SAMUEL W. JOHNSON, M. A HOW CROPS GROW. A TREATISE ON THE CHEMICAL COMPOSITION, STRUCTURE AND LIFE OF THE PLANT, FOR STUDENTS OF AGRICULTURE. WITH NUMEROUS ILLUSTRATIONS AND TABLES OF ANALYSES BY SAMUEL W. JOHNSON, M. A., a PROFESSOR OP THEORETICAL AND AGRICULTURAL CHEMISTRY IN THE 8 HEP FIELD SCIENTIFIC SCHOOL OF YALE UNIVERSITY ; DIRECTOR OP THE CONNECTICUT AGRICULTURAL EXPERIMENT STATION; MEMBER OP THE NATIONAL ACADEMY OP SCIENCES. REVISED AND ENLARGED EDITION. NEW YORK: OBANGE JUDD COMPANY, 1900 Entered, according to Act of Congress, in the year 1890, by tht ORANGE JUDD COMPANY, In the Office of the Librarian of Congress, at "Washington. PREFACE. The original edition of this work, first published in 1868, was the result of studies undertaken in preparing instruction in Agricultural Chemistry which the Author has now been giving for three and thirty years. To- gether with the companion volume, "How Crops Feed," it was intended to present concisely but fully the then present state of Science regarding the Nutrition of the higher Plants and the relations of the Atmosphere, Water, and the Soil, to Agricultural Vegetation. Since its first appearance, our knowledge of the subject treated of in the present volume has largely participated in the remarkable advances which have marked all branches of Science during the last twenty years and it has been the writers' endeavor in this revised edition to post the book to date as fully as possible without greatly enlarging its bulk or changing its essential character. In attempting to reach this result he has been doubly embarassed, first, by the great and rapidly increasing amount of recent publications in which the materials for revision must be sought, and, second, by the fact that official duties have allowed very insufficient time for a careful and compre- hensive study of the literature. In conclusion, it is hoped that while the limits of the book make necessary the omission of a multitude of interesting details, little has been overlooked that is of real importance to a fair presentation of the subjects discussed. in TABLE OF CONTENTS. INTRODUCTION 1 DIVISION I.— CHEMICAL COMPOSITION OF THE PLANT. CHAP. L— THE VOLATILE PART OF PLANTS 12 § 1. Distinctions and Definitions.. 12 §2. Elements of the Volatile Part of Plants 14 § 3. Chemical Affinity 29 §4. Vegetable Organic Compounds or Proximate Elements 36 1. Water 37 2. Carbhydrat.es 39 3. Vegetable Acids 75 4. Fats 83 i». Albuminoids and Ferments 87 6. Amides 114 7. Alkaloids 120 8. Phosphorized Substances 122 CHAP. II.— THE ASH OF PLANTS 126 §1. Ingredients of the Ash 126 >cui-iiifiiil I i<- Elements 127 Carbon and its Compounds 128 Sulphur and its Compounds 129 Phosphorus and its Compounds 132 Chlorine and its Compounds 132 Silicon and its Compounds 134 Metallic Elements 138 Pot assium and its Compounds 138 Sodium and its Compounds 139 Calcium and its Compounds 139 Magnesium and its Compounds 140 Iron and its Compounds 141 Manganese and its Compounds 142 Salts 143 Carbonates 144 Sulphates 146 Phosphates 147 Chlorides 149 Nitrates 149 §2. Quantity, Distribution, and Variations of the Ash 151 Table of Proportions of Ash in Vegetable Matter 152 § 3. Special Composition of the Ash of Agricultural Plants 1G1 1. Constant Ingredients 161 2. Uniform composition of normal specimens of given plants 161 Table of Ash-analyses 164 3. Composition of Different parts of Plant 171 4. Like composition of similar plants 173 5. Variability of ash of same species 174 6. What is normal composition .of the ash of a plant? 177 7. To what extent is each ash-ingredient essential or accidental 180 Water-culture 180 Essential ash-ingredients 186 Is Sodium Essential to Agricultural Plants ? 186 Iron indispensable 192 Manganese unessential 193 Is Chlorine indispensable ? 194 Silica is not essential 197 Ash-ingredients taken up in excess 201 Disposition of superfluous matters 203 State of Ash-ingredients in plant 207 § 4. Functions of the Ash-ingredients 210 CHAP. III. — § 1. Quantitative Relations among the Ingredients of Plants 220 § 2. Composition of the plant in successive stages of growth 222 Composition and Growth of the Oat Plant 223 V Vt TABLE OP CONTENTS. DIVISION n.— THE STRUCTURE OF THE PLANT AND OFFICES OF ITS ORGA.NS. CHAP. I.— GENERALITIES 241 Organism, Organs 242 CHAP. IL— PRIMARY ELEMENTS OF ORGANIC STRUCTURE 24:; § 1. The Vegetable Cell 243 $2. Vegetable Tissues 254 CHAP. III.— VEGETATIVE ORGANS 256 § 1 . The Root 256 ( Mlices of Root 260 Apparent Search for Food 263 Contact of Roots with Soil 266 Absorption by Root 269 Soil Roots, Water Roots, Air Roots 273 § 2. The Stem 2*2 Buds 283 Layers, Tillering 286 Root-stocks 287 Tubers 288 Structure of the Stem — 289 Endogenous Plants 290 Exogenous Plants : 2!«i Sieve-cells 303 § 3. Leaves 306 Leaf Pores 309 Exhalation of Water Vapor 311 Offices of Foliage 314 CHAP. IV.— REPRODUCTIVE ORGANS 315 § 1. The Flower 316 Fertilization 319 Hybridizing 324 Species. Varieties 326 § 2. Fruit 330 Seed 332 Embryo 333 § 3. Vitality of seeds and their influence on the Plants they produce 335 Duration of Vitality 335 Use of old and unripe seeds ;j:{8 Density of seeds 339 Absolute weight of seeds 340 Signs of Excellence 345 Ancestry. Race-vigor 346 DIVISION III.