained4 ,when either hmatin1 or hmatoporphyrin is oxidized1 hmatinic acid imide identical with that obtained from tioporphyrin is obtained4 ,also1 when hmatoporphyrin is reduced1 hmopyrrole identical with that from tioporphyrin is obtained4 ,thus1 it would appear that the unit structural groups in hmatin and in chlorophyll are identical2 although chlorophyll may exhibit more variations in isomeric arrangement of these structural units than have been found in hmatin4 ,hence1 it is apparent that the only essential difference in composition between chlorophyll and hmatin is that in the former the structural units are linked together by iron1 while in the latter1 the same units are united through magnesium as the linking element4 ,further1 it is known that while iron is not a constituent element in the chlorophyll molecule1 it is1 in some unknown way1 absolutely essential to the production of chlorophyll in plants2 plants furnished with an iron-free nutrient solution rapidly become etiolated and photosynthesis stops4 ,the following skeleton formulas have been suggested to indicate the way in which these elements are linked between the structural units in their respective compounds4 -,c ,c- -,c ,c- _/ _/ ,n ,n ,n ,n _/ _/ _/ _/ -,c _/ ,c- -,c _/ ,c- ,m g ,f e -,c _/ ,c- -,c _/ ,c- _/ _/ _/ _/ ,n ,n ,n ,c l ,n _/ _/ -,c ,c- -,c ,c- ,chlorophyll ,hmatin ,it is understood1 of course1 that the mineral element does not furnish the definite means of holding the structural units together as otherwise it would not be possible to remove the iron1 or magnesium1 without breaking down the molecule1 as is done in the case of the porphyrins4 ,the actual binding linkage is undoubtedly between carbon atoms1 as indicated in ,willsttter's formulas for tiophyllin and tioporphyrin 7see page #aji74 ,the attachment of the magnesium to each one of the four nitrogen atoms in the skeleton formula assumes the existence of subsidiary valences of #b-d for magnesium 7and of #c-e for iron71 or of possible oscillating valences similar to those supposed to be exhibited by carbon in its closed-ring arrangements4 ,,properties ,,of ,,the ,,chlorophylls ,the phytyl esters1 or natural chlorophylls1 are amorphous solids2 while the methylethyl esters 7chlorophyllins7 and the free acids 7phyllins7 are crystalline compounds4 ,all of these compounds are easily soluble in ether and alcohol1 but insoluble in water4 ,the chlorophylls and chlorophyllins are practically insoluble in petroleum ether and chloroform2 but the monobasic acids 7pyrrophyllin and phyllophyllin7 and the neutral tiophyllin dissolve easily in chloroform4 ,solutions of the chlorophylls are fluorescent1 being green by transmitted1 and red by reflected light4 ,chlorophyll a is a blue-black solid1 which gives dark green solutions in all of its solvents4 ,chlorophyll b is a dark-green solid1 which yields brilliant green solutions4 ,solutions in ether of glaucophyllin and of cyanophyllin are blue2 of rhodophyllin1 deep violet2 of rubiphyllin1 light violet2 of erythrophyllin1 red2 and of pyrrophyllin and phyllophyllin1 bluish-red4 ,solutions of the porphyrins are all red1 the di-basic ones being usually a bluish-red1 and the simpler ones a brilliant red to deep brownish-red in color4 ,the several chlorophyll derivatives are further distinguished by characteristic differences in their absorption spectra4 ,these differences have been pictured by ,willsttter in his book dealing with the results of his investigations concerning the chlorophylls1 and reproduced in one or two other texts which treat in detail with the physical-chemical properties of these pigments1 but need not be presented in such detail here4 ,,the ,,carotinoids ,the characteristic brilliant green of healthy plant tissues is due to the fact that there are always associated with the dark bluish-green chlorophylls two 7or more7 yellow pigments4 ,these are known as the carotinoids4 ,this group includes the two brilliant yellow pigments1 carotin and xanthophyll1 and the reddish brown fucoxanthin and the brilliant red lycopersicin1 which are similar in their chemical composition4 ,the first two are found universally distributed in plants1 associated with the chlorophylls1 and may be regarded as vegetative pigments1 although the characteristic ornamental yellow and orange colors of many flowers and fruits1 as well as that of the roots of carrots1 etc41 due to these pigments4 ,carotin4--,this pigment occurs in various forms in plants1 both amorphous and crystalline4 ,it crystallizes out of solution in flat plates1 which are orange-red by transmitted light1 and greenish-blue by reflected light1 and have a melting point of #afh4 ,carotin is insoluble in water1 only very slightly soluble in acetone or cold alcohol1 readily soluble in petroleum ether1 ether1 chloroform1 and carbon disulfide4 ,its solutions are strongly fluorescent4 ,its molecular formula is ,c#dj;,h#ef4 ,it is1 therefore1 a hydrocarbon of a very high degree of unsaturation4 ,on exposure to dry air1 it absorbs #cd4c per cent of its own weight of oxygen1 which corresponds to #aa atoms of oxygen1 computed on the basis of the molecular formula ,c#dj;,h#ef1 and would indicate a formula of 7,c#dj;,h#ef7b,o#bc for the oxygenated compound2 this being three oxygen atoms less than would be required to bring the compound to the theoretical stage of saturation represented by the unimolecular formula ,cn,h#bn#b4 ,in moist air1 two more oxygen atoms are absorbed1 probably forming two ,,oh groups in the molecule4 ,moreover1 carotin absorbs iodine4 ,when the calculated amount of iodine is used1 a definite compound having the formula ,c#dj;,h#ef;,i#b is produced2 but in the presence of an excess of iodine another compound having the apparent formula ,c#dj;,h#ef;,i#c 7or #b;,c#dj;,h#ef;,i#b;,i#b7 is obtained4 7,note that #b atoms of iodine plus #ab atoms of oxygen1 or #c of iodine plus #aa of oxygen1 produce the degree of saturation required by the formula ,cn,h#bn#b47 ,it is evident from these experimental data1 that a part of the unsaturated linkage in the carotin molecule is of a type which can easily be saturated by direct addition of oxygen1 while the remainder may be saturated by iodine4 ,the reaction of carotin toward bromine is peculiar4 ,with this element1 it forms a compound having the formula ,c#dj;,h#cf;,br#bb1 indicating the direct addition of two atoms of bromine and the substitution of twenty atoms of this element for the same number of hydrogen atoms4 ,the oxygenated carotins are colorless substances1 while the iodide crystallizes in beautiful dark-violet prisms1 having a coppery red fluorescence4 ,xanthophyll is closely related to carotin4 ,it has the molecular formula ,c#dj;,h#ef,o#b4 ,it absorbs #cf4ee per cent of oxygen 7corresponding to #ac atoms1 which would indicate the formation of two ,,oh groups in addition to the saturation required by the ,cn,h#bn#b formula72 and an iodine addition product having the formula ,c#dj;,h#ef,o#b;,i#b1 which crystallizes in dark-violet needles4 ,xanthophyll differs markedly from carotin in its solubilities1 being insoluble in petroleum ether and only sparingly soluble in carbon disulfide4 ,it may be fairly easily reduced to carotin4 ,this transformation is reversible1 and suggests a similarity to the change from hmoglobin to oxyhmoglobin1 and the reverse1 in the blood of animals1 as a part of their respiration process4 ,separation of the ,chlorophylls1 ,carotin1 and ,xanthophyll4--,these pigments1 which exist together in most plant tissues1 may easily be separated from each other by taking advantage of the differences in their solubilities1 according to the following procedure4 ,grind up a small quantity of the fresh tissue 7leaves of the stinging nettle furnish a conveniently large supply of each of these pigments7 with fine sand in a mortar4 ,cover with acetone1 let stand a few moments and then filter on a ,bchner funnel4 ,pour the filtrate into a separatory funnel1 add an equal volume of ether and two volumes of water4 ,shake up once and then allow the ether layer to separate2 the pigments will be in this layer4 ,drain off the water-acetone layer4 ,now to the etherial solution1 add about half its volume of a concentrated solution of potassium hydroxide in methyl alcohol4 ,shake well and allow to stand until the mixture becomes permanently green4 ,now add an equal volume of water and a little more ether1 until the mixture separates sharply into two layers4 ,the chlorophylls will now be in the lower dilute alcohol layer1 and the carotinoids in the upper ether1 and may be separated by draining of each layer separately4 ,to separate the carotin from xanthophyll place the ether solution in a small open dish and evaporate to a small volume4 ,now add about ten volumes of petroleum spirit and an equal volume of methyl alcohol1 stir up well1 transfer to a separatory funnel and allow the two layers to separate4 ,the carotin will now be in the upper layer of petroleum ether1 and the xanthophyll in the lower alcohol layer2 these layers may be drained off separately and the solvents evaporated in order to recover the pigments in dry form4 ,lycopersicin 7or lycopin7 is a hydrocarbon pigment having the same formula as carotin4 ,it is1 however1 brilliantly red in color1 and crystallizes in a different form and has a different adsorption spectrum from carotin4 ,it is the characteristic pigment of red tomatoes1 and is found also in red peppers4 ,yellow tomatoes have only carotin as their skin-pigment1 while lycopersicin is usually present in the flesh of the ripe fruits of all varieties and in the skin of red ones4 ,it has been shown1 however1 that if varieties of tomatoes which are normally red when ripe1 are ripened at high temperatures1 #ij ,f4 or above1 their skins will be yellow instead of red when fully ripe4 ,hence1 the occurrence of carotin1 or of lycopersicin1 as the skin pigment is determined in part by the varietal character 7being different in different varieties when ripened at normal temperatures7 and in part by the temperature at which the fruit ripens4 ,the two pigments are1 of course1 isomers2 but the difference in their structural arrangement is not known4 ,fucoxanthin1 ,c#dj;,h#ed,o#f1 is a brownish-red pigment1 found in fresh brown alg1 and in some brown sea-weeds4 ,its formula indicates that it is an oxidized carotin4 ,with iodine1 it forms a compound having the formula ,c#dj;,h#ed,o#f;,i#d4 ,it is unlike carotin and xanthophyll in that it has basic properties1 forming salts with acids1 which are blue in color4 ,,phycoerythrin ,,and ,,phycoph,,in ,these are the principal pigments of red and brown seaweeds1 respectively4 ,their most characteristic difference from the pigments of non-aquatic plants is that they are easily soluble in water1 and insoluble in most organic solvents1 such as alcohol1 ether1 etc4 ,at first thought1 this would appear to be impossible1 since the plants grow in water and it would seem that their water-soluble pigments would be continuously dissolved out of the tissues4 ,the reason why this does not occur lies in the fact that these pigments exist in the cells of the seaweeds in colloidal form 7see ,chapter ,,xv71 and1 hence1 cannot diffuse out through the cell-walls4 ,the only way in which they can be extracted from the tissues is by rupturing the cells1 by grinding with sharp sand1 etc41 after which the pigments can readily be dissolved out by water4 ,phycoerythrin is the red pigment4 ,it is a colloidal1 nitrogenous substance1 allied to the proteins 7see ,chapter ,,xiii7 but not a true protein compound4 ,hydrolysis by acids indicates that it contains leucine and tyrosine1 two amino-acids which are constituents of proteins1 along with other bodies of unknown composition4 ,the colloidal solution of phycoerythrin in water has a brilliant rose-red color1 with an orange fluorescence4 ,it readily sets to a gel 7see ,chapter ,,xv71 so that the solution is almost impossible to filter4 ,on this account1 purified solutions of this pigment are very difficult to secure1 and no satisfactory analysis to indicate its composition has yet been obtained4 ,actinically1 it is a complementary pigment to chlorophyll1 that is1 it absorbs the blue and green rays and permits the passage of light which is of the wave length that is absorbed by chlorophyll4 ,phycophin4--,still less is known of the composition of this pigment than of that of phycoerythrin4 ,it is the characteristic pigment of brown seaweeds4 ,it is supposed to exist in the cells of alg1 chiefly as a colorless chromogen1 which becomes first yellow and then brown on exposure to air4 ,associated with it are other pigments1 which have been variously reported as carotin1 phycoxanthin1 etc4 ,,the ,,anthocyans ,these are a group of pigments of red1 blue1 or violet color1 which occur in the flowers1 fruits1 or leaves of many species of plants4 ,they are essentially ornamental pigments1 and constitute a large proportion of the brilliant colors of flowers1 etc4 ,they occur not only dissolved in the cell-sap1 but also as deposits of definite crystals or amorphous compounds in the cell protoplasm4 ,they are all glucosides4 ,when the anthocyans are hydrolyzed1 the sugar molecules are split off and the characteristic hydroxy-derivatives of the three-ring anthocyan nucleus 7figured on page #hc71 known as anthocyanidins1 remain4 ,these anthocyanidins are themselves pigments4 ,they have been shown to be all derivatives of the anthocyan nucleus4 ,the oxygen atom in this nucleus is very strongly basic and exhibits its quadrivalent property by forming stable salts by direct addition of acid radicles4 ,the variation of color of the anthocyanins has been explained by ,willsttter1 as follows2 the red is the acid salt1 the blue is a neutral metallic salt1 and the violet is the anhydride of the anthocyanidin in question1 thus ,cl ,cl ,o ,o ,,ho _/ _/ _/ ,,ko _/ _/ _/ _/ _/ _/ _/ _/ _/ ,c ,o ,c ,red ,blue ,o _/ _/ _/ _/ _/ _/ ,c ,violet ,all of the natural anthocyanin pigments appear to contain a chlorine atom attached directly to the ring oxygen1 as shown in the above partial formulas4 ,in addition1 they have four1 five1 or six hydroxyl 7,,oh71 or methoxy 7,,och#c71 groups attached at various points around the three rings4 ,the following formula for oenidin1 one of the most complex of these anthocyanidins1 will illustrate their structural arrangement4 ,cl ,,och#c ,o _/ ,,ho _/ _/ _/ ,,oh _/ _/ _/ _/ ,,och#c ,,oh ,,oh ,c ,delphinidin is the corresponding compound without the two ,,ch#c groups2 while cyanidin contains only five ,,oh groups2 and pelargonidin1 only four ,,oh groups4 ,the anthocyanin pigments are soluble in water1 alcohol1 and ether1 the solutions being red or blue in color according to the acidity or alkalinity of the medium4 ,their presence in many species of plants is hereditable1 as these plants come true to color from seed1 as in the case of red beets1 red cabbage1 several species of blue berries1 etc4 ,in other cases1 the anthocyanin development depends largely upon the conditions of growth1 particularly those which prevail during the later stages of development3 as in the case of apples1 where the amount of red color in the skin depends to a large extent upon the conditions under which the fruit ripens4 ,anthocyanin pigments often make their appearance late in the season2 in fruits1 etc41 as the result of the normal ripening process but in leaves as the result of shorter daylight illumination accentuated also by sharp frosts4 ,,the ,,anthoxanthins ,the yellow plant pigments1 other than the carotinoids1 are almost without exception glucosides having a xanthone or flavone nucleus4 ,these typical nuclei are illustrated on page #hc4 ,in these nuclei1 as in the anthocyan one1 the oxygen atom is strongly basic and combines with mineral acids to form salts 7the oxygen becoming quadrivalent7 and the color of the pigment depending upon the nature of the combination formed in this way4 ,the anthoxanthin pigments are yellow1 crystalline solids1 which are only slightly soluble in water4 ,they dissolve readily in dilute acids and alkalies1 giving yellow or red solutions which are of the same color in either acid or alkaline media4 ,they are extensively used as yellow dyes4 ,many of the common members of this group have been mentioned in the chapter dealing with the glucosides4 ,the characteristic pigment nucleus of several of these is as follows3 ,chrysin1 found in various species of poplar and mallows1 ,o ,,ho _/ _/ _/ _/ _/ _/ ,,ho ,c ,o ,apigenin1 found in parsley and celery1 as the glucoside apiin1 ,o ,,ho _/ _/ _/ ,,oh _/ _/ _/ ,,ho ,c ,o ,campferol1 found in ,java indigo1 as the glucoside campferitrin1 ,o ,,ho _/ _/ _/ ,,oh _/ ,,oh _/ _/ ,,ho ,c ,o ,fisetin1 found in quebracho wood and fiset wood1 ,o ,,oh ,,ho _/ _/ _/ ,,oh _/ _/ _/ ,c ,o ,quercitrin1 found in oak bark1 horse-chestnut flowers1 and in the skin of onions1 ,o ,,oh ,,ho _/ _/ _/ ,,oh _/ ,,oh _/ _/ ,,ho ,c ,o ,morin1 found in yellow wood 7,morus tinctoria74 ,o ,,ho ,,ho _/ _/ _/ ,,oh _/ ,,oh _/ _/ ,,ho ,c ,o ,gentisin1 found in yellow gentian 7,gentiana lutea71 ,o ,,ch#c,o _/ _/ _/ _/ _/ _/ ,,oh ,,ho ,c ,o ,as a rule1 the most brilliant of these yellow pigments are found in the largest quantities in the bark and wood of various species of tropical plants2 although they are also present1 in smaller amounts1 in the blossoms of species growing in temperate zones4 ,the anthoxanthins are easily converted into anthocyanins1 and vice versa1 by the action of oxidizing and reducing enzymes which are commonly present in the tissues of the plants which develop the pigments4 ,,the ,,production ,,of ,,ornamental ,,pigments ,,in ,,flowers1 ,,etc4 ,the breeding of flowering plants having blossoms of almost any desired color has become a commercial enterprise of large importance4 ,the results which have been obtained1 in many cases1 have been made the object of scientific study of the genetics of color inheritance4 ,these studies have developed certain interesting facts with reference to the chemistry of the development of these ornamental pigments1 which may be briefly mentioned here4 ,in many of the plants which have been studied1 the color of the flowers depends upon several different factors1 as follows3 ,c1 a chromogen 7or color-producing substance7 which is generally a flavone or xanthone glucoside1 and which may be either yellow or colorless4 ,e1 an enzyme which acts upon ,c1 to produce a red pigment4 e1 another enzyme which acts upon the red pigment1 changing it to some other anthocyanin color4 ,a1 an antioxidase1 or antienzyme1 which prevents the action of ,e4 ,r1 an enzyme which changes reds to yellows4 ,thus1 if a plant whose flower contains only the factor ,c be crossed with one which contains the factor ,e1 a red blossom will result1 or if it contains the factor e more intense pigments are developed4 ,but if either ,a or ,r are present1 no change in the color of the original parents will result from the crossing4 ,,the ,,physiological ,,uses ,,of ,,pigments ,the vegetative pigments undoubtedly serve as agencies for regulating the rate of metabolic processes4 ,at the same time1 it is extremely difficult to determine whether the presence of a pigment in any given case is the cause or the effect of the changes in the plant's activities which result from changes in its external environment4 ,the chlorophylls are1 of course1 the regulator of photosynthesis1 absorbing solar energy with which the photosynthetic process may be brought about4 ,the simultaneous presence of carotinoids in varying amounts undoubtedly serves to modify the amount and character of the radiant energy absorbed1 as these pigments absorb a different part of the spectrum of light and hence undoubtedly produce a different chemical activity or actinic effect of the absorbed energy4 ,the variations in depth of color of foliage during different growing conditions1 from a pale yellow when conditions are unfavorable and growth is slow to the rich dark green of more favorable conditions1 is a familiar phenomenon4 ,whether this change in pigmentation is the result of an adjustment of the plant protoplasm1 so that it can absorb a more highly actinic portion of the light1 or is a direct effect of the lack of conditions favorable to chlorophyll-production and active photosynthesis1 has not yet been determined4 ,but there must be some influence other than response to environmental conditions which controls the vegetative color in plants1 since shrubs1 or trees1 which have green1 yellow1 red1 and purple leaves1 respectively1 will grow normally1 side by side1 under identical external conditions of sunlight1 moisture supply1 etc4 ,the hereditary influence must completely overshadow the apparent normal self-adjustment of pigment to energy-absorbing needs1 in all such cases4 ,again1 it appears that there is some definite connection between pigment content and respiration4 ,it is known1 of course1 that the gaseous exchanges involved in animal respiration are accomplished through the reversible change of hmoglobin to oxyhmoglobin1 these being the characteristic blood pigments4 ,the easy change of carotin1 ,c#dj;,h#ef1 to xanthophyll1 ,c#dj;,h#ef,o#b1 and vice versa1 and the reversible changes of the yellow anthoxanthins to the red anthocyanins1 under the influence of the oxidizing and reducing enzymes which are universally present in plants1 would indicate the possibility of the service of these pigments as carriers of oxygen for respiratory activities in plants in a way similar to that in which the blood pigments serve this purpose in the animal body4 ,the fact1 which has been observed in connection with the experimental studies of the development of the lycopersicin1 that tomatoes which normally would become red remain yellow in the absence of oxygen1 indicates that this pigmentation1 at least1 is definitely connected with oxygen supply2 and the further fact that the development of lycopersicin in red tomatoes1 red peppers1 etc41 is dependent upon the temperature at which the fruit ripens1 may indicate a definite connection of this pigment with the need for more oxygen 7or for more heat1 as suggested in the following paragraph7 at these lower temperatures4 ,again1 many investigators have concluded that at least one function of the anthocyanin pigments is to absorb heat rays and so to increase transpiration and other chemical changes4 ,in support of this view1 there may be cited the general presence of such pigments in arctic plants1 their appearance in the leaves of many deciduous trees after a frost in the fall1 etc4 ,indeed1 there is much to support the view that the autumnal changes in foliage pigments have the physiological function of absorbing heat in order to hasten the metabolic processes of ripening and preparation for winter defoliation4 ,the rapid and brilliant changes in foliage coloring after a sharp frost which kills the tissues and makes rapid translocation of the food material of the leaves to the storage organs immediately necessary1 have been explained as the response of the pigmentation of the leaves to the need for increased heat-absorption4 ,on the other hand1 the red pigments of the beet-root1 etc41 which seem to be identical in composition with the other anthocyanin pigments1 can have no such function as those which have just been described4 ,furthermore1 the fact that the pigment often varies in color from red to yellow or brown1 depending upon the temperature under which the tissue is ripening1 makes it an open question whether the pigment is the regulating agency or whether its nature is the result of the environmental conditions4 ,or1 in other words1 it is a question whether these changes in color are a mechanism by which the plant cell adjusts its absorptive powers1 or whether they are only the inevitable result of the changes in temperature upon a pigment material which is present in the cell for an entirely different use4 ,a very interesting side-light upon the color changes which many species of plants undergo when the external temperature falls has been shown by the investigations of the relation of the sugar content of the plant tissues to their pigmentation4 ,it is a well-known fact that not only do many species of deciduous plants show the characteristic reddening of their leaves after frost in the autumn but also many evergreens 7,ligustrum1 ,hedera1 ,mahonia1 etc47 exhibit a marked reddening1 or purpling1 of their foliage during the winter months1 with a return to the normal green color in the spring4 ,earlier investigations1 which have been confirmed by several repetitions1 showed that the red or purple leaves always contain higher percentages of sugar than do green ones of similar types4 ,more recent studies have shown that artificial feeding of some species of plants with abnormally large portions of soluble sugars produces a reddening of the foliage tissues which is apparently identical with that which these tissues undergo as the result of low temperatures4 ,thus1 the connection between the natural winter reddening of foliage and the development of sugar in the tissues during periods of low temperatures 7see page #fd7 seems to be clearly demonstrated4 ,it appears that at least a part of the seasonal changes in color of plants is either the cause of1 or the effect of1 variations in sugar content of the tissues of the plants1 accompanying the changes in external temperatures4 ,oftentimes1 the anthocyanin pigments seem to be associated with sugar production1 as contrasted with the chlorophylls1 which seem to be more favorable to the production of starch4 ,but in this case also1 it is impossible to say whether the pigment is the direct causative agent in the type of carbohydrate production or whether it is the effect of the same external factors which determine1 or modify1 the character of the carbohydrate condensation4 ,,biological ,,significance ,,of ,,ornamental ,,pigments ,the ornamental pigments undoubtedly have definite biological significance4 ,when present in the storage roots1 such as beet-roots1 carrots1 etc41 or in the above-ground parts of plants1 they may have served to protect these organs against herbivorous animals which were accustomed to consume green foods4 ,in flowers1 the brilliant ornamental pigments undoubtedly serve to attract the insects which visit these blossoms in search of nectar1 and in so doing promote cross-fertilization4 ,recent experiments have demonstrated that colors are much more efficient than odors in attracting insects4 ,taken altogether1 it is apparent that the pigments may have a variety of important rles in plants4 ,at the same time1 some of them may be waste products1 with no definite use in the plant economy4 ,,references ,,abderhalden1 ,e4--,biochemisches ,handlexikon1 ,band #f1 ,farbstoffe der ,pflanzen- und der ,tierwelt1 #cij pages1 ,berlin1 #aiaa4 ,,perkin1 ,a4 ,g4 ,,and ,,everest1 ,a4 ,e4--,the ,natural ,organic ,colouring ,matters1 #fee pages1 ,london1 #aiah4 ,,wakemen1 ,,nellie ,a4--,pigments of ,flowering ,plants1 in ,transactions of the ,wisconsin ,academy of ,sciences1 ,arts1 and ,letters1 ,vol4 ,,xix1 ,part ,,ii1 pages #gfg-ijf1 ,madison1 ,wisc41 #aiai4 ,,watson1 ,e4 ,r4--,colour in ,relation to ,chemical ,constitution1 #aig pages1 #fe figs41 #d plates1 ,london1 #aiah4 ,,wheldale1 ,m4--,the ,anthocyan ,pigments of ,plants1 #cjd pages1 ,cambridge1 #aiaf4 ,,willst,,tter1 ,r4 ,,and ,,stoll1 ,a4--,untersuchung ber ,chlorophyllen1 ,methoden und ,ergebnisse1 #dcb pages1 #af figs41 ,berlin1 #aiac4 ,,chapter ,,ix ,,organic ,,acids1 ,,acid ,,salts1 ,,and ,,esters ,organic acids1 either in free form1 or partially neutralized with calcium1 potassium1 or sodium1 forming acid salts1 or combined with various alcohols in the form of esters1 are widely distributed in plants4 ,they occur in largest proportions in the fleshy tissues of fruits and vegetables1 where they are largely responsible for the flavors which make these products attractive as food for men and animals4 ,but organic acids and their salts are also found in the sap of all plants1 and undoubtedly play an important and definite part in the vital processes of metabolism and growth4 ,,chemical ,,constitution ,all organic acids contain one 7or more7 of the characteristic ,o _/_/ acid group1 --,,cooh1 or --,c1 known as carboxyl4 ,this ,,oh group is monovalent1 and in the simplest organic acid1 formic acid 7,h#b;,,co#b71 it is attached to a single hydrogen atom1 thus1 ,h,,cooh4 ,in all other monobasic acids1 it is attached to some other monovalent group1 usually an alkyl radical1 i4e41 a radical derived from an alcohol and containing only carbon and hydrogen 7as methyl1 ,,ch#c1 ethyl1 ,c#b;,h#e1 butyl1 ,c#d;,h#i1 acryl1 ,c#b;,h#c1 etc474 ,hence1 the general formula for all monobasic organic acids is ,r,,cooh1 the ,r representing any monovalent radical4 ,in the simplest dibasic acid1 oxalic 7,h#b;,c#b,o#d71 two carboxyl groups are united to each other1 thus1 ,,hooc,,cooh2 but in the higher members of the series1 the two characteristic acid groups are united through one or more --,,ch#b-- groups1 or their oxy-derivatives 7as ,,hooc,,ch#b;,,cooh1 malonic acid2 ,,hooc,,ch#b;,,ch#b;,,ch#b;,,cooh1 glutaric acid2 ,,hooc,,choh,,ch#b;,,cooh1 malic acid1 etc474 ,polybasic acids1 containing three or more carboxyl groups1 linked together through one or more alkyl carbon atoms1 are also possible1 and a few typical ones 7as ,,cooh ,,hooc,,ch#b;,,coh,,ch#b;,,cooh1 citric acid7 are found in fruits and other plant tissues4 ,the ,h atom of the ,,cooh group may be replaced by metals1 in exactly the same way as it is replaceable in inorganic acids1 producing either neutral or acid salts1 depending upon whether all or only a part of the acid ,h atoms are replaced by the basic element4 ,thus1 with sulfuric acid3 ,,oh ,o,na _/ _/ ,,so#b 7,h#b,,so#d7 ,na,o,h ,,so#b 7,na,h#b,,so#d7 ,h#b,o ,,oh ,,oh ,sulfuric ,acid ,acid sodium sulfate ,,oh ,o,na _/ _/ or1 ,,so#b 7,h#b,,so#d7 #b,na,o,h ,,so#b 7,na#b,,so#d7 #b;,h#b,o ,,oh ,o,na ,sulfuric ,acid ,neutral sodium sulfate ,similarly1 with oxalic acid3 ,,cooh ,,cook 7,h#b;,c#b,o#d7 ,,koh ,h#b,o ,,cooh ,,cooh ,oxalic acid ,acid potassium oxalate or1 ,,cooh ,,cook 7,h#b;,c#b,o#d7 #b,,koh #b;,h#b,o ,,cooh ,,cook ,oxalic acid ,neutral potassium oxalate ,similarly1 the acid ,h atom of either an organic or an inorganic acid may be replaced by the alkyl group of an alcohol1 producing ethereal salts1 or esters4 ,thus1 with nitric acid2 ,,no#b,,oh7,,hno#c7;,c#b;,h#e,,oh ,,no#b,,oc#b;,h#e7;,c#b;,h#e,,no#c7;,h#b ,o ,nitric acid ,ethyl alcohol ,ethyl nitrate ,and1 with acetic acid2 ,,ch#c;,,cooh7,h#d;,c#b,o#b7;,c#b;,h#e,, oh ,,ch#c;,,cooc#b;,h#e;,h#b,o ,acetic acid ,ethyl acetate ,with dibasic or polybasic acids1 either one or more of the carboxyl ,h atoms may be replaced with an alcohol radical1 so that both acid and neutral esters of all such acids are possible4 ,examples of all of these different types of derivatives of organic acids are frequently found in plant tissues4 ,the occurrence1 properties1 and functions of a particular type of glycerol1 and other esters of organic acids1 which are known as fats and waxes1 are not taken into consideration in the following discussions1 but reserved for a subsequent chapter dealing specially with them4 ,,some ,,common ,,organic ,,acids ,free organic acids1 or their mineral salts or volatile esters1 sometimes occur as separate and characteristic individual compounds in particular species of plants1 or fruits2 but much more commonly1 two1 three1 or even more acids or their derivatives1 are associated together4 ,formic acid1 ,h,,cooh 7,h#b;,,co#b71 occurs in free form and in considerable proportions in the leaves of several species of nettle1 where it is responsible for the unpleasant effects of the sting4 ,it may be detected in small amounts in the vegetative parts of many1 if not all1 plants1 especially during periods of rapid growth1 and is probably one of the intermediate products in the photosynthesis of carbohydrates 7see ,chapter ,,iii74 ,higher members of the formic acid series 7as acetic1 ,,ch#c;,,cooh2 propionic1 ,c#b;,h#e;,,cooh2 butyric1 ,c#c;,h#g;,,cooh2 etc47 are often found in small quantities in the leaves of many plants and seem to be characteristically present in certain species4 ,they are easily produced from carbohydrates by bacterial action and1 hence1 are always present in fermenting tissues1 such as silage1 sauerkraut1 etc4 ,furthermore1 the glycerol esters of higher members of this and other monobasic acid series are constituents of all natural fats and oils 7see ,chapter ,x74 ,oxalic acid1 ,,hooc,,cooh 7,h#b;,c#b,o#d71 is found in small amounts in nearly all plants and in relatively large proportions in those of ,oxalis1 rhubarb1 etc4 ,it occurs both as the free acid and as neutral1 or acid1 oxalates of calcium1 potassium1 and1 perhaps1 of magnesium and sodium4 ,solid crystals of insoluble calcium oxalate are often found in plant cells1 and it has been shown that when so deposited the calcium cannot become again available for metabolic uses4 ,it is stated1 further1 that such crystals form only when calcium is in excess in the plant sap2 hence1 the deposition of crystallized calcium oxalate seems to be a device for the avoidance of excessive calcium rather than excessive oxalic acid1 in the plant juices4 ,succinic acid1 ,,hooc,,ch#b;,,ch#b;,,cooh 7,h#f;,c#d,o#d71 occurs in many fruits and vegetables1 and is also found in some animal tissues4 ,in fruits1 it is usually associated with its derivatives1 malic and tartaric acids4 ,malic acid1 ,,hooc,,ch#b;,,choh,,cooh 7,h#f;,c#d,o#e71 occurs in apples and in many small fruits1 and in many vegetables4 ,acid calcium malate is now produced commercially as a bye-product from the manufacture of syrups from fruit juices1 and is used as a substitute for cream of tartar in the manufacture of baking powders4 ,tartaric acid1 ,,hooc,,choh,,choh,,cooh 7,h#f;,c#d,o#f71 is found in many fruits1 but most characteristically in the grape1 where it occurs as the mono-potassium salt4 ,during the fermentation of grape juice into wine1 this salt is deposited in considerable quantities in the bottom of the wine-casks4 ,this crude product is collected and sold under the name argols4 ,from these argols1 pure acid potassium tartrate is obtained by decolorization and recrystallization1 and constitutes the cream of tartar of commerce4 ,,cooh ,citric acid1 ,,hooc,,ch#b;,,coh,,ch#b;,,cooh 7,h#h;,c#f,o#g71 occurs in large proportions in lemons1 and associated with malic acid in strawberries1 cherries1 currants1 etc4 ,it is also found in small quantities in the seeds of the common leguminous vegetables1 beans1 peas1 etc4 ,tannic acid occurs widely distributed in the plant kingdom as a constituent of the special type of glucosides known as tannins1 whose properties and functions have already been discussed 7see ,chapter ,,vii74 ,,physiological ,,uses ,,of ,,organic ,,acids ,no conclusive evidence concerning the rle of organic acids in plant1 or animal1 growth1 has yet been produced4 ,there can be no doubt that the hypothetical carbonic acid and its acid and normal salts have a significant effect in regulating the acidity or alkalinity of plant juices1 or body fluids1 and so determining the nature of the enzymic activities and colloidal conditions of the biological systems 7see ,chapters ,,xiv and ,,xv74 ,it is probable that other organic acids1 such as formic1 acetic1 oxalic1 and succinic acids1 in plants and sarco-lactic acid1 in animal tissues1 perform similar regulatory rles2 but there seems as yet to be no indication as to why different acids should be used for this purpose by different species1 or organisms2 or as to the methods by which they perform their specific functions1 whatever these may be4 ,in plants1 the organic acids are usually in solution in the sap4 ,when the plant ripens1 they generally disappear1 either being neutralized by calcium1 or other bases1 and deposited as crystals in the leaves or stems1 or else used up in the synthesis of other organic compounds4 ,small proportions of these acids are usually present in mature seeds1 and the percentage increases materially during germination1 indicating that they play an important rle in insuring the proper conditions for the conversion of the reserve food of the seed into soluble materials available for the nutrition of the young growing plant4 ,,biological ,,significance ,,of ,,fruit ,,acids1 ,,etc4 ,the occurrence of organic acids1 or their derivatives1 which have pronounced odors or flavors1 in the flesh surrounding the seeds of fruits1 in the endosperm of vegetable seeds1 or in the tubers1 etc41 of perennial plants1 thus making them attractive as food for animals and men1 undoubtedly serves to insure a wider distribution of the reproductive organs of these plants2 a fact which has unquestionably had a marked influence upon the survival of species in the competitive struggle for existence during past eras and in the development and cultivation of different species by man4 ,indirect evidence that the proportion of these attractive compounds present in certain species may have been considerably increased by the processes of natural selection in the past is furnished by the many successful attempts to increase the percentage of such desirable constituents in fruits or vegetables by means of artificial selection of parent stocks by skillful plant breeders4 ,,chapter ,x ,,fats ,,and ,,oils1 ,,waxes1 ,,and ,,lipoids ,included in this group are several different kinds of compounds which have similar physical properties1 and which1 in general1 belong to the type of organic compounds known as esters1 i4e41 alcoholic salts of organic acids4 ,the terms oil1 fat1 and wax1 are generally applied more or less indiscriminately to any substance which has a greasy feeling to the touch and which does not mix with1 but floats on1 water4 ,there are many oils which are of mineral origin which are entirely different in composition from natural fats4 ,these have no relation to plant life and will not be considered here4 ,the natural fats1 vegetable oils1 and plant waxes are all esters4 ,there is no essential difference between a fat and an oil1 the latter term being usually applied to a fat which is liquid at ordinary temperatures4 ,the waxes1 however1 are different in chemical composition from the fats and oils1 being esters of monohydric alcohols of high molecular weight1 such as cetyl alcohol1 ,c#af;,h#cc,,oh1 myristic alcohol1 ,c#cj;,h#fa,,oh1 and cholesterol1 ,c#bg;,h#de,,oh2 whereas the fats and oils are all esters of the trihydric alcohol glycerol1 ,c#c;,h#e7,,oh7#c4 ,lipoids are much more complex esters1 having some nitrogenous1 or phosphorus-containing1 group and sometimes a sugar in combination with the fatty acids and glycerol which make up the characteristic part of their structure4 ,in general1 waxes and lipoids have a harder consistency than fats3 but this is not always the case1 since wool-fat and spermaceti1 both of which are true waxes in composition1 are so nearly liquid in form as to be commonly called fats2 while certain true fats1 like ,japan wax1 are so hard as to be commonly designated as waxes4 ,it is plain that physical properties alone cannot be relied upon in the classification of these bodies4 ,in fact1 there is no single definite property by which members of this group can be accurately identified4 ,there are many other types of substances belonging to entirely different chemical groups1 which have oily1 or fat-like1 properties4 ,a4 ,,fats ,,and ,,oils ,,occurrence ,fats and oils are widely distributed in plants4 ,they occur very commonly in the reproductive organs1 both spores and seeds1 as reserve food material4 ,in fungi1 oils are often found in the spores1 but sometimes also in sclerotia1 mycelia1 or filaments4 ,for example1 the sclerotia of ergot have been found to contain as much as #fj per cent of oil4 ,in higher plants1 many seeds contain high percentages of oil1 so as to make them commercial sources for edible or lubricating oils1 such as olive oil1 rape-seed oil1 cottonseed oil1 castor oil1 corn oil1 sunflower-seed oil1 etc41 etc4 ,nuts often contain large proportions of oil1 the kernel of the ,brazil nut1 for example1 sometimes contains as high as #gj per cent of oil1 while an oil content of #ej per cent1 or more1 is common in almonds1 walnuts1 etc4 ,oils also occur as reserve food material in other storage organs of plants1 such as the tubers of certain flowering plants1 and the roots of many species of orchids4 ,sometimes the appearance of oils in the stems of trees1 or the winter leaves of evergreens1 seems to be only temporary and to occur only during periods of very low temperatures4 ,much less frequently1 fats or oils are found in the vegetative organs of plants1 as in the leaves of evergreens4 ,their appearance and functions in these organs seem to be much less certain than in the other cases cited above2 although in rare cases a considerable proportion of oily material has been found to exist in definite association with the chloroplasts4 ,the vegetable fats and oils have many important industrial uses4 ,some of them1 such as olive oil1 cottonseed oil1 cocoanut oil1 etc41 are largely used as human food4 ,others1 as castor oil1 are used as lubricants4 ,the so-called drying oils 7see page #acb71 such as linseed oil1 etc41 are used in the manufacture of paints and varnishes4 ,some cheap vegetable oils are used as the basis for the manufacture of soaps1 etc4 ,hence1 industrial plants and processes for the extraction of oils from plant tissues are of very great economic importance4 ,,chemical ,,constitution ,the fats 7of either plant or animal origin7 are glycerides1 i4e41 glycerol esters of organic acids4 ,as has been pointed out1 esters are derived from organic acids and alcohols in exactly the same way that mineral salts are derived from inorganic acids and metallic bases4 -------- ,thus1 ,na,,oh ,h,,ono#b7;,,hno#c7 ,na,n,o#c ,h#b,o -------- ,base ,acid ,salt ----------- and1 ,c#b;,h#e,,oh ,h,,ooc,h ,c#b;,h#e,,ooc,h ,h#b,o ----------- ,alcohol ,acid ,ester --------------- or1 ,r,,oh ,h,,ooc,r ,r,,ooc,r ,h#b,o --------------- ,any alcohol ,any acid ,any ester ,glycerol is1 however1 a trihydric alcohol1 i4e41 it contains three replaceable 7,,oh7 groups4 ,its formula is ,c#c;,h#e7,,oh7#c1 or ,,ch#b,,oh,,choh,,ch#b,,oh4 ,hence1 three molecules of a monobasic acid are required to replace all of its 7,,oh7 groups4 ,for example1 ,c#b;,h#e,,oh ,,hooc,c#ag;,h#ce ,,ch#b,,ooc,c#ag;,h#ce ,,choh ,,hooc,c#ag;,h#ce ,,chooc,c#ag;,h#ce #c;,h#b,o ,c#b;,h#e,,oh ,,hooc,c#ag;,h#ce ,,ch#b,,ooc,c#ag;,h#ce ,it is theoretically possible1 of course1 to replace either one1 two1 or three of the 7,,oh7 groups in the glycerol with acid radicals1 thus producing either mono-1 di-1 or triglycerides4 ,if the primary alcohol groups in the glycerine molecule are designated by 7#a7 and the secondary one by 7#b71 thus1 ,,ch#b,,oh7#a7;,,choh7#b7;,,ch#b,,oh7#a7 1 it is conceivable that there may be either 7#a7 or 7#b7 monoglycerides1 either 7#a1 #a7 or 7#a1 #b7 diglycerides1 or a triglyceride1 depending upon which of the 7,,oh7 groups are replaced4 ,compounds of all of these types have been produced by combinations of glycerol with varying proportions of organic acids under carefully controlled conditions2 and all of them found to possess fat-like properties4 ,all natural fats are triglycerides1 however4 ,most natural fats are mixtures of several different triglycerides in each of which the three 7,,oh7 groups of the glycerol has been replaced by the same organic acid radical1 as in the example of stearin shown above4 ,but recent investigations have shown that some of the common animal fats1 and perhaps some plant oils1 may be made up of mixed glycerides1 i4e41 those in which the different 7,,oh7 groups have been replaced by different acid groups1 as oleo-stearin1 oleo-stearo-palmitin1 etc4 ,,the ,,acids ,,which ,,occur ,,in ,,natural ,,fats ,the acids which1 when combined with glycerol1 produce fats are of two general types4 ,the first of these are the so-called fatty acids having the general formula ,cn,h#bn#a;,,cooh4 ,these are the saturated acids1 i4e41 they contain only single-bond linkages in the radical which is united to the ,,cooh group2 hence1 they cannot take up hydrogen1 oxygen1 etc41 by direct addition4 ,the second type are the unsaturated acids belonging to several different groups1 as discussed below1 but all having one or more double-linkages between the carbon atoms of the alkyl radical which they contain4 ,because of these double linkages1 they are all able to take on oxygen1 hydrogen1 or the halogen elements1 by direct addition4 ,when exposed to the air1 for example1 these unsaturated acids1 or the oils derived from them1 take up oxygen1 increasing in weight1 and becoming solid or hard and stiff4 ,hence1 natural oils which contain considerable proportions of glycerides of these unsaturated acids are known as drying oils and are largely used in the manufacture of paints1 varnishes1 linoleums1 etc42 while oils which contain little of these glycerides are known as non-drying1 and are used for food1 for lubrication1 or for other technical purposes in which it is essential that they remain in unchanged fluid condition when exposed to the air4 ,the following are some of the more important of the acids which occur as glycerides in natural fats3 ,saturated ,acids3 7a7 ,acetic1 or stearic1 acid series--general formula1 ,cn,h#bn#a;,,cooh4 7#a7 ,formic acid1 ,h,,cooh1 occurs free in nettles1 ants1 etc4 7#b7 ,acetic acid1 ,,ch#c;,,cooh1 occurs free in vinegar4 7#c7 ,butyric acid1 ,c#c;,h#g;,,cooh1 in butter fat4 7#d7 ,capric acid1 ,c#i;,h#ai;,,cooh1 in butter fat and cocoanut oil4 7#e7 ,myristic acid1 ,c#ac;,h#bg;,,cooh1 in cocoanut oil and spermaceti4 7#f7 ,palmitic acid1 ,c#ae;,h#ca;,,cooh1 in palm oil and many fats4 7#g7 ,stearic acid1 ,c#ag;,h#ce;,,cooh1 in most fats and oils4 ,intervening members of this series1 such as caprylic acid1 ,c#g;,h#ae;,,cooh1 and lauric acid1 ,c#aa;,h#bc;,,cooh1 are also found in smaller quantities in cocoanut and palm nut oils1 in butter fat1 and in spermaceti2 while higher members of the series1 as arachidic acid1 ,c#ai;,h#ci;,,cooh1 and lignoceric acid1 ,c#bc;,h#dg;,,cooh1 are found in peanut oil2 and cerotic acid1 ,c#be;,h#ea;,,cooh1 and melissic acid1 ,c#bi;,h#ei;,,cooh1 in beeswax and carnauba wax4 ,unsaturated ,acids3 7b7 ,oleic acid series--general formula1 ,cn,h#bn-#a;,,cooh4 7#a7 ,crotonic acid1 ,c#c;,h#e;,,cooh1 occurs in croton oil4 7#b7 ,oleic acid1 ,c#ag;,h#cc;,,cooh1 occurs in many fats and oils4 7#c7 ,brassic acid1 ,c#ba;,h#da;,,cooh1 occurs in rape-seed oil4 7#d7 ,ricinoleic acid1 ,c#ag;,h#cb,,oh,,cooh1 occurs in castor oil4 7c7 ,linoleic acid series--general formula1 ,cn,h#bn-#c;,,cooh4 7#a7 ,linoleic acid1 ,c#ag;,h#ca;,,cooh1 occurs in linseed and other drying oils4 7d7 ,linolenic acid series--general formula1 ,cn,h#bn-#e;,,cooh4 7#a7 ,linolenic acid1 ,c#ag;,h#bi;,,cooh1 occurs in many drying oils4 ,it will be observed that all of these acids contain a multiple of two total carbon atoms4 ,no acid containing an uneven number of carbon atoms has been found in a natural fat4 ,furthermore1 the acids which occur most commonly in natural fats are those which contain eighteen carbon atoms2 in fact1 more than #hj per cent of the glycerides which compose all animal and vegetable fats are those of the ,c#ah acids4 ,this fact1 in addition to the one that the sugars and starches all contain multiples of six carbon atoms in their molecules1 indicates a very great biological significance of the chain of six carbon atoms4 ,this has been alluded to in connection with the discussion of the biological significance of molecular configuration 7see page #eg7 and will be mentioned again in other connections4 ,,the ,,alcohols ,,which ,,occur ,,in ,,natural ,,fats ,glycerol1 as has been pointed out1 is by far the most common alcoholic constituent of natural fats and oils4 ,this substance1 which is familiar to everyone under its common name glycerine1 is a colorless1 viscid liquid having a sweetish taste4 ,it is a very heavy liquid 7specific gravity #a4bg7 which mixes with water in all proportions and when in concentrated form is very hygroscopic4 ,glycerine is made from fats and oils by commercial processes which clearly prove that the constitution of fats is as described above4 ,the fat is boiled with a solution of caustic soda and is decomposed1 the sodium of the alkali taking the place of the glyceryl 7,c#c;,h#e7 group1 the latter combining with three 7,,oh7 groups from the three molecules of alkali necessary to decompose the fat4 ,a sodium salt of the organic acid1 or soap1 and glycerol are thus produced1 and are separated by saturating the hot solution with common salt1 which causes the soap to separate out as a layer on the surface of the liquid1 which1 on cooling1 solidifies into a solid cake1 which is then cut and pressed into the familiar bars of commercial soap4 ,from the remaining solution1 the glycerine is recovered by evaporation and distillation under reduced pressure4 ,taking stearin1 a common fat1 as the example1 the reaction which takes place in the above process may be expressed by the following equation3 ,c#c;,h#e7;,c#ag;,h#ce;,,coo7#c #c,na,o,h #c;,c#ag;,h#ce;,c,o,o,na ,stearin ,sodium stearate--a soap ,c#c;,h#e7,,oh7#c4 ,glycerol ,this process1 since it yields soap as one of its products1 is called saponification4 ,all fats1 when saponified1 yield soaps and either glycerol or 7more rarely7 some of the other alcohols which are described below4 ,glycerine is also prepared from fats by hydrolysis with superheated steam4 ,using olein1 a glyceride which is present in olive oil and many common fats1 as the example in this case1 the equation for the reaction is3 ,c#c;,h#e7;,c#ag;,h#cc;,,coo7#c #c;,h#b,o #c;,c#ag;,h#cc;,,cooh ,olein ,steam ,oleic acid ,c#c;,h#e7,,oh7#c ,glycerol ,in this case the free fatty acid1 instead of a soap1 is the product which is obtained in addition to glycerol4 ,in the equations presented above1 a single glyceride has been used as the example in each case4 ,in the saponification1 or hydrolysis1 of natural fats and oils which1 as has been shown1 are mixtures of many glycerides1 the resultant soaps1 or fatty acids1 are mixtures of as many compounds as there were individual glycerides of the original fat1 but the glycerol is identical in every case4 ,when glycerol is heated with dehydrating agents1 it is easily converted into acrolein1 an unsaturated aldehyde having a peculiar characteristic pungent odor4 ,hence1 the presence of glycerol1 or glycerides1 in any substance may usually be detected by mixing the material with anhydrous acid potassium sulfate and heating the mixture in a test tube1 when the characteristic odor of acrolein will appear4 ,glycerol possesses all the characteristic properties of an alcohol1 forming alcoholates with alkalies1 esters with acids1 etc4 ,it is an active reducing agent1 being itself easily oxidized to a variety of different products depending upon the strength of the oxidizing agent used and the conditions of the experiment4 ,microorganisms affect it in a variety of ways1 either converting it into simple fatty acids1 or condensing it into longer-chain compounds4 ,open-chain monohydric alcohols1 higher members of the ethyl alcohol series1 such as cetyl1 ,c#af;,h#cc,,oh1 carnaubyl1 ,c#bd;,h#di,,oh1 ceryl1 ,c#bf;,h#ec,,oh1 and melissyl1 ,c#cj;,h#fa,,oh1 are found in the esters which constitute the major proportion of the common waxes4 ,cholesterol and phytosterol are empirical names for certain closed-ring1 monohydric alcohols which are found in relatively small amounts in all fats1 the former term designating those found in animal fats and the latter those of plant origin4 ,their composition has not yet been definitely established4 ,they are known to contain two1 or three1 closed rings1 probably of the phenanthrene type2 to form dichlor- and dibrom- addition products1 showing that they contain one side-chain double linkage2 and to yield ketones when oxidized1 indicating that they are secondary alcohols4 ,they form acetyl esters1 or acetates1 which can be separated from each other and identified by their crystal forms and melting points4 ,because of this fact and of the further fact that they are present in detectable quantities in practically all fats and oils1 they afford a qualitative means of distinguishing between fats of animal and of plant origin4 ,this possibility is the most interesting fact known concerning these complex alcohols2 although their presence as esters in all plant and animal fats indicates that they must have some biological function4 ,phytosterol is not a single alcohol1 but a mixture of at least two1 which have been separated and studied as sitosterol1 ,c#bg;,h#dc,,oh1 and stigmasterol1 ,c#cj;,h#di,,oh4 ,as has been said1 these are found in small proportions in all vegetable fats1 being present in largest amounts in oily seeds1 especially those of the legumes4 ,the saponification of esters of cholesterol and phytosterol is a difficult and unsatisfactory process2 but since this affords the only known means to distinguish between fats of plants and of animal origin1 its technique has been fairly well worked out1 and the process used in the study of the changes which take place in plant fats when they are used by animals as food4 ,,hydrolysis ,,and ,,synthesis ,,of ,,fats ,the reaction for the hydrolysis of fats has been discussed in connection with the process for the manufacture of glycerine4 ,this reaction takes place very slowly with cold water alone1 can be easily brought about by the action of superheated steam1 and much more easily and rapidly in the presence of some catalyst 7sulfuric acid is an especially effective catalyst for this purpose74 ,fats can be artificially synthetized by heating mixtures of glycerol and fatty acids1 under considerable pressure1 for some time at temperatures of #bjj to #bdj ,c42 or by heating a mixture of the disulfuric ester of glycerol with a fatty acid dissolved in sulfuric acid4 ,recently1 fatty acids have been prepared from carbohydrates1 by first breaking the hexoses down into three-carbon compounds1 then carefully oxidizing these to pyruvic acid1 ,,ch#c;,,co,,cooh1 which can then be condensed into acids having longer chains4 ,the violent reagents and long-continued processes which must be employed for the artificial hydrolysis or synthesis of the fats are in sharp contrast with the easy and rapid transition of carbohydrates to fats1 and vice versa1 which take place in both plant and animal nutrition4 ,,the ,,extraction ,,of ,,oils ,,from ,,plant ,,tissues ,there are three types of methods which are employed for the extraction of oil from oil-bearing seeds1 etc41 either as a commercial industry or for the purposes of scientific study4 ,these are 7#a7 by pressure2 7#b7 extraction with volatile solvents2 and 7#c7 boiling the crushed seeds or fruits with water4 ,by the first method1 the seeds are first cleaned1 then decorticated 7hulls removed71 crushed or ground1 then subjected to intense pressure in an hydraulic press4 ,in the commercial process1 the ground seeds are first pressed at ordinary temperature1 which yields cold-drawn oil1 then the press cake is heated and pressed again1 whereby hot-drawn oil is obtained4 ,the crude oil is refined by heating it to coagulate any albumin which it may contain1 and is sometimes bleached by different processes before it is marketed4 ,the press cake from many seeds1 such as flaxseed 7linseed71 cottonseed1 etc41 is ground up and sold for use as stock feed4 ,in the second method1 the finely crushed seeds are treated with solvents such as gasoline or carbon bisulfide1 in an apparatus which is so arranged that the fresh material is treated first with solvent which has already passed through various successive lots of material and has become highly charged with the oil1 followed by other portions which contain less oil1 and finally by fresh solvent1 whereby the last traces of oil are removed from the material4 ,the saturated solvent is transferred to suitable boilers and the solvent distilled off and condensed for repeated use1 leaving the oil in the boiler in very pure form4 ,extraction by boiling with water is sometimes used in the preparation of castor oil and olive oil4 ,in such cases1 the crushed seeds are boiled with water and the oil skimmed off as fast as it rises to the surface4 ,,identification ,,of ,,fats ,,and ,,oils ,fats and oils are identified by determinations of their physical properties1 such as specific gravity1 melting point1 refractive index1 etc41 and by certain special color reactions for particular oils2 or by measurements of certain chemical constants1 such as the percentage of free fatty acids which they contain1 the saponification value 7i4e41 the number of milligrams of ,,koh required to completely saponify one gram of the fat71 the iodine number 7percentage by weight of iodine which is absorbed by the unsaturated fatty acids present in the fat71 percentage of water-insoluble fatty acids obtained after saponification and acidifying the resultant soap1 etc41 etc4 ,most of these tests must be carried out under carefully controlled conditions in order to insure reliable identifications1 and need not be discussed in detail here4 ,full directions for making such tests1 together with tables of standard values for all common fats and oils1 may be found in any reference book on oil analysis4 ,,physiological ,,use ,,of ,,fats ,,and ,,oils ,in animal organisms1 fats are the one important form of energy storage4 ,they also form one of the most important supplies of energy reserve material in plants4 ,carbohydrates commonly serve this purpose in those plants whose storage reservoirs are in the stems1 tubers1 etc42 but in most small seeds the reserve supply of energy is largely in the form of oil1 and even in those seeds which have large endosperm storage of starch1 the embryo is always supplied with oil which seems to furnish the energy necessary for the first germinative processes4 ,fats are the most concentrated form of potential energy of all the different types of organic compounds which are elaborated by plants4 ,this is because they contain more carbon and hydrogen and less oxygen in the molecule than any other group of substances of vegetable 7or animal7 origin4 ,it has been pointed out that a quantity of fat capable of yielding #ajj large calories of heat will occupy only about #ab cc4 of space1 whereas from #abe to #bbe cc4 of space in the same tissue would be required for the amount of starch of glycogen necessary to yield the same amount of heat1 or energy1 when oxidized4 ,the fats undoubtedly catabolize first by hydrolysis into glycerol and fatty acids1 and then by oxidation possibly first into carbohydrates and then finally into the end-products of oxidation1 namely1 carbon dioxide and water4 ,the following hypothetical equation to represent the oxidation of oleic acid into starch1 suggested by ,detmer1 is interesting as a suggestion of how much oxygen is required and how much heat would be liberated by such a transformation3 ,c#ah;,h#cd,o#b #bg,o #b7;,c#f;,h#aj,o#e7 #f;,,co#b #g;,h#b,o ,complete oxidation of oleic acid to the final end-products1 carbon dioxide and water1 would require much more oxygen1 thus3 ,c#ah;,h#cd,o#b #ea,o #ah;,,co#b #ag;,h#b,o4 ,hence1 ,detmer's reaction would yield only approximately one-half the total energy available in the acid2 but it does indicate the possibility of redevelopment of fatty acids or fats from the unoxidized carbohydrate material which remains in the equation4 ,moreover1 there is abundant evidence to show that1 in both animal and plant tissues1 energy changes are brought about chiefly by the transformation of fats into carbohydrates and vice versa4 ,many different hypotheses have been put forward concerning the mode of transformation of fats into carbohydrates1 and the changes which take place in oily seeds during their germination have been carefully studied by many investigators4 ,the following seem to be fairly well established facts4 ,first1 that fats as such may be translocated from cell to cell1 since cell-walls and cell protoplasm seem to be permeable to oil if it is a sufficiently fine emulsion2 or they may be hydrolyzed into glycerol and fatty acids and translocated from cell to cell in these forms and recombined into fats in the new location4 ,second1 that fats are formed from glucose in some plants1 from sucrose and from starch in others1 and from mannite and similar compounds in still other species4 ,third1 that in germination the fatty acids are used up in the order of their degree of unsaturation1 those which contain the largest number of double-bond linkages being used first1 and the saturated acids last of all4 ,fourth1 that the sugar produced by the oxidation of fats is derived either from the glycerol or from the fatty acids of the fat1 depending upon the nature of the latter4 ,if the fat is saturated1 the glycerine is converted into sugar while the fatty acids are oxidized2 but if the fat contains large proportions of unsaturated acids1 these contribute to the formation of sugar4 ,recent studies seem to show that in the animal body fats serve an important function in connection with the production of antibodies to disease germs4 ,but there is as yet no evidence to show that fats and oils have any similar function in plant tissues4 ,the fact that they are found almost wholly in the storage organs of plants seems to indicate that their use as food reserve material is their principal1 if not their sole1 function in the plant economy4 ,b4 ,,the ,,waxes ,waxes are most commonly found in or on the skin of leaves or fruits4 ,they are similar to fats in chemical composition1 except that1 instead of being glycerides1 they are esters of monohydric alcohols of high atomic weight4 ,the term wax1 when used in the chemical sense1 has reference to this particular type of esters rather than to any special physical properties which the compound possesses1 and both solid and liquid waxes are known4 ,carnauba wax1 found on the leaves of the wax-palm 7,copernicia cerifera7 contains ceryl alcohol 7,c#bc;,h#ec,,oh7 and myricyl alcohol 7,c#cj;,h#fa,,oh7 esters of cerotic acid 7,c#be;,h#ea;,,cooh7 and carnaubic acid 7,c#bc;,h#dg;,,cooh74 ,it is the best known vegetable wax4 ,poppy wax is composed chiefly of the ceryl ester of palmitic acid 7,c#ag;,h#ce;,,cooh74 ,since waxes contain no glycerol1 they give no odor of acrolein when heated with dehydrating agents1 do not become rancid1 and are less easily hydrolyzed than the fats4 ,they are soluble in the same solvents as the fats1 but generally to a less degree4 ,the facts that waxes are impervious to water and usually occur on the surfaces of plant tissues have led to the conclusion that their chief function is to provide against the too-rapid loss of water by evaporation from these tissues4 ,this seems to be borne out by the common experience that many fresh fruits and vegetables will keep longer without shriveling if their waxy coating is undisturbed4 ,no other function than that of regulation of water losses has been suggested for the plant waxes4 ,c4 ,,the ,,lipoids ,the lipoids1 or lipins1 as some authors prefer to call them1 are substances of a fat-like nature which are found in small quantities in nearly all plant and animal tissues and in considerable proportions in nerve and brain substance1 in egg yolk1 etc41 and in the seeds of plants4 ,when hydrolyzed1 they yield fatty acids or derivatives of fatty acids and some other group containing either nitrogen only or both nitrogen and phosphorus4 ,the facts that they are extracted from tissues by the same solvents which extract fats and that they yield fatty acids when hydrolyzed account for the name lipoid1 which comes from the ,greek word meaning fat4 ,some writers1 who object to the word lipoid as a group name1 prefer to call these substances the fat-like bodies4 ,the first group of lipoids to be studied were those which occur in the brain2 and the name cerebroside was given to those lipoids which1 when hydrolyzed1 yield fatty acids1 a carbohydrate and a nitrogen-containing compound but no phosphoric acid2 while those lipoids which contain both nitrogen and phosphorus were called phosphatides4 ,substances which correspond in composition to both these types are found in plant tissues and the same class names are applied in a general way to lipoids of either plant or animal origin4 ,plant lipoids have not been studied to nearly the same extent as have those which occur in the animal body2 and certain observers believe that there are significant differences between the lipoids of plants and those of animal origin4 ,however1 most investigators use the same methods of study and the same systems of nomenclature for these fat-like substances1 regardless of their origin4 ,,lecithin ,this phosphatide is by far the best-known lipoid4 ,it occurs in the brain1 the heart1 the liver1 and in the yolk of the eggs of many animals2 and either lecithin or a substance so nearly like it in character as to be regarded by most investigators as identical with it1 is present in small1 but constant1 quantities in nearly all seeds1 especially those of leguminous plants4 ,in many legume seeds1 it constitutes from #ej to #fj per cent of the ether extract1 or crude fat1 which can be extracted from the crushed seeds1 using ether as the solvent4 ,lecithin is a glyceride4 ,only two of the 7,,oh7 groups of the glycerol are replaced by fatty acids1 however2 the third being replaced by phosphoric acid1 ,h#c,,po#d1 or ,,po7,,oh7#c1 which1 in turn1 has one of its hydrogen atoms replaced by the base choline4 ,choline is a nitrogenous base1 or amine1 which may be regarded as ammonium hydroxide with three of its hydrogen atoms replaced by methyl groups and the fourth by the ethoxyl group1 the latter being the ethyl group with an ,,oh in place of one of its hydrogens4 ,thus1 ,ammonium hydride ,choline ,h ,h ,,ch#c ,c#b;,h#d,,oh _/ _/ ,h-,n ,,ch#c-,n _/ _/ ,h ,,oh ,,ch#c ,,oh ,without the choline1 lecithin would be a di-fatty acid derivative of glycero-phosphoric acid4 ,these relations may be seen in the following formulas3 ,glycerol ,glycero-phosphoric acid ,fatty ,acid ,,ch#b,,oh ,,ch#b,,oh ,,oh ,,hooc,r _/ _/ ,,choh ,,ch--,o--,p,o ,,ch#b,,oh ,,ch#b,,oh ,,oh ,choline ,lecithin ,,hoc#b;,h#d ,,ch#b,,ooc,r ,,oh _/ _/ 7,,ch#c7ctrb,n ,,ch---,o---,p,o ,c#b;,h#d _/ _/ _/ _/ ,ntrb7,,ch#c7c ,,ho ,,ch#b,,ooc,r ,o _/ ,,ho fatty acid _/ ,or1 glycerol-fatty acid ,choline ,lecithin ,h#b,o phosphoric acid ,there are many different possible linkages of the constituent groups which make up the lecithin molecule4 ,in the first place1 if the 7,,oh7 groups of the glycerol molecule be numbered 7#a7 and 7#b71 thus1 ,,ch#b,,oh 7#a7 ,,choh 7#b7 ,,ch#b,,oh 7#a7 the fatty acid radicals may be attached either in one 7#a7 position and one 7#b7 position1 or in the two 7#a7 positions2 hence1 two forms of glycero-phosphoric acid are possible1 thus fatty acid fatty acid _/ _/ 7,a7 glycerol--fatty acid 7,b7 glycerol--phosphoric acid phosphoric acid fatty acid ,again1 the choline may be attached to the phosphoric acid either through its alcoholic 7,,oh7 group or through its basic 7,n7 group1 thus ,,oh ,,oh _/ _/ -,p,o ,c#b;,h#d -,p,o _/ ,o ,ntrb7,,ch#c7c or1 ,o-,ntrb7,,ch#c7c _/ ,,ho ,c#b;,h#d,,oh ,the facts that in the arrangement 7,b7 the central carbon atom of the glycerol would be asymmetric1 and that both lecithin and the glycero-phosphoric acid derived from it by hydrolysis are optically active1 prove that formula 7,b7 correctly represents the arrangement of that part of the lecithin molecule2 and there is ample theoretical and experimental evidence to prove that the choline linkage is through the alcoholic 7,,oh7 group4 ,hence the formula for lecithin indicating the linkage as shown above is the correct one4 ,the fatty acids in the lecithin molecule may be different in lecithins from different sources1 just as they are different in fats from different sources4 ,both oleic acid and a solid fatty acid have been found in the hydrolysis products of lecithin from leguminous seeds4 ,in certain lupine seeds1 the fatty acids present in the lecithin appear to be palmitic and stearic4 ,,other ,,plant ,,phosphatides ,phosphatides other than lecithin are common in plants4 ,in these1 various sugars replace part or all of the glycerol as the alcoholic part of the ester4 ,percentages of sugar varying from mere traces up to #ag per cent of the weight of material taken1 have been found in the products of hydrolysis of phosphatides prepared from vetch seeds1 potato tubers1 plant pollens1 and whole wheat meal4 ,furthermore1 betaine ,,ch#b _/ 7tri-methyl glycocoll1 ,,oc ,ntrb7,,ch#c7c7 _/ ,o and perhaps other vegetable amines 7see ,chapter ,,xii7 sometimes replace choline as the basic group in the phosphatides4 ,,plant ,,cerebrosides ,bodies similar to the animal cerebrosides seem to occur in many plant tissues1 since plant lipoids which yield no phosphorus when hydrolyzed have often been isolated4 ,the sugar which constitutes the alcoholic portion of their structure appears to be galactose in every case which has been reported4 ,beyond this1 little is known of the structure of these plant cerebrosides1 as they are very difficult to prepare in pure form and not easily hydrolyzed4 ,,physiological ,,uses ,,of ,,lipoids ,lipoids are so universally present in plant and animal tissues and so commonly found in those parts of the organism in which vital phenomena are most pronounced 7brain1 heart1 embryo of egg1 embryo of seeds1 etc471 that it is evident that they must play some important rle in the activity of living protoplasm4 ,there is1 as yet1 however1 no definite and certain knowledge of what this rle is4 ,various theories concerning the matter have been put forward in recent years4 ,for example1 ,overton1 in #aija1 presented the idea that every living cell is surrounded by a semi-permeable membrane consisting of lipoid material1 which regulates the passage into and out of the cell of substances necessary to its metabolism and growth4 ,recent investigations by ,osterhout and others indicate1 however1 that ,overton's hypothetical lipoid membrane is not essential to a proper explanation of the migration into and out of the cell protoplasm of nutritive materials1 etc4 ,other investigators have cited results which appear to indicate that lipoids play an important1 but as yet unknown1 part in the process of fat metabolism4 ,others go even further than this1 and argue that since the extraordinary rapidity of the chemical changes which take place in plant protoplasm indicates the necessity of the presence there of exceedingly labile substances1 and since both fats and proteins are relatively stable compounds1 it is possible that the lipoids1 which contain both nitrogenous and fatty acid groups1 play an exceedingly important part in the metabolism processes4 ,bang1 in particular1 has pointed out 7in #aiaa7 that the lipoids are probably the most labile of all the components which constitute the colloidal system known as plant protoplasm4 ,the importance of such considerations will be more apparent after the relation of colloidal phenomena to the activities of plant cell contents has been more fully discussed 7see ,chapter ,,xvi74 ,experimental studies of the physiological uses of lipoids have thus far been devoted almost exclusively to those of animal tissues4 ,they have been seriously hampered by the difficulty of securing properly purified extracts of lecithin and similar lipoids4 ,the same labile character which apparently makes them so important in the chemical changes in the cell makes them equally unstable compounds to work with in attempting to secure pure preparations for the purposes of experimental study4 ,on this account1 there is1 as yet1 no certain knowledge concerning their actual physiological uses4 ,it is evident1 however1 that they have some really important rle to play1 which opens up a promising field for further study4 ,,references ,,abderhalden1 ,e4--,biochemisches ,handlexikon1 ,band #c1 ,fette1 ,wachse1 ,phosphatide1 ,cerebroside1 444 #cdj pages1 ,berlin1 #aiaa4 ,,hopkins1 ,e4--,the ,oil-,chemist's ,handbook1 #gb pages1 ,new ,york1 #aijb4 ,,leathes1 ,j4 ,b4--,the ,fats1 #ach pages1 ,monographs on ,biochemistry1 ,london1 #aiac4 ,,lewkowitsch1 ,j4--,chemical ,technology and ,analysis of ,oils1 ,fats1 and ,waxes1 ,vol4 ,i1 #edb pages1 #ed figs42 ,vol4 ,,ii1 #haf pages1 #bj figs42 and ,vol4 ,,iii1 #djf pages1 #bh figs41 ,london1 #aiji4 ,,maclean1 ,h4--,lecithin and ,allied ,substances1 #bjf pages1 ,monographs on ,biochemistry1 ,london1 #aiac4 ,,southcombe1 ,j4 ,e4--,chemistry of the ,oil ,industries1 #bjd pages1 #ac figs41 ,london1 #aiah4 ,,chapter ,,xi ,,essential ,,oils ,,and ,,resins ,included in this group are all those substances to which the characteristic odors of plants are due1 along with others similar in structure and possessing characteristic resinous properties4 ,they have no such uniformity in composition as is exhibited by the oils which are included among the fats and waxes2 but belong to several widely different chemical groups4 ,furthermore1 there is no sharp dividing line between the essential oils and certain esters of organic acids on the one hand and the fats on the other4 ,for example1 if an aromatic fluid essence is a light fluid1 non-viscid1 and easily volatile1 it is usually classed with the organic esters2 denser liquid substances1 of oily or waxy consistency1 and with comparatively slight odor and taste are usually fats1 while oils of similar physical properties but possessing strong characteristic odors are classed as essential oils1 regardless of their chemical composition4 ,included in this general class are compounds having a great variety of chemical structures2 e4g41 hydrocarbons1 alcohols1 phenols1 organic sulfides and sulfocyanides1 etc4 ,many of these compounds are crystalline solids at ordinary temperatures1 but melt to oily fluids at higher temperatures4 ,the characteristic property which assigns any given plant extract to this group is that it has a strikingly characteristic odor or taste1 often accompanied by some definite physiological effect1 or medicinal property4 ,these compounds may be either secretions or excretions of plants1 sometimes normally present in the healthy tissue1 and sometimes produced as the result of injury or disease4 ,the essential oils and the resins often occur associated together in the plant2 or1 the resins may develop from the oily juice of the plant after exposure to the air4 ,,the ,,essential ,,oils ,these may be divided1 according to their chemical composition1 into two major groups2 7#a7 the hydrocarbon oils1 or terpenes1 and 7#b7 the oxygenated and sulfuretted oils4 ,the terpenes are of three different types1 namely3 7a7 the hemiterpenes1 ,c#e;,h#h1 unsaturated compounds of the valerylene series1 of which isoprene 7found in crude rubber7 is the best-known example2 7b7 the terpenes proper1 ,c#aj;,h#af1 which constitute the major proportion of the whole group2 and 7c7 the polyterpenes 7,c#e;,h#h7n1 of which colophene and caoutchouc are the most common examples4 ,eleven different terpenes having the formula ,c#aj;,h#af have been isolated from various plant juices1 and their molecular arrangement carefully worked out4 ,the following three examples will serve as typical of the general structural arrangement of these hydrocarbons3 ,limonene ,camphene ,pinene ,h ,c _/ _/ _/ _/ _/ ,,ch#c ,h _/ _/ ,c ,c _/,,ch#c ,,ch#c _/ ,,ch#c _/ ,h#c;,c _/ ,,ch#b _/ _/ ,c ,h#b;,c ,,ch ,c ,,ch#b _/ _/ _/ ,,ch#c ,,hch _/ _/ ,h#b;,c ,,ch#b ,,ch#b;,c ,,ch#b _/ _/ _/ _/ _/ _/ _/ ,,ch ,c _/ ,,hc ,,ch ,c ,h _/_/ _/_/ _/_/ ,h#b;,c ,,ch#c _/_/ _/_/ _/_/ _/_/ _/_/ _/_/ ,c ,,ch#c ,a discussion of the evidence which supports these formulas as properly represented the molecular arrangements of the various isomeric forms would be out of place here1 as its only particular interest is in connection with the medicinal effects of the different compounds4 ,it is clear1 however1 that they are six-membered hydrocarbon rings1 with additional hydrocarbon groups attached to one or more of the carbon atoms in the ring4 ,different modifications1 or varieties1 of the terpenes constitute the main proportions of the oils of turpentine1 bergamot1 lemon1 fir needles1 eucalyptus1 fennel1 pennyroyal1 etc4 ,the oxygenated essential oils may be either alcohols1 aldehydes1 ketones1 acids1 esters1 or phenols1 derived from either five-membered or six-membered closed-ring hydrocarbons4 ,they are usually present in the plant oil in mixtures with each other or with a terpene4 ,since most of them have pronounced physiological or medicinal properties1 their structure has been well worked out1 in most cases2 but it seems to be hardly worth while to present these matters in detail here1 as they are of interest chiefly on account of their medicinal properties rather than their botanical functions4 ,borneol1 ,c#aj;,h#ag,,oh1 and menthol1 ,c#aj;,h#ai,,oh1 are typical alcohols4 ,the latter is a crystalline substance1 which melts at #db1 which is present in peppermint oil1 both as the free alcohol and as an ester of acetic acid4 ,amyl acetate1 ,,ch#c;,,cooc#e;,h#aa1 and linalyl acetate1 ,,ch#c;,,cooc#aj;,h#ag1 the latter occurring in the oils of lavender and bergamot1 are typical esters classed as essential oils4 ,as examples of the aldehyde oils1 benzoic aldehyde1 ,c#f;,h#e;,,cho1 oil of bitter almonds1 and cinnamic aldehyde1 ,c#f;,h#e;,,ch,,chcho1 found in the oils of cinnamon and cassia1 may be cited4 ,camphor1 ,c#aj;,h#af,o1 is a ketone1 having the following structural formula3 ,h ,c _/ _/ _/ _/ _/ _/ ,,ch#b ,,ch#b ,,ch#c-;,c-,,ch#c ,,ch#b ,c,o _/ _/ _/ _/ _/ _/ ,c ,,ch#c ,there are a considerable number of essential oils which are phenols4 ,thymol1 ,c#f;,h#c7;,,ch#c77;,c#c;,h#g7,,oh1 in oil of thyme1 and carvacrol1 its isomer1 in oil of hops1 are familiar examples4 ,o-,c,o _/ ,coumarin1 the anhydride of cinnamic acid ,c#f;,h#d 1 ,,hc,,ch is an example of an acid substance which is classed as an essential oil1 even though it is a solid at ordinary temperatures4 ,it has an odor and flavor similar to that of vanillin1 the essential flavoring material of the vanilla bean1 and is often used as a substitute for the latter in the preparation of artificial flavoring extracts4 ,of the essential oils containing sulfur1 there are two common examples2 oil of mustard1 allyl isosulfocyanide1 ,c#c;,h#e,,ncs1 and oil of garlic1 allyl sulfide 7,c#c;,h#e7b,s4 ,the latter is present in onions1 garlic1 water cress1 radishes1 etc41 the difference in flavor of these vegetables being due to the fact that the allyl sulfide is united with other different groups in the glucoside arrangement1 in the different plants4 ,similarly1 mustard oil is not present in mustard seeds as such1 but as a glucoside which1 when hydrolyzed by the enzyme myrosin which is always present in other cells of the same seeds1 yields ,c#c;,h#e,,ncs1 ,,khso#d1 and ,c#f;,h#ab,o#f4 ,,the ,,resins ,the resins were formerly supposed to be the mother substances from which the terpenes are derived4 ,it is now known1 however1 that they are the oxidation products of the terpenes4 ,their exact structure is still a matter of some uncertainty1 as their peculiar resinous character makes them very difficult to study by the usual methods of chemical investigations4 ,resins are divided into two classes3 7a7 the balsams1 and 7b7 the solid or hard resins4 ,canada balsam and crude turpentine are familiar examples of the first class4 ,they consist of resinous substances1 dissolved in or mixed with fluid terpenes4 ,ordinary resin1 or colophony1 consists chiefly of a monobasic acid having the empirical formula ,c#bj;,h#cj,o#b1 known as sylvinic acid1 whose exact structure is not known4 ,its sodium salt is used as the basis for cheap soaps4 ,the hard resins are amorphous substances of vitreous character1 which consist of very complex aromatic acids1 alcohols1 or esters1 combined with other complicated structures1 known as resenes1 whose definite chemical nature is not yet known4 ,among the hard resins are many substances which are extensively used in the manufacture of varnishes1 such as copal1 amber1 dammar1 sandarach1 etc4 ,there are also resinous substances1 such as asafoetida1 myrrh1 gamboge1 etc41 which are mixtures of gums 7see ,chapter ,,vi7 and true resins4 ,some of these have considerable commercial value for medicinal or technical uses4 ,,physiological ,,uses ,,and ,,biological ,,significance ,,of ,,essential ,,oils ,no theory has yet been advanced concerning the possibility of the use of essential oils and resins by plants in their normal metabolic processes4 ,the very great diversity in their chemical nature makes it impossible that they should all be considered as having the same physiological function1 if indeed any of them actually have any such function4 ,it is evident that those aromatic compounds which occur as normal secretions of plants and which give to the plants their characteristic odors may act either as an attraction to animals which might utilize the plants as food and so serve to distribute the seed forms1 or as a repellent to prevent the too rapid destruction of the leaves1 stems1 or seeds of certain species of plants whose slow-growing habits require the long-continued growth of these portions of the plant for the perpetuation of the species4 ,the presence of these compounds in larger proportions in those species of conifers1 etc41 which grow in tropical regions1 in competition with other rapid-growing vegetation1 suggests the latter possibility4 ,it must be admitted1 however1 that their presence in such cases may be the result of climatic conditions1 as indicated by the fact that most spice plants are tropical in habit1 rather than the result of their protective influence in the struggle for survival during past ages4 ,many of the oils and resins which are secreted as the result of injury by disease or wounds have marked antiseptic properties and undoubtedly serve to prevent the entrance into the injured tissue of destructive organisms4 ,but apart from these possible protective influences which may have had an important effect upon the preservation and perpetuation of the species of plants which secrete them1 there is no known biological necessity for the presence of these aromatic substances in plants4 ,,references ,,abderhalden1 ,e4--,biochemisches ,handlexikon1 ,band #g1 ,gerbstoffe1 ,flechtenstoffe1 ,saponine1 ,bitterstoffe1 ,terpene1 ,aetherische ,oele1 ,harze1 ,kautschuk1 #hbb pages1 ,berlin1 #aiab4 ,,allen',s ,commercial ,organic ,analysis1 ,vol4 ,,iv1 ,resins1 ,rubber1 ,guttapercha1 and ,essential ,oils1 #dfa pages1 #g figs41 ,philadelphia1 #aiaa 7#dth ed474 ,,heusler1 ,f41 trans4 by ,pond1 ,f4 ,j4--,the ,chemistry of the ,terpenes1 #deg pages1 ,philadelphia1 #aijb4 ,,parry1 ,e4 ,j4--,the ,chemistry of ,essential ,oils and ,perfumes1 #dja pages1 #bj figs41 ,london1 #ahii4 ,,chapter ,,xii ,,the ,,vegetable ,,bases ,we come1 now1 to the consideration of the characteristically nitrogenous compounds of plants4 ,none of the groups of compounds which have been considered thus far have1 as a group1 contained the element nitrogen4 ,this element is present in the chlorophylls and in certain other pigments1 but not as the characteristic constituent of the molecular structure of the group of compounds1 nor do these compounds serve as the source of supply of nitrogen for the plant's needs4 ,the characteristic nitrogen-containing compounds may all be regarded as derived from ammonia1 or ammonium hydroxide1 by the replacement of one or more hydrogen atoms with organic radicals of varying type and complexity4 ,if the group1 or groups1 which be considered as having replaced a hydrogen atom in ammonia1 in such compounds1 is an alkyl group1 the compound is strongly basic in character and is known as an amine2 whereas if the replacing group is an acid radical1 the resulting compound may be neutral 7known as acid amides71 or weakly acid 7known as amino-acids7 in type4 ,compounds of the first type constitute the vegetable bases2 while those of the second type are the proteins4 ,the vegetable bases may be divided into three groups4 ,these are 7a7 the plant amines1 which are simple open-chain amines2 7b7 the alkaloids1 which are comparatively simple closed-ring amines1 containing only one nitrogen atom in any single ring2 and 7c7 the purine bases1 which are complex compounds containing a nucleus with four carbon atoms and four nitrogen atoms arranged alternately to form a double-ring group4 ,,the ,,plant ,,amines ,the simple amines bear the relation to ammonia1 or ammonium hydroxide1 represented by the following formulas1 in which the ,r indicates any simple alkyl radical3 ,h ,r ,r ,r ,r ,r ,h ,h _/ _/ _/ _/ _/ _/ ,n-,h ,n-,h ,n-,h ,n-,r ,n-,r ,n-,h _/ _/ ,h ,h ,r ,r ,r ,,oh ,h ,,oh ,ammonia ,primary ,secondary ,tertiary ,quaternary ,ammonium amine amine amine amine hydroxide ,the simple amines which occur in animal tissues are known as ptomaines and leucomaines4 ,the ptomaines are all decomposition products resulting from the putrefactive decay of proteins caused by moulds or bacteria4 ,some of these are highly toxic1 producing the so-called ptomaine-poisoning2 while others are wholly innocuous4 ,they are all simple amines4 ,putrescine1 di-amino butane1 ,,nh#b;,,ch#b;,,ch#b;,,ch#b;,,ch#b,,nh#b 1 and cadaverine1 di-amino pentane1 ,,hn#b7;,,ch#b7e,,nh#b1 are common non-toxic ptomaines1 resulting from the decay of meat4 ,neurine1 trimethyl-ethylene ammonium hydroxide1 7,,ch#c7c7;,c#b;,h#c7,,noh1 is a violently poisonous ptomaine produced in the decay of fish4 ,amines of similar structure to these are occasionally found in living animal tissues4 ,such compounds are known as leucomaines1 to distinguish them from the ptomaines1 which are found only in dead material4 ,corresponding in structure and properties to these amines of animal origin1 there is a series of basic substances1 found in many plants1 known as the plant amines4 ,the following are common examples3 ,trimethyl amine1 7,,ch#c7c,n1 is a very volatile compound1 found in the flowers of several species of the ,rose family1 the leaves of certain weeds1 etc4 ,when crushed1 these tissues give off a very fetid odor1 which is due to this amine4 ,choline1 muscarine1 and betaine are plant amines which are closely related to each other and to neurine 7the toxic ptomaine7 in composition and structure1 as shown in the following formulas3 ,,ch#b;,,ch#b,,oh ,,ch#b;,,cho _/ _/ 7,,ch#c7c,n 7,,ch#c7c,n ,,oh ,,oh ,choline ,muscarine ,,ch#b;,,co ,,ch,,ch#b _/ _/ _/ 7,,ch#c7c,n _/ 7,,ch#c7c,n _/ ,o ,,oh ,betaine ,neurine ,choline and betaine are non-toxic2 while muscarine and neurine are violent poisons4 ,choline and muscarine occur in certain toadstools4 ,betaine and choline often occur together in the germs of many plants4 ,betaine is found in the beet root and the tubers of ,jerusalem artichoke4 ,choline occurs alone in the seeds and fruits of many plants1 sometimes as the free amine1 but more often as a constituent of lecithin 7see page #ada74 ,phenyl derivatives of simple amines are sometimes found in --- _/ plants4 ,hydroxyphenylethyl amine1 ,,ho-,c ,,ch#b;,,ch#b,,nh#b1 _/ --- --- _/ found in ergot1 and hordeine1 ,,ho-,c ,,ch#b;,,ch#b,n7,,ch#c7b1 _/ --- found in barley1 are examples4 ,the former has marked medicinal properties4 ,there is no known physiological use for these simple amines in plants4 ,by some investigators1 they are regarded as intermediate products in the synthesis or decomposition of proteins2 but it would seem that if this were a normal procedure1 these amines would occur in varying proportions in all plants1 under different conditions of metabolism1 instead of in practically constant proportions in only a few species1 as they do4 ,,alkaloids ,these are a group of strong vegetable bases whose nitrogen atom is a part of a closed-ring arrangement4 ,as a rule1 alkaloids are colorless1 crystalline solids1 although a few are liquids at ordinary temperatures4 ,they are generally insoluble in water1 but easily soluble in organic solvents4 ,being strong bases1 they readily form salts with acids1 and these salts are usually readily soluble in water4 ,alkaloids are usually odorless2 although nicotine1 coniine1 and a few others1 have strong1 characteristic odors4 ,most of them have a bitter taste1 and many of them have marked physiological effects upon animal organisms1 so that they are extensively used as narcotics1 stimulants1 or for other medicinal purposes4 ,most of the alkaloids contain asymmetric carbon atoms and are1 therefore1 optically active1 usually levorotatory1 although a few are dextrorotatory4 ,the alkaloids are precipitated out of their solutions by various solutions of chemical compounds1 known as the alkaloidal reagents3 iodine dissolved in potassium iodide solution gives a chocolate-brown precipitate2 tannic acid1 phosphotungstic acid1 phosphomolybdic acid1 and mercuric iodide solutions give colorless1 amorphous precipitates2 while gold chloride and platinic chloride solutions give crystalline precipitates1 many of which have sharp melting points and can be used for the identification of individual alkaloids4 ,there are a great many specific color reactions for individual alkaloids1 which are important to toxicologists and pharmacists1 but which it would not be desirable to consider in detail here4 ,the alkaloids are conveniently divided into groups1 according to the characteristic closed-ring arrangements which they contain4 ,the several closed-ring arrangements which are found in common alkaloids1 and upon which their grouping is based1 may be illustrated by the following formulas3 ,h ,h ,h ,h#b;,c---,,ch#b _/ ,c ,c _/_/ _/ ,h#b;,c ,,ch#b ,,hc ,,ch ,h#b;,c ,,ch#b _/ ,n ,,hc ,,ch ,h#b;,c ,,ch#b _/ _/ ,h ,n ,n ,pyrrolidine1 ,c#d;,h#i,n ,pyrridine1 ,c#e;,h#e,n ,h ,piperidine1 ,c#e;,h#aa,n ,h ,h _/ ,h ,c _/ ,h#b;,c-----,c-----,,ch#b ,h#b;,c ,,ch#b ,,nh ,,ch#b ,,hc ,,ch _/ or ,h#b;,c-----,c-----,,ch#b ,n _/ ,h _/ ,h ,h#b;,c-----,,ch#b ,tropane1 ,c#g;,h#ac,n ,h ,h ,h ,h ,c ,c ,c ,c _/_/ _/ _/_/ _/ ,,hc ,c ,,ch ,,hc ,c ,,ch ,,hc ,c ,,ch ,,hc ,c ,n _/ _/_/ _/ _/_/ ,c ,n ,c ,c ,h ,h ,h ,quinoline1 ,c#i;,h#h,n ,isoquinoline1 ,c#i;,h#h,n ,the common alkaloids are distributed in the several groups as follows3 ,pyrridine--piperidine group2 piperine1 coniine1 nicotine4 ,pyrrolidine group2 hygrine and stachydrine4 ,tropane group2 atropine1 hyoscine1 cocaine1 lupinine4 ,quinoline group2 quinine1 cinchonine1 strychnine1 brucine4 ,isoquinoline group2 papaverine1 hydrastine1 morphine1 codeine1 berberine4 ,the composition and properties of the individual alkaloids have been extensively studied1 because of their medicinal uses4 ,as they have no known metabolic use to the plants which elaborate them1 it will not be worth while to consider all of these investigations in detail here4 ,the following facts with reference to certain typical members of each group will serve to illustrate the general constitution and properties of the alkaloids4 ,piperine1 ,c#ag;,h#ai,o#c1 is found in black peppers4 ,its constitution is represented by the following formula1 the group which is united to the piperidine ring1 in this case1 being piperic acid3 ,h#b ,c _/ ,h#b;,c ,,ch#b _/ --,o ,h#b;,c ,,ch#b _/ ,,ch#b ,n----,,oc,,ch,,ch,,ch,,ch-- _/ _/ --,o ,coniine1 ,c#h;,h#ag,n1 is found in the umbelliferous plant1 ,conium maculatum4 ,structurally1 it is a propyl-piperidine1 represented by the following formula3 ,h#b ,c _/ ,h#b;,c ,,ch#b ,h#b;,c ,,ch-,c#c;,h#g _/ ,n ,h ,nicotine1 ,c#aj;,h#ad,n#b1 is the alkaloid of tobacco leaves4 ,it is an extremely poisonous1 oily liquid1 with a strong odor and a burning taste4 ,its structural formula shows it to contain both a pyrridine ring and a pyrrolidine ring1 linked together thus ,h ,c ,h#b;,c---,,ch#b _/ ,,hc ,c------,,hc ,,ch#b _/ ,,hc ,,ch ,n _/_/ ,n ,,ch#c ,hygrine1 ,c#g;,h#ac,,no1 from coca leaves1 is an acetic acid salt of pyrrolidine1 represented by the following formula3 ,h#b;,c---,,ch--,,oc,,ch#c ,h#b;,c ,,ch#b _/ ,n ,,ch#c ,atropine and hyoscyamine1 ,c#ag;,h#bc,,no#c1 are optical isomers4 ,atropine is an extremely poisonous1 white crystalline compound1 which is obtained from deadly nightshade and henbane1 and used in medicine1 in minute doses1 as an agent for reducing temperature in acute cases of fevers4 ,structurally1 it is a tropic acid ester of tropane1 represented by the following formula3 ,h#b;,c---,,ch--------,,ch#b ,c#f;,h#e ,n-,,ch#c ,,chooc---,,ch ,h#b;,c---,,ch--------,,ch#b ,,ch#b,,oh ,cocaine1 ,c#ag;,h#ba,,no#d1 is found in coca leaves4 ,it is a white crystalline solid1 which is largely used as a local ansthetic for minor surgical operations4 ,its structural formula is ,h#b;,c---,,ch--------,,hc-,,ooc,,ch#c ,n-,,ch#c ,,hc-,,ooc,c#f;,h#e ,h#b;,c---,,ch---------,,ch#b ,it is1 therefore1 a di-ester of acetic and benzoic acids with tropane4 ,cinchonine1 ,c#ai;,h#bb,n#b,o1 and quinine1 ,c#bj;,h#bd,n#b,o#b1 are alkaloids found in cinchona bark4 ,they are white crystalline solids1 which are extensively used in medicine4 ,they have been shown to contain a quinoline group combined with modified piperidine groups1 as represented in the following formulas3 ,h ,n ,c _/ _/ _/ _/ ,h#b;,c ,,hch ,,ch-,,ch,,ch#b _/ _/ ,,ch-,,choh-,,hc ,,hch ,,ch#b _/ ,n ,cinchonine ,h ,n ,c _/ _/ _/ _/ ,h#b;,c ,,ch-,,ch,,ch#b _/ _/ ,,ch-,,choh-,,hc ,,ch#b _/ ,n ,quinine ,strychnine1 ,c#ba;,h#bb,n#b,o#b1 brucine1 ,c#ba;,h#bj7,,och#c7,n#b,o#b1 and curarine are three alkaloids which are present in the seeds of several species of ,strychnos4 ,they are all highly poisonous4 ,beyond the fact that when they are hydrolyzed they yield quinoline and indole1 their composition is unknown4 ,morphine1 ,c#ag;,h#ai,,no#c1 is the chief alkaloid of opium1 which is the dried juice of young pods of the poppy4 ,both the alcoholic solution of opium 7known as laudanum7 and morphine itself are extensively used in medicine as narcotics to deaden pain4 ,morphine has an exceedingly complex structure1 being a combination of an isoquinoline and a phenanthrene nucleus1 which is probably correctly represented by the following formula3 ,h ,h#b ,c ,c _/_/ _/ ,,hoc ,c ,,ch#b ,c ,c ,n-,,ch#c _/ _/ _/ _/ ,c ,,ch ,o ,,hc ,,ch#b _/ _/ ,,hc ,c ,h#b;,c ,,ch _/ ,c ,h#b ,codeine1 ,c#ag;,h#ah7,,och#c7,,no#b1 which is also found in opium1 is a methyl derivative of morphine4 ,papaverine1 laudanosine1 narcotine1 and narceine are four other alkaloids found in opium4 ,they each contain an isoquinoline nucleus1 combined by one bond to a benzene ring1 with one or more methyl groups and three or more methoxy 7,,och#c7 groups attached at various points around the three characteristic rings4 ,the following formula for laudanosine will illustrate their structure3 _/ _/ ,,ch#c,o ,,och#c ,,ch#c,o ,n-,,ch#c _/ _/ _/ ,,och#c _/ ,h#b;,c----------------,,ch ,the above discussions of the composition of typical alkaloids clearly indicate the extreme complexity of their molecular structure4 ,it is generally supposed that they are formed by the decomposition of proteins4 ,but they are developed in only a few particular species of plants and are always present in these plants in fairly constant quantities4 ,hence1 it appears that1 in these species1 the production of alkaloids is in some way definitely connected with protein metabolism2 but it is certain that this is not a common relationship1 as it is manifested by such a limited number of species of plants1 and there is absolutely no knowledge as to its character and functions4 ,some authorities prefer to regard the alkaloids as waste-products of protein metabolism2 but here1 again1 it is difficult to understand why such products should result in certain species of plants and not in others4 ,,the ,,purine ,,bases ,this is a group of compounds1 widely distributed in both plant and animal tissues1 all of which are derivatives of the compound known as purine1 ,c#e;,h#d,n#d4 ,all of the naturally occurring compounds of this group may be regarded as derived from purine1 either by the addition of oxygen atoms1 or by the replacing of one or more of its hydrogen atoms with a methyl 7,,ch#c7 group or an amino 7,,nh#b7 group4 ,the following structural formula represents the arrangement of the purine nucleus1 the numbers being used to designate the nitrogen or carbon atoms to which the additional atoms1 or groups1 are attached in the more complex compounds of the group4 ,in purine itself1 the four hydrogen atoms are attached in the #b1 #f1 #g1 and #h positions4 #f #a,n,c-- #g --#b;,c #e;,c---,n-- #h;,c-- _/_/ #c,n--#d;,c--#i,n ,the double bonds1 in each case except those between the #d and #e carbon atoms1 are easily broken apart and readjusted1 so that other atoms or groups can be attached to any atom in the nucleus except the #d and #e carbon atoms4 ,in all of the statements with reference to the structure of the purine bases1 the term oxy is used to mean an oxygen atom attached by both its bonds to one of the carbons in the nucleus1 instead of its customary use to mean the monovalent ,,oh group replacing a hydrogen1 as in the case of all other nomenclature of organic compounds4 ,with this understanding1 reference to the numbered nucleus formula above will make plain the structure of all of the purine bases which are included in the following list3 ,hypoxanthine1 ,c#e;,h#d,n#d,o1 #f-monoxypurine4 ,xanthine1 ,c#e;,h#d,n#d,o#b1 #b1f-;dioxypurine4 ,uric acid1 ,c#e;,h#d,n#d,o#c1 #b1f1h-trioxypurine4 ,adenine1 ,c#e;,h#c,n#d,,nh#b1 #f-;aminopurine4 ,guanine1 ,c#e;,h#c,n#d,,onh#b1 #b-;amino-#f-oxypurine4 ,theobromine1 ,c#e;,h#b,n#d,o#b7;,,ch#c7b #c1g-;dimethyl-#b1f-;dioxypurine1 or dimethyl xanthine4 ,theophylline1 ,c#e;,h#b,n#d,o#b7;,,ch#c7b #a1c-;dimethyl-#b1f-;dioxypurine4 ,caffeine1 ,c#e;,,hn#d,o#b7;,,ch#c7c #a1c1g-trimethyl-#b1f-;dioxypurine1 or trimethyl xanthine4 ,in order to make these structural relationships quite clear1 the following formulas for uric acid and for caffeine are presented as typical examples3 ,h ,n--,c,o ,,ch#c--,n--,c,o ,o,c ,c--,n-,h ,o,c ,c--,n-,,ch#c ,c,o ,,ch _/ _/_/ ,,hn--,c--,n-,h ,,ch#c-,n--,c--,n ,uric acid ,caffeine ,uric acid is found in the excrement of all animals2 in the urine of mammals1 and in the solid excrement of birds and reptiles4 ,it is not known to occur in plants4 ,xanthine and hypoxanthine occur in animal urine1 and also in the tissues of both plants and animals4 ,adenine and guanine are constituents of all nucleic acids 7see below7 and1 hence1 are found in all plant and animal tissues4 ,guanine is the chief constituent of the excrement of spiders1 and is found also in ,peruvian guano4 ,it is also a constituent of the scales of fishes4 ,caffeine1 theophylline1 and theobromine are not found in animal tissues1 but are fairly widely distributed in plants4 ,caffeine and theobromine are the active constituents of tea leaves and coffee seeds and are found also in cacao beans and kola nuts4 ,the use of these three compounds in the metabolism of the plants which elaborate them is wholly unknown4 ,they are not so directly related to protein metabolism as are the other purine bases4 ,the purine bases1 other than the three mentioned in the preceding paragraph1 are undoubtedly intermediate products in protein metabolism4 ,in animals1 they constitute a large proportion of the waste-products from the use of proteins in the body4 ,it is not clear that there are similar waste-products in plant metabolism1 however4 ,in both plants and animals1 the purine bases which are a part of the nucleic acids undoubtedly play an important and essential part in growth1 since they form the major proportion of the nucleus1 from which all cell-division proceeds4 ,,the ,,pyrimidine ,,bases ,these compounds do not occur free in plants2 but since they are constituent groups in the plant nucleic acids 7see below71 a brief explanation of their composition is desirable4 ,they are nitrogenous bases1 similar to1 but somewhat simpler than1 the purine bases4 ,their general composition and structural relationships are illustrated by the following typical formulas3 ,n,c-,h ,h-,n--,c,o ,h-,c ,c-,h ,o,c ,c-,h ,n--,c-,h ,h-,n--,c-,h ,pyrimidine ,uracil ,c#d;,h#d,n#b ,c#d;,h#d,n#b,o#b #b1f-;dioxypyrimidine ,n,c-,,nh#b ,h-,n--,c,o ,o,c ,c-,h ,o,c ,c-,,ch#c ,h-,n--,c-,h ,h-,n--,c-,h ,cytosine ,thymine ,c#d;,h#c,n#b,,onh#b ,c #d;,h#c,n#b,o#b;,,ch#c #b1oxy-#f-;amino-pyrimidine #b1f-;dioxy-#e-methyl-pyrimidine ,,the ,,nucleic ,,acids ,the nuclei of cells are composed almost wholly of complex organic salts1 in which proteins constitute the basic part and nucleic acids the acid part4 ,these salts1 or esters1 are known under the general name nucleoproteins4 ,the composition of the proteins is discussed in detail in the following chapter1 and it seems desirable to present a brief discussion of the constitution of the nucleic acids here2 although they are essentially acids rather than vegetable bases4 ,the nucleic acids are complex compounds consisting of a carbohydrate1 phosphoric acid1 two purine bases1 and two pyrimidine bases4 ,so far as is known1 all animal nucleic acids are identical and all plant nucleic acids are identical2 but those of plant origin differ from those found in animal cells in the character of the carbohydrate and that of one of the pyrimidine bases which are present in the molecule1 as shown in the following tabulation of their composition3 ,animal nucleic acid ,plant nucleic acid ,phosphoric acid ,phosphoric acid ,hexose 7levulose7 ,pentose 7d-ribose7 ,guanine ,guanine ,adenine ,adenine ,cytosine ,cytosine ,thymine ,uracil ,the structure of the plant nucleic acid may be represented by the following formula3 ,,oh ,o,p--,o--carbohydrate-guanine group ,o ,o,p--,o--carbohydrate-adenine group ,o ,o,p--,o--carbohydrate-uracil group ,o ,o,p--,o--carbohydrate-cytosine group ,,oh ,that this is probably a correct representation of the general arrangement in this compound1 is indicated by the fact that by different methods of hydrolysis it is possible to split off either the purine and pyrimidine bases1 leaving a carbohydrate ester of phosphoric acid2 or the phosphoric acid1 leaving carbohydrate combinations with the nitrogenous bases4 ,nucleic acid1 prepared from animal glands which contain large proportions of it1 is a white powder1 which is insoluble in water1 but when moistened forms a slimy mass4 ,it is almost insoluble in alcohol1 but dissolves readily in alkaline solutions1 forming a colloidal solution which readily gelatinizes 7see chapter on ,colloids74 ,solutions of nucleic acids are optically active1 probably because of the carbohydrate constituents4 ,from their structure and properties1 it is apparent that nucleic acids are on the border line between carbohydrates1 plant amines1 and proteins4 ,they undoubtedly play an important part1 both in cell-growth and in the synthesis of proteins from carbohydrates and ammonium compounds4 ,references ,,barger1 ,,geo4--,the ,simpler ,natural ,bases1 #bae pages1 ,monographs on ,biochemistry1 ,london1 #aiad4 ,,fischer1 ,e4--,untersuchungen in der ,puringruppe1 #ahhb-aijf1 #fjh pages1 ,berlin1 #aijg4 ,,henry1 ,t4 ,a4--,the ,plant ,alkaloids1 #dff pages1 ,philadelphia1 #aiac4 ,,jones1 ,w4--,the ,nucleic ,acids1 #aah pages1 ,monographs on ,biochemistry1 ,london1 #aiad4 ,,pictet1 ,a4--,la ,constitution ,chimique des ,alcaloides ,vegetaux1 #dba pages1 ,paris1 #ahig 7#b;d ed474 ,,vaughan1 ,v4 ,c4 and ,,novy1 ,f4 ,g4--,ptomaines1 ,leucomaines1 ,toxins and ,antitoxins1 #fjd pages1 ,philadelphia1 #ahif1 7#c;d ed474 ,,winterstein1 ,e4 and ,,trier1 ,g4--,die ,alkaloide1 #cdj pages1 ,berlin1 #aiaj4 ,,chapter ,,xiii ,,proteins ,the proteins are the most important group of organic components of plants4 ,they constitute the active material of protoplasm1 in which all of the chemical changes which go to make up the vital phenomena take place4 ,combined with the nucleic acids1 they comprise the nucleus of the cell1 which is the seat of the power of cell-division and1 hence1 of the growth of the organism4 ,germ-cells are composed almost exclusively of protein material4 ,hence1 it is not an over-statement to say that proteins furnish the material in which the vital powers of growth and repair and of reproduction are located4 ,a recognition of their importance is reflected in the use of the name protein1 which comes from a ,greek word meaning pre-eminence1 or of first importance4 ,in addition to the proteins which constitute the active protoplasm1 plants also contain large amounts of reserve1 or stored1 proteins1 especially in the seeds4 ,in the early stages of growth1 the proteins are present in largest proportions in the vegetative portions of the plant2 but as maturity approaches1 a considerable proportion of the protein material is transferred to the seeds4 ,,general ,,composition ,,of ,,proteins ,the plant proteins are fairly uniform in their percentage composition4 ,the analyses of some sixteen different plant proteins show the following maximum limits of percentages of the different chemical elements which they contain3 ,carbon1 #ej4gb-ed4bi2 hydrogen1 #f4hj-g4jc2 nitrogen1 #ae4hd-ai4jc2 oxygen1 #bj4hf-bd4bi2 sulfur1 #j4ag-a4ji4 ,animal proteins vary more widely1 both in percentage composition and in properties1 than do those of plant origin4 ,protein molecules are very large and1 in the case of the so-called conjugated proteins in particular1 their structure is very complex4 ,the molecular weight of some of the proteins has been determined directly1 in the case of those particular ones which can be prepared in proper form for the usual determination of molecular weight by the osmotic pressure method2 and has been computed for various others1 from the percentage of sulfur found on analysis1 or 7in the case of the hmoglobin of the blood7 from the proportion by weight of oxygen absorbed4 ,from these determinations and computations1 the following formulas for certain typical proteins have been calculated3 for zein 7from ,indian corn71 ,c#gcf;,h#aafa,n#ahd,o#bjh,s#c2 for gliadin 7from wheat71 ,c#fhe;,h#ajfh,n#aif,o#baa,s#e2 for casein 7from milk71 ,c#gjh;,h#aacj,n#ahj,o#bbd,s#d,p#d2 for egg-albumin1 ,c#fif;,h#aabe,n#age,o#bbj,s#h4 ,these few examples will serve to illustrate the enormous size and complexity of the protein molecule4 ,the conjugated proteins are still more complex than the simple proteins whose formulas are here presented4 ,fortunately for the purposes of the study of the chemistry of the proteins1 however1 it has been found that most of the common plant proteins1 known as the simple proteins1 can easily be hydrolyzed into their constituent unit groups1 which are the comparatively simple amino-acids1 whose composition and properties are well understood4 ,a study of the results of the hydrolysis of some twenty common plant proteins has shown that it is rarely possible to recover the amino-acids in sufficient quantities to account for a full #ajj per cent of the material used1 the actual percentage of amino-acids recovered usually totaling from #fj to #hj per cent4 ,the remaining material is supposed to be also composed of amino-acids which are linked together in some arrangement which is not broken apart by any method of hydrolysis which has yet been devised4 ,this view is borne out by the fact that substances which exhibit all the characteristic properties of proteins have been artificially synthetized1 by using only amino-acid compounds4 ,animal proteins often show a much larger proportion of unhydrolyzable material than do plant proteins4 ,,amino-,,acids ,,and ,,peptid ,,units ,the products of hydrolysis of the common simple proteins are all amino-acids4 ,these are ordinary organic acids with one 7or more7 of the hydrogen atoms of the alkyl group replaced by a --,,nh#b 7or sometimes by a --,,nh--7 group4 ,they may be regarded as ammonia1 ,,nh#c1 with one of its hydrogen atoms replaced by an acid radical2 or as the acid with one of its hydrogens replaced by the ,,nh#b group4 ,for example1 an amino-acid derived from acetic acid1 ,,ch#c;,,cooh1 is glycine1 or amino-acetic acid1 ,,ch#b,,nh#b;,,cooh2 from propionic acid1 ,,ch#c;,,ch#b;,,cooh1 there may be obtained either alpha-amino-propionic acid1 ,,ch#c;,,chnh#b;,,cooh1 or beta-amino-propionic acid1 ,,ch#b,,nh#b;,,ch#b;,,cooh1 etc4 ,all of the amino-acids which result from the hydrolysis of proteins are alpha-amino-acids1 that is to say1 the ,,nh#b group is attached to the alpha-carbon atom1 i4e41 the one nearest to the ,,cooh group4 ,hence1 the general formula for all the amino-acids which are found in plants is ,r,,chnh#b;,,cooh4 ,these amino-acids contain both the basic ,,nh#b group and the acid ,,cooh group4 ,for this reason1 they very easily unite together1 in the same way that all acids and bases unite1 to form larger molecules1 the linkage taking place between the basic ,,nh#b group of one molecule and the acid ,,cooh group of the other1 as indicated by the following equation3 ,r ,r ,r ,r ---------- ,,hooc,c,n-,h ,,ho,,oc,c,,nh#b ,,hooc,c,n-,,oc,c,,nh#b ,h#b,o ---------- ,h ,h ,h ,h ,h ,h ,it is obvious that the compound thus formed still contains a free ,,nh#b group and a free ,,cooh group1 and is1 therefore1 capable of linking to another amino-acid molecule in exactly the same way2 and so on indefinitely4 ,in actual laboratory experiments1 as many as eighteen of these amino-acid units have been caused to unite together in this way1 and the resulting compounds thus artificially prepared have been found to possess the characteristic properties of natural proteins4 ,these artificially prepared1 protein-like1 substances have been called polypeptides1 and the individual amino-acids which unite together to form them are called peptides4 ,thus1 a compound which contains three such units linked together is called a tripeptid2 one which contains four1 a tetrapeptid4 ,the use of the term peptid was suggested by the fact that these amino-acids are produced from the hydrolysis of proteins by the digestive enzyme pepsin4 ,the peptid units of any such complex as those which have been referred to in the preceding paragraphs may be linked together in a great variety of ways4 ,thus1 in a tetrapeptid containing units which may be designated by the letters a1 b1 c1 and d1 the arrangement may be in the orders abcd1 bacd1 acbd1 dbca1 etc41 etc4 ,similarly1 the same peptid unit may appear in the molecule in two or more different places4 ,hence1 the number of possible combinations of amino-acids into protein molecules is very great4 ,further1 it is possible that the peptid units in natural proteins may be united together through other linkages than the one illustrated above1 as they often contain alcoholic ,,oh groups in addition to the basic ,,nh#b groups1 and these ,,oh groups may form ester-linkages with the acid 7,,cooh7 groups of other units4 ,still other acid and basic groups are present in some of the amino-acids which have been found in natural proteins1 so that the possibility of variation in the polypeptid linkages is almost limitless4 ,,individual ,,amino-,,acids ,,from ,,proteins ,about twenty different amino-acids have been isolated from the products of hydrolysis of natural proteins1 and this number is being added to from time to time1 as the methods of isolation and identification of these compounds are improved4 ,many of these same amino-acids have been found in free form in plant tissues1 particularly in rapidly growing buds1 or shoots1 or in germinating seeds1 where they undoubtedly exist as intermediate products in the transformation of proteins into other types of compounds4 ,these amino-acids1 grouped according to the characteristic groups which they contain1 are as follows3 ,a4 ,monoamino-monocarboxylic acids3 ,glycine1 ,c#b;,h#e,,no#b1 ,,ch#b,,nh#b;,,cooh1 amino-acetic acid4 ,alanine1 ,c#c;,h#g,,no#b1 ,,ch#c;,,chnh#b;,,cooh1 amino-propionic acid4 ,serine1 ,c#c;,h#g,,no#c1 ,,ch#b,,oh,,chnh#b;,,cooh1 oxy-amino-propionic acid4 ,,ch#c ,valine1 ,c#e;,h#aa,,no#b1 ,,ch,,chnh#b;,,cooh1 _/ ,,ch#c amino-isovalerianic acid4 ,,ch#c ,leucine1 ,c#f;,h#ac,,no#b1 ,,ch,,ch#b;,,chnh#b;,,cooh1 _/ ,,ch#c amino-isocaproic acid4 ,,ch#c ,isoleucine1 ,c#f;,h#ac,,no#b1 ,,ch,,chnh#b;,,cooh1 _/ ,c#b;,h#e amino-methylethyl-propionic acid4 _/ ,phenylalanine1 ,c#i;,h#aa,,no#b1 ,,ch#b;,,chnh#b;,,cooh1 phenyl-amino-propionic acid4 _/ _/ ,tyrosine1 ,c#i;,h#aa,,no#c1 ,,ch#b;,,chnh#b;,,cooh1 ,,oh paraoxy-phenylalanine4 _/ ,cystine1 ,c#f;,h#ab,n#b,o#d,s#b1 ,,hooc,,chnh#b;,,ch#b,s-,,sh#b;,c ,,chnh#b;,,cooh1 di7thio-amino-propionic acid74 ,b4 ,monoamino-dicarboxylic acids3 ,aspartic acid1 ,c#d;,h#g,,no#d1 ,,hooc,,ch#b;,,chnh#b;,,cooh1 amino-succinic acid4 ,glutamic acid1 ,c#e;,h#i,,no#d1 ,,hooc,,ch#b;,,ch#b;,,chnh#b;,,cooh1 amino-glutaric acid4 ,c4 ,diamino-monocarboxylic acids3 ,ornithine1 ,c#e;,h#ab,n#b,o#b1 ,h#b,n,,ch#b;,,ch#b;,,ch#b;,,chnh#b;,,co oh1 di-amino-valerianic acid4 ,lysine1 ,c#f;,h#ad,n#b,o#b1 ,h#b,n,,ch#b;,,ch#b;,,ch#b;,,ch#b;,,chnh #b;,,cooh1 di-amino-caproic acid4 ,arginine1 ,c#f;,h#ad,n#d,o#b1 ,,nh#b _/ ,,hn,c ,,nh,,ch#b;,,ch#b;,,ch#b;,,chnh#b;,,cooh 1 guanidine-amino-valerianic acid4 ,di-amino-oxysebacic acid1 ,c#aa;,h#ab,n#b,o#c4 ,di-amino-trioxydodecanic acid1 ,c#ab;,h#bf,n#b,o#c4 ,d4 ,monoimido-monocarboxylic acids3 ,proline1 ,c#e;,h#i,,no#b1 ,h#b;,c---,,ch#b ,h#b;,c ,,ch,,cooh1 pyrrolidine-carboxylic _/ acid ,n ,h ,oxyproline1 ,c#e;,h#i,,no#c1 proline with one 7,,oh7 group4 ,e4 ,monoimido-monoamino-monocarboxylic acids4 ,histidine1 ,c#f;,h#i,n#c,o#b1 ,,hc,c--,,ch#b;,,chnh#b;,,cooh1 imidazole-amino-propionic ,n ,,nh acid4 _/ ,c ,h ,tryptophane1 ,c#aa;,h#ab,n#b,o#b1 _/ ---,c--,,ch#b;,,chnh#b;,,cooh1 indole-amino-propionic acid4 ,,ch _/ _/ ,n ,h ,as has been said1 other amino-acids are being found1 from time to time1 as additional proteins are examined1 or as better methods of examination of the cleavage products of the natural proteins are devised4 ,,composition ,,of ,,plant ,,proteins ,the distribution of the different amino-acids in some of the different plant proteins which have been examined in this way is shown in the following table3 ,letter code for column headings3 ,a ,gliadin 7wheat74 ,b ,hordein 7barley seed74 ,c ,zein 7corn74 ,d ,legumin 7vetch74 ,e ,edestin 7hemp74 ,f ,globulin 7squash seed74 ,g ,amandin 7almonds74 ---------------------------------------- ----------------------- ,a ,b ,c ,d ,e ,f ,g ---------------------------------------- ----------------------- ,glycine #j4jb #j4jj #j4jj #j4ci #c4hj #j4eg #j4ea ,alanine #b4jj #j4dc #i4gi #a4ae #c4fj #a4ib #a4dj ,valine #j4ba #j4ac #a4hh #a4cf #f4bj #j4bf #j4af ,leucine #e4fa #e4fg #ai4ee #h4hj #ad4ej #g4cb #d4de ,proline #g4jf #ac4gc #i4jd #d4jd #d4aj #b4hb #b4dd ,phenylalanine #b4ce #e4jc #f4ee #b4hg #c4ji #c4cb #b4ec ,aspartic acid #j4eh 44444 #a4ga #c4ba #d4ej #c4cj #e4db ,glutamic acid #db4ih #dc4ai #bf4ag #ah4cj #ah4hd #ab4ce #bc4ad ,serine #j4ac 8 #a4jb 8 #j4cc 8 8 ,cystine #j4de 8 8 8 #a4jj #j4bc 8 ,tyrosine #a4bj #a4fg #c4ee #b4db #b4ac #c4jg #a4ab ,arginine #c4af #b4af #a4ee #aa4jf #ad4ag #ad4dd #aa4he ,histidine #j4fa #a4bh #j4dc #b4id #b4ai #b4fc #a4eh ,lysine 44444 44444 44444 #c4ii #a4fe #a4ii #j4gj ,tryptophane presentpresent absentpresentpresentpresentpresent ,ammonia #e4aa #d4hg #c4fd #b4ab #b4bh #a4ee #c4gj ---------------------------------------- --------- #ga4df #gh4af #he4bg #fb4fe #hb4ch #ee4gg #ei4jj ---------------------------------------- ----------------------- ,at the time when these analyses were made1 a method for the quantitative estimation of tryptophane had not been devised1 although one is now available4 ,the addition of the percentages of tryptophane and of other amino-acids for which methods of determination are not yet known1 would bring the total1 in each case1 more nearly up to the full #ajj per cent4 ,these data will serve to show how widely the different plant proteins vary in the proportions of the different amino-acids which they contain4 ,animal proteins have been found to be still more variable in composition4 ,in the use of the proteins as food for animals1 it appears that the different amino-acids are in some way connected with the different physiological functions which the proteins have to perform in the animal body3 thus1 tryptophane is absolutely essential to the maintenance of life1 but does not promote growth2 lysine1 on the other hand1 definitely promotes growth1 so that animals which have been maintained without any increase in weight for many months immediately begin to grow when furnished with a diet in which lysine is a constituent2 while arginine seems to be definitely associated with the reproductive function2 and cystine1 with the growth of hair1 feathers1 etc4 ,it is not known whether there is any similar relation of amino-acids to the functions of different proteins in plant metabolism4 ,the separation of the individual amino-acids from the mixture which results from the hydrolysis of any given protein is a long and tedious process and1 at best1 yields only moderately satisfactory results4 ,for that reason1 it has recently been almost entirely abandoned in favor of the separation devised by ,van ,slyke1 which divides the total nitrogenous matter in the mixture resulting from the hydrolysis of a protein into the following groups2 ammonia ,n1 humin 7or melanin7 ,n1 cystine ,n1 arginine ,n1 histidine ,n1 lysine ,n1 amino ,n of the filtrate1 and non-amino ,n of the filtrate4 ,these groups can be conveniently and fairly accurately separated out of the hydrolysis mixture1 by means of various precipitating agents1 and the quantity of ,n in the several precipitates determined by the usual ,kjeldahl method4 ,the actual process for these separations need not be discussed here1 as it is given in detail in all standard text-books dealing with the methods of biochemical analysis4 ,the distribution of the nitrogen in any given protein into these various groups is characteristic for that particular protein1 and the process serves both as a means of identification of individual proteins and a method for tracing their changes through various vital1 or biochemical1 transformations4 ,,general ,,properties ,,of ,,the ,,proteins ,individual proteins differ slightly in their characteristics1 but in general they are all alike in the following physical and chemical properties4#e ,physical ,properties4--7#a7 ,the proteins are all colloidal in character1 that is1 they form solutions in water1 out of which they cannot be dialyzed through parchment1 or other similar membranes4 7#b7 ,all natural proteins1 when in colloidal solution1 may be coagulated1 forming a semi-solid gel1 which cannot again be rendered soluble except by decomposition4 ,the most familiar example of this type of coagulation is that of egg-albumin1 when eggs are cooked4 ,this coagulation may be produced by heat1 by the action of certain enzymes1 or by the addition of alcohol to the solution4 7#c7 ,all solutions of plant proteins are optically active1 rotating the plane of polarized light to the left1 in every case4 7#d7 ,proteins are precipitated out of their solutions1 without change in the composition of the protein1 by saturating the solution with various neutral salts of the alkali1 or alkaline earth1 metals1 such as sodium chloride1 ammonium sulfate1 magnesium sulfate1 etc4 ,this is only another way of saying that the proteins are insoluble in strong salt solutions4 ,separation from solution by the addition of salts is different from coagulation by heat1 etc41 as in this case simple dilution of the salt solution will cause the protein to redissolve1 whereas a coagulated protein cannot be redissolved without some change in its composition4 ,chemical ,properties4 7#a7 ,precipitation reactions4--,the proteins have both acid and basic properties 7due to the presence in their molecules of both free ,,nh#b groups and free ,,cooh groups74 ,bodies of this kind are known as amphoteric electrolytes1 since they yield both positive and negative ions1 if dissociated4 ,the proteins readily form salts1 which are generally insoluble in water1 with strong acids4 ,for this reason1 they are generally precipitated out of solution by the addition of the common mineral acids4 ,they are also precipitated by many of the alkaloidal reagents1 to which reference has been made in the preceding chapter1 namely1 phosphotungstic1 phosphomolybdic1 tannic1 picric1 ferrocyanic1 and trichloracetic acids1 the double iodide of potassium1 mercuric iodide1 etc4 ,the precipitates produced by strong mineral acids are often soluble in excess of the acid1 with the formation of certain so-called derived proteins1 which are probably products of the partial hydrolysis of the protein4 ,the proteins are also precipitated out of solution by the addition of small amounts of salts of various heavy metals1 such as the chlorides1 sulfates1 and acetates of iron1 copper1 mercury1 lead1 etc4 ,this precipitation is different than that caused by the saturation of the solution with the salts of the alkali metals1 as in this case the metal unites with the protein to form definite1 insoluble salts1 which cannot be redissolved except by treatment with some reagent which removes the metal from its combination with the protein 7hydrogen sulfide is commonly used for this purpose74 7#b7 ,color reactions4--,certain specific groups which are present in most proteins give definite color reactions with various reagents4 ,it is apparent that any individual protein will respond to a particular color reaction1 or will not do so1 depending upon whether the particular group which is responsible for the color in question is present in that particular protein4 ,color reactions to which most of the common plant proteins respond are the following ones3 7a7 ,biuret ,reaction4--,solutions of copper sulfate1 added to an alkaline solution of a protein1 give a bluish-violet color if the substance contains two1 or more1 --,,conh-- groups united together through carbon1 nitrogen1 or sulfur atoms4 ,inasmuch as most natural proteins contain several such groups1 the biuret reaction is a very general test for proteins4 7b7 ,millon's ,reaction4--,a solution of mercuric nitrate containing some free nitrous acid 7,millon's reagent7 produces a precipitate which turns pink or red1 whenever it is added to a solution which contains tyrosine1 or a tyrosine-containing protein4 7c7 ,xanthoproteic ,acid ,reaction4--,this is the familiar yellow coloration which is produced whenever nitric acid comes in contact with animal flesh4 ,it is caused by the action of nitric acid on tyrosine4 ,the color is intensified by heating1 and is changed to orange-red by the addition of ammonia4 7d7 ,adamkiewicz's ,reaction4--,if concentrated sulfuric acid be added to a solution of a protein to which some acetic acid 7or better1 glyoxylic acid7 has previously been added1 a violet color is produced4 ,this color will appear as a ring at the juncture of the two liquids1 if the sulfuric acid is poured carefully down the sides of the tube1 or throughout the mixture if it is shaken up4 ,it depends upon the interaction of the glyoxylic acid 7which is generally present as an impurity in acetic acid7 upon the tryptophane group1 and is therefore given by all proteins which contain tryptophane4 7e7 ,molisch's reaction for furfural will be shown by those proteins which contain a carbohydrate group4 ,in applying this test1 the solution to be tested is first treated with a few drops of an alcoholic solution of alpha-naphthol1 and then concentrated sulfuric acid is poured carefully down the sides of the test-tube4 ,if carbohydrates are present1 either free or as a part of a protein molecule1 a red-violet ring forms at the juncture of the two liquids4 7f7 ,sulfur ,test4--,if a drop of a solution of lead acetate be added to a solution containing a protein1 followed by sufficient sodium hydroxide solution to dissolve the precipitate which forms1 and the mixture is heated to boiling1 a black or brown coloration will be produced if the protein contains cystine1 the sulfur-containing amino-acid4 ,,footnotes3 #e ,since the proteins are essentially colloidal in nature1 many of the terms used in the discussions of their properties1 and these properties themselves1 will be better understood after the chapter dealing with the colloidal condition of matter has been studied4 ,a more logical arrangement so far as the systematic study of these properties is concerned would be to take up chapter ,,xv before undertaking the study of the proteins 7this order is actually followed in some texts on ,physiological ,chemistry74 ,but from the standpoint of the consideration of the various groups of organic components of plants1 it seems a better arrangement to consider these groups in sequence1 and then to discuss the various physical-chemical phenomena which govern their activity4 ,however1 it is recommended that the student refer at once to ,chapter ,,xv for an explanation of any terms used here1 which may not be familiar to him2 and that after the study of ,chapter ,,xv1 he return to this chapter dealing with the proteins for an illustrative study of the applications of the principles presented there4 ,,the ,,classification ,,of ,,the ,,proteins ,formerly1 the classification of proteins was based almost wholly upon their solubility and coagulation reactions4 ,more recently1 since their products of hydrolysis have been extensively studied1 their classification has been modified1 in attempts to make it correspond as closely as possible to their chemical constitution and physical properties4 ,as knowledge of these matters progresses1 the schemes of classification change4 ,on that account1 no one definite scheme is universally used4 ,for example1 the ,english system varies considerably from the one commonly used by ,american biochemists1 which is the one presented below4 ,the proteins are divided into three main classes1 as follows3 7#a7 ,simple proteins1 which yield only amino-acids when hydrolyzed4 7#b7 ,conjugated proteins1 compounds of proteins with some other non-protein group4 7#c7 ,derived proteins1 decomposition products of simple proteins4 ,the first two of these classes comprise all the natural proteins2 while the third includes the artificial polypeptides and proteins which have been modified by reagents4 ,these major classes are further subdivided into the following sub-classes1 which depend in part upon the solubilities of the individual proteins1 and in part upon the nature of their products of hydrolysis3 #a4 ,the ,simple ,proteins ,a4 ,albumins--soluble in water and dilute salt solutions1 coagulated by heat4 ,b4 ,globulins--insoluble in water1 soluble in dilute salt solutions1 coagulated by heat4 ,c4 ,glutelins--insoluble in water or dilute salt solutions1 soluble in dilute acids or alkalies1 coagulated by heat4 ,d4 ,prolamins--insoluble in water1 etc41 soluble in #hj per cent alcohol4 ,e4 ,histones--soluble in water1 insoluble in ammonia1 not coagulated by heat4 ,f4 ,protamines--soluble in water and ammonia1 not coagulated by heat1 yielding large proportions of diamino-acids on hydrolysis4 ,g4 ,albuminoids--insoluble in water1 salt solutions1 acids1 or alkalies4 #b4 ,conjugated ,proteins ,a4 ,chromoproteins--compounds of proteins with pigments4 ,b4 ,glucoproteins--compounds of proteins with carbohydrates4 ,c4 ,phosphoproteins--proteins of the cytoplasm1 containing phosphoric acid4 ,d4 ,nucleoproteins--proteins of the nucleus1 containing nucleic acids4 ,e4 ,lecithoproteins--compounds of proteins with phospholipins4 ,f4 ,lipoproteins--compounds of proteins with fats1 existence in nature