— LIFE OF THE PLANT. CHAP. 1.— GERMINATION 349 § i. Introductory 349 § 2. Phenomena of Germination 350 § 3. Condi t inns of Germination 351 Proper Depth of Sowing 355 § 4. Chemical Physiology of Germi nation. 357 Chemistry uf .Malt.' 358 CHAP. II. — § 1. Food of the I'lant when independent of the Seed :«;<; § 2. The. Juices of the Plant. Their Nat lire and .Movement s:;ii!» Flow of Sap 370 Composition of Sap 376 Kinds of Sap 378 Motion of Nutrient Matters 379 §3. Causes of Motion of the Juices :K~> Porosity of Tissues :ix:> 1 111 tii I >it ion 3«»; Liquid Diffusion :VM Osmose or Membrane Diffusion :«I3 Root Act ion ,S!t<( Selective Power of Plant 4111 § 4. Mechanical effects of Osmose 406 APPENDIX. TABLE.— Composit ion of Agricultural Products 409 HOW CROPS GROW. INTRODUCTION. The object of agriculture is the production of certain plants and certain animals which are employed to feed, clothe and otherwise serve the human race. The first aim, in all cases, is the production of plants. Nature has made the most extensive provision for the spontaneous growth of an immense variety of vegetation ; but in those climates where civilization most certainly attains its fullest development, man is obliged to employ art to provide himself with the kinds and quantities of vegetable produce which his necessities or luxuries de- mand. In this defect, or, rather, neglect of nature, ag- riculture has its origin. The art of agriculture consists in certain practices and operations which have gradually grown out of an obser- vation and imitation of the best efforts of nature, or have been hit upon accidentally, or, finally, have been deduced from theory. The science of agriculture is the rational theory and systematic exposition of the successful art. Strictly considered, the art and science of agriculture are of equal age, and have grown together from the ear- 2 HOW CROPS GROW. liest times. Those who first cultivated the soil by dig- ging, planting, manuring and irrigating, had their suffi- cient reason for every step. In all cases, thought goes before work, and the intelligent workman always has a theory upon which his practice is planned. No farm was ever conducted without physiology, chemistry, and physics, any more than an aqueduct or a railway was ever built without mathematics and mechanics. Every suc- cessful farmer is, to some extent, a scientific man. Let him throw away the knowledge of facts and the knowl- edge of principles which constitute his science, and he has lost the elements of his success. The farmer without his reasons, his theory, his science, can have no plan ; and these wanting, agriculture would be as complete a failure with him as it would be with a man of mere science, destitute of manual, financial and executive skill. Other qualifications being equal, the more advanced and complete the theory of which the farmer is the mas- ter, the more successful must be his farming. The more he knows, the more he can do. The more deeply, com- prehensively, and clearly he can think, the more econ- omically and advantageously can he work. That there is any opposition or conflict between science and art, between theory and practice, is a delusive error. They are, as'they ever have been and ever must be, in the fullest harmony. If they appear to jar or stand in con- tradiction, it is because we have something false or incom- plete in what we call our science or our art ; or else we do not perceive correctly, but are misled by the narrowness and aberrations of our vision. It is often said of a ma- chine, that it was good in theory, but failed in practice. This is as untrue as untrue can be. If a machine has failed in practice, it is because it was imperfect in theory. It should be said of such a failure — the machine was good, judged by the best theory known to its inventor, but its incapacity to work demonstrates that the theory had a flaw. INTRODUCTION. 3 But, although art and science are thus inseparable, it must not be forgotten that their growth is not altogether parallel. There are facts in art for which science can, as yet, furnish no adequate explanation. Art, though no older than science, grew at first more rapidly in vigor and in stature. Agriculture was practiced hundreds and thousands of years ago, with a success that does not com- pare unfavorably with ours. Nearly all the essential points of modern cultivation were regarded by the Ro- mans before the Christian era. The annals of the Chi- -\ nese show that their wonderful skill and knowledge were in use at a vastly earlier date. So much of science as can be attained through man's unaided senses, reached considerable perfection early in the world's history. But that part of science which re- lates to things invisible to the unassisted eye, could not be developed until the telescope and the microscope had been invented, until the increasing experience of man and his improved art had created and made cheap the other inventions by whose aid the mind can penetrate the veil of nature. Art, guided at first by a very crude and im- perfectly-developed science, has, within a comparatively recent period, multiplied those instruments