doubtful1 artificial forms easily prepared4 #c4 ,derived ,proteins ,a4 ,primary protein derivatives4 a4 ,proteans--first products of hydrolysis1 insoluble in water4 b4 ,metaproteins--result from further action of acids or alkalies1 soluble in weak acids and alkalies1 but insoluble in dilute salt solutions4 c4 ,coagulated proteins--insoluble forms produced by the action of heat or alcohol4 ,b4 ,secondary protein derivatives4 a4 ,proteoses--products of hydrolysis1 soluble in water1 not coagulated by heat1 precipitated by saturation of solution with ammonium sulfate4 b4 ,peptones--products of further hydrolysis soluble in water1 not coagulated by heat1 not precipitated by ammonium sulfate1 give biuret reaction4 c4 ,peptides--individual amino-acids1 or poly-peptides1 may or may not give biuret reaction4 ,the plant proteins which have been investigated1 thus far1 fall into these groups as follows3 #a;,a4 ,albumins ,leucosin1 found in the seeds of wheat1 rye1 and barley4 ,legumelin1 pea1 horse-bean1 vetch1 soy-bean1 lentil1 cowpea1 adzuki-bean4 ,phaselin1 kidney-bean4 ,ricin1 castor-bean4 #a;,b4 ,globulins ,legumin1 found in the seeds of pea1 horse-bean1 lentil and vetch4 ,vignin1 cowpea4 ,glycinin1 soy-bean4 ,phaseolin1 beans 7,phaseolus spp47 ,conglutin1 lupines4 ,vicilin1 pea1 horse-bean1 lentil4 ,corylin1 hazel nut4 ,amandin1 nuts of almond and peach4 ,juglansin1 seeds of walnut and butternut4 ,excelsin1 ,brazil nut4 ,edestin1 hemp seed4 ,avenalin1 oats4 ,maysin1 corn4 ,castanin1 the seeds of ,european chestnut4 ,tuberin1 potato tubers4 ,and1 crystalline globulins found in the seeds of flax1 squash1 castor-bean1 sesame1 cotton1 sunflower1 radish1 rape1 mustard1 and in cocoanuts1 candlenuts1 and peanuts4 #a;,c4 ,glutelins ,glutenin1 found in the seeds of wheat4 ,oryzenin1 rice4 #a;,d4 ,prolamins ,gliadin1 found in the seeds of rye1 wheat1 with glutenin forms gluten4 ,hordein1 barley4 ,zein1 corn4 #a;,e-#a;,g4 ,histones1 ,protamines and ,albuminoids4--,so far as is now known1 no representatives of these classes are found in plants4 #b4 ,conjugated ,proteins4--,there is no conclusive evidence of the existence in plants of any of the conjugated proteins1 other than the nucleoproteins and the chromoproteins1 the composition and properties of which have been discussed in previous chapters4 ,the nucleoproteins undoubtedly occur in the embryos of many1 if not all1 seeds4 #c4 ,derived ,proteins4--,representatives of the various types of derived proteins are undoubtedly found as temporary intermediate products in plants1 both as products of hydrolysis produced during the germination of seeds and as intermediate forms in the synthesis of proteins4 ,so far as is known1 however1 they do not occur as permanent forms in any plant tissues4 ,they have been prepared in large numbers and quantities1 by the hydrolysis of the natural proteins and the artificial synthesis of polypeptides4 ,in the present state of our knowledge concerning the functioning of the proteins1 no significance in the physiology of plant life1 or metabolism1 is to be attached to the particular type of protein material which it contains1 at least so far as the simple proteins of the cytoplasm are concerned4 ,,differences ,,between ,,plant ,,and ,,animal ,,proteins ,a much larger variety of protein materials is found in animal tissues than in plants4 ,this is undoubtedly because different animal organs perform so much more varied physiological functions than do those of plants4 ,three groups of simple proteins1 the histones1 the protamines1 and the albuminoids1 which are quite common in animal tissues1 are entirely unknown in plants4 ,further1 conjugated proteins of greater complexity and more varied structure are found in animal tissues1 especially in the brain1 nerve-cells1 etc41 than in plants4 ,plant proteins1 in general1 usually contain larger proportions of proline and of glutamic acid than are found in animal proteins2 also more arginine than is found in any of the animal proteins except the protamines1 which contain as high as #he per cent of this amino-acid4 ,of the twenty-five plant proteins which have thus far been hydrolyzed and studied from this standpoint1 all contained leucine1 proline1 phenylalanine1 aspartic acid1 glutamic acid1 tyrosine1 histidine1 and arginine2 two gave no glycine2 two others1 no alanine2 four contained no lysine2 and one1 no tryptophane4 ,zein1 the principal protein of corn contains no glycine1 lysine1 or tryptophane4 ,it is not sufficient to support animal life and promote growth1 if used as an exclusive source for protein for food4 ,,the ,,extraction ,,of ,,proteins ,,from ,,plant ,,tissues ,since proteins are indiffusible1 it is essential that the cell-walls of the tissue shall be thoroughly ruptured as the first step in any process for the extraction of these compounds from plant tissues4 ,this is usually accomplished by grinding the material as finely as possible1 preferably with the addition of sharp quartz sand1 or broken glass1 to aid in the tearing of the cell-wall material4 ,the solvent to be used in extracting the proteins from this finely ground material depends upon the nature and solubility of the proteins which are present1 and also upon whether it is desired to separate the proteins which may be present in the plant1 during the process of the extraction4 ,a glance at the scheme of classification of the proteins will show the following solubilities which serve as a guide to the procedure to be followed3 7a7 proteoses1 albumins1 and some globulins may be extracted with water2 7b7 globulins and most of the water-soluble proteins may be extracted by using a #aj per cent solution of common salt2 7c7 prolamines are extracted by #gj-ij per cent alcohol2 glutelins and prolamins dissolve in dilute acids or dilute alkali4 ,a common procedure is to extract groups 7a7 and 7b71 using a #aj per cent salt solution as the solvent1 and then to separate the albumins1 globulins1 etc41 from this solution by suitable precipitants2 then to treat the material with #hj per cent alcohol1 to extract the prolamines2 and finally with dilute alkali1 to extract the glutelins4 ,the dissolved proteins in each extract can be subsequently purified by dialysis1 precipitation1 etc4 ,the insoluble proteins can be studied only after removing the other materials associated with them in the tissue1 by suitable mechanical or chemical means4 ,,the ,,synthesis ,,of ,,proteins ,,in ,,plants ,the synthesis of proteins in plants is not a process of photosynthesis1 as it can take place in the dark and in the absence of chlorophyll1 or any other energy-absorbing pigment4 ,however1 protein-formation normally takes place in conjunction with carbohydrate-formation4 ,the carbon1 hydrogen1 and oxygen necessary for protein synthesis are undoubtedly obtained from carbohydrates4 ,the nitrogen and sulfur come from the salts absorbed from the soil through the roots and brought to the active cells in the sap4 ,atmospheric nitrogen cannot be used by plants for this purpose1 except in the case of certain bacteria and other low plants1 notably the bacteria which live in symbiosis with the legumes in the nodules on the roots of the host plants4 ,in general1 the sulfur must come in the form of sulfates and the nitrogen in the form of nitrates2 although many plants can make use of ammonia for protein-formation4 ,presumably1 the nitrate nitrogen must be reduced in the plant to nitrites1 and then to ammonia form1 in order to enter the amino-arrangement required for the greater proportion of the protein nitrogen4 ,the mechanism by which ammonia nitrogen becomes amino-acids in the plant is not understood4 ,artificial syntheses of amino-acids1 by the action of ammonia upon glyoxylic acid and sorbic acid1 both of which occur in plants and may be obtained by the oxidation of simple sugars1 have been accomplished1 and it seems probable that similar reactions in the plant protoplasm may give rise to the various amino-acids which unite together to form proteins4 ,nothing is known1 however1 of the process by which the more complicated closed-ring amino-acid compounds1 such as proline1 histidine1 or tryptophane1 are synthetized4 ,the condensation of amino-acids into proteins1 or the reverse decomposition1 is very readily accomplished in all living protoplasm1 under the influence of special protein-attacking enzymes1 which are almost universally present in the cytoplasm4 ,these reactions in connection with the proteins are similar to the easy transformation of sugars to starches1 and vice versa1 under the action of the corresponding carbohydrate-attacking enzymes4 ,,physiological ,,uses ,,of ,,proteins ,there can be no doubt that the all-important rle of proteins1 in either plant or animal tissue1 is to furnish the colloidal protoplasmic material in which the vital phenomena take place4 ,their occurrence in seeds1 and other storage organs1 is1 of course1 in order to provide the protoplasm-forming material for the young seedling plant4 ,they are1 moreover1 the source for the material which goes into some of the secretion groups of organic compounds2 as they are easily broken down by various agents of decomposition into nitrogen-free alcohols1 aldehydes1 and acids1 which produce the essential oils1 pigments1 etc4 ,much1 if not all1 of their physiological activity is due to their colloidal nature1 the importance and effects of which will be more apparent after the chapters dealing with the colloidal condition of matter and with the physical chemistry of protoplasm have been studied4 ,,references ,,abderhalden1 ,e4--,neuere ,ergebnisse auf dem ,gebiete der ,speziellen ,eiweisschemie1 #abh pages1 ,jena1 #aiji4 ,,fischer1 ,e4--,untersuchungen ber ,aminosuren1 ,polypeptide1 und ,proteine1 #ahii-aijf1 #ggj pages1 ,berlin1 #aijf4 ,,mann1 ,g4--,chemistry of the ,proteids1 #fjf pages1 ,london1 #aijf4 ,,osborne1 ,t4 ,b4--,the ,vegetable ,proteins1 #ach pages1 ,monographs on ,biochemistry1 ,london1 #aiji4 ,,plimmer1 ,r4 ,h4 ,a4--,the ,chemical ,constitution of the ,proteins1 ,part ,i1 ,analysis1 #ahh pages2 and ,part ,,ii1 ,synthesis1 etc4 #ajg pages1 ,monographs on ,biochemistry1 ,london1 #aiag4 7#c;d ed474 ,,robertson1 ,t4 ,b4--,the ,physical ,chemistry of the ,proteins1 #dgg pages1 ,new ,york1 #aiah4 ,,schryber1 ,s4 ,b4--,the ,general ,characters of the ,proteins1 #hf pages1 ,monographs on ,biochemistry1 ,london1 #aiji4 ,,underhill1 ,f4 ,p4--,the ,physiology of the ,amino-acids1 #afi pages1 #ac figs4 #a plate4 ,yale ,university ,press1 #aiae4 ,,chapter ,,xiv ,,enzymes ,,and ,,their ,,action ,the characteristic difference between the reactions of inorganic compounds and those of organic substances lies in the rapidity1 or velocity1 of the chemical changes involved4 ,speaking generally chemical reactions take place between substances which are in solution1 so that they may come into sufficiently intimate contact that chemical action between them can take place4 ,there are1 of course1 occasional examples of reactions between dry solids1 such as the explosion of gunpowder1 etc41 but the general rule is that reacting materials must be in either colloidal or true solutions4 ,inorganic materials1 when dissolved in water1 usually ionize very readily4 ,that is1 they are not only disintegrated into individual molecules1 but a considerable proportion of these molecules separate into their constituent ions4 ,when solutions containing ionized compounds are brought together1 conditions for chemical interaction are ideal1 and the reaction proceeds with such tremendous rapidity as to be completed almost instantaneously1 in most cases4 ,organic compounds1 on the other hand1 ionize only very slowly1 if at all4 ,hence1 reactions between organic compounds1 even when they are in solution1 proceed very slowly unless carried on at high temperatures1 under increased pressure1 or under the influence of some catalytic agent4 ,even under the stimulation of these reaction-accelerating agencies1 most chemical changes in organic compounds when carried on in the laboratory1 require several hours or even days and sometimes weeks1 for their completion4 ,but when similar reactions take place in living organisms1 they proceed with velocities which resemble those of inorganic compounds in the laboratory4 ,this difference between the velocity of organic reactions when carried on under artificial conditions in the laboratory 7often spoken of as in vitro7 as compared with that of the same reactions when they take place in a living organism 7in vivo71 is due to the universal presence in the living protoplasm of certain organic catalysts1 known as enzymes4 ,,enzymes ,,as ,,catalysts ,the phenomenon known as catalysis is of common occurrence in both inorganic and organic chemistry4 ,the effect of a small amount of manganese dioxide in aiding in the liberation of oxygen from potassium chlorate is an example which is familiar to all students of elementary chemistry4 ,similarly1 spongy platinum accelerates the oxidation of sulfur dioxide to sulfur trioxide1 in the commercial manufacture of sulfuric acid4 ,again1 the hydrolysis of sucrose into fructose and glucose proceeds very slowly in the presence of water alone1 but if a little hydrochloric acid or sulfuric acid be added to the solution1 the velocity of the hydrolysis is enormously accelerated4 ,many other examples of the accelerating effect of various chemicals upon reactions into which they do not themselves enter1 might be cited4 ,the essential features of all such catalytic actions are3 7#a7 the velocity of the reaction is greatly altered1 usually accelerated2 7#b7 the catalytic agent does not appear as one of the initial substances1 or end-products1 of the reaction1 and is not itself altered by the chemical change which is taking place2 7#c7 the accelerating effect is directly proportional to the amount of the catalyst which is present2 7#d7 relatively small amounts of the catalyst produce very large results in the reacting mixture2 and 7#e7 the catalysts cannot themselves initiate reactions1 but only influence the velocity of reactions which would otherwise take place at a different rate 7usually much more slowly7 in the absence of any catalytic agent4 ,enzymes conform to all of these properties of catalysts1 and are commonly defined as the catalysts of living matter4 ,they are almost universally present in living organs of every kind1 and perform exceedingly important functions1 both in the building-up of synthetic materials and in the rendering soluble of the food of both plants and animals1 so that it can be translocated from place to place through the tissues of the organism4 ,enzymes differ from inorganic catalysts in being destroyed by heat1 in not always carrying the reaction to the same stage as does the inorganic catalyst which may accelerate the same reaction1 and in producing different changes in the same substance by different enzymes4 ,the name enzyme comes from ,greek words meaning in yeast1 as the nature and effect of the enzyme involved in the alcoholic fermentation of sugars by yeast were those which were first recognized and understood4 ,it was at first thought1 by ,pasteur and his students1 that fermentation is the direct result of the life activities of the yeast plant4 ,later1 it was found that water extracts from sprouted barley1 from almond seeds1 and from the stomach1 pancreas1 etc41 were able to bring about the decomposition of starch1 of amygdalin1 and of proteins1 respectively1 in a way which seemed to be quite comparable to the fermentative action of yeasts4 ,hence1 it was thought that there were two varieties of active agents of this kind1 one composed of living cells and the other non-living chemical compounds1 and these were called the organized ferments and the unorganized ferments1 respectively4 ,however1 in #ahig1 ,bchner found that by grinding yeast cells with sharp sand until they were completely disintegrated and then submitting the mass to hydraulic pressure1 he could obtain a clear liquid1 entirely free from living cells1 which was just as active in producing fermentation as was the yeast itself4 ,this discovery paved the way for a long series of investigations1 which have conclusively demonstrated that there is no distinction between organized and unorganized ferments1 that all living organisms perform their characteristic functions by means of the enzymes which they contain1 and that these enzymes can bring about their characteristic catalytic effects outside the cell1 or tissue which elaborates them1 just as well as within it1 provided only that the conditions of temperature1 acidity or alkalinity of the medium1 etc41 are suitable for the particular enzyme action which is under consideration4 ,,general ,,properties ,,of ,,enzymes ,since enzymes are catalysts1 it is plain that an accurate description of their activity should1 in each case1 refer to the influence which they exert upon some definite reaction velocity4 ,but since the phrases necessary to describe such an effect are cumbersome and inconvenient1 and since most of the reactions which are accelerated by the catalytic action of enzymes are either simple hydrolyses1 changes in oxygen content1 or other simple decompositions or condensations1 which will otherwise proceed so slowly as to be practically negligible1 it is customary to speak of the enzyme as acting upon the material in question4 ,it should be understood1 however1 that this is a misstatement1 as the enzyme cannot actually initiate a reaction1 or act upon any substance2 it only acts as a catalyzer to accelerate the action of water1 oxygen1 etc41 upon the material in question4 ,generally speaking1 most enzymes are colloidal in form and1 hence1 do not diffuse through membranes such as the cell-walls4 ,some of them perform their characteristic functions only within the cell1 or organ1 which elaborates them1 and can be obtained outside these tissues for purposes of study only by first rupturing the cell-wall or other membrane with which they are surrounded4 ,such enzymes are known as intracellular4 ,others are regularly secreted by glands which discharge them onto other organs1 as the stomach or intestines of animals1 where they perform their useful functions2 or1 as in the case of germinating seeds1 they move to other parts of the organ1 and can be extracted from the tissue by simple treatment with water4 ,these are known as the extracellular enzymes4 ,enzymes are specific in their action4 ,any given enzyme affects only a single reaction2 or at most acts only upon a single group of compounds which have similar molecular configuration4 ,usually it is only a single compound whose decomposition is accelerated by the action of a particular enzyme2 but there are a few enzymes1 such as maltase 7which acts on all alpha-glucosides7 and emulsin 7which acts on all beta-glucosides7 which act catalytically upon groups of considerable numbers of similar compounds4 ,enzymes1 like all other catalysts1 act more energetically at increased temperatures2 but for each particular enzyme there is an optimum temperature1 7usually between #dj and #fe7 above which the destructive effect of the temperature upon the enzyme itself more than offsets the accelerating influence of the increased temperature4 ,at still higher temperatures 7usually #hj to #ajj7 the enzymes are killed1 i4e41 rendered permanently inactive4 ,all enzymes are killed by boiling the solutions in which they are contained4 ,dry preparations of enzyme material can withstand somewhat higher temperatures1 for somewhat longer periods of time1 than can the same enzyme in moist condition or in solution4 ,when an enzyme has once been inactivated by heating1 or killed1 it can never be restored to activity again4 ,enzymes are extremely sensitive to acids1 bases1 or salts1 their activity being often enormously enhanced or1 in other cases1 entirely inhibited1 by the presence in the reacting medium of very small amounts of free acids1 or bases1 or even of certain neutral salts4 ,for example1 pepsin1 the enzyme of the stomach will act only in the presence of a slightly acid medium and is wholly inactive in a mixture which contains even the slightest amount of free alkaline material2 while trypsin1 the similar enzyme of the intestine1 acts only under alkaline conditions4 ,practically all enzymes are rendered inactive1 but not destroyed1 by the presence of either acid or alkali in excess of ,n_/#aj strength4 ,many will act only in the presence of small quantities of certain specific neutral salts2 while1 on the other hand1 other salts are powerful inhibitors of enzyme action4 ,enzymes often differ from the protoplasm which secretes them in their response to antiseptics1 such as toluene1 xylene1 etc41 which inhibit the activity or growth of the cell1 but have no effect upon the activity of the enzymes which it contains4 ,,the ,,chemical ,,nature ,,of ,,enzymes ,nothing is known with certainty concerning the chemical nature of enzymes4 ,being colloidal in nature1 they adsorb carbohydrates1 proteins1 fats1 etc41 so that active enzyme preparations often respond to the characteristic tests for these groups of substances2 and many investigators have reported what has1 at first1 seemed to be conclusive evidence that some particular enzyme which they have studied is either a carbohydrate1 a protein1 or some other type of organic compound4 ,later investigations have always shown1 however1 that if the preparation in question be submitted to the digestive action of the enzymes which hydrolyze the particular type of substances to which it is supposed to belong1 the material will lose its characteristic protein1 or carbohydrate1 etc41 properties1 without losing its specific activity1 thus clearly indicating that the substance which responds to the characteristic tests for some well-known type of organic compounds is present as an impurity and is not the enzyme itself4 ,the present state of knowledge concerning the nature of enzymes seems to indicate that1 like the inorganic catalysts1 they may vary widely in chemical composition2 and that their tremendous catalytic effects are due1 in part at least1 to their colloidal nature4 ,this will be better understood and appreciated after the phenomena associated with the colloidal condition have been considered 7see the following chapter74 ,,nomenclature ,,and ,,classification ,since nothing is known of the chemical composition of enzymes1 they can only be studied by considering the effects which they produce4 ,this is reflected in the systems which have been adopted for their nomenclature and classification4 ,as they were first supposed to be proteins1 the earlier representatives of the group were given characteristic names ending with the suffix in1 similar to that of the proteins4 ,since this idea has been found to be incorrect1 however1 a system of nomenclature has been adopted which assigns to each enzyme the name of the material upon which it acts1 followed by the suffix ase4 ,thus1 cellulase is the enzyme which accelerates the hydrolysis of cellulose2 glucase1 that acting upon glucose2 amylase1 that acting upon starch 7amylum71 etc4 ,the substance upon which the enzyme acts 7or1 strictly speaking1 the substance whose hydrolysis1 oxidation1 or other chemical change1 is catalytically affected by the enzyme7 is called the substrate4 ,most enzymes are catalysts for hydrolysis reactions and are1 hence1 classed as hydrolytic in their action1 and may be spoken of as hydrolases4 ,those which accelerate oxidation are called oxidases2 while those that stimulate reduction reactions are reductases2 those that aid in the splitting off of ammonia1 or amino-acid groups1 are deaminases2 and those that aid in the splitting off of ,,co#b from ,,cooh groups are carboxylases1 etc4 ,the hydrolytic enzymes are further subdivided into the sucroclastic 7sugar-splitting71 or sucrases2 the lipoclastic 7fat-splitting71 or lipases2 the esterases 7ester-splitting72 proteoclastic 7protein-splitting71 or proteases2 etc4 ,,occurrence ,,and ,,preparation ,,for ,,study ,enzymes are present in all living matter4 ,in animal tissues1 they occur in the largest amounts in those glands or organs where active vital processes take place1 as in the brain1 the digestive tract1 blood1 etc4 ,in plants1 they may be found in all living cells1 and are especially abundant in the seeds1 where they serve to render soluble and available to the young plant the stored food materials4 ,the enzymes of moulds1 and other parasitic plants1 are usually extracellular in type1 being secreted for the purpose of making the material of the host plant available to the parasite4 ,extracellular enzymes are also developed in seeds during germination1 in order that the stored food material of the endosperm may be rendered soluble and translocated into the tissues of the growing seedling4 ,but most other plant enzymes are intracellular in type4 ,hence1 in all preparations of plant enzymes for study1 or for commercial use1 the first step in the process is1 necessarily1 a thorough rupturing of the cell-walls of the plant material4 ,the rupturing of the cells may be accomplished in a variety of ways1 as follows3 7#a7 mechanical disintegration1 as by grinding in a mortar with sharp sand2 7#b7 freezing the material1 by treatment with liquid air1 then grinding2 7#c7 killing the cells by drying1 by treatment with alcohol or acetone1 then grinding the mass in a paint mill with toluene2 7#d7 killing the cells by chemicals 7sulfuric acid1 #j4e to #a4j per cent1 or other suitable agents7 followed by extraction with water2 7#e7 autolysis1 or self-digestion1 in which the cells are mixed with toluene or some other antiseptic which kills the cells without injuring the enzymes1 then the material is minced or ground up and suspended in water containing the antiseptic1 until the enzymes dissolve the cell-walls and so escape into the liquid--this process being especially adapted to the preparation of active extracts from yeasts1 which contain the necessary cell-wall dissolving enzymes to facilitate autolysis4 ,enzymes may be separated out of the aqueous extract obtained from cells ruptured by any of the above methods1 by precipitation with alcohol1 acetone1 or ether1 in which they are insoluble2 but if this is done1 the precipitate must be at once filtered off and rapidly washed and dried1 as prolonged contact with these precipitating agents greatly diminishes the activity of most enzymes4 ,or1 they may be adsorbed out of solution on gelatinous1 or colloidal1 materials1 like aluminium hydroxide1 or various hydrated clays4 ,if the dry preparations obtained in any of these ways are contaminated by carbohydrates1 proteins1 etc41 these may be removed by treatment with suitable digesting enzymes obtained from the saliva1 gastric1 and pancreatic juices1 and the digested impurities washed out with #fj to #hj per cent alcohol1 leaving the enzyme preparation in a purified but still active form4 ,in any study of the strength1 or possible catalytic effects1 of an enzyme preparation1 it is necessary1 first1 to determine what particular reaction it affects1 by qualitative tests with various substrate materials1 such as starch1 sugars1 glucosides1 proteins1 etc41 and then to determine quantitatively its accelerating effect upon the reaction in question4 ,the latter may be done by measuring either the time required to carry a unit quantity of the substrate material through any determined stage of chemical change1 or the quantity of the substrate which is changed in a unit period of time4 ,it would not be profitable to go into a detailed discussion here of the methods of making these quantitative measurements of enzyme activity4 ,such discussions must necessarily be left to special treatises on methods of study of enzyme action4 ,it may be said1 however1 that generally both the qualitative tests for1 and the quantitative measurements of1 the accelerating influence of enzymes depend upon the observation of some change in the physical properties of the substrate material1 such as the optical activity1 electrical conductivity1 or viscosity1 of its solution4 ,in some cases1 it is convenient to make an actual quantitative determination of the amount of end-products produced in a given time1 as in the inversion of cane sugar1 the hydrolysis of maltose1 etc41 but such determinations necessarily involve the removal of some of the reaction mixture for the purposes of the determinations1 and are not1 therefore1 suitable for the study of the progressive development of the reaction which is being studied4 ,enzymes are found in all parts of the animal organism and those which are active in the digestion of food1 the metabolism of digested material1 the coagulation of blood1 etc41 have been extensively studied4 ,a discussion of these animal enzymes would be out of place in such a text as this1 however1 and the following list includes only enzymes which are known to occur in plant tissues4 ,these well-known enzymes will serve as examples of the several general types which have thus far been isolated and studied4 ------------------- ---------------------------------------- --------- ,class and ,type4 ,enzyme4 ,substrate4 ,end-products4 ,found in4 ---------------------------------------- ----------------------------- ,i4 ,hydrolases 7a7 ,esterases ,lipase ,fats ,glycerol and ,oily seeds fatty acids 7b7 ,carbohydrases ,sucrase or ,sucrose ,glucose and ,yeasts invertase fructose ,maltase ,maltose and ,glucose1 etc4,barley malt all alpha- glucosides ,dextrinase ,dextrin ,maltose ,malt ,inulase ,inulin ,fructose ,artichokes1 etc4 ,amylase or ,starch ,maltose ,malt1 etc4 diastase ,cellulase ,cellulose ,maltose ,bacteria ,pectinase ,pectose ,arabinose ,fruits ,cytase ,hemi- ,mono- ,nuts1 celluloses saccharides seeds1 etc4 7c7 ,glucosidases ,emulsin ,amygdalin ,glucose1 ,almond and all etc4 kernels1 beta- etc4 glucosides ,maltase ,all alpha- ,glucose1 ,barley malt glucosides etc4 ,myrosin ,sulfur- ,glucose1 ,mustard containing etc4 seeds glucosides ,rhamnase ,xanthorhamnin,rhamnose1 ,rhamnus etc4 spp4 ,phytase ,phytin ,inosite and ,bran coats ,h#c,,po#d of seeds 7d7 ,proteases ,erepsin ,proteins ,amino-acids ,many plants ,papain ,proteins ,amino-acids ,papaws ,bromelin ,proteins ,amino-acids ,many plants ,nuclease ,nucleo- ,proteins and ,many plants proteins nucleic acid ,,ii4 ,oxidases 7a7 ,catalases 44444444 ,hydrogen ,water and ,nearly peroxide oxygen all plants 7b7 ,peroxidases 44444444 ,organic ,active ,nearly peroxides oxygen all plants 7c7 ,oxidases 44444444 ,chromogens ,pigments ,many plants ,alcohols and ,acids ,many plants phenols 7d7 ,reductases 44444444 444444444 444444444 ,many plants ,,iii4 ,deaminases ,urease ,urea ,ammonia and ,,co#b ,guanase ,guanine ,xanthine ,adenase ,adenine ,hypoxanthine ,,iv4 ,carboxylases 7a7 44444444 ,keto-acids ,aldehydes and ,,co#b 7b7 44444444 ,amino-acids ,amines and ,,co#b ,v4 ,coagulation ,pectase ,coagulates 4444444444 ,fruits enzymes pectic bodies ,,vi4 ,fermentation ,zymase ,glucose1 etc4,alcohol and ,yeasts enzymes ,,co#b ,lactic acid,fatty acids ,lactic acid ,bacteria ferment ,butyric ,fatty acids ,butyric acid ,bacteria acid ferment ---------------------------------------- ---------------------------- ,the above list includes only the more common and best-known plant enzymes4 ,it seems reasonable to suppose that for every individual type of organic compound which may occur in general plant groups1 or even in single species1 there is a corresponding enzyme available to affect its physiological alterations4 ,indeed1 new preparations of active enzymes from special types of plants and new evidences of the existence of enzymes in various plant organisms are continuously being reported4 ,a few of the most common specific representatives of individual groups of enzymes may be briefly described1 as follows3 ,amylase 7or diastase1 as it was first named and is still commonly called7 is probably the most widely distributed enzyme of plants4 ,it is found in practically all bacteria and fungi2 in practically all seeds 7it has been found in active form in seeds which were known to be over fifty years old72 in all roots and tubers2 and in practically all leaves1 where it is located in the stroma of the chloroplasts4 ,it appears to exist in two modifications1 known1 respectively1 as 7a7 translocation diastase and 7b7 diastase of secretion4 ,the first form is found in the cells of ungerminated seeds1 in leaves1 shoots1 etc4 ,it remains in the cells where reserve starch is stored and aids in the transformation of starch into soluble materials for translocation from cell to cell4 ,it is active at a lower temperature than the second form1 its optimum temperature being #de to #ej4 ,the second form is secreted by the scutellum1 and perhaps by the aleurone cells1 of germinating seeds1 being produced by special glandular tissue4 ,it aids in the hydrolysis of the starch for the use of the growing embryo4 ,its optimum temperature is #ej to #ee4 ,the activity of amylase is accelerated by the presence of small quantities of neutral salts1 especially by sodium chloride and disodium phosphate4 ,it acts best in neutral solutions1 its activity being inhibited1 although the enzyme itself is not destroyed1 by the presence of more than minute traces of free mineral acid or alkali4 ,sucrase 7or invertase7 is present in almost all species of yeasts1 where it serves to convert unfermentable sucrose into glucose and fructose1 which are readily fermentable4 ,invertase is also present in moulds and other microorganisms2 and in the buds1 leaves1 flowers1 and rootlets of those higher order plants which store their carbohydrate reserves in the form of sucrose4 ,it appears that sucrose1 while easily soluble1 is not readily translocated1 or utilized1 by plants until after it has been hydrolyzed into its constituent hexoses4 ,the optimum temperature for invertase is #ej to #ed2 it is killed if heated1 in the moist condition1 to #gj4 ,its activity is increased by the presence of small amounts of free acids2 but is inhibited by free alkalies4 ,zymase is the active alcoholic fermentation enzyme of yeasts4 ,it accelerates the well-known reaction for the conversion of hexose sugars into alcohol and carbon dioxide1 namely1 ,c#f;,h#ab,o#f #b;,c#b;,h#e,,oh #b;,,co#b4 ,because of its scientific interest and industrial importance in the fermentation industries1 its action has been extensively studied4 ,it acts only in the presence of soluble phosphates and of a coenzyme 7see below7 which is dialyzable and not destroyed1 which is probably an organic ester of phosphoric acid4 ,the significance of the molecular configuration of the hexose sugars in their susceptibility to action by zymase has already been discussed in detail 7see page #ef74 ,the optimum temperature for zymase action is #bh to #cj4 ,the enzyme is killed by heating to #de to #ej in solution1 or to #he if in dry preparation4 ,proteases of the erepsin type1 i4e41 those which break proteins down to amino-acids instead of only to the proteose or peptone stage1 as is characteristic of the enzymes of the trypsin type1 are widely distributed in plants4 ,except in the case of the two which occur in large amounts in certain special fruits 7papain in papaws1 and bromelin in pineapples71 they are very difficult to prepare in pure form for study4 ,in general1 all proteolytic actions1 even when accelerated by active enzymes1 proceed much more slowly than do the hydrolyses of carbohydrates or fats4 ,it seems that metabolic changes of the complex protein molecules are much more difficult to bring about and take place much more slowly than do those of the energy-producing types of compounds4 ,the presence of proteolytic enzymes in most vegetative cells1 and in seeds1 may be demonstrated1 however1 by studying the action of extracts of these tissues upon soluble proteins4 ,the best-known example of this type of enzymes is the protease of yeast2 but similar ones may be found in germinating seeds4 ,these vegetable proteases are usually most active in neutral or only faintly alkaline solutions1 and their activity is nearly always inhibited by even traces of free acids4 ,most laboratory studies of proteolytic enzymes are carried on with preparations of the powerful members of this class of enzymes which are found in the digestive tract of animals1 namely1 the pepsin of the gastric juice1 which acts in the acid medium1 in the stomach1 and the trypsin of the pancreatic juice1 which acts in the alkaline medium of the intestinal tract4 ,but even these powerful proteases require several hours for the transformation of an amount of soluble albumin into its amino-acid constituents which is equivalent to the amount of starch which is hydrolyzed to maltose by diastase in a very few minutes4 ,enzymes which govern oxidative changes1 known respectively1 as catalases and oxidases1 are almost universally present in plants4 ,catalase decomposes peroxides1 with the liberation of free oxygen4 ,it is1 therefore1 necessary to the final step in the process of photosynthesis1 as elucidated by ,usher and ,priestley 7see page #bf71 and serves to prevent the destructive action of hydrogen peroxide upon chlorophyll4 ,the almost universal presence of oxidases in plant tissues has been repeatedly demonstrated4 ,they are present in especially large amounts in tissues which are being acted upon by parasitic fungi or are combating unfavorable conditions of growth4 ,the oxidases1 in such cases1 seem to be the agents by which the plant is able to stimulate its metabolic activities to overcome the unfavorable environment for its normal development4 ,in vegetables and fruits1 the common browning1 or blackening1 of the tissues when cut surfaces are exposed to the air has been demonstrated to be due to the catalytic oxidation of the tannins or of certain amino-acids1 especially tyrosine1 under the influence of the oxidases which are present in the tissues4 ,in fact1 most pigmentation phenomena are due to changes in the oxygen content of the chromogens of the cells of the plant1 under the influence of the oxidases which are present in the protoplasm of the cells in question4 ,hence1 the oxidases may be said to be the controlling agencies for both the energy-absorbing activities and for respiration in plants4 ,,the ,,nature ,,of ,,enzyme ,,action ,the mechanism by which an enzyme accomplishes its catalytic effects has been the object of extensive studies during recent years1 especially since the discovery by ,bchner that enzymes could be isolated in solutions entirely free from the disturbing influence of growing cells4 ,several theories concerning the mode of this catalytic action have been advanced4 ,the earliest and simplest of these was that the enzyme simply creates an environment favorable for the particular chemical reaction to take place1 as by exposing large surfaces of the substance in question to the action of the hydrolytic1 or other effective1 agent1 by means of surface adsorption of the substrate material on the colloidal enzyme4 ,however1 more recent investigations clearly indicate that there is an actual combination between the substrate material and the enzyme1 which combination then breaks down with a resultant change in the substrate material and a freeing of the enzyme for repeated recombination with additional substrate1 with the net result that the chemical change in the substrate material is enormously accelerated4 ,that such a combination between substrate and enzyme actually exists has been demonstrated in two different ways3 7a7 experimentally1 by mixing together solutions of an enzyme and of its substrate1 each of which is filterable through paper or through a porous clay filter1 with the result that the active material in the combined solutions will not pass through these same filters2 and 7b7 mathematically1 by a study of the curves representing the reaction velocities of typical reactions which are proceeding under the influence of an enzyme1 which show that so long as there is a large excess of substrate material present1 the accelerating influence of the catalyst is uniform over given successive periods of time1 but that when the quantity of substrate material becomes smaller than that which permits the maximum combining power of the enzyme to be exercised1 the reaction velocity immediately slows up4 ,again1 the fact that the specificity of the action of an enzyme1 i4e41 the limitation of the action of that enzyme to a specific single compound or group of similar compounds1 is definitely related to the molecular configuration of the molecule of the substrate1 as has been found to be true in all those cases where the molecular configuration of the substrate material has been established 7see pages #ef to #eh71 is an added indication that there is some kind of a union between the enzyme and the substrate as a first step in the catalytic process4 ,as to the nature of this supposed combination of substrate and enzyme1 two theories are held4 ,the first is that this union is in the form of an actual molecular combination1 or chemical compound1 and the other is that it is a purely physical1 or colloidal complex4 ,the latter view has by far the greater weight of theoretical and experimental evidence in its support4 ,the relation of electrolytes to the catalytic effect of enzymes1 the appearance of the reacting masses under the ultramicroscope1 and the effect of heat upon the reacting mixtures1 all point to the conclusion that the phenomenon is colloidal rather than molecular in character4 ,this view also makes the remarkable catalytic effects which take place in living protoplasm1 which undoubtedly exists in the colloidal condition1 much more easily understood4 ,this phase of the matter will be much more apparent after the chapter dealing with the physical chemistry of the protoplasm has been studied4 ,a further indication that the mechanism of enzyme activity is colloidal in character lies in the fact that1 so far as is known1 all reactions which are catalyzed by specific enzymes are reversible and the same enzyme will accelerate the velocity of the reaction in either direction1 the direction in which the reaction goes being determined by the conditions surrounding the reacting material at the time4 ,it was formerly supposed that enzymes catalyze only decomposition reactions and that the synthetic reactions of living tissues are produced by means of some other force or agency4 ,this view supported the idea of a chemical union of the enzyme with the substrate which1 when it breaks down1 breaks the molecule of the substrate material into some simpler form1 or forms4 ,but it is now known that the reaction which is influenced by the enzyme will be catalyzed in either direction by the specific enzyme which fits the particular substrate material at every point of its molecular configuration1 as the glove fits the hand4 ,the contrast between this fitting of the enzyme to the entire configuration of the molecule1 and the union at a single point or group which is characteristic of chemical linkages1 is apparent4 ,as examples of the synthetic action of the same enzyme which1 under other conditions1 accelerates the decomposition of the same material1 there may be cited the demonstrated synthesis of isomaltose from glucose by maltase2 the production of ethyl butyrate from alcohol and butyric acid2 and the synthetic production of artificial fats1 by the aid of the pancreatic lipase2 and the apparent synthesis of a protein from the same amino-acids which may be obtained from it by hydrolysis under the influence of the same protease1 but under different environmental conditions4 ,,activators ,,and ,,inhibitors ,the activity of enzymes is strongly influenced by the presence in the solution of other bodies1 usually1 although not always1 electrolytes4 ,this is probably due1 in most cases at least1 to the action of the electrolyte upon the colloidal condition of the enzyme4 ,all enzymes do not respond alike to the action of the same electrolyte1 however4 ,the activity of certain enzymes is enormously increased by the presence of a small amount of acid2 while the action of another may be absolutely inhibited by the same acid in the same concentration4 ,thus1 the activity of the amylase found in the endosperm of many seeds is instantly stopped by adding to the solution enough sulfuric acid to make it two-hundredth normal in strength2 while the same concentration of acid actually accelerates the activity of some of the proteases4 ,formaldehyde1 hydrocyanic acid1 and soluble fluorides usually inhibit both the activity of a cell and of the enzymes which it contains2 while other antiseptics1 such as toluene1 xylene1 etc41 prevent the growth of the cell1 or organism1 without interfering with the activity of the enzymes which may be present4 ,by the use of this latter type of antiseptics1 it is possible to distinguish between chemical changes which are involved in the actual development of a cell and those which can be brought about in other media by means of the enzymes which are contained in the cell4 ,any substance which increases the catalytic activity of an enzyme is known as an accelerator1 or activator2 while one which prevents this activity is called an inhibitor1 or paralyzer4 ,a type of accelerating influence quite different from that of electrolytes is found in the effect of certain amino-acids upon enzyme action4 ,the influence of small amounts of asparagine in enormously increasing the hydrolytic effect of amylase is an example4 ,there is no known explanation for this type of activation of the enzyme4 ,the influence of activators1 or inhibitors1 in providing favorable or unfavorable conditions for the action of an enzyme1 should not be confused with the relation to the enzyme itself of what are known as coenzymes and antienzymes1 discussed in the following paragraph4 ,,coenzymes ,,and ,,antienzymes ,in the cases of many enzymes of animal tissues1 it has been found that they are absolutely inactive unless accompanied by some other substance which is normally present in the gland1 or protoplasm1 which secretes them4 ,thus1 the bile salts are absolutely necessary to the activity of trypsin1 in its characteristic protein-splitting action4 ,such substances are known as coenzymes4 ,they can usually be separated from their corresponding enzymes by dialysis1 the coenzyme passing through the parchment membrane4 ,such coenzymes are not killed by boiling the dialyzate1 and the activity of the enzyme is restored by adding the boiled dialyzate to the liquid which remains within the dialyzer4 ,the best known example of a coenzyme in plant tissues is in connection with the activity of the zymase of yeast cells4 ,if yeast juice be filtered through a gelatin filter1 the colloidal enzymes which are left behind are entirely inactive in producing fermentation1 but may be restored to activity again by mixing with the filtrate4 ,an examination of this filtrate1 which contains the coenzyme for zymase1 shows that it contains soluble phosphates and some other substance whose exact nature has not yet been determined1 both of which are necessary to the activity of the zymase4 ,the phosphates seem to enter into some definite chemical combination with the substrate sugars1 while the other coenzyme seems to be necessary in order to make possible the final breaking down of the sugar-phosphate complex by the zymase4 ,this phenomenon of coenzyme relationship is not very frequently observed in plant enzyme studies1 probably because the coenzyme 7if there be such1 in the case which is under observation7 usually accompanies the enzyme itself through the various processes of extraction and purification of the material for study4 ,however1 care must be taken in all cases when dialysis is employed1 to see that a possible coenzyme is not separated from an otherwise active preparation4 ,an entirely different type of phenomenon is that exhibited by antienzymes4 ,these are found in the various intestinal worms which live in the digestive tracts of animals2 and prevent the digestive action of the enzymes of the stomach and intestines upon these worms4 ,probably similar antienzymes are located in the mucous linings of the intestinal tract itself1 and serve to prevent the auto-digestion of these organs by the active enzymes with which they are almost continually in contact4 ,the difference between an antienzyme1 which protects material which would otherwise be subject to the attack of an enzyme1 and an inhibitor1 which renders the enzyme itself inactive1 is apparent4 ,so far as is known1 however1 no such substances as antienzymes are present in plant tissues2 although the question as to why the proteoclastic enzymes which are elaborated by a given mass of protoplasm do not attack the protoplasm itself1 might well be raised4 ,,zymogens ,it is apparent that1 since enzymes are produced by protoplasm for the special needs of any given moment or stage of development1 there must be a preliminary stage1 or condition1 in which they do not exert their characteristic catalytic effect4 ,when in this stage1 the compound is known as proenzyme1 or zymogen4 ,in this stage1 it is inactive1 but can be made to exhibit its catalytic effect1 usually by bringing it into contact with a suitable activator4 ,when once so activated1 however1 it cannot be returned again to the inactive state4 ,this phenomenon has been studied in connection with the zymogens of the digestive proteases1 pepsin and trypsin4 ,trypsinogen may be rendered active by contact with either calcium salts or with another substance 7apparently itself an enzyme7 known as enterokinase1 which is secreted in the intestinal tract4 ,similarly1 proenzymes have been reported as occurring in numerous plant tissues4 ,these proenzymes are believed to be present in the plant cells in the form of definite characteristic granules1 which may be observed under the microscope1 and which disappear when the enzyme becomes active4 ,thus1 proinulase has been reported as occurring in artichoke tubers3 prolipase1 in castor beans2 proinvertase1 in several species of fungi2 and1 probably1 prooxidase1 in tobacco leaves4 ,in the case of the last-named zymogen1 it has been observed that after the zymogen has been once activated1 as in response to the need for increased activity due to the entrance of the germs of certain leaf-diseases1 it can once again produce a second supply of the enzyme1 but the process cannot again be repeated4 ,calcium salts1 or very dilute acids1 are usually energetic activators of proenzymes4 ,,physiological ,,uses ,,of ,,enzymes ,there can be no doubt that enzymes exert a tremendously important influence in vital phenomena1 by determining the rate at which the chemical changes which are involved in these phenomena shall proceed4 ,since they do not initiate reactions1 and since they may catalyze reversible reactions in either direction1 it cannot be said that they determine the type of reactions which will take place in any given mass of protoplasm2 but1 undoubtedly1 they do exert a determining influence upon the rate at which the reaction will proceed1 after the protoplasmic activity has determined the direction in which it shall go4 ,without the intervention of these catalyzing agents1 it would be impossible for reactions between these non-ionized organic components of the cell contents to come to completion with anything like the marvelous rapidity with which these changes must take place in order to permit the organism to grow1 to perform its necessary vital functions1 or to adjust itself to the changes in its environmental conditions4 ,since the number of different reactions which take place within a living cell is very great1 and since these chemical changes are extremely variable in type1 it follows that the number of different enzymes which must exist in either a plant or an animal organism is likewise very large4 ,for example1 fourteen different enzymes have been isolated from the digestive system1 and at least sixteen from the liver1 of animals4 ,they are universally present in living protoplasm of every kind1 from the most minute bacterium to the largest forest trees1 in the plant kingdom2 and from the amoeba to the whale1 in animals4 ,while there is a great variety of enzymes which may be produced by a single individual organism1 the same enzyme may be found in the greatest variety of organisms2 as1 for example1 the protease trypsin1 which has been found in several species of bacteria1 in the carnivorous plant known as ,venus' ,fly ,trap1 and in the human pancreas1 as well as that of all other animals4 ,,further ,,studies ,,needed ,from the discussions which have been presented in this chapter1 it is apparent that the enzymes play a tremendously important part in vital phenomena1 by controlling the rate at which the biochemical reactions take place in the cells of the living organism4 ,the means by which the protoplasm elaborates these all-important chemical compounds are as yet absolutely unknown4 ,even the nature of the enzymes themselves is still a matter of speculation and study4 ,much intensive study is needed and should be given to these matters1 for the purpose of elucidating the methods by which the enzymes accomplish their remarkable catalytic effects1 and1 if possible1 the actual chemical nature of the enzymes themselves4 ,it is conceivable1 of course1 that if the latter object of these studies should ever be reached1 it might be possible to synthetize enzymes artificially1 and so to develop a means for the artificial duplication of the synthesis of organic compounds with the same velocity that this is done in the plant cells4 ,such a result would have a scientific interest fully as great as did ,whler's artificial synthesis of urea1 which proved that there is no essential difference in character between the compounds which are the products of living organisms and those which are produced in the laboratory2 and1 at the same time1 might have an immensely more important practical bearing1 since it would lead the way to the artificial production of the carbohydrates1 proteins1 fats1 etc41 for which we are now dependent upon plant growth as the source of these materials for use as human food4 ,references ,,bayliss1 ,w4 ,m4--,the ,nature of ,enzyme ,action1 #ahf pages1 ,monographs on ,biochemistry1 ,london1 #aiai 7#dth ed474 ,,euler1 ,h41 trans4 by ,,pope1 ,t4 ,h4--,general ,chemistry of the ,enzymes1 #cai pages1 #g figs41 ,new ,york1 #aiab4 ,,effront1 ,j41 trans4 by ,,prescott1 ,s4 ,c4--,enzymes and their ,application1--,enzymes of the ,carbohydrates1 #cce pages1 ,new ,york1 #aijb4 ,,effront1 ,j41 trans4 by ,,prescott1 ,s4 ,c4--,biochemical ,catalysts in ,life and ,industry--,proteolytic ,enzymes1 #gfc pages1 ,new ,york1 #aiag4 ,,green1 ,j4 ,r4--,the ,soluble ,ferments and ,fermentation1 #eab pages1 ,cambridge1 #aija1 7#b;d ed474 ,,grus1 ,j4--,biologie und ,kapillaranalyse der ,enzyme1 #bbg pages1 #eh figs41 #c plates1 ,berlin1 #aiab4 ,,harden1 ,a4--,alcoholic ,fermentation1 #aef pages1 #h figs41 ,monographs on ,biochemistry1 ,london1 #aiad4 ,,plimmer1 ,r4 ,h4 ,a4--,the ,chemical ,changes and ,products ,resulting from ,fermentations1 #ahd pages1 ,london1 #aijc4 ,,oppenheimer1 ,c41 trans4 by ,,mitchell1 ,c4 ,a4--,ferments and their ,actions1 #cdc pages1 ,london1 #aija4 ,,chapter ,,xv ,,the ,,colloidal ,,condition ,reference has frequently been made1 in preceding chapters1 to the fact that proteins1 enzymes1 lipoids1 etc41 exist in the protoplasm of plants and animals in the colloidal condition4 ,the properties and uses of these compounds by plants depend so much upon this fact that1 before proceeding to the consideration of the actual physical chemistry of protoplasm itself1 it will be appropriate and profitable to give some attention to the nature and significance of the colloidal condition of matter and of some of the phenomena which grow out of it4 ,every discussion of the colloidal condition in general properly begins with reference to the work of the ,english physicist1 ,thomas ,graham1 who carried on his investigations of the so-called colloids through a period of forty years1 beginning with #ahea4 ,his most important results were published1 however1 from #ahfa to #ahfd4 ,graham studied the diffusibility of substances in solution through the parchment membrane of a simple dialyzer4 ,as a result of his earlier investigations1 he divided all the chemical compounds which were known to him into two groups1 which he called crystalloids and colloids1 respectively1 the first including those substances which readily diffused through the parchment membrane and the second those which diffused only very slowly or not at all4 ,he at first thought that crystalloids are always inorganic compounds1 while colloids are of organic origin4 ,he soon learned1 however1 that this distinction in behavior is not always related to the organic or inorganic nature of the compound4 ,he further discovered that the same individual chemical element or compound may exist sometimes in crystalloidal1 and sometimes in colloidal1 form4 ,this latter discovery led to the conclusion that diffusibility depends upon the condition1 rather than upon the nature1 of the material under observation4 ,as a result of the long series of investigations which were stimulated by ,graham's work1 the modern conception is that diffusibility is a condition of matter when in minute subdivision1 or in solution1 in some liquid1 as contrasted with its state1 or condition1 when existing alone4 ,that is1 the state of a substance may be either gaseous1 liquid1 or solid2 and its condition when in solution may be either crystalloidal or colloidal4 ,substances which are in crystalloidal form1 in true solution1 exist there in molecular or ionized condition2 but1 as will be pointed out below1 when in the colloidal condition they exist in aggregates which are somewhat larger than molecules1 but not large enough to be visible as individual particles under the ordinary microscope1 even under the highest magnification which has yet been obtained4 ,colloidal particles are1 however1 generally visible under the ,zigmondy ultramicroscope4 7,see below47 ,the use of the word colloid as a noun1 or as the name for a substance which is in the colloidal condition1 is of the same nature as the use of the words gas1 liquid1 and solid1 in such statements as ice is a solid1 water is a liquid1 or steam is a gas1 etc42 i4e41 the noun represents a state or condition rather than an actual object or thing4 ,hence1 the expression enzymes are colloids1 means only that enzymes exist in the colloidal condition1 and not that enzymes represent a definite type of substances having the group name colloids4 ,,the ,,colloidal ,,condition ,a ,,dispersion ,,phenomenon ,when one substance is distributed through the mass of another substance1 the mixture is said to be a two-phase system1 composed of the dispersed phase1 or substance1 and the dispersion medium1 or continuous phase1 through which the other substance is distributed4 ,the following examples illustrate the possibilities of such two-phase systems3 7#a7 ,dispersion medium a gas4 7a7 ,disperse phase a liquid--mist in the air4 7b7 ,disperse phase a solid--smoke or dust in air4 7#b7 ,dispersion medium a liquid4 7a7 ,disperse phase a gas--foams4 7b7 ,disperse phase a liquid--emulsions4 7c7 ,disperse phase a solid--suspensions4 7#c7 ,dispersion medium a solid4 7a7 ,disperse phase a gas--solid foams1 pumice stone1 etc4 7b7 ,disperse phase a liquid--liquid inclusions in minerals4 7c7 ,disperse phase a solid--alloys1 colored glass1 etc4 ,although the same general principles of physical chemistry apply to all two-phase systems1 the term colloidal condition is commonly used only in connection with a particular type of dispersions1 in which the dispersion medium is a liquid and the dispersed material is either a solid or a liquid4 ,thorough and careful studies have shown that when a solid or a liquid is introduced into another liquid1 and becomes dispersed or distributed through it1 the mixture may be either a true solution1 a colloidal solution1 or a mechanical suspension4 ,the characteristic differences between these three conditions may be tabulated as follows3 although the significance of some of the phrases used will not be apparent until the phenomena in question have been considered in some detail4 ---------------------------------------- ------------------------------- ,true ,solutions4 ,colloidal ,solutions4 ,suspensions4 ---------------------------------------- ------------------------------- 7a7 ,particles of the disperse phase are3 ,in molecular ,in colloidal ,in mechanical subdivision subdivision subdivision ,invisible ,visible under ,visible under ultrascope microscope or to naked eye ,less than #a #a to #a in diameter ,greater than #a in in diameter#f diameter ,pass through filters ,pass through filters ,do not pass through and parchment membranes but not through filters or parchment parchment ,in molecular motion ,in ,brownian movement ,in gravitational movement 7b7 ,the system exhibits3 ,high osmotic pressure ,low osmotic pressure ,no osmotic pressure ,transparency ,tyndall phenomenon ,is generally opaque ,no gel-formation ,forms gels ,no gel-formation ---------------------------------------- ------------------------------- ,,footnotes3 #f #a is one-thousandth of a millimeter2 #a is one-thousandth of a 1 or one millionth of a millimeter4 ,it is recognized by all students of these matters that it is not possible to draw a sharp dividing line between these three types of conditions1 and that they shade into each other1 in many cases2 but in general it may be said that a colloidal solution is one in which the dispersed particles are usually between #e and #bjj in diameter1 are difficultly or not at all diffusible through the membrane of a simple dialyzer1 cannot be filtered out of solution1 do not settle out under the action of gravitation1 and are visible only under the ultramicroscope2 and one which has certain peculiar optical1 osmotic1 and other physical and chemical properties4 ,since colloidal particles are very minute in size1 they possess very large relative surface areas as compared with their total mass or volume1 very high surface tension1 and a relatively high surface energy as compared with their total1 or molecular1 energy4 ,these properties bring into play1 in a substance which is in the colloidal condition1 in a remarkable degree1 all the phenomena which are associated with surface boundaries between solids and liquids1 liquids and gases1 etc4 ,the properties arising out of the colloidal condition are of such tremendous importance in connection with the vital phenomena exhibited by cell protoplasm that it is necessary to give some detailed consideration to them here4 ,many large volumes dealing with this condition of matter have been written1 and it is very difficult to condense even the most important facts concerning it into a few pages1 but an attempt has been made to present in this brief summary the most essential facts and principles involved in the colloidal phenomena4 ,,nomenclature ,,and ,,classification ,colloidal mixtures may exist in two different forms3 one1 in which the mixture is fluid and mobile1 like a true solution1 is known as a sol2 and the other1 which is a semi-solid1 or jelly-like1 form1 is known as a gel4 ,sols may be easily converted 7or set7 into gels1 by changes of temperature or of the electrolyte content1 or by changes in the concentration of the mixture1 etc41 and in most cases gels can be converted again into sols4 ,in some cases1 however1 gel-formation is irreversible1 the gels are permanent and cannot be changed back again into sols by any known change in environmental conditions4 ,depending upon whether the liquid dispersion medium is water1 alcohol1 ether1 etc41 sols are known as hydrosols1 alcosols1 ethersols1 etc42 and gels as hydrogels1 alcogels1 etc4 ,sols in which the disperse phase is a solid are known as suspensoids2 while those in which it is a liquid are emulsoids4 ,thus1 sols of most inorganic compounds1 of dextrin1 gelatin1 and 7probably7 of casein1 etc41 are suspensoids2 while sols of egg-albumin1 of oils1 etc41 are emulsoids4 ,the classification of these substances into suspensoids and emulsoids is1 however1 more a matter of convenience than of real difference in composition1 since it is practically impossible to say whether many of the organic substances which normally exist in colloidal form are themselves liquids or solids1 when in the non-dispersed form4 ,,conditions ,,necessary ,,to ,,the ,,formation ,,of ,,sols ,suspensoids differ from mechanical suspension of solids in a liquid in that in the latter the solid particles settle toward the bottom of the mixture1 because of the effect of the attraction of gravity upon them4 ,the rate at which such particles settle depends upon the size and density of the particle and the viscosity of the liquid1 and can be roughly calculated from the formula for ,stokes' law for the rate of falling of a spherical body in a liquid4 ,this formula is ,v #br#b7s - s7g _/ #in2 ,v velocity of the falling body1 in millimeters per second2 r radius of the particle1 in millimeters2 s specific gravity of the solid2 s specific gravity of the liquid2 g the attraction of gravity1 in dynes2 n the viscosity of the liquid4 ,for example1 if this formula be applied to determine the rate at which the particles of gold of the size of those in a red gold sol would settle1 if they were in mechanical suspension in water 7r #aj1 or one-ten-thousandth of a millimeter2 s #ai4c2 s #a2 g #ihj1 and n #j4ja71 it will be found that such particles will settle at the rate of approximately #j4jadf millimeter per hour1 or a little over #aj mm4 7#j4d inch7 per month4 ,hence1 the settling of such particles1 if in mechanical suspension1 would be measurable1 although very slow4 ,shaking up the suspension would cause the particles to rise through the liquid again4 ,but in a gold sol1 or suspensoid1 which contains particles of gold of the size used in this calculation1 the gold particles do not settle1 even at the slow rate as calculated above4 ,they remain uniformly distributed throughout the liquid for an indefinite period or time4 ,the reason for this phenomenon undoubtedly lies in the fact that these minute particles carry an electric charge1 which1 is of the same sign for all of the particles and results in a repellent action which keeps the particles in constant motion4 ,this constant motion may easily be conceived to keep the particles uniformly distributed throughout the liquid1 just as constant shaking would keep those of a mechanical suspension uniformly distributed through the mixture4 ,the sign of the electric charge on the particles of a sol may be either negative or positive1 depending upon the chemical nature and dielectric constants of the two phases of the system4 ,the proportion of the total electric charge of the system which is of the opposite sign to that borne by the dispersed particles is1 of course1 borne by the liquid which constitutes the other phase4 ,the origin of this electric charge on the colloidal particles is1 as yet1 not known with certainty2 but it seems probable that it is due to a partial ionization of these small particles1 similar to1 but not so complete as1 that which takes place when compounds which are soluble go into true solution in water1 or other solvents which bring about the dissociation of dissolved substances4 ,the conditions necessary to bring a solid substance into a colloidal mixture with some liquid1 or1 in other words1 to produce a suspensoid sol1 require that the proportion of liquid to solid shall be large and some means of disintegrating the material which is to be dispersed into very fine particles4 ,many common chemical reactions1 if carried out in very dilute solutions1 result in the production of sols1 especially if a small amount of some emulsoid is present in the reacting mixture2 sols produced in this way are very stable1 and the emulsoid which is used in stabilizing the sol is known as a protective colloid4 ,direct methods of disintegration2 such as reduction by chemical agents1 discharge of a strong electrical current through the substance which is to be dispersed while it is submerged in the liquid1 alternate treatment of finely ground material with alkali and acid so as to frequently change the electric charge1 etc41 are utilized for bringing inorganic compounds into the colloidal state4 ,suspensoids usually contain less than #a per cent of the solid dispersed through the liquid4 ,in fact1 extreme dilution is one of the necessary conditions for suspensoid-formation4 ,emulsoids are much more easily produced than are suspensoids4 ,the property of forming an emulsoid seems to be much more definitely a characteristic of the substance in question than does the formation of sols from solids which1 under other conditions1 may form true solutions4 ,this difference may be due to the fact that the liquids which easily form emulsoids 7usually those of organic origin7 have very large molecules1 so that the transfer from molecular to colloidal condition involves much less change in such cases than it does in the case of solid 7inorganic7 substances of relatively low molecular weight4 ,this view of the matter is further borne out by the fact that solids which have very large molecules 7generally of organic origin7 take on the colloidal form much more readily than do those of small molecular size4 ,at the same time1 a given liquid may form a true emulsoid when introduced into one other liquid and a true solution when introduced into another4 ,thus1 soaps form emulsoids with water 7true hydrosols72 but dissolve in alcohol to true solutions1 in which they affect the osmotic pressure1 the boiling point of the liquid1 etc41 in exactly the same way that the dissolving of other crystalloids in water affects the properties of true aqueous solutions4 ,again1 ordinary tannin1 when dissolved in water1 produces a sol1 which froths easily1 is non-diffusible1 etc42 but when dissolved in glacial acetic acid1 it produces a true solution4 ,the concentration of the disperse phase may be much greater in the case of emulsoids than it can be in suspensoids4 ,this is probably because the dispersed particles do not carry so large an electric charge and are not in such violent motion4 ,,gel-,,formation ,the one property which most sharply distinguishes sols from true solutions is their ability to set into a jelly-like1 or gelatinous semi-solid1 mass1 known as a gel1 without any change in chemical composition1 or proportions1 of the two components of the system4 ,in the gel1 the two components are still present in the same proportions as in the original sol2 but the mixture becomes semi-solid instead of fluid in character4 ,thus1 an agar-agar sol containing #ih per cent of water sets into a stiff gel2 while many other gels which contain #ij to #ie per cent of water can be cut into chunks with a knife and no water will ooze from them4 ,the water is not in chemical union with the solid matter in the form of definite chemical hydration1 however1 as the same gel is formed with all possible variations in the water content4 ,gels may be either rigid1 as in the case of those of silicic acid1 etc41 or elastic1 as are those of gelatin1 egg-albumin1 agar-agar1 etc4 ,the latter are the common type of gels among organic colloids4 ,they can be easily changed in shape1 or form1 without any change in total volume4 ,in gel-formation1 the two phases of the system take a different relationship to each other4 ,the disperse1 or solid1 phase becomes associated into a membrane-like1 or film1 structure1 surrounding the liquid phase in a cell-like arrangement4 ,that is1 the whole mass takes on a structure similar to a honeycomb except that the cells are roughly dodecahedral in shape1 instead of the hexagonal cylinders in which the bees arrange their comb cells1 in which the original disperse phase constitutes the cell-walls and the original liquid1 or continuous phase1 represents the cell-contents4 ,the cells of an elastic gel resemble closely the cells of a plant tissue in many of their physical properties4 ,they are roughly twelve-sided in shape1 as this is the form into which elastic spherical bodies are shaped when they are compressed into the least possible space4 ,imbibition and ,swelling of ,gels4--,when substances which are natural gels1 such as gelatin1 agar-agar1 various gums1 etc41 are submerged in water1 they imbibe considerable quantities of the liquid and the cells become distended so that the mass of the material swells up very considerably4 ,this swelling will take place even against enormous pressures4 ,for example1 it has been found that the dry gel from sea-weeds will swell to #ccj per cent of its dry volume1 if immersed in water under ordinary atmospheric pressure2 but that it will increase by #af per cent of its own volume when moistened1 if under a pressure of #db atmospheres4 ,during the swelling of gels by imbibition of water1 the total volume of the system 7i4e41 that of the original dry gel plus that of the water absorbed7 becomes less4 ,for example1 a mixture of gelatin and water will1 after the gelatin has swelled to its utmost limit1 occupy #b per cent less space than the total volume of the original gelatin and water4 ,it has been computed that a pressure equivalent to that of #djj atmospheres would be necessary to compress the water to an extent representing this shrinkage in volume4 ,on the other hand1 gels when exposed to the air lose water by evaporation1 shrink in volume1 and finally become hard inelastic solids1 as in the case of the familiar forms of glue1 gelatin1 agar-agar1 gum arabic1 etc4 ,the difference in the relation of gels and that of non-colloidal solids to water may be illustrated by the different action of peas1 beans1 etc41 and of a common brick1 when immersed in water4 ,each of these substances1 under these conditions1 absorbs1 or imbibes1 water2 but the peas and beans swell to more than twice their original size and become soft and elastic1 while the brick undergoes no change in size1 elasticity1 or ductility4 ,in all cases of colloidal swelling1 the swollen body possesses much less cohesion1 and greater ductility1 than it had before swelling4 ,the essential difference in the two types of imbibition is that in the case of the non-swelling substances the cohesion1 or internal attraction of the molecules of the material1 is too great to permit them to be forced apart by the water2 while in colloidal swelling1 the particles are forced apart to such an extent as to make the tissue soft and elastic4 ,it is possible1 of course1 to make this separation go still further1 until there is an actual segregation of the molecules1 when a true solution is produced2 for example1 gum arabic when first treated with water swells into a stiff gel1 then into a soft gel1 and finally completely dissolves into a true solution4 ,reversibility of ,gel-formation4--,in some cases1 the change of a sol to a gel is an easily reversible one4 ,glue1 gelatin1 various fruit jellies1 etc41 melt to a fluid sol at slightly increased temperatures and set again to a gel on cooling1 and the change can be repeated an indefinite number of times4 ,on the other hand1 many gels cannot be reconverted into sols2 that is1 the gelation process is irreversible4 ,for example1 egg-albumin which has been coagulated by heat cannot be reconverted into a sol2 casein of milk when once clotted by acid cannot again be converted into its former condition1 etc4 ,irreversible gelation is usually spoken of as coagulation4 ,some coagulated gels1 by proper treatment with various electrolytes1 etc41 can be converted into sols1 the process being known as peptization2 but in such peptized hydrosols1 the material usually exists in a different form than originally1 having undergone some chemical change during the peptization1 and the coagulation and peptization cannot be repeated1 that is1 the process is not a definitely reversible one4 ,importance of ,gel-formation4--,from the physiological point of view1 gel-formation is undoubtedly the most important aspect of colloidal phenomena4 ,in the first place1 the ability to absorb and hold as much as #hj to #ij per cent of water in a semi-solid structure is of immense physiological importance4 ,in no other condition can so large a proportion of water1 with its consequent effect upon chemical reactivity1 be held in a structural1 or semi-solid1 mass4 ,but a vastly more significant feature of the conditions supplied by the gel lies in the fact that the non-water phase1 or phases1 of the system are spread out in a thin film1 or membrane1 thus giving it enormous surface as compared with its total volume4 ,this effect is easily apparent if one thinks of the enormous surface which is exposed when a tiny portion of colloidal soap is blown out into a soap-bubble several inches in diameter4 ,this condition brings into play all the phenomena resulting from surface boundaries between solids and liquids1 liquids and liquids1 liquids and gases1 etc41 from surface tension1 surface energy1 etc4 ,among these effects may be cited those of adsorption1 increased chemical reactivity due to enlarged areas of contact1 permeability and diffusion1 etc41 the importance of which in the vital phenomena of cell-protoplasm will be discussed in detail in the following chapter4 ,,general ,,properties ,,of ,,colloidal ,,solutions ,non-diffusibility4--,the most characteristic property of all sols is the failure of the suspended particles to pass through a parchment1 or any similar dialyzing membrane4 ,visibility under the ,ultramicroscope4--,the particles of a sol1 in contrast with the molecules of a true solution1 are visible as bright scintillating points under the ultramicroscope4 ,this is a modification of the type of dark-field illumination of the ordinary microscope1 as applied to microscopic studies1 in which the solution to be studied is contained in a small tube or box of clear glass which is mounted on the stage of an ordinary microscope and instead of being illuminated from below by transmitted light is illuminated by focusing upon it the image of the sun1 or of some other brilliant source of light such as an electric arc1 by passing the rays from the source of light through a series of condensing lenses which are adjusted at the proper distance and angles to bring the image of the illuminating body within the tube containing the substance which is to be examined and in the line of vision of the microscope4 ,obviously1 this results in intense illumination of any particles in the solution which come within this brilliant image of the sun1 or arc1 and therefore renders visible particles which are of less diameter than the wave-length of ordinary light 7#dej to #gfj for the visible spectrum7 and1 hence1 are not visible by the ordinary means of illumination in the direct line of vision4 ,it will be apparent that what is seen in the field of the ultramicroscope is not the particles themselves1 but rather the image of the sun 7or other illuminating body7 falling upon the particles which come within the image1 just as one does not see the paper but only the image of the sun when the rays from the sun are brought to a focus upon a sheet of paper through any ordinary convex lens1 or burning glass4 ,hence1 the ultramicroscope gives no idea of the shape1 color1 or size of the particles upon which the image falls2 but it does permit the counting of the number of particles within a given area1 and a study of their movements1 from which it is possible1 by mathematical computations1 to calculate the relative size of the particles themselves4 ,repeated studies have shown that particles of the sizes between #e and #bej in diameter1 which are visible under the ultramicroscope1 are sufficiently small to bring about the surface phenomena which are known as properties of colloidal solutions4 ,further1 the ultramicroscope permits the observation of the growth1 or disintegration1 under various chemical reagents1 of the individual colloidal particles1 which appear as scintillating points in the field of the microscope2 and the study of changes in relationships during gel-formation1 peptization1 etc4 ,the ,tyndall ,phenomenon4--,colloidal solutions exhibit this phenomenon2 that is1 if a bright beam of light be passed through a sol which is contained in a clear glass vessel having parallel vertical sides1 and the solution be viewed from the side1 it appears turbid and often has a more or less bluish sheen4 ,this effect is due to the small particles in the sol1 of polarizing the light which is reflected from them1 the blue rays being bent more than are those in the other part of the spectrum4 ,the ,tyndall phenomenon is similar in its effect in making the tiny particles of the sol visible to the illumination of the dust particles in the air of a darkened room when a ray or narrow beam of light passes through it4 ,in a true molecular solution1 the particles are too small to be visible by this mode of illumination4 ,other ,optical ,properties4--,sols are generally translucent and opalescent2 many of them are highly colored1 some of the sols of gold1 platinum and other heavy metals possessing particularly brilliant colors4 ,in general1 metallic suspensoids are red1 violet1 or some other brilliant color2 while inorganic suspensoids are bluish white1 and emulsoids generally blue to bluish white4 ,formation of ,froth1 or ,foam4--,colloidal solutions1 especially those of the natural proteins1 fats1 glucosides1 gums1 and the artificial soaps1 have a strong tendency to produce froth1 or foam1 when shaken2 this being due to the enormous surface tension resulting from the finely divided condition of the dispersed material4 ,low ,osmotic ,pressure4--,all colloidal solutions exhibit a very low osmotic pressure2 the freezing point of the dispersion medium is lowered only very slightly and its boiling point is only very slightly raised by the presence of the dispersed particles in it4 ,precipitation by ,electrolytes4--,sols of all kinds are precipitated1 or caused to form gels1 by the addition of electrolytes1 since these cause a disturbance of the electric charge on the dispersed particles1 to which the colloidal condition is due4 ,in the case of most emulsoids and of a few of the suspensoids1 this change converts the mass into a stiff gel2 but in that of many of the metallic suspensoids1 the dispersed particles are gathered together into larger aggregates1 which settle out of the liquid in the form of a gelatinous precipitate4 ,in the latter case1 the effect is usually spoken of as precipitation by electrolytes2 while in the former1 it is called coagulation1 or gelation4 ,the effectiveness of the various electrolytes in bringing about this change is proportional to their valency2 bivalent ions are from #gj to #hj times1 and trivalent ions about #fjj times as effective as monovalent ions4 ,further1 all sols in which the dispersed particles carry a charge of the opposite sign likewise precipitate both suspensoids and emulsoids4 ,a demonstration of the presence of an electric charge on the particles of a sol and a determination of its sign can be made by placing the solution in a ,u tube1 with a layer of distilled water above the sol in each arm of the tube1 and then passing an electric current through the contents of the tube1 keeping the electrodes in the distilled water1 so that the migration of the particles toward one pole or the other can be observed by their appearance in the clear water at that end of the tube2 or by passing an electric current through the observation chamber of an ultramicroscope1 in which the solution under examination has been placed1 and observing the migration of the particles across the field toward either one or the other 7positive or negative7 electrode4 ,emulsoids and suspensoids differ in their properties in the following respects4 ,suspensoids are always very dilute1 containing less than #a per cent of the dispersed solid2 while emulsoids may be prepared with widely varying proportions of the two component liquids4 ,suspensoids have a viscosity which is only slightly greater than that of the liquid phase when it exists alone1 and their viscosity varies with the proportion of dispersed solid which is present in the sol2 while emulsoids have a very high viscosity in all cases4 ,emulsoids usually form stiff gels when treated with electrolytes2 while suspensoids more commonly yield gelatinous precipitates under the same conditions4 ,suspensoids and emulsoids which carry electric charges of opposite sign mutually precipitate each other4 ,but emulsoids often protect suspensoids from precipitation by electrolytes1 by forming a protective film around the particles of the suspensoids1 which prevents the aggregation of the particles into the precipitate form4 ,,adsorption ,if a sol be precipitated or coagulated by the action of an electrolyte1 substances which may be present in solution in the liquid of the sol are carried out of solution and appear in the gel or precipitate4 ,this phenomenon is known as adsorption1 which means the accumulation of one substance or body upon the surface of another body1 as contrasted with absorption1 which means the accumulation of one substance within the interior of another4 ,since substances which are in the colloidal form have very large relative surface areas1 it follows that the opportunity for surface adsorption on colloidal materials is very great4 ,surface adsorption is a common phenomenon4 ,it was extensively studied by the physicist1 ,willard ,gibbs1 who showed that adsorption will take place whenever the surface tension of the adsorbing body will be lowered by the concentration in its surface layer of the material which is available in the solution or other surrounding medium4 ,as applied to colloidal phenomena1 adsorption may be exhibited in either one of four different ways1 as follows3 7#a7 ,a crystalloidal substance which is in solution may be adsorbed on the colloidal particles of a hydrosol1 so that if the mixture be dialyzed1 or filtered through a so-called ultrafilter 7i4e41 a filter with pores so small that it will retain colloidal particles7 the dissolved crystalloid will remain with the separated colloidal particles1 or the dissolved crystalloid will not react chemically as it would in a free solution4 ,for example1 if to a solution of methylene blue1 which dyes wool readily1 there be added a small quantity of albumin 7a colloidal substance71 the dye is adsorbed by the albumin and will no longer color wool with anything like the same readiness4 7#b7 ,during gel-formation1 electrolytes and other soluble substances which may be present in solution in the liquid may adsorbed out of the solution and appear in the gel4 ,for example1 a precipitate of aluminium hydroxide1 or of silicic acid1 is nearly always contaminated with the soluble salts which are present in the solution1 and can be prepared in pure form only by repeated filtering1 redissolving1 and reprecipitating4 7#c7 ,colloidal substances may be removed from sols by being adsorbed upon porous materials like charcoal1 fuller's earth1 hydrated silicates1 etc4 ,for example1 animal charcoal 7or bone black7 is used commercially for the clarification of sugar solutions1 because it adsorbs out of these solutions the colloidal proteins1 coloring matters1 etc41 with which they are contaminated4 7#d7 ,finally1 colloids mutually adsorb each other1 as in the case of the protective colloids previously referred to4 ,certain characteristics of adsorption phenomena are of interest and importance from both the physiological and the industrial point of view4 ,the following may be mentioned3 7a7 ,amount of adsorption4 ,relatively more material is adsorbed out of dilute solutions than out of more concentrated ones4 ,an increase of ten times in the concentration of the dissolved material results in only four times as much adsorption by the colloidal substance which may be introduced into the two solutions4 ,in this1 adsorption differs from chemical action1 as the latter is proportional to the concentration of the reacting material which is present in the solution4 7b7 ,adsorption out of different liquids1 by the same adsorbing body1 is different in amount4 ,it is usually greatest out of water4 ,hence1 many dyes may be adsorbed out of water by charcoal1 porous clay1 etc41 and if the latter be then introduced into alcohol1 or ether1 the dye goes back into solution in these latter liquids4 ,this process is often used industrially and in the laboratory for the purification of such substances when they are present in impure form in aqueous solutions4 7c7 ,selective adsorption4 ,different substances are not adsorbed out of the same solvent to the same extent by the same adsorbing agent4 ,advantage is taken of this fact when filter paper is used in the so-called capillary analysis to separate different dyes1 or other colloidal materials which have been stained different colors1 into alternate layer by reason of the different rate at which the paper adsorbs the different materials out of the solution in which they are present together4 7d7 ,similar relative adsorption by different adsorbing agents4 ,although different adsorbing agents may possess varying active surfaces and hence1 variable adsorbing power1 or rates of adsorption1 they adsorb the same relative amounts of different materials2 i4e41 if substance ,a adsorbs more of ,x than it does of ,z out of any given solution1 substance ,b will likewise adsorb more of ,x than of ,z out of the same solution2 although the actual amounts adsorbed by ,a may be quite different from those adsorbed by ,b4 ,,catalysis ,,affected ,,by ,,the ,,colloidal ,,condition ,the velocity of a chemical reaction is the net result of opposing influences4 ,it is directly proportional to the chemical affinity of the reacting bodies and inversely proportional to the so-called chemical resistance4 ,the first factor1 chemical affinity1 is not easily measured1 as it depends upon both the mass of the reacting molecules1 atoms1 or ions1 and their attraction for each other4 ,but if1 as the result of chemical affinity1 a reaction takes place1 it is evident that the time required for its completion 7which measures the velocity of the reaction7 is made up of two separate periods4 ,the first is the time required for the reacting molecules to come into contact2 and the second is that required for the molecular rearrangement which constitutes the reaction4 ,clearly1 the time required for the substances to come into molecular contact will be greatly diminished if they are mutually adsorbed in large quantities on the extended surface area of some colloidal catalyst which is present in the mixture rather than scattered throughout its entire volume4 ,the application of this principle to the catalysis of hydrolytic reactions is not apparent1 if it is considered that the ,h#b,o molecules which cause the hydrolysis are those of the solvent itself2 but is clear on the assumption 7which is discussed in the following chapter7 that the water which enters into a colloidal complex is in multimolecular form1 represented by the formula 7,h#b,o7n1 in which the oxygen atoms are quadrivalent and1 hence1 much more active chemically than as illustrated in the simple solvent action of water4 ,hence1 the surface adsorption of reacting bodies by a colloidal catalyst may have a very important influence in decreasing the time required to bring the reacting molecules into intimate contact1 and so increasing the velocity of the reaction4 ,but the colloidal condition of the catalyst may also aid in decreasing the chemical resistance which tends to slow up the reaction4 ,chemical resistance may be understood to be the internal molecular friction of the densely packed atoms within the reacting molecule1 which tends to prevent the molecular rearrangement and so to prolong the second period of the reaction time4 ,to overcome this friction and so decrease the reaction time1 some form of energy is necessary4 ,if there be present in the solution in which the reaction is taking place some colloidal catalyst1 and if the reacting bodies are concentrated at the surface boundaries between the two phases of the colloidal system1 they may be conceived to be within the sphere of influence of the surface energy of the dispersed particles of the catalyst1 so that this may furnish the energy necessary to overcome the chemical resistance of the reacting bodies1 and so to speed up the second portion of the reaction time4 ,from these considerations1 it would appear that the colloidal condition of such catalysts as enzymes1 etc41 has much to do with their ability to increase reaction velocities1 both by reducing the time necessary for the reacting bodies to come into molecular contact and by furnishing the energy to overcome the chemical resistance to the molecular rearrangement which constitutes the reaction itself4 ,evidence in favor of the accuracy of this view of the nature of the catalytic action of colloidal substances is afforded by the facts that catalysts accelerate the velocity of reversible reactions in either direction and that they do not change the point of final equilibrium1 in any case2 that is1 they do not affect the nature or direction of the reaction1 but only accelerate a chemical change which would otherwise take place more slowly because of the stability 7or chemical resistance7 of the molecules involved1 or their inability to come quickly into intimate molecular contact4 ,these facts and principles have been clearly established in many studies of the nature of enzyme action 7enzymes are typical colloidal catalysts7 and probably apply equally well to the action of other types of colloidal catalysts4 ,on the other hand1 the catalytic action of certain inorganic and non-colloidal substances1 such as the action of acids in accelerating the hydrolysis of carbohydrates1 etc41 may be conceived to be due to chemical influences upon the internal molecular resistance1 which are similar in their effects1 but entirely different in their mechanism1 from the physical effects of the surface boundary phenomena of the colloidal catalysts4 ,,industrial ,,applications ,,of ,,colloidal ,,phenomena ,large numbers of industrial processes are based upon colloidal phenomena4 ,many of these processes were known and practiced long before the nature of the phenomenon itself was understood4 ,but with the coming of the knowledge of the nature1 causes1 and possibilities of the control1 of the colloidal condition of the materials involved1 immense improvements in the economy of the process1 or the quality of the end-products1 have been worked out1 in many cases4 ,many volumes of treatises concerning the industrial applications of colloidal phenomena have been written4 ,any discussion of these would be out of place here2 but the following list of examples will serve to illustrate the immense importance of these matters both in industry and to the needs of everyday life3 the tanning of leather2 the dyeing of fabrics2 vulcanizing rubber2 mercerizing cotton2 sizing textile fabrics2 manufacture of mucilages and glues2 manufacture of hardened casein goods2 manufacture of celluloid2 production of colloidal graphite for lubrication2 the prevention of the smoke nuisance by electric deposition2 the purification of sewage2 the manufacture of soaps2 the manufacture of butter1 cheese1 and ice cream2 fruit jellies1 salad dressings1 etc4 ,this list could be extended to a great length1 but is already long enough to emphasize the very great importance and practical value of colloidal phenomena in daily life4 ,,natural ,,colloidal ,,phenomena ,many of the phenomena of nature are colloidal in character4 ,these may be observed in the mineral1 the animal1 and the vegetable kingdoms4 ,here1 again1 a lengthy discussion of the nature of these phenomena would be out of place in this connection1 and a few typical examples will serve to illustrate the general importance in nature of this property of matter4 ,in the soil1 the following properties are easily recognizable as definite colloidal phenomena3 water-holding capacity of clays1 silts1 loams1 etc42 adsorption 7or fixation7 of soluble plant foods so that they are not readily leached out of the soil by drainage2 flocculation and deflocculation of clay1 etc4 ,in the animal body2 the contraction of muscles1 the conveyance of nerve stimuli1 etc41 are undoubtedly accomplished by colloidal changes2 and the existence of insoluble casein and fat in colloidal form in milk insures the proper nourishment of the young of nearly all species of animals4 ,in both plants and animals1 as will be pointed out in the following chapter1 practically all the vital activities of the cell protoplasm are definite manifestations of colloidal phenomena4 ,enzymes perform their catalytic functions by reason of their colloidal form4 ,proteins exist in colloidal form and are the seat of all vital functions4 ,the regulation of the passage of materials into and out of the cell is governed by minute changes in the electrolyte concentration1 etc41 which produce enormous changes in the colloidal character of the protoplasm4 ,it is apparent1 therefore1 that the study of the colloidal condition of matter and of the properties arising out of it is of immense importance to the biochemist4 ,no other single field is capable of yielding more fruitful results to the plant physiologist1 in his studies of the response of plants to changes in their environment1 or of the mechanism by which plants perform their internal functions4 ,references ,,bechhold1 ,h41 trans4 by ,,bullowa1 ,j4 ,g4 ,m4--,colloids in ,biology and ,medicine1 #dfc pages1 #ed figs41 ,new ,york1 #aiai4 ,,burton1 ,e4 ,f4--,the ,physical ,properties of ,colloidal ,solutions1 #bjj pages1 #ah figs41 ,london1 #aiaf4 ,,cassuto1 ,l4--,der ,kolloide ,zustand der ,materie1 #beb pages1 #ah figs41 ,dresden and ,leipzig1 #aiac4 ,,liesegang1 ,r4 ,e4--,beitrge zu einer ,kolloidchemie des ,lebens1 #add pages1 ,dresden1 #aiji4 ,,ostwald1 ,w41 trans4 by ,,fischer1 ,m4 ,h4--,theoretical and ,applied ,colloid ,chemistry1 #bah pages1 #dc figs41 ,new ,york1 #aiaa4 ,,ostwald1 ,w41 trans4 by ,,fischer1 ,m4 ,h4--,a ,handbook of ,colloid-,chemistry1 #bgh pages1 #fj figs41 ,philadelphia1 #aiae4 ,,taylor1 ,w4 ,w4--,the ,chemistry of ,colloids1 #cbh pages1 #bb figs41 ,new ,york1 #aiae4 ,,zigmondy1 ,r41 trans4 by ,,alexander1 ,j4--,colloids and the ,ultramicroscope1 #bch pages1 #b plates1 ,new ,york1 #aiji4 ,,zigmondy1 ,r41 trans4 by ,,spear1 ,e4 ,b4--,the ,chemistry of ,colloids1 #bgd pages1 #ci figs41 ,new ,york1 #aiag4 ,,chapter ,,xvi ,,the ,,physical ,,chemistry ,,of ,,protoplasm ,thus far1 we have considered the chemical nature of the various groups of compounds which are found in the tissues of living organisms1 laying emphasis upon those which are of plant origin4 ,these compounds constitute the material1 or machinery1 of the cell1 and their various transformations furnish the energy for its operation4 ,we come now to a study of the mode of its operation1 or the processes of vital phenomena4 ,our knowledge of these matters is not yet far enough advanced to permit a definite statement as to whether there is any difference between the protoplasm of plant tissues and that of animal origin in their modes of action1 or in the physical-chemical changes which constitute the vital phenomena in the two groups of living organisms4 ,thus far1 no such differences have been discovered4 ,hence1 in the following discussions1 no attempt is made to differentiate between animal and plant protoplasm4 ,most of the facts and principles which are here presented have been developed as the result of the study of the physiological chemistry of animal life4 ,no similar careful study of plant chemistry has yet been carried out2 but preliminary studies seem to indicate that the same general principles apply to all protoplasm1 regardless of whether it is of plant or of animal origin4 ,it is possible1 of course1 that further studies of plant protoplasm will render necessary some modifications of some of these views as applied to the growth of plants2 but they are believed to represent the best which is now known of the physical chemistry of the plant-cell activities4 ,,heterogeneous ,,structure ,,of ,,the ,,cell ,examination of cell protoplasm under the microscope reveals that it is not a simple homogeneous mass4 ,in the first place1 it has a definite structure1 composed of 7a7 a nucleus2 7b7 numerous granular bodies of different sizes and kinds2 and 7c7 a clear mass of colloidal material1 which 7if observed under the ultramicroscope1 or photographed by ultra-violet light7 is apparently made up of very minute particles of many different types of materials2 the whole mass1 in the case of plant protoplasm1 being generally surrounded by 7d7 a differentiated layer known as the cell-wall4 ,the actual internal structural arrangement of the clear colloidal mass is uncertain2 but its properties indicate that it may be considered to be like a mass of foam 7resembling a compact mass of soap-bubbles7 the compartments of the foam being1 of course1 very minute and the films themselves almost infinitely thin1 the contents of each compartment being probably liquid1 and the whole composing a typical colloidal gel of complex composition4 ,this conception may not be accurate in every detail1 but it seems to fit very closely the conditions and reactions of cell protoplasm4 ,furthermore1 it is obvious that the definite structure1 or form1 of the cell is essential to its life2 since1 if the structure be destroyed by any kind of mechanical injury 7freezing of the cell contents1 resulting in the puncturing of the membranes by ice crystals2 rupturing of the films1 or cell-walls1 by grinding with sharp sand1 etc47 so as to bring about an intermingling of the parts which are segregated from each other in the organized structure1 there results an immediate exhibition of abnormal chemical actions1 accompanied by the liberation of carbon dioxide1 and the death of the cell4 ,a proper mental picture of the organization of the cell structure and of the interrelation of all its working parts is suggested by the figure of a well-organized chemical factory1 with the different chemical transformations which are involved in the whole process being carried on in different portions1 or rooms1 of the factory1 with the various intermediate and final products regularly and systematically transported from one room to another as they are needed to keep each individual step in the whole process going at the proper rate1 and with the different parts of the whole factory working in smooth coordination with each other4 ,any disturbance of the mechanism in any particular room1 or any abnormal condition which breaks down the coordination or results in the mixing of the reagents or processes of adjoining rooms in improper order or proportions1 produces instant destruction of the normal process1 abnormal reactions take place1 and the factory output is interrupted4 ,no other conception than this one of a definite structure and coordination of the different working parts of a cell can adequately account for the great variety of chemical changes which are constantly going on in any given cell4 ,it is wholly inconceivable that a homogeneous mass of all the varying chemical compounds which are contained in any given quantity of protoplasm could either exist or produce any regular sequence of chemical reactions4 ,structure1 or organization of the cell-contents into separate colloidal compartments1 and the segregation of cell-contents into masses having different functions1 is essential to any reasonable conception of how the cell performs its various activities4 ,the best understanding of the structural arrangement is afforded by the conception that protoplasm consists of a colloidal gel1 or sometimes a very viscid sol1 containing water1 salts1 carbohydrates1 fats1 proteins1 and enzymes4 ,evidence in favor of this conception is afforded by the appearance of protoplasm under a high-power microscope1 and by the close resemblance of the processes which go on in it1 and its responses to external stimuli1 to those of an artificial gel of similar chemical composition4 ,two different conceptions of the form in which the chemical components exist in this mass have been advanced4 ,one is that they are in true molecular unions1 known as biogens1 and that the reactions which take place in the mass may1 therefore1 be studied from the same basis as are reactions between similar substances when they take place in a beaker or test tube in the laboratory4 ,it would seem1 however1 that the constantly varying proportions of the materials themselves1 and the lack of homogeneity of cell contents1 afford insurmountable difficulties to this conception as a basis for the study of cell activities4 ,the other1 and seemingly more reasonable1 conception is that these bodies exist in the form of colloidal complexes1 whose composition may vary within wide limits and whose reactions are responsive to the usual phenomena incident to the colloidal condition of matter4 ,according to the latter conception1 vital activities of cell protoplasm may be due to changes in water content1 to electrical disturbances1 to the phenomena resulting from the conditions brought about by surface boundaries between the different phases of the gel1 to varying osmotic pressure1 to changes in chemical reaction1 etc41 and may be controlled by various stimuli of chemical1 physical1 or mechanical nature4 ,this conception seems1 therefore1 to fit most closely the actual conditions under which the protoplasm exists and carries on its vital functions4 ,with this conception in mind1 we may now proceed to a consideration of how the various components of the complex organic colloidal system1 and their specific properties1 can affect its chemical activities4 ,the components of the system are1 of course1 water1 salts1 and the various organic compounds 7fats1 proteins1 carbohydrates1 and enzymes in all cells2 and other groups1 such as essential oils1 tannins1 pigments1 etc41 in cells which have certain special functions to perform7 which constitute the solid phase of the colloidal mixture4 ,in addition to the definite chemical properties of each of these component groups1 which have been studied in detail in preceding chapters1 there are many physical1 or physical-chemical1 properties of the system as a whole1 and of its component parts1 which are of the utmost importance in the physiological activities of the protoplasm4 ,these we may now proceed to consider in some detail4 ,,water ,water constitutes the largest proportion of the weight of active protoplasm4 ,in living cell contents 7except those of such bodies as resting seeds1 etc471 water comprises from #gj to #ie per cent of the total weight of the substance2 the average proportion being usually between #he and #ij per cent4 ,the fact that protoplasmic material can exist in turgid form with such high percentages of water as these is due1 as has been pointed out1 to its existence as a colloidal gel4 ,it is because of this condition that increases in the proportion of water generally increase the turgidity1 or turgor1 of the protoplasm2 instead of1 as in all other cases1 rendering the mixture less solid and more labile4 ,losses of water from the protoplasmic gel decrease its swollen condition and so render the tissue soft and flabby2 while increases in water content swell the gel and make the tissue stiff and turgid4 ,no other condition than that of a colloidal gel could respond in this way to changes in water content4 ,the formula which is commonly assigned to water is the simplest possible one2 namely1 ,h#b,o4 ,but if the water were really as simple as this1 the compound would boil at a very low temperature1 would have a very low surface tension1 etc42 whereas its actual boiling point1 surface tension1 etc41 are much higher than those of other compounds having a higher molecular weight than is indicated by the formula ,h#b,o4 ,actual measurements of the physical properties of water indicate that at the temperature at which water is a vapor its formula is at least 7,h#b,o7#b2 while at lower temperatures1 at which it exists as a liquid1 its formula may be 7,h#b,o7#c1 or 7,h#b,o7#d1 or even more complex still4 ,the cause for this association of the compound into multiple molecules undoubtedly lies in the extra valences of the oxygen4 ,in many organic compounds oxygen is undoubtedly tetravalent1 and it may be easily conceived that in these complex molecular groupings in the water it exhibits this same property2 the possible molecular arrangements being represented by the formulas ,h ,h ,h ,h _/ _/ ,h-,o-,o-,h ,o,o and etc4 _/ ,h-,o-,o-,h ,h ,h _/ ,h ,h ,such molecules may be conceived to break down very easily1 leaving the extra valences of the oxygen available to form linkages with other atoms or molecules4 ,this may constitute one of the ways in which water exerts its remarkable effects both as a solvent and as an accelerator of all kinds of chemical reactions4 ,other organic compounds which contain tetravalent oxygen are exceedingly active chemically1 and there seems to be much to commend this view of the chemical structure of the water molecule4 ,probably the most remarkable property of water is its power of solution4 ,no other liquid surpasses water as a solvent4 ,this power1 as has been pointed out1 is supposed to be due to1 or in some way correlated with1 the extra valences of the oxygen atoms1 which may perhaps unite with similar extra valences of other substances with which the water is brought into contact1 and so cause the latter to enter into solution4 ,all kinds of substances dissolve in water1 and when in solution1 or even when only moistened1 are much more active chemically than when dry4 ,this property of water contributes greatly to the possibilities of the chemical reactions which constitute life processes4 ,water1 likewise1 has a higher dielectric constant than any other common liquid4 ,this means that it does not readily conduct electricity1 or readily permit electric equilibrium to be established in it2 or1 in other words1 that it is a good insulator4 ,this property permits the existence in it simultaneously of materials having opposite electric charges1 or the so-called ionization phenomena2 hence1 water is the best-known ionizing medium1 and ionization favors chemical reactivity4 ,again1 water has a very high specific heat1 a fact which is of the utmost biological importance4 ,it takes more heat to raise the temperature of one gram of water through one degree than is required to produce the same result in any other known substance2 or1 stated the other way around1 a given amount of heat will cause less change in temperature of water than of any other known substance4 ,further1 the latent heat of liquefaction and of vaporization 7i4e41 the amount of heat required to change the substance from solid to liquid and from liquid to gaseous state1 respectively7 is greater for water than for any other common substance4 ,these facts are of very great importance in cell-protoplasm4 ,the high specific heat of water provides that the heat liberated by the chemical reactions which take place in the protoplasm can be absorbed by the water of the cell contents1 and given off again to other reactions1 with very slight effect upon the temperature of the protoplasm itself4 ,hence1 violent changes in temperature1 which might be disastrous to the life of the cell1 are prevented by the high specific heat of the water which it contains4 ,similarly1 the high latent heat of liquefaction of water1 resulting in the giving up of large quantities of heat before it can become solid1 or freeze1 tends to prevent freezing and thawing of the cell contents with sudden changes of external temperatures at or near the freezing temperature of water4 ,as a result of its physical properties1 as just briefly described1 water accelerates all kinds of chemical reactions in protoplasm1 both by solution and by ionization of such substances as undergo electric dissociation2 and serves to regulate the temperature of the protoplasmic mass4 ,furthermore1 in organic tissues1 most of the important chemical reactions of the protoplasm are reversible hydrolyses2 i4e41 water actually enters into the reaction or is liberated by it1 and the equilibrium point of the reaction is changed by the proportions of water which are present in the reacting mass4 ,hence1 the presence of large proportions of water in the colloidal complex known as protoplasm has a very important influence upon its possibilities of biological reactions4 ,,salts ,active protoplasm contains mineral salts in solution4 ,these are of the same general nature as those found in sea-water1 which is the original habitat of the earlier evolutionary forms of living matter4 ,or1 it might be said that both plants and sea-water derive their mineral salts from the same source1 namely the soluble salts of the soil4 ,recent investigations have shown that the proportions of sodium ions to calcium ions in sea-water are precisely those which maintain fats1 proteins1 etc41 in a true colloidal emulsion2 and that comparatively small variations in the ratio of these two cations produce very marked effects upon the colloidal conditions of these substances in an artificial colloidal preparation1 which resemble very closely the changes which apparently take place in cell protoplasm under the influence of narcotics1 or nerve stimulants1 in blood-coagulation1 in the parthogenetic development of germ cells1 in cancerous growth of tissues1 etc4 ,in other words1 in so far as it has been studied in this respect1 cell plasma exhibits exactly the same responses to variations in the proportions of salts 7electrolytes7 in solution1 that artificial emulsions of oils 7fats7 in water do2 and the normal1 or critical1 equilibrium proportion of these electrolytes for all colloidal complexes is that in which they occur in sea-water4 ,it must be admitted that there is as yet no definite evidence that the observations which have been made upon the protoplasm of animal tissues will apply equally well to plant cell protoplasm4 ,but many of the phenomena which have been studied in animal tissues have what are apparently similar1 if not identical1 effects in plant tissues1 and it seems reasonable to suppose that these conclusions apply generally to protoplasm of either animal or plant origin4 ,the effects which salts produce in protoplasm are undoubtedly due to the fact that1 when in solution1 they readily ionize and conduct the electric current4 ,a discussion of the nature and importance of the theory of dissociation of electrolytes in solution1 or the so-called ionization theory1 which has done so much to clear up otherwise unexplainable properties of solutions1 would be out of place here4 ,but it may be noted that the ionized condition of salts in solution accounts for the avidity1 or strength1 of acids and bases2 for the increased osmotic pressure of such solutions2 for the conduction of the electric current through solutions2 and for the effects of these dissolved electrolytes upon the colloidal condition of many substances1 since this is due to the electric charge on the dispersed particles4 ,hence1 the presence of salts in solution in the water of the protoplasm has a tremendous influence upon the osmotic pressure 7which governs the movement of dissolved materials into and out of the cell protoplasm72 upon the colloidal condition of the cell contents 7which controls all the effects due to the surface boundary phenomena which are discussed below and which are responsible for a large part of the remarkable chemical activity of the protoplasm72 upon the electrical phenomena 7which constitute many of the stimulations which the protoplasm receives72 and upon the acidity or alkalinity of the cell contents 7which determine the nature of the respiratory1 or oxidation1 reactions of the protoplasm and1 indirectly1 its life or death74 ,the general nature of these physical-chemical properties of the protoplasm and of the relation of electrolytes in solution to them may now be considered in some detail4 ,,osmotic ,,pressure ,osmotic pressure is one of the chief factors in controlling the amount of water in the protoplasm4 ,as is well known1 the phenomenon known as osmosis is the passage of solvents1 or of dissolved substances1 into or out of any tissue1 or substance1 through the membrane which surrounds it4 ,in the case of a cell1 the membrane in question may be either the cell-wall or the internal colloidal films which are distributed throughout the entire mass of the cell contents4 ,from the standpoint of their relation to osmosis1 membranes may be either impermeable1 in which case neither solvent nor dissolved materials can pass through them2 semi-permeable1 which permit the passage of the solvent1 but not that of dissolved crystalloidal substances2 or permeable1 which permit the free passage through them of both solvents and solutes4 ,the first and last of these types of membranes have no effect upon osmotic pressure2 but osmotic pressure is at once set up whenever a semi-permeable membrane is interposed between solutions of different concentrations4 ,it is due to the molecular motion of both the liquid and the dissolved solids1 as a result of which a greater number of molecules are bombarding1 or pressing upon the membrane from the side of the more concentrated solution4 ,this sets up an unequal pressure upon the two sides of the membrane1 and if the latter be semi-permeable there will result a passage of the liquid through the membrane toward the denser solution so as to equalize the pressure4 ,the resultant tendency is for the solutions on the two sides of the membranes to become equal in concentration by movement of the liquid from the less dense to the more dense portion1 instead of by movement of the dissolved materials toward the less dense part of the solution as in the case of diffusion when solutions of different concentrations are brought in contact with no membrane to interfere with free diffusion4 ,osmotic pressure tends1 therefore1 to force the movement of solvents through semi-permeable membranes from more dilute toward more concentrated solutions4 ,protoplasm acts in general as an approximately semi-permeable membrane or material4 ,for example1 if the concentration of sugar in any given mass of protoplasm becomes greater1 by reason of the photosynthetic activity1 osmotic pressure is set up and water enters the mass1 thus preventing loss of turgidity due to increased concentration4 ,similarly1 any other increase in concentration of synthetic products is compensated for by entrance of water because of increased osmotic pressure1 unless the products are insoluble and1 therefore1 incapable of effecting the osmotic pressure4 ,hence1 osmotic pressure provides for the movement of water into and out of protoplasm and so tends to keep the proportion of water uniform throughout the entire tissue4 ,it will at once occur to the reader1 however1 that if the statements in the preceding paragraph were unqualifiedly true1 and if the protoplasmic mass were absolutely semi-permeable in character1 there would be no possibility of the passage of dissolved solids into or out of the cell2 i4e41 if the protoplasm acted as an ideally semi-permeable membrane1 only water could pass into or out of it4 ,but we know that mineral salts from the soil must pass into any cell before the synthesis of proteins1 etc41 can proceed1 and that the fats1 carbohydrates1 proteins1 etc41 which are synthetized in vegetative cells pass from these to other organs of the plant for use or storage4 ,the obvious explanation for this condition of things in the plant is that protoplasm 7and1 indeed1 this is equally true for practically all known membranes7 is not absolutely impermeable to dissolved crystalloids2 or1 in other words1 semi-permeability generally means only that the solvent passes through the membrane more readily and more rapidly than do the dissolved materials in it4 ,even colloidal materials will diffuse through most common membranes1 although at so slow a rate that the process is scarcely observable by ordinary methods of study4 ,hence1 the actual permeability of the protoplasm permits the movement of both water and dissolved solids from one part of the organism to another2 but its approximation of semi-permeability produces osmotic pressure and induces freer movement of water than of dissolved substances1 and so provides for turgidity of the cells and for equalization of the water content of different portions of the protoplasmic mass4 ,it is clear1 therefore1 that osmotic pressure plays an important part in the physical mechanism of cell activities and in the regulation of the proportion of water contained in the protoplasm1 with its consequent effects upon the chemical reactions which may go on in the cell4 ,actual measurements of the osmotic pressure of plant cell have been made4 ,the results are more or less uncertain1 because1 as has been pointed out1 a plant cell is not a definite quantity of uniform protoplasm surrounded by an ideal semi-permeable membrane1 but is instead a mass of living matter which is approximately semi-permeable throughout its entire volume and is in a constantly changing condition because of the anabolic and catabolic activities which are going on in it2 but values have been obtained which show a normal osmotic pressure as high as fourteen atmospheres in the cells of very turgid plants1 such as those of some of the green alg4 ,animal cells probably have an osmotic pressure similar to that of the blood which circulates around them1 which is approximate that of seven atmospheres4 ,,surface ,,boundary ,,phenomena ,in the preceding chapter1 a brief consideration of the phenomena arising at surface boundaries was presented4 ,it was pointed out that when any substance exists in the colloidal1 or dispersed1 condition1 it has relatively enormous surface area and that1 consequently1 enormous surface boundaries between the dispersed phase and the dispersion medium exist in all colloidal mixtures4 ,since protoplasm is conceived to exist in the form of a colloidal gel1 having a foamlike structure1 it is apparent that it has these enormous surface boundaries between the different phases of the system1 and that the phenomena arising from this condition are of great importance in its biological activities4 ,the following necessarily brief discussion will serve to give some indication of the physiological importance of the surface boundaries in such a system4 ,it is easy to see that the molecules which are in the surface layers at the interface1 where two phases of a colloidal system are in contact1 are under the influence of forces quite different from those which are acting upon the molecules in the interior of either phase4 ,it is apparent that the molecules in the surface layer are exposed on the inner side to the attraction and influence of similar molecules1 while on the opposite1 or outer1 side they are exposed to the influence of molecules of an entirely different kind4 ,this results in a state of tension1 known as surface tension1 with the development of resultant forces and energy which profoundly affect the chemical reactivity of the molecules which are present in this surface layer4 ,the so-called surface energy1 which results from this surface tension1 produces marked increases in the possibility of chemical reaction between the materials which are present at the surface boundaries4 ,in colloidal gels1 this effect is so pronounced1 in many cases1 as to completely overshadow other types of influences upon reaction velocities4 ,also1 the surface layer of a liquid is compressed by its surface tension1 to such an extent that the solubility of substances in this surface layer is greatly increased over that of the same substances in the interior of the liquid1 which results in greatly increased concentration of dissolved substances in the surface layer1 and so increases the rate of chemical changes which take place there1 as contrasted with the rate of the same reactions going on in the interior of the solution4 ,this latter consideration seems to be the factor of largest influence in colloidal catalysis4 ,but in addition to the increased rate of reaction in the surface layer due to the increased energy available there and to the increased concentration of dissolved substances1 there is the possibility that the act of concentration itself bring into play molecular forces which give rise to a resultant increase in chemical potential1 or chemical affinity1 of the reacting materials1 such as has been observed to result in other concentrated solutions4 ,a discussion of the theoretical and mathematical considerations upon which this conception is based would be out of place here1 but there is ample experimental evidence to indicate its soundness4 ,further1 as has been pointed out1 colloidal phenomena are essentially due1 in large part at least1 to the electric charges on the dispersed particles4 ,electric charges accumulate at the surface of any charged body4 ,hence1 the surface layers in any colloidal system carry its electric charges in highest concentration1 and all of the chemical changes which are stimulated by electrical phenomena are most strongly influenced at the surface boundaries between the different phases of the system4 ,this latter consideration affords a satisfactory explanation of the well-known depressing1 or stimulating1 action of electrolytes1 especially acids and bases1 upon the enzymic catalysis of protoplasmic reactions4 ,these few1 brief statements are sufficient to indicate how extensively the chemical activities of colloidal protoplasm are influenced by the phenomena arising from the surface boundaries between different materials1 which are present in such enormous extent in a colloidal gel4 ,surface boundary phenomena in a heterogeneous system1 such as we have seen protoplasm to be1 provide the possibilities for many reactions which would otherwise take place very slowly1 if at all4 ,mere subdivision of the protoplasmic materials into the film1 or foam1 structure brings into play energies which may predominate over all other types of energy in the system4 ,here1 too1 effects may be extraordinarily modified by slight changes in environment1 which effects could not be explained by any considerations which govern ordinary chemical reactions4 ,here1 we deal with adsorption and other colloidal phenomena1 rather than with ordinary stoichiometric combinations4 ,indeed1 it is not too much to say that the differences between the chemical phenomena which are called vital and those which take place in ordinary laboratory reactions are due to the fact that the former are manifestations of the interchanges of energy between the different phases of a heterogeneous colloidal system1 while the latter are governed by the laws of ordinary stoichiometric combinations4 ,,electrical ,,phenomena ,,of ,,protoplasm ,the investigations of this phase of the physical chemistry of protoplasm have dealt almost exclusively with animal tissues and reactions1 and have included the study of such phenomena as nerve impulses1 muscular contractions1 heart-beats1 glandular secretions1 etc4 ,tissues which respond to nerve1 or brain1 control are1 of course1 not found in plants4 ,but there is plenty of experimental evidence to show that plant protoplasm carries electrical charges and exhibits electrical