and means of research whereby science has expanded to her present proportions. The progress of agriculture is the joint work of theory and practice. In many departments great advances have been made during the last hundred years ; especially is this true in all that relates to implements and machines, and to the improvement of domestic animals. It is, however, in just these departments that an improved theory has had sway. More recent is the development of agriculture in its chemical and physiological aspects. In these directions the present century, or we might almost say the last fifty years, has seen more accomplished than all previous time. 4 HOW CROPS GROW. The first book in the English language on the subjects which occupy a good part of the following pages, was written by a Scotch nobleman, the Earl of Dundonald, and was published at London in 1795. It is entitled: "A Treatise showing the Intimate Connection that sub- sists between Agriculture and Chemistry." The learned Earl, in his Introduction, remarked that " the slow pro- gress which agriculture has hitherto made as a science is to be ascribed to a want of education on the part of the cultivators of the soil, and the want of knowledge in such authors as have written on agriculture of the intimate connection that subsists between the science and that of chemistry. Indeed, there is no operation or process, not merely mechanical, that does not depend on chemistry, which is defined to be a knowledge of the properties of bodies, and of the effects resulting from their different combinations. " Earl Dundonald could not fail to see that chemistry was ere long to open a splendid future for the ancient art that always had been and always is to be the prime support of the nations. But when he wrote, how feeble was the light that chemistry could throw upon the fundamental questions of agricultural science ! The chemical nature of atmospheric air was then a discovery of barely twenty years' standing. The composition of water had been known but twelve years. The only a- - count of the composition of plants that Earl Dundonald could give was the following: "Vegetables consist of mucilaginous matter, resinous matter, matter analogous to that of animals, and some proportion of oil. * * Besides these, vegetables contain earthy matters, formerly held in solution in the newlv-taken-in juices of the growing vegetable." He further explains by mentioning on subsequent pages that starch belongs to the mucil- Mninous matters, and that, on analysis by fire, vegetables yield soluble alkaline salts and insoluble phosphate of lime. But these salts, he held, were formed in the pro- INTKODUCTION". 5 cess of burning, their lime excepted, and the fact of their being taken from the soil and constituting the indispen- sable food of plants, his Lordship was unacquainted wilh. The gist of agricultural chemistry with him was, that plants are "composed of gases with a small proportion of calcareous matter;" for "although this discovery may appear to be of small moment to the practical farmer, yet it is well deserving of his attention and notice, as it throws great light on the nature and food of vegetables." The fact being then known that plants absorb carbonic acid from the air, and employ its carbon in their growth, the theory was held that fertilizers operate by promoting the conversion of the organic matter of the soil or of composts into gases, or into soluble humus, which were considered to be the food of plants. The first accurate analysis of a vegetable substance was not accomplished until fifteen years after the publication of Dundonald's Treatise, and another like period passed before the means of rapidly multiplying good analyses had been worked out by Liebig. So late as 1838, the Got- tingen Academy offered a prize for a satisfactory solution of the then vexed question whether the ingredients of ashes are essential to vegetable growth. It is, in fact, during the last fifty years that agricultural chemistry has come to rest on sure foundations. Our knowledge of the structure and physiology of plants is of like recent devel- opment. What immense practical benefit the farmer has galhered from this advance of science ! Chemistry has ascertained what vegetation absolutely demands for its growth, and points out a multitude of sources whence the requisite materials for crops can be derived. Cato and Columella knew indeed that ashes, bones, bird- dung and green manuring, as well as drainage and aera- tion of the soil, were good for crops ; but that carbonic acid, potash, phosphate of lime, and compounds of nitro- gen are the chief pabulum of vegetation, they did not 6 HOW CROPS GROW. know. They did not know that the atmosphere dissolves the rocks, and converts inert stone into nutritive soil. These grand principles, understood in many of their de- tails, are an inestimable boon to agriculture, and intelli- gent farmers have not been slow to apply them in prac- tice. The vast trade in phosphatic and Peruvian guano, and in nitrate of soda ; the great manufactures of oil of vitriol, of superphosphate of lime, of fish fertilizers ; and. the mining of fossil bones and of potash salts, are