phenomena which are similar in character to those of animal tissues4 ,in fact1 it has been shown that the contraction of the lobes of the ,venus' fly trap1 when they close over an imprisoned insect1 are accompanied by electrical phenomena in the leaf tissues which are precisely similar to those which take place in an animal muscle when it contracts4 ,it seems probable that many of the observations and conclusions which have been derived from the study of the electrical disturbances in animal tissues may later be found to have definite applications to the vital phenomena of plant cells4 ,hence1 it seems proper to give some brief consideration to these matters here4 ,the statement has been made that every active living cell is essentially an electric battery1 and it is believed that every activity of living matter1 such as the rhythmic contraction of the heart1 the passage of a nerve impulse1 etc41 is accompanied by an electric disturbance in the protoplasm of the tissues in question4 ,experimental proof of this electrical disturbance has been repeatedly obtained1 by connecting a delicate galvanometer in a circuit through the living tissue which is undergoing different activities and obtaining widely varying readings of the instrument as the different phenomena are in progress1 or by connecting the instrument with muscular tissue and observing its fluctuations with either the irregular contractions of a voluntary muscle or with the rhythmic contractions of a heart muscle4 ,by means of such investigations as those just mentioned1 it has been found that the part of the protoplasm which is most active is always electro-negative to the part which is less so2 that is1 the electric current flows from the more active to the less active portion of the protoplasm4 ,many different explanations of the origin of the electric current which develops when the protoplasm is stimulated into activity have been suggested2 but none of them have1 as yet1 any experimental confirmation4 ,the most that can be said is that whenever any stimulus excites the protoplasm into activity1 there is instantly developed in it an electrical disturbance1 which continues as long as the action is in progress4 ,recent investigations1 which have shown that there is a direct relation between many of the vital processes of protoplasm and the ratio of the electrolytes which it contains1 particularly the ratio of sodium and potassium to calcium1 would seem to indicate that the development of the electrical disturbance is a direct result of variations in the proportions of the salts of these metals1 either brought about by1 or themselves causing1 changes in the permeability of the protoplasm1 following the stimulus which determines the nature of the activity which it is to undergo4 ,but there is as yet no indication concerning the mechanism by which this stimulation1 with its resultant electrical phenomena1 is transmitted to the protoplasm and accomplishes its characteristic effects4 ,,acidity ,,or ,,alkalinity ,,of ,,protoplasm ,the preceding sections of this chapter have dealt almost exclusively with the physical properties of protoplasm2 including the phenomena of solution1 ionization1 surface boundary effects1 and electrical disturbances1 and their probable effects upon the chemical reactions which constitute its biological activities4 ,it is necessary now to consider another phase of the physical chemistry of protoplasm1 namely1 its chemical reaction1 whether acid1 alkaline1 or neutral1 the effects of variation of this condition upon the activity of the protoplasm1 and the mechanism by which it tends to preserve its own proper reaction in this respect4 ,the earlier methods of investigation of the chemical reaction of protoplasm were all based upon its color reactions to various staining agents4 ,these sometimes led to erroneous conclusions1 because of the effects of the staining agent itself upon the tissue2 some stains are poisonous and result in the death of the protoplasm1 others do not easily penetrate the semi-permeable colloidal mass1 others are themselves changed by the oxidizing or reducing action of the protoplasm1 etc4 ,again1 colloidal adsorption effects often lead to the so-called capillary segregation of added staining materials4 ,so that this method of study must be used with great care1 or wholly erroneous conclusions will be reached1 and many of the earlier reports have subsequently been found to be incorrect4 ,the recent improvements in the apparatus and methods for the determination of hydrogen-ion concentration have afforded a much more trustworthy method of determining the actual acidity or alkalinity of such materials than is obtained by color reactions1 and this method is now being extensively used in the study of the reaction of active protoplasm4 ,it must be kept in mind that protoplasm is an heterogeneous mass and not an homogeneous solution1 so that it is not always possible to determine the actual conditions as to neutrality of different parts of the protoplasm of a single cell1 for example4 ,hence1 one of the best methods of determining the reaction which is favorable to the life and activity of any given type of protoplasm is to investigate the reaction of a liquid medium in which the cells live and grow2 this plan being based upon the assumption that a cell is not likely to have a reaction different from that of the medium which is favorable to its growth4 ,the results of all of the many investigations which have dealt with this problem point to the conclusion that the normal reaction for living protoplasm is either neutral or very faintly alkaline2 but that it becomes acid when the cell is working in the absence of sufficient oxygen1 and after the death of the cell4 ,the first effect of a change in the reaction toward acidity of the protoplasm is a decrease in the rate of respiration of the tissue1 while increased alkalinity stimulates respiratory activity4 ,whet carried to the point of actual acidity1 the respiratory coefficient becomes negative1 and the cell actually gives off carbon dioxide because of the stoppage of the synthetic processes4 ,a second effect of change in reaction of protoplasm is to alter the enzymic activity of the cell4 ,as has been pointed out1 enzymes are extraordinarily sensitive to minute changes in the reaction of the medium in which they are working4 ,a change toward acidity in protoplasm immediately results in the stimulating of carbohydrate-splitting enzymes1 which increases the supply of easily oxidizable simple carbohydrates1 thereby tending to compensate for the decrease in respiratory activity4 ,further1 increase in acidity increases proteolysis1 thereby liberating alkaline ammonia-derivatives which tend to neutralize the rising acidity and so to restore normal neutrality or alkalinity4 ,thus it will be seen that in the very great sensitivity of its enzyme catalysts to slight changes in the reaction of the medium1 the protoplasm possesses a very efficient mechanism for regulating changes and restoring equilibrium1 if the latter be disturbed by any abnormal conditions4 ,it should also be noted1 at this point1 that the almost universal presence in protoplasm of salts of carbonic and phosphoric acids acts as an additional buffer against pronounced changes in reaction of the material2 the bicarbonates acting by means of their ready release or absorption of carbon dioxide1 and the phosphates by their easy change from mono-sodium phosphate to di-sodium phosphate1 and vice versa1 the former being slightly acid and the latter slightly alkaline in reaction4 ,a third effect of increasing acidity is that it induces increased imbibition of water by the colloidal gel and causes swelling of the tissue4 ,after death1 when the reaction of the protoplasm becomes pronouncedly acid1 this swelling often proceeds to the point of rupturing of the cell-wall1 or internal membranes of the protoplasm1 thus permitting the entrance of the putrefactive bacteria and hastening the decay of the tissue4 ,finally1 comparatively slight variations in the reaction of the protoplasm produce enormous changes in its colloidal condition1 affecting in a very marked degree its permeability1 its power of adsorption1 etc4 ,it is clear1 therefore1 that variations in the chemical reaction of protoplasm profoundly affect its colloidal condition1 its enzymic activity1 and its respiratory processes4 ,this necessarily brief survey is sufficient to indicate how important to the activity of the protoplasm is the chemical reaction of the material1 and the mechanism with which it is provided for maintaining the favorable condition of neutrality or slight alkalinity4 ,,summary ,it is evident that1 within the limits of a single chapter1 it has been possible to give only a very brief and incomplete discussion of some of the most important applications of the principles of physical chemistry to the properties and activities of protoplasm4 ,therefore1 it may be profitable to summarize briefly these into a series of definite statements which may serve as a review of the principles which have been discussed in the preceding chapters1 as applied to the activities of protoplasm4 ,protoplasm is a complex hydrogel1 composed of an heterogeneous mixture of proteins1 fats1 and carbohydrates1 arranged in a foamlike structure1 the compartments of the gel being filled with an aqueous solution of the soluble organic products of synthesis and of varying proportions of mineral salts which are of the same general nature as those of sea-water4 ,the gel is not uniform throughout the volume of any given cell1 but is differentiated in different parts into what are known as the nucleus1 the chloroplasts1 the plasma of the cell1 etc4 ,the vital activities of the cell consist in chemical reactions which are controlled by comparatively slight changes in the electrolyte distribution1 or other environmental changes which affect the colloidal condition of the mass and1 generally speaking1 result in changes of the water content of the plasma1 most such chemical changes being essentially reversible hydrolytic reactions4 ,the components of active protoplasm are in a condition most favorable to chemical reactions by reason of the enormous surface area of the colloidal material1 resulting in abundance of available energy1 intimate contact of the reacting materials1 and the nearest possible approach to the condition of true solution which can be obtained without the loss of stable form and structure4 ,the reactions which take place in cell protoplasm1 as a result of the action of either physical or chemical stimuli1 are accompanied by electrical disturbances1 which may be either caused by1 or the result of1 changes in the electrical charges of the mineral salts which are present in the gel4 ,such changes1 like the chemical reactions which they accompany1 may be regarded as reversible and mutually self-regulatory2 so that the protoplasm has not only the possibilities of enormous chemical reactivity1 but also the mechanism for self-regulation of its actions1 the products or results from any given series of changes generally tending to reverse the process by which they are proceeding and so to restore the condition of normal equilibrium4 ,finally1 the most characteristic difference between the reactions which go to make up the vital activities of a living cell and those of the same chemical substances when in inanimate form in the laboratory lies in the presence in the colloidal mass of the accelerating catalysts known as enzymes1 which are produced by the protoplasm itself in some way which is as yet wholly unknown2 and which not only add to the possibilities of rapid chemical change which are afforded by the colloidal nature of the material1 but also1 because of their extreme sensitiveness to minute changes in environmental conditions1 serve to govern both the rate and the direction of the individual chemical reactions which constitute the vital activities of the protoplasmic mass4 ,these enzymes are not distributed uniformly through any given cell1 or organism1 but are localized in different parts of the cell or tissue and so give to its different parts the ability to perform their various different functions4 ,references ,,atkins1 ,w4 ,r4 ,g4--,some ,recent ,researches in ,plant ,physiology1 #cbh pages1 #bh figs41 ,london1 #aiaf4 ,,czapek1 ,f4--,chemical ,phenomena of ,life1 #aeb pages1 ,new ,york1 #aiaa4 ,,czapek1 ,f4--,ueber eine ,methode zur direkten ,bestimmung der ,oberflchenspannung der ,plasmahaut von ,pflanzen1 #hf pages1 #c figs41 ,jena1 #aiab4 ,h,,ber1 ,m4 ,r4--,physikalische ,chemie der ,zelle und der ,gewebe1 #fga pages1 #ee figs41 ,leipzig1 #aiaa4 ,,livingston1 ,b4 ,e4--,the ,rle of ,diffusion and ,osmotic ,pressure in ,plants1 #adi pages1 ,chicago1 #aijc4 ,,mcclendon1 ,j4 ,f4--,physical ,chemistry of ,vital ,phenomena1 #bdh pages1 ,princeton ,university ,press1 #aiag4 ,,macdougal1 ,d4 ,t4--,hydration and ,growth1 ,publication ,no4 #big1 ,carnegie ,institution of ,washington1 #agf pages1 #eb figs41 ,washington1 ,d4 ,c41 #aibj4 ,,speigel1 ,l41 trans4 by ,,luedeking1 ,c4 and ,,boylston1 ,a4 ,c4--,chemical ,constitution and ,physiological ,action1 #aee pages1 ,new ,york1 #aiae4 ,,thompson1 ,d',a4 ,w4--,on ,growth and ,form1 #gic pages1 #djh figs41 ,cambridge1 #aiag4 ,,willows1 ,r4 ,s4 and ,,hatschek1 ,e4--,surface ,tension and ,surface ,energy and their ,influence on ,chemical ,phenomena1 #aaf pages1 #ba figs41 ,new ,york1 #aiai1 7#b;d ed474 ,,chapter ,,xvii ,,hormones1 ,,auximones1 ,,vitamines1 ,,and ,,toxins ,reference has frequently been made1 in preceding chapters1 to the effect of various stimulating or inhibiting agencies upon the physiological activities of plant protoplasm4 ,in the main1 these agencies are external to the plant and are either physical1 such as changes of temperature1 amount of light received1 etc42 or chemical1 such as variations in the salts received from the soil1 or common ansthetics applied to the plants by man4 ,a plant grows normally under certain conditions to which it has become adjusted by hereditary acquirements4 ,when these conditions are altered1 the effect upon the functioning of the plant protoplasm may be either stimulating or depressing4 ,extreme changes in environmental conditions generally result in the death of the plant2 but changes which do not result in the lethal condition affect the plant by either stimulating it to more rapid physiological activity or by depressing its normal growth or functions4 ,as has been pointed out1 the same external influence1 either chemical or physical1 which acts as a stimulant if it differs only slightly from normal conditions1 may become depressing1 or positively toxic1 if present to a larger extent4 ,there is also the possibility of the elaboration by the plant itself of internal agents1 or substances1 which may have a definite stimulating or inhibitory effect upon its metabolism and growth4 ,the study which has been given to these matters has practically all been carried on within very recent years and is still in progress4 ,most of it is still in the experimental stage1 in which no definite conclusions are as yet possible4 ,hence1 the most that can be done at present is to give a brief review of the suggestions which have been made thus far1 as indicative of the uncertainty of our present knowledge of these matters and of the general trend of the investigations which are now in progress4 ,substances which are elaborated by plants and which are supposed to have a definite stimulating or beneficial effect upon the activities of the plant which produces them1 or to influence the physiological activities of other plants with which these substances come in contact through either the parasitic or the symbiotic relation1 have been variously discussed under the names hormones1 auximones1 and vitamines2 while injurious substances are generally known as toxins4 ,whether these different terms actually represent different definite types of substances1 or whether there are actually different groups of stimulating or inhibitory agents produced in plants1 is uncertain2 but the following brief statements will serve to indicate the general nature of the suggestions which have been put forward and of the experimental work which is now in progress4 ,,hormones ,the term hormone was first used to designate certain stimulating substances which are supposed to exist in the intestinal tracts of animals and to cause the glands to elaborate and secrete their characteristic enzymes4 ,the supposed hormones are not themselves active in performing the digestive functions of the glandular secretions1 but are the exciting1 or stimulating1 agents which cause the glands to secrete their active enzymes4 ,the same term has been used1 by certain plant physiologists1 to designate any agency1 either external or internal1 which stimulates plant protoplasm to abnormal activity4 ,it has been pointed out that there are a variety of substances1 which are themselves chemically neutral1 that are powerful stimulants of vital activity if used in only minute proportions1 but are powerful poisons if present in larger amounts4 ,many of the alkaloids act in this way upon the animal organism2 while chloroform1 toluene1 and even some of the more complex hydrocarbons1 act similarly upon the tissues of plants1 and ether vapor is known to be a powerful stimulant in accelerating the flowering of plants and the ripening of fruits4 ,it has been shown that the vapors of all such substances readily penetrate the protoplasm of leaves1 seeds1 etc41 even when the same parts are impermeable to most mineral salts1 sugars1 etc42 and that upon entrance to the protoplasm of a leaf1 or a seed1 they tremendously stimulate its metabolic activity4 ,these hormones1 as a class1 are chemical substances which have very little attraction for1 or power of combination with water2 and it has been suggested that the ease with which they penetrate the protoplasm is due to the fact that they are not held at the surface by combination with the active water molecules which are present in the surface layer4 ,the principal effect which is supposed to be produced by these hormones is the stimulation of the enzymic activity1 particularly that of the degenerative processes which take place late in the plant's life1 at the flowering or ripening periods4 ,many of the changes which take place normally at ripening time1 such as the change in color from green to yellow or red and finally to brown or black1 when the fruit or vegetable is fully ripe1 can be greatly accelerated by treatment with these substances4 ,hormones are similar in type to the ethereal salts1 or esters1 which constitute the natural essential oils that develop in many plants at this stage of their growth4 ,hence1 it seems probable that these changes in plants which are maturing naturally may be hastened by the hormone action of the esters and similar bodies which are developed in largest quantities at that stage4 ,it has been pointed out that the characteristic group which is present in many natural glucosides is of the same general type as the hormone substances which are used in the artificial stimulation of the flowering or ripening changes4 ,this fact1 together with the possibility of the liberation of greater percentages of these aromatic compounds from their glucoside combinations at the later periods of plant growth1 is assumed1 by some plant physiologists1 to account for the change from synthetic to degenerative processes at this stage of the plant's development4 ,further1 it has been suggested that the autumnal coloration of leaves1 and their dropping from the stems of the plant1 as well as the ripening of seeds1 is probably determined by the liberation in the plant1 at that stage of its growth1 or as a result of changed climatic conditions at that particular season of the year1 of the hormones which either initiate or hasten the special enzymic changes which distinguish the degenerative from the synthetic processes of the plant4 ,similarly1 it has been suggested that parasitic fungi are able to penetrate the host plant by first excreting hormones which bring about degenerative changes in the tissues of the host plant and so make it more easily penetrable by the hyphae of the parasite4 ,it will be seen that1 in general1 hormones are a type of substances 7possibly often present in plants in the form of glucosides7 which are supposed to stimulate the degenerative 7or katabolic7 vital processes in contrast to the synthetic 7or anabolic7 changes4 ,it has been suggested that they do this in either one of two ways2 namely1 by favoring the introduction of water into the protoplasm and so diluting the cell contents1 changing the osmotic pressure1 etc42 or by bringing about a separation of the colloidal layers1 or films1 of the protoplasmic complex1 producing a result similar to that produced by freezing the tissues4 ,these ideas have been suggested by studies of the changes in the equilibrium of protoplasm when foreign substances are introduced into it4 ,these studies have not as yet been brought to the stage of final conclusions1 and the ideas presented must be considered as suggestive rather than as conclusive4 ,,vitamines ,vitamines1 as contrasted with hormones1 are supposed stimulants of synthetic metabolic processes1 or accelerators of growth1 rather than of degenerative processes4 ,the term vitamine was first used to designate the substance1 or substances1 which must be present in the diet of animals in order that the animal organism may grow4 ,absence of these substances from the food of the animal results in the stoppage of growth of young animals and in various so-called deficiency diseases 7such as beri-beri1 scurvy1 polyneuritis1 etc47 of adults4 ,this means that the animal organism is altogether unable to elaborate its own vitamines1 and extended investigations have indicated that the vitamines necessary for animal uses are wholly of plant origin4 ,the name vitamine was first used because it was supposed that these substances are chemical compounds of the amine type and1 since they are necessary to normal life processes of animals1 the name vitamine seemed to represent both their chemical character and their functions4 ,later investigations have caused doubt as to the accuracy of the first belief as to their chemical nature1 and various other names have been suggested for the general group of substances which have the observed beneficial effects2 while such specific names as fat-soluble ,a1 water-soluble ,b1 etc41 have been used to designate individual types of these accessory food substances4 ,however1 the term vitamine is such a convenient one and is so generally recognized and accepted that it will probably continue to be used1 at least until some more definite knowledge of the nature and composition of these growth-promoting1 disease-preventing1 and reproduction-stimulating food constituents is obtained4 ,the following definition of the term vitamines gives a satisfactory conception of the nature and functions of these substances1 so far as they are yet known4 ,vitamines2 constitute a class of substances the individuals of which are necessary to the normal metabolism of certain living organisms1 but which do not contribute to the mineral1 nitrogen1 or energy factors of the nutrition of those organisms4 ,as sub-groups of the vitamines1 there have already been recognized the growth-promoting1 fat-soluble ,a2 the antineuritic ,b1 and the antiscorbutic ,c4 ,until very recently1 the investigations of vitamines have dealt exclusively with their relation to human nutrition2 although it has been generally believed that the vitamines themselves are elaborated only by plants4 ,it was generally recognized1 however1 that those plants1 or parts of plants1 which are capable of very rapid growth or metabolic changes1 such as germs1 spores1 leaves1 etc41 are generally the richest source for vitamines for animal needs4 ,hence1 there seemed to be considerable basis for the assumption that the elaboration of these substances by plants is definitely connected with their own metabolic needs4 ,recently1 investigations of the functions of vitamines in the growth of plants have been begun4 ,these are still in progress1 but the following conclusions seem to be justified at the present time3 7a7 ,potato tubers appear to contain growth-promoting substances which are essential to the proper growth of the sprouts4 ,whether these are the same substances which are efficient in the prevention of scurvy in men has not yet been investigated4 7b7 ,baker's yeast is probably dependent upon a supply of vitamines in the medium in which it is to grow4 ,yeast itself1 after having grown in barley wort1 is one of the most important sources of vitamines for animal uses or for purposes of investigations of vitamine activity4 ,but it has been reported that a yeast cell will not grow in an artificial medium which contains all the essential nutrients for yeast but has no vitamines of other plant origin in it4 ,the addition of barley wort1 containing the vitamines from barley germs1 or any other similar supply of vitamines1 induces rapid growth and the storage of vitamines in the growing yeast masses4 7c7 ,the growth of many bacteria is either wholly dependent upon or greatly stimulated by the presence of vitamine-like substances in the medium upon which the microorganisms grow4 7d7 ,sclerotinia cinerea1 the brown rot fungus of peaches and plums1 will grow only in a medium which contains1 in addition to the essential sugar1 salts1 and nitrogenous material1 vitamines derived from either the natural host plant tissues or other plant sources4 ,these may be of two types 7namely1 a vegetative factor and a reproductive factor7 or two different manifestations of activity of the same vitamine substance4 ,but both of these factors must be provided before the fungus can make its characteristic growth4 ,there is1 as yet1 no conclusive evidence on many of the matters concerning the relation of vitamines to plant growth4 ,but it seems that these substances are of almost universal occurrence in the organic world2 that they are not of the same general type as other substances which are essential to the nutrition of plants or animals1 but have specific stimulating or regulating effects upon the physiological activities of the organism2 that the vitamines which are essential to animal life are elaborated by plant tissues1 but that in the case of the bacilli of certain human diseases there seems to be some indication that the affected tissues of the animal host produce vitamines which are essential1 or favorable1 to the growth of the parasitic organism4 ,there seems1 therefore1 to be evidence of a mutual relation between plants and animals with respect to their nutritional needs for the so-called vitamines4 ,but the evidence concerning the function of these substances in the tissues of the organism which elaborates them is1 as yet1 inadequate to provide any clear conception of the reason for their development or of the mechanism by which they are elaborated4 ,neither is there1 as yet1 any conclusive evidence concerning the chemical nature of the substances themselves4 ,,auximones ,certain investigations have indicated that bacteria1 at least1 develop exogenous vitamines which are beneficial to the growth of other plants4 ,these are the so-called auximones4 ,for example1 bacterized peat seems to contain auximones which may be isolated from the peat and exert a beneficial effect upon the growth of various seed-plants1 including common farm crops4 ,neither the original experimental data1 nor the theories which have been advanced to account for the observed beneficial effects of the supposed auximones have1 as yet1 sufficient confirmatory evidence definitely to establish their soundness4 ,but it seems that there is a probability that some plants1 at least1 do elaborate vitamines1 or auximones1 which are useful to other plants4 ,,toxins ,toxins are substances which affect injuriously the normal activities of the organism4 ,as has been pointed out1 they may be the same substances which1 in lesser concentrations1 exert a stimulating effect upon the same organism4 ,hence1 it is probably inaccurate to discuss the toxins as a distinct group of substances4 ,there are1 however1 a large number of water-soluble chemical substances which are injurious to all living protoplasm1 even at concentrations considerably less than the point of osmotic equilibrium in the juices of the protoplasm4 ,these substances may act either directly or indirectly upon the protoplasm1 but at certain concentrations they always affect it injuriously4 ,in the main1 these toxins are external agents of other than plant origin2 although chemical substances developed by one plant may be toxic to other plants1 or even to other organs of the same plant than those in which they are elaborated4 ,toxins may be either general 7i4e41 injurious to all types of plants71 or specific 7i4e41 injurious to only certain species7 in their action4 ,examples of specific toxicity are of only minor importance in plant studies4 ,they seem to be generally explainable on the basis of some unusual lack of resistance or failure of the susceptible plants to be able to exclude the entrance of these injurious substances into the protoplasm by selective adsorption1 or to convert the injurious substances into insoluble and non-injurious forms1 as is done by other plants which are not susceptible to injury by these specific poisons4 ,hence1 particular attention need not be given to this type of toxins4 ,toxic substances may act injuriously upon plant tissues in a variety of ways4 ,many electrolytes1 especially the salts of the heavy metals of high valency1 coagulate protein material and the entrance of such substances into the protoplasm causes disturbances in the colloidal condition which cannot be otherwise than injurious to its normal activities4 ,similarly1 formaldehyde and many other organic compounds may affect the colloidal properties of the protoplasmic gel in such a way as to injure the plant tissues4 ,the same substance is sometimes much more injurious to the tissues of one part of a plant than it is to those of another part of the same plant4 ,thus1 the rootlets of a young growing plant are much more susceptible to injury by many mineral salts than are the vegetative parts of the same plants2 while ansthetics of various kinds generally exhibit their greatest injurious effects upon the leaves1 or synthetizing cells4 ,again1 the mycelia of fungi are much more easily killed by toxic agents used as fungicides than are the spores of the same fungi4 ,some of these observed differences in toxicity may be due to differences in the physiological effect of the substance upon the protoplasm of the tissues which it enters1 and others may be due to differences in the resistance of the protoplasm1 or of its protective coverings1 to penetration by the toxic material4 ,indeed1 the possibilities of different types of toxic action1 and of resistance to it by individual plants and species1 are so varied that it is not possible to divide toxic agents into specific groups according to the nature of their injurious action upon the plant cell4 ,they are1 therefore1 more commonly grouped into classes according to their chemical nature and economic significance as fungicides1 as follows3 inorganic and organic acids2 caustic alkalies2 salts of the heavy metals2 hydrocarbon gases2 formaldehyde2 alcohols and ansthetics2 nitrogenous organic compounds2 and miscellaneous decomposition productions of organic origin4 ,the following brief review of some of the results of the experimental studies of the toxicity of different compounds belonging to these several groups will serve to indicate the general trend of the investigations of these matters which have thus far been made4 ,acids4--,the common inorganic acids 7hydrochloric1 nitric1 and sulfuric7 kill the rootlets of common farm crops when the latter are immersed for twenty to twenty-four hours in solutions of these acids containing from three to five parts per million of free acid4 ,acetic acid must be about five times as concentrated as this1 and other organic acids may be much more concentrated still before they produce the same injurious effects4 ,the toxic effect of all these acids is greatly reduced in soil cultures1 or if particles of sand1 graphite1 clay1 filter paper1 etc41 are suspended in the solutions containing the acids1 the reduction in toxic effect being probably due to the adsorption of the acids upon the solid particles4 ,hence1 the concentrations which limit the toxic effects of these acids in water solutions cannot be taken as representing the condition with which the same plant will have to contend when growing under normal cultural conditions4 ,alkalies4--,the caustic alkalies must usually be present in from five to ten times as great concentrations as those of the mineral acids1 in order to produce the same injurious effects upon the rootlets of common plants4 ,the so-called alkali of soils is not alkali at all1 but is neutral soluble salts present in sufficient concentration to exert a toxic effect4 ,salts of the heavy metals are especially toxic to rootlets of plants4 ,salts of copper1 mercury1 and silver1 have been found to kill the roots of seedlings immersed in them for twenty-four hours when present in proportions of less than three parts per ten million1 while salts of many other heavy metals are toxic when present in concentrations of less than one part per million4 ,the salts of the alkali metals are considerable less injurious than are those of the heavy metals1 but even these exert their familiar injurious effect if present in concentrations which1 measured by the ordinary standards1 would still be regarded as very dilute solutions4 ,illuminating gas1 and similar hydrocarbon gases1 kill plants when present in the atmosphere in as little as one part per million4 ,leaves1 buds1 and roots are all alike sensitive to this toxic effect1 the nature of which is not yet understood4 ,formalin1 or formaldehyde1 is a penetrating toxic agent for nearly all plant cells1 and is commonly used as a fungicide for the destruction of parasitic fungi4 ,it probably affects the colloidal condition in some way similar to its hardening effect upon gelatin1 etc4 ,the toxic effect of many different organic compounds is so varied in its nature and extent that it is impossible to give any satisfactory brief review of its manifestations4 ,recent investigations appear to indicate that organic products of decomposition of plant residues in the soil may exert powerfully toxic effects upon succeeding generations of the same1 or of different1 plants growing on the land4 ,but the experimental data and conclusions concerning these matters are not yet accepted without question by all students of plant science or of the problems of the productivity of the soil4 ,in fact1 it is yet an open question whether toxic soil constituents are really an important factor in the so-called unproductivity of certain soils4 ,alkaloids1 and even the amino-acids which are produced in the tissues of some species of plants1 while not toxic to the plants or organs which elaborate them1 sometimes exhibit strikingly toxic action upon other plant organs with which they are brought into contact4 ,there is1 as yet1 no satisfactory explanation of this difference in behavior between plant tissues toward various organic toxic substances4 ,in fact1 the whole subject of the toxic action of various substances upon plants needs much more study before it is brought to the point where it will afford definite knowledge of either the physiological problems involved or of their practical applications in questions of soil productivity1 etc4 ,,chapter ,,xviii ,,adaptations ,most of the discussions which have been presented in the preceding chapters have dealt with the types of compounds1 the kinds of reactions1 and the mechanism for the control of these1 which are exhibited by plants under their normal conditions for development4 ,the results of the evolutionary process have produced in the different species of plants certain fixed habits of growth and metabolism4 ,so definitely fixed are these that in each particular species of plants each individual differs from other individuals1 which are of the same age and have had the same nutritional advantages and environmental opportunities for growth1 by scarcely perceptible variations1 if at all4 ,indeed1 this fixed habit of development makes possible the classification of plants into genera1 species1 etc4 ,while different species of plants1 given the same conditions of nutrition and environment1 produce organs of the widest conceivable variety in form1 color1 and function2 within the same species1 the form and size of leaves1 the position and branching of the stem1 the color1 size1 and shape of the flower1 the coloration and markings of the fruit1 etc41 are relatively constant and subject to only very slight modifications4 ,it is unnecessary to say that the mechanism1 or the impulses1 which govern the morphological characters of the tissues which any given species of plants will elaborate out of the crude food material which it receives from the soil and atmosphere1 are wholly unknown to science4 ,it is the commonly accepted assumption that the fixed habit of growth of the species is transmitted from generation to generation through the chromosomes of the germ cells4 ,but the nature of the elements1 or substances1 which may be present in the chromosomes1 which influence the character of the organs which will develop months later1 after the plant which grows from the germ cell has gone through its various stages of vegetative growth1 is still altogether unknown4 ,there can be no question1 however1 that some influence produces a fixity of habit of growth and development which is almost inevitable in its operation4 ,but while this unvarying habit of growth is one of the fixed laws of plant life1 there are occasional deviations from it4 ,a plant which1 under normal conditions of growth1 develops in a certain fixed way1 when exposed to unusual environmental conditions1 may1 and often does1 alter its habit of growth in what may metaphorically be said to be an attempt to adjust itself to the new conditions4 ,numerous examples of this phenomenon might be cited4 ,certain alg1 which grow normally in water at a temperature of #bj to #cj and which are killed if the temperature rises above #de1 have been grown for successive generations in water the temperature of which has been gradually raised1 until they produce apparently normal growth in water the temperature of which is as high as #gh2 also1 certain types of alg normally grow in the water of hot springs at temperatures of #he to #ij1 and others in arctic sea-water the temperature of which sometimes falls to -#a4h and never rises above #j ,c4 ,this phenomenon of the adjustment of a species of plants to new conditions1 which in the case of farm crops is sometimes called acclimatization1 is of common occurrence and is often utilized to economic advantage in the introduction of new strains of crops into new agricultural districts4 ,again1 the normal development of plants may be altered as the result of injury or mutilation4 ,thus1 if the ear is removed from the stalk of ,indian corn1 at any time after flowering1 there always results an abnormal storage of sucrose in the stalk1 instead of the normal storage of starch in the kernels4 ,similarly1 midsummer pruning of fruit trees generally results in the production of abnormally large number of fruit buds on the remaining limbs4 ,many other familiar examples of alteration of normal development in response to1 or as the result of1 abnormal conditions of growth might be cited4 ,,types ,,of ,,adaptations ,to designate these different alterations of normal growth1 several different terms have been used4 ,among these1 adaptation1 accommodation1 and adjustment have been commonly used by different biologists4 ,sometimes these are used interchangeably1 and sometimes different terms are used to designate different types of response to altered conditions of growth4 ,inasmuch as there seems to be no generally accepted usage of these different terms1 only one of them1 namely1 the word adaptation will be used here2 and different manifestations of this phenomenon will be distinguished by using appropriate adjectives1 as physiological adaptations1 chromatic adaptations1 morphological adaptations1 etc4 ,two markedly different types of responses to altered conditions1 or of adjustment to environment1 may be recognized4 ,in the first of these1 for which we will use the term physiological adaptation1 the species of plant simply acquires the ability to exist and grow normally under conditions which formerly inhibited its growth4 ,thus1 we may speak of the phenomena mentioned above as acclimatization as the physiological adaptation of the crop to the new conditions of growth4 ,in general1 physiological adaptations include such variations in the characters or habits of growth of plants as results in differences in resistance to heat or to cold1 relations to water1 aggressiveness in competition with other plants1 etc4 ,in such cases1 no modification of the morphological characters of the plant can be observed1 the changes which take place in the structure of the plant 7if1 indeed1 there be any such changes7 must be only minor adjustments of the protoplasm to meet the new environmental needs4 ,in the second type of adaptations1 for which we will use the term morphological adaptations1 the structure1 or color1 or some other morphological character of the plant is actually changed in some easily recognizable way1 in order that the plant may be better adjusted to its environment4 ,as examples of morphological adaptations1 there may be cited the change in color of sea-weeds with increasing depth in the sea1 and other examples of chromatic adaptation which are discussed below2 the development of fewer1 or a larger number1 of buds on the above-ground stems of plants1 in response to decreases1 or increases1 in the available supply of food2 the alteration in the size and shape of the leaves of many plants when they are grown in shade2 the dwarfing of plants at high altitudes1 or under conditions of severe drought2 the development of underground storage organs for certain species of shrubs and trees which grow in regions that are subject to periodical burning-over1 in such a way as to destroy the above-ground