indus- tries largely or entirely based upon and controlled by chemistry in the service of agriculture. Every day is now the witness of new advances. The means of investigation, which, in the hands of the scien- tific experimenter, have created within the writer's mem- ory such arts as photography and electro-metallurgy, and have produced the steam-engine, the telegraph, the tele- phone and the electric light, are working and shall ever- more continue to work progress in the art of agriculture. This improvement will not consist so much in any re- markable discoveries that shall enable us to '• grow two blades of grass where but one grew before;" but in the gradual disclosure of the reasons of that which we have long known, or believed we knew; in the clear separa- tion of the true from the seemingly true, and in the ex- change of a wearying uncertainty for settled and positive knowledge. It is the boast of some who affect to glory in the suf- ficiency of practice and decry theory, that the former is based upon experience, which is the only safe guide. But this is a one-sided view of the matter. Theory is also based upon experience, if it be worth the name. The fancies of an ignorant and undisciplined mind are not theory as that term is properly understood. Theory, in the strict scientific sense, is always a deduction from facts, and the best deduction of which the stock of facts in our possession admits. It is therefore also the inter- INTRODUCTION". 7 pretation of facts. It is the expression of the ideas which facts awaken when submitted to a fertile imagination and well-balanced judgment. A scientific theory is intended for the nearest possible approach to the truth. Theory is confessedly imperfect, because our knowledge of facts is incomplete, our mental insight weak, and our judg- ment fallible. But the scientific theory which is framed by the contributions of a multitude of earnest thinkers and workers, among whom are likely to be the most gifted intellects and most skillful hands, is, in these days, to a great extent worthy of the Divine truth in nature, of which it is the completest human conception and ex- pression. Science employs, in effecting its progress, essentially the same methods that are used by merely practical men. Its success is commonly more rapid and brilliant, because its instruments of observation are finer and more skill- fully handled ; because it experiments more industriously and variedly, thus commanding a wider and more fruit- ful experience ; because it usually brings a more culti- vated imagination and a more disciplined judgment to bear upon its work. The devotion of a life to discovery or invention is sure to yield greater results than a desul- tory application made in the intervals of other absorbing pursuits. It is then for the interest of the farmer to avail himself of the labors of the man of science, when the latter is willing to inform himself in the details of practice, so as rightly'to comprehend the questions which press for a solution. Agricultural science, in its widest scope, comprehends a vast range of subjects. It includes something from nearly every department of human learning. The natu- ral sciences of geology, meteorology, mechanics, physics, chemistry, botany, zoology and physiology, are most in- timately related to it. It is not less concerned with so- cial and political economy. In this treatise it will not be 8 HOW CROPS GROW. attempted to touch, much less cover, all this ground, but some account will be given of certain subjects whose un- derstanding will be of the most direct service to the agri- culturist. The Theory of Agriculture, as founded on chemical, physical and physiological science, in so far as it relates to the Chemical Composition, the Structure and the Life of the Plant, is the topic of this volume. Some preliminary propositions and definitions may be serviceable to the reader. Science deals with Matter and Force. Matter is that which has weight and bulk. Force is the cause of changes in matter — it is appre- ciable only by its effects upon matter. Force resides in and is inseparable from matter. Force manifests itself in motion and change. All matter is perpetually animated by force — is there- fore never at rest. What we call rest in matter is simply motion too fine for our perceptions. The different kinds of matter known to science have been resolved into some seventy chemical elements or sim- ple substances. The elements of chemistry are forms of matter which have thus far resisted all attempts at their simplification or decomposition. In ordinary life we commonly encounter but twelve kinds of matter in their elementary state, viz. : Oxygen, Carbon, Mercury, Tin, Nitrogen, Iron, Copper, Silver, Sulphur, Zinc, Lead, Gold. The numberless other substances with which we are familiar, are mostly compounds of the above, or of twelve other elements, viz.: Hydrogen, Silicon, Calcium, Manganese, Phosphorus, Potassium, Magnesium, Chromium, Chlorine, Sodium, Aluminum, Nickel. INTRODUCTION". 9 So far as human agency goes, these chemical elements are indestructible as to quantity, and not convertible one into another. We distinguish various natural manifestations of force which, acting on or through matter, produce all material phenomena. In the subjoined scheme the recognized forces are to some extent classified and defined, in a man- ner that may prove useful to the reader. Act at sensi- ble uiul in- sensible distances Repulsive Attractive and Repulsive LIGHT HEAT (ELECTRICITY ) MAGNETISM | Radiant | Inductive ( (iKAVITATION Cosmical •Physical COHESION Act only at ( IJYSTALLIZATION insensible • distances Attractive I ADHESION SOLUTION Molecular OSMOSI: [AFFINITY . Atomic Chemical VITALITY Organic Biological Within human experience the different kinds of force are mostly convertible each into the others, and must therefore be regarded as fundamentally one and the same. Force, like matter, is indestructible. Force acting on a body may either increase its Kinetic Energy, or be stored up in it as Potential Energy. Kinetic (or ac- tual) energy is the energy of a moving body. Potential (or possible) energy is the energy which a body may be able to exert because of its state or position. A falling stone or running clock gives out actual energy. The stone while being raised, or the clock while winding, ac- quires and stores potential energy. In a similar manner kinetic solar energy, reaching the earth as light, heat and chemical force, rot only sets in operation the visible ac- tivities of plants, but accumulates in them a store of po- tential energy which, when they serve as food or fuel, re- appears as kinetic energy in the forms of animal heat, muscular and nervous activity, or as fire and light. The sciences that more immediately relate to agricult- ure are Physics, Chemistry and Biology. 10 HOW CROPS GROW. Physics, or "natural philosophy," is the science which considers the general properties of matter and such phenomena as are not accompanied by essential change in its obvious qualities. All the forces in the preceding scheme, save the last two, manifest themselves through matter without destroying or masking the matter itself. Iron may be hot, luminous, or magnetic, may fall to the ground, be melted, welded, and crystallized ; but it re- mains iron, and is at once recognized as such. The forces whose play does not disturb the evident characters of sub- stances are physical. Chemistry is the science which studies the proper- ties peculiar to the various kinds of matter, and those phenomena which are accompanied by a fundamental change in the matter acted on. Iron rusts, wood burns, and both lose all the external characters that serve for their identification. They are, in fact, converted into other substances. Chemical attraction, affinity, or chem- ism, as it is variously termed, unites two or more ele- ments into compounds, unites compounds together into more complex compounds ; and, under the influence of heat, light, and other agencies, is annulled or overcome, so that compounds resolve themselves into simpler com- binations or into their elements. Chemistry is the science of composition and decomposition ; it considers the laws and results of affinity. Biology, or physiology, unfolds the laws of the propagation, development, sustenance, and death of liv- ing organisms, both plants and animals. When we assert that the object of agriculture is to de- velop from the soil the greatest possible amount of cer- tain kinds of vegetable and animal produce at the least cost, we suggest the topics which are most important for the agriculturist to understand. The farmer deals with the plant, with the soil, with manures. These stand in close relation to each other, INTRODUCTION". 11 and to the atmosphere which constantly surrounds and acts upon them. How the plant grows, — the conditions under which it flourishes or suffers detriment, — the ma- terials of which it is made, — the mode of its construction and organization, — how it feeds upon the soil and air, — how it serves as food to animals, — how the air, soil, plant, and animal stand related to each other in a per- petual round of the most beautiful and wonderful trans- formations,— these are some of the grand questions that come before us ; and they are not less interesting to the philosopher or man of culture, than important to the farmer who depends upon their practical solution for his comfort ; or to the statesman, who regards them in their bearings upon the weightiest of political considerations. DIVISION 1. CHEMICAL COMPOSITION OF THE PLANT. CHAPTER 1. THE VOLATILE PAET OF PLANTS. v !