storage stems1 etc4 ,hence1 the two terms1 as we will use them here1 may be defined as follows3 morphological adaptation is a change in the structural character of the species in order that it may be better fitted to meet the needs of the new conditions of growth2 while physiological adaptation is an acquired power to survive and develop under abnormal conditions1 which is not accompanied by any visible change in the characteristic structure of the species4 ,both of these types of adjustment may be either hereditary 7or evolutionary71 or spontaneous in their origin and development4 ,changes which are evolutionary are fixed by heredity and become definite habits of growth in the species4 ,their origin may be explained in either one of two ways2 namely1 the so-called increase by use1 and the survival of the fittest4 ,the hypothesis of increase by use1 as an explanation of adaptations1 is based upon the well-known observation that1 in animals1 muscles and other organs increase in volume as they are extensively used2 and the assumption of the application of this principle to the phenomenon of adaptation supposes that the modification of any given structure or composition is the result of the hereditary accumulations of increased size resulting from use1 or of atrophy from disuse4 ,the survival of the fittest theory supposes that individuals of a species differ from each other by spontaneous variations1 and that in the competitive struggle for existence those forms which are best adapted to the environmental conditions survive while the others perish4 ,the contrast between these two views is that the first holds that adaptation proceeds by development1 and the second that it proceeds by variation and elimination2 the first presupposes the existence in the organism of a mechanism for response to changing conditions1 and the second assumes that there are chance variations followed by the death through competition of the forms which are not able to meet the needs of the environment4 ,confusion arises whenever an attempt is made to apply either of these theories to all kinds of adaptations4 ,the idea of increase by use can be applied with some satisfaction to certain morphological adaptations in animal structure2 and to such phenomena as the increase in strength of the branches of fruit trees1 either with or without corresponding increase in size1 as the load of fruit increases4 ,but it certainly cannot apply to color change in surface pigmentation of either animals or plants1 which is one of the most common forms of adaptation4 ,furthermore1 it is difficult to conceive the general application of this idea to alterations of habits of growth of plants1 since a plant cannot have any such thing as a voluntary control over the amount of use which it makes of its different organs in response to changes of environment4 ,the common form of statement that a plant develops an organ1 or a process to meet a certain need1 or modifies its habits of growth to meet a change of environment are1 of course1 purely metaphorical1 and can only be taken to mean that such processes are mechanical responses to changes in external conditions4 ,the nature of the mechanism by which these responses are accomplished is1 as yet1 wholly unknown4 ,there is accumulating a large mass of experimental evidence which goes to show that1 while both temperature and light are very important factors in determining the type of changes which will take place in a living organism1 the so-called photochemical action of light is by far the most potent of all the climatic factors which influence the course of development of a plant4 ,but we have1 as yet1 no inkling of how the protoplasm of the plant adjusts or controls its responses to variations in any of these external factors4 ,with these general considerations in mind1 we may now proceed to the consideration of certain particular types of adaptations4 ,,chromatic ,,adaptations ,adaptations have been observed in both the energy-absorbing pigments of the general tissues and in the ornamental epidermis pigments of plants4 ,the former are by far the most important from the physiological point of view2 while the latter may have interesting biological significance4 ,under nearly all conditions of growth of land plants1 the supply of the chlorophylls and their associated pigments provides for the absorption of solar energy far in excess of the amount necessary for the photosynthetic assimilation of all the carbon dioxide which is available to the plant4 ,it has been shown that an active green leaf1 on an ,august day1 can absorb eight times as much radiant energy as would be required to assimilate all the carbon dioxide present in the air over its surface4 ,no land plant1 under normal conditions1 develops supplementary pigments in order to utilize other than the parts of the spectrum which are absorbed by chlorophyll and its associated pigments4 ,but deep-sea plants show quite a different phenomenon of pigment development4 ,water is a blue liquid4 ,at depths of #dj feet or more1 the light which penetrates is devoid of red rays1 feeble in yellow1 and is characteristically green or blue in color4 ,now1 the red rays of the spectrum are the ones which are most efficient for photosynthesis4 ,sea weeds which grow at these depths are brilliantly red in color1 at intermediate depths they are brown1 and at the surface they are green1 in the same latitudes4 ,while it is possible that the temperature of the water at these different depths may have something to do with the chemical synthesis of the pigments1 it appears plain that this color change at increasing depths is a definite adaptation to provide for the absorption of the solar energy which is available at these depths4 ,it has been shown that these pigments of deep-sea plants are additional to1 and not substitutes for1 the chlorophylls1 etc4 ,the latter pigments are present in normal amounts1 but are supplemented by those which absorb the green and blue portion of the spectrum4 ,hence1 this type of adaptation might be conceived to be a survival of the fittest1 resulting in the natural selection of individuals of the highest total pigmentation4 ,but1 on the other hand1 there is experimental evidence to show that plants possess some means of varying their pigmentation in response to the character of the light which comes to them4 ,for1 it has been found that a complete change in color of certain highly colored plants can be produced in a single generation1 by growing the plants in boxes or chambers whose walls are composed entirely of differently colored glass1 so that the plants within receive light of only a particular part of the spectrum4 ,in such cases1 the plant1 starting with an initial natural color1 changes through a succession of colors until it finally reaches equilibrium at one which provides for the proper absorption of the right kind of light from the new supply which is available to it4 ,hence1 it seems proper to conclude that chromatic adaptation is not a process of natural selection1 but a definite result of an actual mechanism for adaptation to changed environmental conditions of supply of radiant energy4 ,,structural ,,adaptations ,changes in structure to meet special conditions of growth may be of several different types4 ,one of these1 which is often cited as an example of adaptation 7in this case1 the term is used with a significance quite different than that in which it is being used here7 is that of the development of unusual and often fantastic shapes of flowers1 which are so related to the anatomy of certain species of insects that visit these flowers in search of nectar1 that provision for the cross-fertilization of the plants is insured1 in that the pollen from the anthers of one flower becomes lodged on the body of the insect as it is withdrawing from the flower in such a way that it comes in contact with the pistil of a second flower as the insect enters it4 ,such flowers often have such peculiar shapes and lengths of nectar tubes1 etc41 that only a single species of insect1 whose anatomical shape is adapted to that particular blossom shape can enter the flower in its search for nectar4 ,it is clear that this form of morphological adaptation is a highly specialized one1 which can only be the result of a long process of evolutionary development4 ,it is obvious that the plant cannot possibly possess a mechanism1 or ability1 to alter its flower form in order to make it conform to the shape and length of the proboscis1 or other body parts1 of a particular species of insect4 ,either the insect or the plant1 or both1 must go through a process of evolutionary development in order to arrive at this form of mutual adaptation4 ,a form of true morphological adaptation 7in the sense in which we have been using the term7 is exhibited by many species of plants1 which are provided with many more buds1 or growing points1 than ever actually begin to grow4 ,for example1 the single plumule which develops from a germinating wheat embryo has at its upper end a hundred or more tiny growing points4 ,at the proper stage of its growth1 several of these tiny buds begin to grow into individual separate stems1 and the new wheat plant thus produces several stems from one seed and root system1 a process known as the stooling4 ,the number of stems in a single stool depends upon the number of the potential growing points which are stimulated into growth4 ,it varies from only two or three up to as many as thirty or forty1 and is apparently controlled by the favorable or unfavorable conditions of climate or nutrition at the time when the stooling takes place4 ,the plant is thus provided with a mechanism for adapting its possibilities of growth to the supply of growth-promoting material which is available to it4 ,many other plants produce far more buds than ever develop into growing tissues1 and buds which1 under normal conditions1 remain dormant1 under altered conditions start into growth and so provide for an adaptation of the total mass of the growing plant to correspond with the altered conditions of growth4 ,the actual means by which certain buds are stimulated into growth while others remain dormant1 or are inhibited from growing1 are as yet unknown4 ,two theories have been advanced4 ,one is that the growing buds absorb all available nutrition and the others remain dormant by reason of lack of growth-promoting material4 ,the other is that the vegetating 7growing7 tissue elaborates and sends to other parts of the organism one or more substances1 which actually inhibit growth of the other parts1 as dormant buds1 etc4 ,the experimental evidence which has been presented thus far is inconclusive1 but seems to favor the distribution of nutritional material as the governing factor1 although there is some evidence which seems to indicate that a supposed growth-inhibiting substance is actually translocated from rapidly-vegetating tissues to other parts of the plant4 ,there is1 however1 no explanation of how the buds1 or other tissues1 which do grow get their initial stimulus1 while the dormant buds do not4 ,after growth has once started1 the changes in osmotic pressure due to the accumulation and translocation of synthetized materials can account for the movement of new nutritional material for the synthetic processes into the growing organ2 but this would not account for the selective stimulation of only a part of the buds1 or possible growing points1 of a plant1 or for an adaptational development of others under altered conditions of growth4 ,the form of morphological adaptation which has been discovered in the course of the study of the native vegetation of the campos of ,brazil 7which have a very dry season and have been regularly burned over by the natives for many generations7 in which the papilionaceous shrubs have developed underground trunks1 or stems1 and seem actually to profit in luxuriance of growth when the rainy season comes on by reason of this morphological adaptation to the unusual environmental conditions1 is wholly inexplicable by any present knowledge of the science of plant growth4 ,,physiological ,,adaptations ,the type of adjustment to environmental conditions which does not result in any recognizable alteration in the structure of the plant1 but simply permits it to grow under new conditions1 manifests itself in many ways4 ,these adjustments are usually associated with differences in temperature during the growing season1 and for this reason1 most such examples of adaptation have been studied in connection with possible temperature reactions upon the growing organism4 ,however1 recent investigations seem to point strongly to the conclusion that the amount of light rather than the temperature of the new surroundings is the most important influence in determining the physiological processes known as the acclimatization of plants4 ,for example1 a very elaborate series of investigations has shown that the flowering stage in the development of plants is determined by the length of the daylight period per day1 irrespective of the actual amount of vegetative growth which the plant has made4 ,thus1 tobacco plants1 which during a period of long days grow to the height of #h or #aj feet before blossoming1 if grown at the same temperature in periods of short days 7or if kept in the dark during a portion of the longer days7 will blossom when less than #c feet in height and when the total mass of vegetative material which has been produced is less than one-third of that of the gigantic plants of the same variety grown with longer periods of illumination per day4 ,this same principle has been found to hold good for many widely different types of plants4 ,in some species1 however1 flowering is favored by long days1 and vegetative growth by short daylight illumination4 ,but in all species which have been studied1 there seems to be a direct relation between the length of day1 or the total illumination per day1 and the normal or abnormal functioning of the plant4 ,it is apparent that at least the physiological function of sexual reproduction 7flowering and seed-production7 is determined by the length of daylight illumination4 ,the duration of daylight per day which is necessary to induce the blossoming of the plants varies for different species1 but it is constant for individuals of the same species4 ,this adaptation of stage of growth to duration of daily illumination must1 therefore1 be an evolutionary character of the species4 ,hence1 it appears that in many cases physiological adaptation may be a direct response of the life-processes of the plant to the daily length of photochemical stimulation which it receives from solar light4 ,but there is1 as yet1 no explanation of how this 7or any other7 influence actually changes the vital processes of the plant protoplasm so as to bring about either a morphological adaptation of structure or a physiological adaptation of functions to altered conditions of growth4 ,,concluding ,,statements ,enough has been said to show how very inconclusive and unsatisfactory is our knowledge of the phenomena known as adaptation4 ,even the nomenclature used by different scientists to describe its various manifestations is confused and misleading4 ,for example1 certain crops are said to be adapted 7i4e41 suited7 to certain types of soils1 and vice versa2 crops are said to be adapted to given agricultural districts1 etc4 ,in this chapter1 an attempt has been made to arrange in some semblance of order some of the known manifestations of alteration of fixed habits of growth of plants in response to changes of environment1 and to point out some of the suggestions of possible explanations of these phenomena which have been presented by different investigators4 ,this presentation cannot be considered as anything other than an introduction to a field of study which is as yet almost entirely unexplored1 and1 like all other unexplored territory1 is full of mysteries4 ,if the study of this chapter serves to stimulate interest in these mysteries and wonders of plant life1 its purpose will have been accomplished4 ,,index ,bold-face figures indicate main references ,accelerators1 #aif4 ,accessory substances1 #ai4 ,achroo-dextrin1 #fa4 ,acid1 acetic1 #abe1 #abf1 #abh1 #acb1 #acc1 #aff4 arabic1 #fh4 arachidic1 #acc4 aspartic1 #afh1 #agg4 brassic1 #acc4 butyric1 #abf1 #acc4 capric1 #acc4 caprylic1 #acc4 carnaubic1 #adj4 cerotic1 #acc1 #adj4 citric1 #abe1 #abg4 convolvulinic1 #ha4 crotonic1 #acc4 diamino-oxysebacic1 #afi4 diamino-trioxydodecanic1 #afi4 digallic1 #if4 ellagic1 #if4 euxanthic1 #hd4 formic1 #be1 #abf1 #abh1 #acb4 galactonic1 #db4 gallic1 #if4 geddic1 #fi4 gluconic1 #db4 glucuronic1 #db1 #dc4 glutamic1 #afh1 #agg4 glycero-phosphoric1 #adb4 hydrocyanic1 #gg4 jalapinic1 #ha4 lauric1 #acc4 lignoceric1 #acc4 linoleic1 #acc4 linolenic1 #acc4 malic1 #abd1 #abg4 malonic1 #abd4 mannonic1 #db4 melissic1 #acc4 meta-pectic1 #fh1 #gj4 mucic1 #fh4 myristic1 #acc4 nitric1 #abe4 nucleic1 #afb4 oleic1 #acc4 oxalic1 #fh1 #abd1 #abe1 #abf1 #abh4 palmitic1 #acc1 #adj4 parapectic1 #gj4 pectic1 #ca1 #gj4 phosphoric1 #ada1 #adb1 #afb4 propionic1 #abf1 #aff4 pyrocatechuic1 #if4 quercitannic1 #ih4 racemic1 #ed4 ricinoleic1 #acc4 ruberythric1 #hc4 saccharic1 #db1 #fh4 salicylic1 #ha4 sarco-lactic1 #abh4 stearic1 #aca1 #acc4 succinic1 #abg1 #abh4 sulfuric1 #abe4 sylvinic1 #adi4 talonic1 #db4 tannic1 #ig1 #abg4 tartaric1 #abg4 uric1 #afj4 xanthoproteic1 #agc4 ,acid amides1 #aea4 ,acidity of protoplasm1 #bcd4 ,acid glucosides1 #ha4 ,acid potassium oxalate1 #abe4 ,acid potassium sulfate1 #hh4 ,acid salts1 #abd4 ,acids as toxins1 #bdf4 ,acid sodium sulfate1 #abe4 ,acrolein1 #ace4 ,acrose1 #bh4 ,activators1 #aif4 ,adamkiewicz's reaction1 #agc4 ,adaptations1 #bdi4 ,adenase1 #aij4 ,adenine1 #afj1 #afb4 ,adipo-celluloses1 #gd4 ,adsorption1 #bad4 sculetin1 #ha1 #hb4 sculin1 #ha1 #hb4 tiophyllin1 #ajf1 #ajg1 #aji4 tioporphyrin1 #ajh1 #aji1 #aaj4 ,alanine1 #afh1 #agg4 ,albumins1 #age1 #agf4 ,albuminoids1 #age1 #agf4 ,alcogel1 #bje4 ,alcohol1 ethyl1 #dj1 #abe4 benzyl1 #hj4 carnaubyl1 #ace4 ceryl1 #ace1 #adj4 cetyl1 #abi1 #ace4 coniferyl1 #hj4 melissyl1 #ace4 myricyl1 #abi1 #adj4 phytyl1 #ajd1 #aje4 polyhydric1 #ca4 ,alcohol glucosides1 #hj4 ,alcosol1 #bje4 ,aldehyde1 benzoic1 #adh4 cinnamic1 #adh4 formic 7see formaldehyde74 glyceric1 #ce4 ,aldehyde glucosides1 #hj4 ,aldehydrol1 #df4 ,aldonic acids1 #db1 #dd4 ,aldose1 #cb4 ,alizarin glucosides1 #gh4 ,alkalinity of protoplasm1 #bcd4 ,alkalies as toxins1 #bdg4 ,alkali salts1 #aj1 #bdg4 ,alkali soils1 #aj1 #ad4 ,alkaloidal reagents1 #aed1 #agb4 ,alkaloids1 #ah1 #bj1 #aea1 #aec1 #bdh4 ,allose1 #cf1 #cg4 ,allyl isosulfocyanide1 #hh1 #hi1 #adh4 ,allyl sulfide1 #adh4 alpha-glucose1 #df4 alpha-glucosides1 #ee4 alpha-methyl glucoside1 #dg4 ,altrose1 #cf1 #cg4 ,aluminium1 #d4 ,amandin1 #agj1 #agf4 ,amines1 #aea4 ,amino-acids1 #f1 #aea1 #aff1 #agi1 #bdh4 ,ammonia1 #aeb4 ,ammonium hydroxide1 #adb1 #aeb4 ,ammonium salts1 #f4 ,amorphous chlorophyll1 #ajd1 #aje ,amphoteric electrolytes1 #agb4 ,amygdalase1 #hg4 ,amygdalin1 #ha1 #hf4 ,amyl acetate1 #adh4 ,amylase1 #ahf1 #ahi1 #aia4 ,amylo-cellulose1 #fj4 ,amylo-dextrin1 #fa4 ,amylo-pectin1 #fj4 ,amylose1 #fj4 ,anergic food1 #b1 #ag4 ,animal nucleic acids1 #afb4 ,antagonism1 #ad4 ,anthocyans1 #hc1 #ajb1 #aae1 #aba4 ,anthocyanidins1 #aaf4 ,anthocyanin1 #ajb4 ,anthoxanthins1 #aag4 ,anthraquinone1 #hc4 ,antienzymes1 #abj1 #aig1 #aih4 ,antioxidase1 #abj4 ,antiscorbutic ,c1 #bdc4 ,apigenin1 #hd1 #aah4 ,apiin1 #hd4 ,apiose1 #hd4 ,araban1 #fi4 ,arabinose1 #ce1 #dd1 #fh1 #fi1 #hh4 ,arabinosides1 #ef4 ,arbutin1 #gg1 #gi4 ,arginine1 #afi1 #aga1 #agg4 ,arsenic1 #ac4 ,asymmetric carbon atom1 #cc4 ,atropine1 #aee1 #aef4 ,autotrophic plants1 #af1 #ah4 ,auximones1 #bci1 #bdj1 #bdd4 ,available plant food1 #d4 ,avenalin1 #agf4 ,baptigenin1 #gi4 ,baptisin1 #gi4 ,beeswax1 #acc4 ,beet sugar 7see sucrose74 ,berberine1 #aee4 ,betaine1 #aeb4 beta-glucase1 #ee4 beta-glucose1 #df4 beta-glucosides1 #ee4 beta-methyl glucoside1 #dg4 ,biogens1 #bbc4 ,biological significance1 #ai4 ,biuret reaction1 #agc4 ,borneol1 #adh4 ,boron1 #ac4 ,bromelin1 #ahi4 ,brucine1 #aee1 #aeg4 ,buffers1 #bcf4 ,butter fat1 #acc4 ,butyric acid ferment1 #aij4 ,cadaverine1 #aeb4 ,caffeine1 #afj4 ,calcifuges1 #i4 ,calciphiles1 #i4 ,calcium1 #c1 #e1 #i1 #aj1 #ad1 #fh4 ,calcium oxalate1 #abf4 ,campferitrin1 #aah4 ,campferol1 #aah4 ,camphene1 #adg4 ,camphor1 #adh4 ,cane sugar 7see sucrose74 ,caoutchouc1 #adg4 ,capillary segregation1 #bce4 ,carbohydrases1 #ahi4 ,carbohydrates1 #ah1 #bj1 #ba1 #cj1 #afc1 #bcd4 ,carbon dioxide1 #b1 #c1 #ah1 #ba1 #bb1 #bc1 #bd1 #dj1 #bbb4 ,carbonic acid1 #bbg4 ,carbon monoxide1 #bd4 ,carboxyl1 #abd4 ,carboxylases1 #ahf1 #aij4 ,carnauba wax1 #acc1 #adj4 ,carotin1 #aab1 #aac1 #aba4 ,carotinoids1 #ajb1 #aaa4 ,carvacrol1 #adh4 ,casein1 #afe4 ,castanin1 #agf4 ,castor oil1 #acj4 ,catalases1 #aij1 #aic4 ,catalysis1 #ahb4 ,catalysts1 #ag1 #be1 #ahc4 ,catechol tannins1 #ig4 ,catechin1 #ig4 ,catechu tannins1 #ig4 ,cellobiose1 #eb4 ,cell structure1 #bba4 ,cellulase1 #ga1 #ahf1 #ahi4 ,celluloid1 #gc4 ,cellulose1 #bj1 #de1 #fc1 #fg1 #gb4 ,cell-wall1 #i1 #ab1 #bbb4 ,cerebrosides1 #ada1 #add4 ,chemical resistance1 #baf4 ,cherry gum1 #fh4 ,chinovose1 #ce4 ,chlorine1 #ab4 ,chlorophyll1 #aj1 #aa1 #ba1 #bg1 #ajb1 #aje1 #aaj1 #aaa1 #aac1 #abb1 #bed4 ,chlorophyll a1 #ajc1 #ajf1 #ajg1 #aaa4 ,chlorophyll b1 #ajc1 #ajf1 #ajh1 #aaa4 ,chlorophyllase1 #ajd4 ,chlorophyllin a1 #ajf1 #ajg4 ,chlorophyllin b1 #ajf1 #ajg4 ,cholesterol1 #abi1 #acf4 ,choline1 #hi1 #ajc1 #ada1 #adb1 #aeb4 ,chromatic adaptations1 #bea1 #bec4 ,chromogens1 #ib1 #aai4 ,chromo-proteins1 #age4 ,chrysin1 #aag4 ,cinchonine1 #aee1 #aeg4 ,coagulated proteins1 #age4 ,coagulation enzymes1 #aij4 ,cocaine1 #aee1 #aeg4 ,cocoanut oil1 #acc4 ,codeine1 #aee1 #aeh4 ,coenzymes1 #aig4 ,cold-drawn oils1 #acg4 ,collodion1 #gc4 ,colloidal phenomena1 #ag1 #bjb4 ,colloidal solutions1 #bjd4 ,colloids1 #bjb4 ,colophene1 #adg4 ,colophony1 #adi4 ,compound celluloses1 #ga1 #gc4 ,conglutin1 #agf4 ,coniferin1 #hj4 ,coniine1 #aee1 #aef4 ,conjugated proteins1 #afe1 #agd1 #age4 ,continuous phase1 #bjc4 ,convolvulin1 #ha4 ,copper1 #ac1 #bdg4 ,cork tissue1 #ii1 #aja4 ,corn oil1 #acj4 ,corylin1 #agf4 ,cottonseed oil1 #acj4 ,critical elements1 #d4 ,crude fat1 #ada4 ,crystalline chlorophyll1 #ajd1 #aje4 ,crystalloids1 #bjb4 ,cumarin1 #ha1 #adh4 ,curarine1 #aeg4 ,cuto-celluloses1 #gd4 ,cyanidin1 #he1 #aaf4 ,cyanin1 #he4 ,cyanophore glucosides1 #hf4 ,cyanophyllin1 #ajg1 #ajh4 ,cyanoporphyrin1 #ajh4 ,cymarigenin1 #ij4 ,cymarin1 #ij4 ,cymarose1 #ij4 ,cystine1 #afh1 #aga4 ,cytase1 #gb1 #ahi4 ,cytosine1 #afa1 #afb4 ,daphnetin1 #ha1 #hb4 ,daphnin1 #ha4 ,deaminases1 #ahf1 #aij4 ,delphinidin1 #he1 #aaf4 ,delphinin1 #he4 ,derived proteins1 #agc1 #age1 #agg4 ,dextrin1 #ei1 #fa4 ,dextrinase1 #ahi4 d-galactose1 #cc4 d-glucose1 #cc4 ,dextrosans1 #ei4 ,dextrose 7see glucose74 ,dhurrin1 #hg4 ,diastase 7see amylase74 ,diastase of secretion1 #aia4 ,digitaligenin1 #hi4 ,digitalin1 #hi4 ,digitogenin1 #hi4 ,digitonin1 #hi1 #ij4 ,digito-saponin1 #ij4 ,digitoxigenin1 #hi4 ,digitoxin1 #hi4 ,digitoxose1 #hi4 ,diglycerides1 #aca4 ,diose1 #cj4 ,dioxyacetone1 #ce4 ,dipeptides1 #afg4 ,disaccharides1 #ca1 #dh4 ,dispersed phase1 #bjc4 ,dispersion medium1 #bjc4 ,dispersion phenomena1 #bjc4 ,drying oils1 #acb4 ,dulcitol series1 #cf4 ,edestin1 #agj1 #agf4 ,egg-albumin1 #afe4 ,electrical phenomena of protoplasm1 #bcc4 ,electrolytes1 #bac1 #bbg4 ,emulsoids1 #bjf1 #bad4 ,emulsions1 #bjf4 ,emulsin1 #ee1 #gg1 #hg1 #ahd1 #ahi4 ,enol1 #dd1 #ef4 ,enzymes1 #ag1 #ah1 #ai1 #bj1 #bc1 #bf1 #abj1 #aba1 #aha1 #ahc1 #aid1 #aii1 #bbd4 ,erepsin1 #ahi4 ,erythro-dextrin1 #fa4 ,erythrophyllin1 #ajg4 ,erythrose1 #ce4 ,essential elements1 #d4 ,essential oils1 #ah1 #adf1 #adg1 #bbd4 ,esterases1 #ahf1 #ahi4 ,esters1 #abd1 #abe1 #abi4 ,ether extract1 #ada4 ,etherial salts 7see esters74 ,ethersol1 #bje4 ,ethyl acetate1 #abe4 ,ethyl nitrate1 #abe4 ,excelsin1 #agf4 ,extracellular enzymes1 #ahd4 ,fats1 #ah1 #bj1 #abi1 #bbd1 #bbg4 ,fat-soluble ,a1 #bdc4 ,fatty acids1 #acb1 #adb4 ,fehling's solution1 #ci1 #dg4 ,fermentability1 #dj4 ,ferments 7see enzymes74 ,ferric salts1 #aa4 ,ferrous salts1 #aa4 ,fisetin1 #aah4 ,flavone1 #hb1 #hc1 #ajb4 ,flavonol1 #hd4 ,food1 #a4 ,formaldehyde1 #bb1 #bc1 #be1 #bf1 #bg1 #bdg4 ,frame-work material1 #bj1 #fg4 ,fraxetin1 #hb4 ,fraxin1 #hb4 ,fructose1 #bc1 #bh1 #cb1 #cf1 #ch1 #da1 #dd1 #de1 #dg1 #eg1 #afb4 ,fructosides1 #da1 #db4 ,fruit sugar 7see fructose74 ,fucose1 #ce4 ,fucoxanthin1 #ajb1 #aab1 #aad4 ,galactans1 #dg1 #ei1 #fc1 #gb4 ,galactoheptose1 #cf4 ,galactooctose1 #cf4 ,galactose1 #cb1 #cf1 #ch1 #de1 #dg1 #eg1 #gb1 #gg4 ,galactosides1 #da1 #db4 ,gaultherin1 #ha4 ,gel1 #agb1 #bje1 #bjh4 ,gelation1 #baj4 ,gel-formation1 #bjh1 #baa4 ,gentianose1 #eb1 #ec4 ,gentiobiose1 #di1 #eb1 #ec4 ,gentisin1 #aai4 ,gitaligenin1 #hi4 ,gitalin1 #hi4 ,gitogenin1 #hi4 ,gitonin1 #hi4 ,glaucophyllin1 #ajg4 ,gliadin1 #afe1 #agj1 #agf4 ,globulins1 #agj1 #age1 #agf4 ,glucase1 #ahf4 ,glucodecose1 #dd4 ,glucoheptose1 #cf1 #dd4 ,glucononose1 #cf4 ,glucooctose1 #cf4 ,glucoproteins1 #age4 ,glucose1 #bc1 #bh1 #cb1 #cf1 #cg1 #dj1 #da1 #db1 #dc1 #dd1 #de1 #df1 #eg1 #gg4 ,glucosidases1 #ahi4 ,glucosides1 #ah1 #bj1 #da1 #dh1 #ee1 #gf1 #ia1 #ic4 ,glue1 #baj4 ,glutelins1 #age1 #agf4 ,glutenin1 #agf4 ,glycerine 7see glycerol74 ,glycerol1 #abi1 #aca1 #acd1 #adb4 ,glycine1 #aff1 #afh1 #agg4 ,glycinin1 #agf4 ,glycogen1 #ei1 #fa4 ,glycyphyllin1 #gi4 ,graminin1 #ei1 #fb4 ,granulose1 #fj4 ,grape sugar 7see glucose74 ,guanase1 #aij4 ,guanine1 #afj1 #afb4 ,gulose1 #cf1 #cg4 ,gum arabic1 #fh4 ,gums1 #fb1 #fg1 #fh4 ,gum tragacanth1 #fi4 ,gun-cotton1 #gc4 ,hmatin1 #aaj4 ,hmatinic acid imide1 #aji4 ,hmatoporphyrin1 #aaj4 ,hmoglobin1 #aaj4 ,hmopyrrole1 #aji4 ,helicin1 #ha4 ,hemi-celluloses1 #fc1 #ga4 ,hemi-terpenes1 #adg4 ,heptoses1 #cj4 ,hesperidin1 #gi4 ,hesperitin1 #gi1 #hj4 ,heterotrophic plants1 #af4 ,hexosans1 #ei1 #fg4 ,hexoses1 #bb1 #bh1 #cj4 ,histidine1 #afi1 #agg4 ,histones1 #age1 #agf4 ,honey sugar 7see fructose74 ,hordein1 #aec1 #agj1 #agf4 ,hormones1 #ib1 #bci1 #bdj4 ,hot-drawn oils1 #acg4 ,humins1 #fg4 ,hydrastine1 #aee4 ,hydrazones1 #dj1 #di4 ,hydrocellulose1 #gc4 ,hydrogen peroxide1 #bf1 #bg1 #aij4 ,hydrogel1 #bje4 ,hydrolases1 #ahf1 #ahi4 ,hydroquinone1 #gg1 #gi4 ,hydrosol1 #bje4 ,hydroxy-phenyl ethyl amine1 #aec4 ,hygrine1 #aee1 #aef4 ,hyoscine1 #aee4 ,hyoscyamine1 #aef4 ,hypoxanthine1 #afj4 ,idain1 #he4 ,idose1 #cf1 #cg4 ,illuminating gas as a toxin1 #bdg4 ,imbibition1 #bji4 ,impermeable membranes1 #bbh4 ,indian yellow1 #hd4 ,indican1 #gh1 #he4 ,indigo1 #gh1 #hd4 ,indigotin1 #he4 ,indole1 #aeh4 ,indoxyl1 #he4 ,inhibitors1 #aif4 ,intracellular enzymes1 #ahd4 ,inulin1 #ei4 ,inulinase1 #fb1 #ahi4 ,invertase1 #ej1 #ahi1 #aia4 ,invert sugar1 #dg1 #ej4 ,iodine number1 #ach4 ,ionization phenomena1 #bbf4 ,iridin1 #gi4 ,irigenin1 #gi1 #hj4 ,iron1 #c1 #e1 #aa1 #aaj4 ,isochlorophyllin a1 #ajf1 #ajg1 #ajh4 ,isochlorophyllin b1 #ajf1 #ajg1 #ajh4 ,isohmopyrrole1 #aji4 ,isoleucine1 #afh4 ,isomaltose1 #ea4 ,isomerism1 #cb4 ,isoprene1 #adg4 ,isoquercitrin1 #hd4 ,isoquinoline1 #aee4 ,jalapin1 #ha4 ,japan wax1 #abi4 ,juglansin1 #agf4 ,ketose1 #cb4 ,lactam1 #ajd4 ,lactase1 #ef4 ,lactic acid ferment1 #aij4 ,lactone1 #ajd4 ,lactose1 #de1 #di1 #eb4 ,laudanosine1 #aeh4 ,laudanum1 #aeh4 ,lecithin1 #g1 #ada1 #adb1 #adc4 ,lecithoproteins1 #age4 ,legumelin1 #agf4 ,legumin1 #agj1 #agf4 ,leucine1 #aae1 #afh1 #agg4 ,leucomaines1 #aeb4 ,leucosin1 #agf4 l-galactose1 #cc4 l-glucose1 #cc4 ,levulosans1 #ei1 #fb4 ,levulose 7see fructose74 ,lichenin1 #fb4 ,light1 #ba1 #bec1 #beg4 ,lignocelluloses1 #gd4 ,lignose1 #ca4 ,limettin1 #hb4 ,limonene1 #adg4 ,linalyl acetate1 #adh4 ,linseed oil1 #acc4 ,lipases1 #ahf1 #ahi4 ,lipins 7see lipoids74 ,lipoids1 #abi1 #adj4 ,lipoproteins1 #age4 ,lupinine1 #aee4 ,lycopersicin1 #ajb1 #abb1 #aad4 ,lysine1 #afi1 #aga1 #agg4 ,lyxose1 #ce4 ,magnesium1 #c1 #e1 #i1 #aj1 #aa1 #ac1 #ad1 #fh4 ,maltase1 #ee1 #ahd1 #ahi4 ,maltose1 #de1 #di1 #ea1 #eb4 ,malvidin1 #he4 ,malvin1 #he4 ,mandelo-nitrile1 #gh1 #hh4 ,mandelo-nitrile glucoside1 #gg1 #hg4 ,manganese1 #d1 #ac4 ,manna1 #dg4 ,mannans1 #ei1 #fb1 #fc1 #gb4 ,mannite1 #dg4 ,mannitol1 #dg4 ,mannitol series1 #cf4 ,mannoheptose1 #cf1 #dd4 ,mannononose1 #cf4 ,mannooctose1 #cf4 ,mannosans 7see mannans74 ,mannose1 #cb1 #cf1 #cg1 #da1 #dd1 #de1 #dg1 #eg1 #gb4 ,mannosides1 #db4 ,maple sugar 7see sucrose74 ,maysin1 #agf4 ,melibiose1 #di1 #eb4 ,melizitose1 #eb4 ,menthol1 #adh4 ,mercerizing cotton1 #gc4 ,mercury1 #bdg4 ,merosinigrin1 #hh4 ,metallic salts1 #ac1 #bbd1 #bbg1 #bcg1 #bdg4 ,metal proteids1 #ad4 ,meta-pectin1 #gj4 ,metaproteins1 #age4 ,methylethylmalein imide1 #ajh4 ,methyl glucosides1 #db4 ,methyl pentoses1 #ce4 ,methyl salicylate1 #ha4 ,middle lamella1 #fg1 #gj4 ,millon's reaction1 #agc4 ,molisch's reaction1 #agd4 ,monoglycerides1 #aca4 ,monohydric alcohols1 #ace4 ,monosaccharides1 #ca1 #ce1 #de4 ,morin1 #aai4 ,morphine1 #aee1 #aeh4 ,morphological adaptations1 #bea1 #beb1 #bee4 ,mucilages1 #fg1 #gj4 ,muco-celluloses1 #gd4 ,muscarine1 #aeb4 ,mustard oils1 #hh1 #adh4 ,mustard oil glucosides1 #hh4 ,mutarotation1 #df1 #di4 ,myrosin1 #gg1 #hh1 #adi1 #ahi4 ,myrtillidin1 #he4 ,myrtillin1 #he4 ,narceine1 #aeh4 ,narcotine1 #aeh4 ,natural selection1 #bed4 ,neurine1 #aeb4 ,nicotine1 #aee1 #aef4 ,nitrates1 #f4 ,nitrile reaction1 #dc4 ,nitriles1 #dc1 #dd4 ,nitrogen1 #c1 #e1 #f1 #aea1 #afd4 ,non-drying oils1 #acb4 ,non-essential elements1 #d4 ,non-reducing sugars1 #ci1 #di4 ,nonoses1 #ca4 ,normal celluloses1 #gb4 ,nuclease1 #ahi4 ,nucleoproteins1 #afb1 #age4 ,nutrients1 #a4 ,octoses1 #ca4 ,,oenidin1 #he1 #aaf4 ,,oenin1 #he4 ,oils1 #abi4 ,oil of bergamot1 #adh4 ,oil of bitter almonds1 #hf1 #adh4 ,oil of cassia1 #adh4 ,oil of cinnamon1 #adh4 ,oil of garlic1 #adh4 ,oil of lavender1 #adh4 ,oil of mustard1 #adh4 ,olive oil1 #acj4 ,opium1 #aeh4 ,organic acids1 #ah1 #abd1 #bdh4 ,organized ferments1 #ahc4 ,ornamental pigments1 #ajb1 #abc4 ,ornithine1 #afi4 ,oryzenin1 #agf4 ,osazones1 #dj1 #da1 #di4 ,osmotic pressure1 #bac1 #bbh4 ,osones1 #da4 ,oxidases1 #ahf1 #aij1 #aic4 ,oxime1 #dd4 ,oxycellulose1 #gc4 ,oxycumarin glucosides1 #ha4 ,oxygenated oils1 #adg4 ,oxyhydroquinone1 #ie4 ,oxyproline1 #afi4 ,ponidin1 #he4 ,ponin1 #he4 ,palm oil1 #acc4 ,papain1 #ahi4 ,papaverine1 #aee1 #aeh4 ,para-dextran1 #fb4 ,para-isodextran1 #fb4 ,paralyzers1 #aif4 ,para-pectin1 #gj4 ,parasites1 #af4 ,peanut oil1 #acc4 ,pectase1 #ga4 ,pectinase1 #ahi4 ,pectins1 #bj1 #ca1 #fg1 #gj4 ,pecto-celluloses1 #gd4 ,pectose1 #ca1 #gj4 ,pelargonidin1 #he1 #aaf4 ,pelargonin1 #he4 ,pentosans1 #ca1 #fg1 #fh1 #gb4 ,pentoses1 #cj1 #afb4 ,pepsin1 #afg4 ,peptids1 #aff1 #afg1 #agf4 ,peptones1 #agf4 ,permeable membranes1 #bbh4 ,peroxidases1 #aij4 ,persimmons1 #ajj4 ,persuelose1 #cf4 ,phophytin1 #ajg1 #ajh4 ,phaselin1 #agf4 ,phaseolin1 #agf4 ,phenol1 #ie4 ,phenol glucosides1 #gi4 ,phenyl alanine1 #afh1 #agg4 ,phenyl hydrazine1 #dj4 ,phlein1 #fb4 ,phloretin1 #gi4 ,phloridzin1 #gi4 ,phloroglucinol1 #ie4 ,phosphates1 #g4 ,phosphatides1 #ada1 #adc4 ,phosphoproteins1 #age4 ,phosphorus1 #c1 #e1 #g4 ,photo-chemical action of light1 #bec1 #beg4 ,photolysis1 #bf4 ,photosynthesis1 #g1 #h1 #ah1 #ba1 #bb1 #bd1 #bed4 ,phycoerythrin1 #ajb1 #aae4 ,phycophin1 #ajb1 #aae4 ,phyllins1 #ajf1 #ajg4 ,phyllophyllin1 #ajg4 ,phyllopyrrole1 #aji4 ,physiological adaptations1 #beb1 #beg4 ,physiological use1 #ai4 ,phytase1 #ahi4 ,phytochlorin1 #ajh4 ,phytorhodin1 #ajh4 ,pigment glucosides1 #hb4 ,pigments1 #ah1 #ajb1 #bbd1 #bed4 ,pinene1 #adg4 ,piperidine1 #aed4 ,piperine1 #aee4 ,plant amines1 #aea1 #aeb1 #afc4 ,plant food1 #a4 ,plant nucleic acids1 #afb4 ,polybasic acids1 #abd4 ,polyhydric alcohols1 #ca4 ,polypeptides1 #afg4 ,polysaccharides1 #ei4 ,polyterpenes1 #adg4 ,poppy wax1 #adj4 ,populin1 #hj4 ,porphyrins1 #ajh4 ,potassium1 #c1 #e1 #h1 #aj1 #ac1 #ad4 ,primary amines1 #aeb4 ,proenzymes1 #aih4 ,proinulase1 #aii4 ,proinvertase1 #aii4 ,prolamins1 #age1 #agf4 ,proline1 #afi1 #agg4 ,prolipase1 #aii4 ,prooxidase1 #aii4 ,protamines1 #age1 #agf4 ,proteans1 #age4 ,proteases1 #ahf1 #ahi1 #aib4 ,protective colloids1 #bji4 ,proteins1 #g1 #ah1 #bj1 #aea1 #afb1 #afc1 #afd1 #bbd4 ,proteoses1 #age4 ,protoplasm1 #ag1 #bf1 #bba4 ,prulaurasin1 #hg4 ,prunase1 #hg4 ,prunasin1 #hg4 ,ptomaines1 #aeb4 ,purine1 #aei4 ,purine bases1 #aea1 #aei1 #afb4 ,purpurin1 #hc4 ,putrescine1 #aeb4 ,pyrimidine1 #afa4 ,pyrimidine bases1 #afa1 #afb4 ,pyrocatechol1 #ie4 ,pyrogallol1 #ie4 ,pyrogallol tannins1 #ig4 ,pyroxylin1 #gc4 ,pyrrophyllin1 #ajg4 ,pyrridine1 #aed4 ,pyrrolidine1 #aed4 ,quaternary amines1 #aeb4 ,quercetin1 #hd1 #aah4 ,quercitrin1 #hd4 ,quinine1 #aee1 #aeg4 ,quinoline1 #aee1 #aeh4 ,radiant energy1 #ai4 ,raffinose1 #de1 #eb1 #ec4 ,rape-seed oil1 #acj4 ,reducing sugars1 #ci1 #di4 ,reductases1 #ahf1 #aij4 ,reserve food1 #ba4 ,resenes1 #adi4 ,resins1 #ah1 #adf1 #adi4 ,resorcinol1 #ie4 ,respiration1 #ah1 #aba1 #bce1 #bcf4 ,rhamnase1 #gg1 #ahi4 ,rhamnetin1 #hd4 ,rhamnose1 #ce1 #eb1 #gg1 #gi4 ,rhodeose1 #ce1 #ha4 ,rhodophyllin1 #ajg4 ,ribose1 #ce4 ,ricin1 #agf4 ,rubiadin1 #hc4 ,rubiphyllin1 #ajg4 ,saccharide1 #ca4 ,salicin1 #hj4 ,saligenin1 #hj4 ,salinigrin1 #ha4 ,salts1 #bbd1 #bbg1 #bcg4 ,sambunigrin1 #hg4 ,sapogenins1 #ij4 ,saponification1 #acd4 ,saponification value1 #ach4 ,saponins1 #ij4 ,sapotoxins1 #ij4 ,saprophytes1 #af4 ,saturated acids1 #acb4 ,scopolin1 #hb4 ,secalin1 #fc4 ,secondary amines1 #aeb4 ,secretions1 #bj4 ,sedoheptose1 #cf4 ,semipermeable membranes1 #bbh4 ,sensitizers1 #bg4 ,serine1 #afh4 ,silicates1 #ab4 ,silicon1 #d1 #ab4 ,silver1 #bdg4 ,simple proteins1 #afe1 #agd1 #age4 ,sinalbin1 #hi4 ,sinalbin mustard oil1 #hi4 ,sinapin acid sulfate1 #hi4 ,sinigrin1 #hh4 ,sinistrin1 #fb4 ,sitosterol1 #acf4 ,skimmetin1 #ha1 #hb4 ,skimmin1 #ha4 ,soaps1 #acd1 #bjh4 ,sodium1 #d1 #i1 #ab1 #ac1 #ad4 ,sodium stearate1 #acc4 ,sol1 #bje4 ,soluble starch1 #fj4 ,sorbitol1 #dh4 ,sorbose1 #cf1 #ch1 #de1 #dh4 ,specific rotatory power1 #ch1 #ci4 1 of fructose1 #ci1 #dg4 1 of galactose1 #di4 1 of glucose1 #ci1 #dg4 1 of maltose1 #ea4 1 of raffinose1 #ec4 1 of sucrose1 #ci4 ,spermaceti1 #abi1 #acc4 ,stachydrine1 #aee4 ,stachyose1 #ed4 ,starch1 #h1 #bb1 #bh1 #cj1 #ca1 #de1 #ei1 #fd4 ,starch paste1 #fj4 ,stearin1 #aca1 #acd4 ,stereo-isomerism1 #cb4 ,stigmasterol1 #acf4 ,structural adaptations1 #bee4 ,structural isomerism1 #cb4 ,strychnine1 #aee1 #aeg4 ,substrate1 #ahf4 ,sucrase 7see invertase74 ,sucrose1 #bh1 #di1 #fd4 ,sugars1 #h1 #ah1 #bb1 #bh1 #cj1 #ca4 ,sulfur1 #c1 #e1 #aa1 #adh4 ,sulfuretted oils1 #adg1 #adh4 ,sulfur test1 #agd4 ,sunflower-seed oil1 #acj4 ,surface boundary phenomena1 #bca4 ,surface energy1 #bca4 ,surface tension1 #bca4 ,survival of the fittest1 #bed4 ,suspensoids1 #bjf1 #bad4 ,suspensions1 #bjf4 ,synergic foods1 #b1 #bj4 ,synthesis1 #ah4 ,tagatose1 #cf1 #ch1 #eg4 ,talose1 #cf1 #ch1 #db1 #eg4 ,tannins1 #ah1 #id1 #ig1 #ii1 #ajj1 #abg1 #bjh1 #bbd4 ,tannon group1 #if4 ,terpenes1 #adg4 ,tertiary amines1 #aeb4 ,tetrapeptids1 #afg4 ,tetrasaccharides1 #ed4 ,tetrose1 #cj1 #ce4 ,theobromine1 #afj4 ,theophylline1 #afj4 ,thioglucose1 #hh4 ,threose1 #ce4 ,thymine1 #afa1 #afb4 ,thymol1 #adh4 ,toxins1 #ac1 #bci1 #bdj1 #bde4 ,translocation diastase1 #aia4 ,trehalase1 #ea4 ,trehalose1 #di1 #ej4 ,triglycerides1 #aca4 ,trimethyl amine1 #aeb4 ,trimethyl glycocoll1 #adc4 ,triose1 #cj1 #ce4 ,trioxymethylene1 #bb1 #bc4 ,tripeptids1 #afg4 ,trisaccharides1 #ca1 #eb4 ,triticin1 #ei1 #fb4 ,tryptophane1 #afi1 #aga1 #agg4 ,tuberin1 #agf4 ,turanose1 #di1 #ec4 ,tyndall phenomena1 #bab4 ,tyrosine1 #aae1 #afh1 #agg4 ,unavailable plant food1 #d4 ,ultrafilter1 #bae4 ,ultramicroscope1 #bjc1 #bjd1 #bje1 #baa4 ,unorganized ferments1 #ahc4 ,unsaturated acids1 #acb1 #ach4 ,uracil1 #afa1 #afb4 ,urease1 #aij4 ,valine1 #afh4 ,vanillin1 #hj1 #adh4 ,vegetable bases1 #ah1 #aea4 ,vicianin1 #hh4 ,vicilin1 #agf4 ,vignin1 #agf4 ,vitamines1 #bci1 #bdj1 #bdb4 ,volatile oils1 #bj1 #adg4 ,water1 #c1 #ba1 #bb1 #bc1 #bbd4 ,water-soluble ,b1 #bdc4 ,waxes1 #ah1 #abi1 #adj4 ,weathering1 #d4 ,wood gum1 #fh4 ,wool fat1 #abi4 ,wound gum1 #fh1 #fi4 ,xanthine1 #afj4 ,xanthone1 #hb1 #hc1 #ajb4 ,xanthophyll1 #aab1 #aac1 #aba4 ,xanthopurpurin1 #hc4 ,xanthorhamnin1 #eb1 #hd4 ,xylan1 #fi4 ,xylose1 #ce1 #fh1 #fi4 ,xylosides1 #ef4 ,yeast1 #fa4 ,zein1 #afe1 #agj1 #agf1 #agg4 ,zinc1 #ac4 ,zymase1 #ea1 #ef1 #aij1 #aib4 ,zymogens1 #aih4 ,transcriber's ,notes3 ,the original spelling and minor inconsistencies in the spelling and formatting have been maintained4 ,the following words have been variably hyphenated in the original3 oxy7-7cumarin1 tri7-7saccharides1 sugar7-7like1 mono7-7saccharides1 sea7-7weeds1 di7-7sodium1 foam7-7like1 di7-7basic1 aldo7-7hexoses1 chromo7-7proteins1 galacto7-7octose1 gluco7-7octose1 keto7-7hexoses1 ligno7-7celluloses1 manno7-7octose1 para7-7pectic1 di7-7saccharides1 poly7-7saccharides4 ,the variable hyphenation has been retained in this version4 ,formatting3 ,text in italics was marked using underscores 7text7 and bold text using equals 7text74 ,the greek characters alpha and beta were marked as alpha and beta ,triple bonds were marked as trb in order to keep the lt#a-text4 ,vertical double bonds are marked with a broken bar 4 ,on page #abj the illustration of the decomposition of chlorophyll a and chlorophyll b could not be displayed due to its complex structure4 ,on page #adg the incorrect formulas of sitosterol1 ,c#bg;,h#dc,,oh and stigmasterol1 ,c#cj;,h#di,,oh were not changed due to the fact that the pure compounds were first isolated in #aibf after this book was published4 ,the table below lists all corrections applied to the original text4 p #c3 ,abderhalden's ,biochemische ,handlexicon - ,handlexikon p #aj3 with the blood pigment1 haematin - hmatin p #ae3 special type1 or unusual origin4 - period added p #ag3 that the photo-synthesis - photosynthesis p #bj3 ,experiments with algae - alg p #ba3 that when algae - alg p #bf3 ,experiments1 #bid pages1 #di - period deleted p #cf3 acts as a powerful anaesthetic - ansthetic p #dj3 ,die ,chemie der ,chlorophyll - ,die ,chemie des ,chlorophylls p #da3 many other poly-atomic - polyatomic p #ed3 ,left parenthesis at ,c#f of ,aldopentose deleted p #ee3 glucose yeilds - yields p #fj3 see pages - see page p #fa3 when heated to #hb ,c - #hb ,c p #fe3 power of #adh4 - #adh4 p #fg3 attack other dissacharides - disaccharides p #gd3 ,secalan - ,secalin p #gg3 ,erganzungsband - ,ergnzungsband p #gg3 ,handbuch der ,kohlenhydrate1 - closing quotes added p #hf3 ,erganzungsband - ,ergnzungsband p #hh3 has not yet been determined4 - period added p #hg3 by a plane hexagon1 thus ,illustration3 hexagon4 - period added p #ie3 ,c#ba;,c#bj,o#ab - ,c#ba;,h#bj,o#ab p #if3 blue grapes1 oenin - oenin p #if3 glucose oenidin - oenidin p #ig3 reactions of amydalin - amygdalin p #ih3 reactions of amgdalin - amygdalin p #ajg3 ,gallic acid1 - period changed to comma p #aab3 ,diospyrus - ,diospyros p #aad3 the following formulas3 - semicolon changed to colon p #aba3 obtained from aetioporphyrin - tioporphyrin p #aba3 that from tioporphryin - tioporphyrin p #abb3 chlorophylls are fluorescent1 - period changed to comma p #abb3 and red by reflected - comma deleted p #abb3 properties of these pigments1 - period changed to comma p #abc3 roots of carrots1 etc41 - second period changed to comma p #abc3 due to these pigments4 - period added p #abd3 ,,oh groups an addition - ,,oh groups in addition p #abd3 ,buchner funnel - ,bchner funnel p #abf3 that it contains leucin - leucine p #abf3 leucine and tyrosin - tyrosine p #acd3 ,willsttter - ,willsttter p #ace3 malonic acid - space added p #acg3 ,c#c;,h#e;,,cooh - ,c#c;,h#g;,,cooh p #ach3 commercially as a bye-product - by-product p #adf3 of the experiment4 ,microrganisms - ,microorganisms p #aed3 or through its basic 7,,oh7 group - or through its basic 7,n7 group p #aeh3 oxygenated and sulphuretted - sulfuretted p #afa3 ,aetherische ,oele1 ,harze1 - comma added p #afa3 ,f4 trans4 - period added p #afb3 ,,heusler1 ,f41 additional comma added p #afd3 ergot1 and hordeine - hordein p #aga3 ,c#e;,h#d,n#d,o#b1 - comma added p #aga3 gaunine - guanine p #agg3 ,,ch#c;,,chnh,,cooh - ,,ch#c;,,chnh #b;,,cooh p #agi3 monoamino-monocarboxylic acids3 - period changed to colon p #aha3 ,hystidine - ,histidine p #aha3 ,amadinn - ,amandin p #ahd3 which contains tyrosin - tyrosine p #ahd3 or a tyrosin-containing - tyrosine-containing p #ahe3 nitric acid on tyrosin - tyrosine p #ahf3 acids1 or alkalies4 - period added p #ahg3 ,juglansin1 - comma added p #ahg3 of walnut and butternut4 - period added p #ahg3 barley4 - period added p #aib3 reactions when caried - carried p #aig3 which accelerates the hydyrolysis - hydrolysis p #aih3 are further sub-divided - subdivided p #bjj3 ,butryic acid ferment - ,butyric acid ferment p #bjb3 and other microrganisms - microorganisms p #bjc3 alcohol and carbon dixoide - dioxide p #bje3 especially tyrosin - tyrosine p #bjf3 masses under the ultra-microscope - ultramicroscope p #bab3 ,j4 trans - ,j41 trans4 - comma added p #bah3 chemical nature and dialectric - dielectric p #bca3 ,dresden and ,leipsig - ,leipzig p #bca3 ,leisegang - ,liesegang p #bca3 ,beitrage - ,beitrge p #bcc3 observed under the ultra-microscope - ultramicroscope p #bcf3 is undoubtedly tetravalent1 period changed to comma p #bcg3 has a higher dialectric - dielectric p #bci3 ,as in well known - ,as is well known p #bda3 the organism to amother - another p #bdb3 having a foam-like - foamlike p #bdi3 ,bestimmung der ,oberflachenspannung - ,oberflchenspannung p #bdi3 ,the ,role of ,diffusion - ,the ,rle of ,diffusion p #bej3 ,,speigel1 ,l41 additional comma added p #beb3 of combination with4 water - of combination with water p #bee3 upon which the micro-organisms - microorganisms p #beh3 heavy metals2 hydro-carbon - hydrocarbon p #bfa3 ,campferitirin - ,campferitrin p #bfa3 ,certain algae - alg p #bfa3 certain types of algae - alg p #bfb3 mentioned above as acclimitization-acclimatization p #bgj3 succinic1 #abg1 #abh4 - period added p #bgj3 metapectic - meta-pectic p #bga3 mellisyl - melissyl p #bga3 myriscyl - myricyl p #bga3 ,asymetric - ,asymmetric p #bgb3 ,carbon dioxide1 #b1 #c1 #ah1 #ba1 #bb1 #bc1 - comma added p #bgc3 ,curarin - ,curarine p #bgd3 ,hesperitin1 #gi1 - period changed to comma p #bge3 ,linayl - ,linalyl p #bge3 ,leucosine - ,leucosin p #bge3 ,lupenine - ,lupinine p #bgf3 ,methylethylmallein imide - ,methylethylmalein imide p #bgf3 ,mryosin - ,myrosin p #bgf3 ,oil of lavendar - lavender p #bgf3 ,oxy-hydroquinone - ,oxyhydroquinone p #bgg3 ,photo-chemical action of light - ,photochemical action of light p #bgg3 ,proteases1 #ahf1 #ahi1 #ajb - ,proteases1 #ahf1 #ahi1 #aib p #bgh3 ,sorbose1 - period changed to comma