• DISTINCTIONS AND DEFINITIONS. ORGANIC AND INORGANIC MATTER. —All matter may be divided into two great classes — Organic and Inorganic. Organic matter is the product of growth, or of vital organization, whether vegetable or animal. It is mostly combustible, i. e., it may be easily set on fire, and burns away into invisible gases. Organic matter either itself constitutes the organs of life and growth, and has a pecu- liarly organized structure, inimitable by art, — is made up of cells, tubes or fibres (wood and flesh) ; or else is a mere result or product of the vital processes, and desti- tute of this structure (sugar and fat). All matter which is not a part or product of a living organism is inorganic or mineral matter (rocks, soils, water, and air). Most of the naturally-occurring forms of inorganic matter which directly concern agricultural chemistry are incombustible, and destitute of anything like organic structure. By the processes of combustion and decay, organic matter is disorganized or converted into inorganic matter, while, on the contrary, by vegetable growth inorganic matter is organized, and becomes organic, 13 14 HOW CROPS GRO\V. Organic matters are in general characterized by com- plexity of constitution, and are exceedingly numerous and various ; while inorganic bodies are of simpler com- position, and comparatively few in number. VOLATILE AND FIXED MATTER. — All plants and ani- mals, taken as a whole, and all of their organs, consist of a volatile and fixed part, which may be separated by burning ; the former — usually by far the larger share — passing into and mingling with the air as invisible gases ; the latter — forming, in general, but from one to five per cent, of the whole — remaining as ashes. EXPERIMENT 1.— A splinter of wood heated in the flame of a lamp takes fire, burns, and yields i-nlntih- nnitti-r. which consumes with flame, and ashes, which are the only visible residue of the combustion. Many organic bodies, products of life, but not essential vital organs, as sugar, citric acid, etc., are completely volatile when in a state of purity, and leave no ash. USE OF THE TERMS ORGANIC AND INORGANIC.— -It is usual among agricultural writers to confine the term or- ganic to the volatile or destructible portion of vegetable and animal bodies, and to designate their ash-ingredients as inorganic matter. This is not an entirely accurate distinction. What is found in the ashes of a tree or of a seed, in so far as it was an essential part of the organism, was as truly organic as the volatile portion, and, by sub- mitting organic bodies to fire, they may be entirely con- verted into inorganic matter, the volatile as well as the fixed parts. ULTIMATE ELEMENTS THAT CONSTITUTE THE PLANT.— Chemistry has demonstrated that the volatile and de- structible part of organic bodies is chiefly made up of four substances, viz. : carbon, oxygen, hydrogen, and nitrogen, and contains two other elements in lesser quantity, viz. : sulphur and phosphorus. In the ash we may find phos- phorus, sulphur, silicon, chlorine, potassium, sodium, cal- THE VOLATILE PART OP PLANTS. 15 cium, magnesium, iron, and manganese, as well as oxy- gen, carbon, and nitrogen.* These fourteen bodies are elements, which means, in chemical language, that they cannot be resolved into other substances. All the varieties of vegetable and ani- mal matter are compounds, — are composed of and may be resolved into these elements. The above-named elements being essential to the or- ganism of every plant and animal, it is of the highest im- portance to make a minute study of their properties. ELEMENTS OF THE VOLATILE PART OF PLANTS. For the sake of convenience we shall first consider the elements which constitute the combustible part of plants, viz. : Carbon, Nitrogen, Sulphur, Oxygen, Hydrogen, Phosphorus. The elements which belong exclusively to the ash will be noticed in a subsequent chapter. Carbon, in the free state, is a solid. We are familiar with it in several forms, as lamp-black, charcoal, black- lead, and diamond. Notwithstanding the substances just named present great diversities of appearance and physical characters, they are identical in a certain chem- ical sense, as by burning they all yield the same product, viz. : carbonic acid gas, also called carbon dioxide. That carbon constitutes a large part of plants is evi- dent from the fact that it remains in a tolerably pure state after the incomplete burning of wood, as is illus- trated in the preparation of charcoal. * Rarely, or to a slight extent, lithium, rubidium, iodine, bromine, fluorine, barium, copper, zinc, titanium, and boron. 16 HOW CROPS GROW. EXP. 2. — If a splinter of dry pine wood be set on fire and the burning end be gradually passed into the mouth of a narrow tube (see figure 1), whereby the supply of air is cut off, or if it be thrust into sand, the burning is incomplete, and a stick of charcoal re- mains. Carbonization and Charring are terms used to express the blackening of organic bodies by heat, and are due to the separation of carbon in the free or uncombined state. The presence of carbon in animal matters also is shown by subjecting them to incomplete com- bustion. EXP. 3. — Hold a knife-blade in the flame of a tallow candle ; the full access of air is thus prevented,— a portion of carbon ~~ .. escapes combustion, and is deposited on the blade in the form °' ' of lamp-black. Oil of turpentine and petroleum (kerosene) contain so much carbon that a portion ordinarily escapes in the free state as smoke, when they are set on fire. When bones are strongly heated in closely-covered iron pots, until they cease yielding any vapors, there remains in the vessels a mixture of impure carbon with the earthy matter (phosphate of lime) of the bones, which is largely used in the arts, chiefly for refining sugar, but also in the manufacture of fertilizers under the name of animal char- coal, or bone-black. Lignite, bituminous coal, anthracite, coke — the porous, hard, and lustrous mass left when bituminous coal is heated with a limited access of air, and the metallic ap- pearing gas-carbon that is found lining the iron cylinders in which illuminating coal-gas is prepared, all consist largely or chiefly of carbon. They usually contain more or less incombustible matters, as well as a little oxygen, hydrogen, nitrogen, and sulphur. The different forms of carbon possess a greater or less degree of porosity and hardness, according to their origin and the temperature at which they are prepared. Carbon, in most of its forms, is extremely indestructi- THE VOLATILE PAKT OF PLANTS. 17 ble under ordinary circumstances. Hence stakes and fence posts, if charred before setting in the ground, last much longer than when this treatment is neglected. The porous varieties of carbon, especially wood char- coal and bone-black, have a remarkable power of absorb- ing gases and coloring matters, which is taken advantage of in the refining of sugar. They also destroy noisome odors, and are used for purposes of disinfection. Carbon is the characteristic ingredient of all organic compounds. There is no single substance that is the ex- clusive result of vital organization, no ingredient of the animal or vegetable produced by their growth, that does not contain this element. Oxygen. — Carbon is a solid, and is recognized by our senses of sight and feeling. Oxygen, on the other hand, is an air or gas, invisible, odorless, tasteless, and not dis- tinguishable in any way from ordinary air by the unas- sisted senses. It exists in the free (uncombined) state in the atmos- phere we breathe, but there is no means of obtaining it pure except from some of its compounds. Many metals unite readily with oxygen, forming compounds (oxides) which by heat separate again into their ingredients, and thus furnish the means of procuring pure oxygen. Iron and copper, when strongly heated and exposed to the air, acquire oxygen, but from the oxides of these metals (forge cinder, copper scale) it is not possible to separate pure oxygen. If, however, the metal mercury (quicksil- ver) be kept for a long time near the temperature at which it boils, it is slowly converted into a red powder (red precipitate, red oxide of mercury, or mercuric ox- ide), which on being more strongly heated is decomposed, yielding metallic mercury and gaseous oxygen in a pure state. The substance usually employed as the most convenient source of oxygen gas is the white salt called potassium 18 HOW CROPS GROW. chlorate. Exposed to heat, this body melts, and present- ly evolves oxygen in great abundance. EXP. 4.— The following figure illustrates the apparatus employed for preparing and collecting this gas. A tube of difficultly fusible glass, 8 inches long and J inch wide, con- tains the red oxide of mercury or potassium chlorate.* To its mouth is connected, air-tight, by a cork, a narrow tube, the free extremity of which passes under the shelf of a tub nearly filled with water. The shelf has, beneath, a funnel-shaped cavity opening above by a narrow orifice, over which a bottle filled with water is inverted. Heat being Fig. 2. applied to the wide tube, the common air it contains is first expelled, and presently, oxygen bubbles rapidly into the bottle and displaces the water. When the bottle is full, it may be corked and set aside, and its place supplied by another. Fill four pint bottles with the gas, and set them aside with their mouths in tumblers of water. From one ounce of potassium chlorate about a gallon of oxygen gas may be thus obtained, which is not quite pure at first, but becomes nearly so on standing over water for some hours. When the escape of gas becomes slow and cannot be quickened by inn-eased heat, remove the delivery- tube from the water, to prevent the latter receding and breaking the apparatus. As this gas makes no peculiar impressions on the senses, *The potassium chlorate is best mixed with about one-quarter its weight Of powdered black oxide of manganese, as this facilitates the preparation, and renders the heat of a common alcohol lamp sufficient. THE VOLATILE PART OF PLANTS. 19 we employ its behavior toward other bodies for its recog- nition. EXP. 5. — Place a burning splinter of wood in a vessel of oxygen (lifted for that purpose, mouth upward, from the water). The flame is at once greatly increased in brilliancy. Now remove the splinter from the bottle, blow out the flame, and thrust the still glowing point into the oxygen. It is instantly relighted. The experiment may be repeated many times. This is the usual test for oxygen gas. Combustion. — When the chemical union of two bodies takes place with such energy as to produce visible phe- nomena of fire or flame, the process is called combustion. Bodies that burn are combustibles, and the gas in which a substance burns is called a supporter of combustion. Oxygen is the grand supporter of combustion, and nearly all cases of burning met with in ordinary experi- ence are instances of chemical union between the oxygen of the atmosphere and some other body or bodies. The rapidity or intensity of combustion depends upon the quantities of oxygen and of the combustible that unite within a given time. Forcing a stream of air into a fire increases the supply of oxygen and excites a more vigorous combustion, whether it be done by a bellows or result from ordinary draught. Oxygen exists in our atmosphere to the extent of about one-fifth of the bulk of the latter. When a burning body is brought into unmixed oxygen, its combustion is, of course, more rapid than in ordinary air, four-fifths of which is a gas, presently to be noticed, that is compara- tively indifferent in its chemical affinities toward most bodies. In the air a piece of burning charcoal soon goes out ; but if plunged into oxygen, it burns with great rapidity and brilliancy. EXP. 6.— Attach a slender bit of charcoal to one end of a sharpened wire that is passed tlu-ou^h a wide cork or card; heat the charcoal to redness in the flame of a lamp, and then insert it into a bottle of oxy- gen, Fig. 3. When the combustion lias declined, a suitable test applied HOW CROPS GROW. to the air of the bottle will demonstrate that another invisible gas has taken the place of the oxygen. Such a test \x/iini--iruti'.r.* On pouring some of this into the buttle and agitating vigorously, the previously clear liquid becomes milky, and, oil standing, a white deposit, or jii-i-cijiitti/r. as tin- chemist terms it, gathers at the bottom of the vessel. Carbon, by thus uniting to oxygen, yields <•« i-lmnir m-itl. gas, which in its turn combines with lime, producing carbonate of lime. These substances will be further noticed in a subsequent chapter. Metallic iron is incombustible in the at- mosphere under ordinary circumstances, but if heated to redness and brought into pure oxygen gas, it burns as readily as wood burns in the air. Fig. 3. EXP. 7.— Provide a thin knitting-needle, heat one end red hot, and sharpen it by means of a file. Thrust the point thus made into a splinter of wood (a bit of the stick of a match, J inch long); pass the other end of the needle through a wide, flat cork for a support; set the wood on fire, and immerse the needle in a bottle of oxygen, Fig. 4. After the wood consumes, the iron itself takes fire and burns with vivid scintillations. It is converted into two distinct <>;> -ittrxoj 'iron, of which one,— ferric oxide, — will be found as a yellowish-red coating on the sides of the bottle ; the other,— magnetic oxide,— will fuse to black, brittle globules, which falling, often melt quite into the glass. Fig. 4. The only essential difference between these and ordi- nary cases of combustion is the intensity with which the process goes on, due to the more rapid access of oxygen to the combustible. Many bodies unite slowly with oxygen, — oxidize, as it is termed, — without these phenomena of light and intense heat which accompany combustion. Thus iron rusts, lead tarnishes, wood decays. All these processes are cases of oxidation, and cannot go on in the absence of oxygen. Since the action of oxygen on wood and other organic matters at common temperatures appears to be analogous * To prepare lime-water, put a piece of unslaked lime, as large as a chestnut, into a pint of water, and after it lias fallen to powder, agitate the whole fora few minutes in a well-stoppered bottle. On standing, the excess of lime will settle, and the perfectly clear liquid above it is ready for use. THE VOLATILE PAKT OF PLANTS. 21 in a chemical sense to actual burning, Liebig has pro- posed the term eremacausis (slow burning), to designate the chemical process of oxidation which takes place in decay, and which is concerned in many transformations, as in the making of vinegar and the formation of salt- peter. * Oxygen is necessary to organic life. The act of breath- ing introduces it into the lungs and blood of animals, where it aids the important office of respiration. Ani- mals, and plants as well, speedily perish if deprived of free oxygen, which has therefore been called vital air. Oxygen has a nearly universal tendency to combine with other substances, and form with them new com- pounds. With carbon, as we have seen, it forms carbonic acid gas or carbon dioxide. With iron it unites in vari- ous proportions, giving origin to several distinct oxides. In decay, putrefaction, fermentation, and respiration, numberless new products are formed, the results of its chemical affinities. Oxygen is estimated to be the most abundant body in nature. In the free state, but mixed with other gases, it constitutes one-fifth of the bulk of the atmosphere. In chemical union with other bodies, it forms eight-ninths of the weight of all the water of the globe, and one-third of its solid crust, — its soils and rocks, — as well as of all the plants and animals which exist upon it. In fact, there are but few compound substances occurring in or- dinary experience into which oxygen does not enter as a necessary ingredient. Nitrogen. — This body is the other chief constituent of the atmosphere, of which it makes up about four-fifths the bulk, and in which its office would appear to be * Recent investigation has demonstrated that the oxidations which Liebig classed under the term cremacausis. arc for the most part strict- ly dependent on the vital processes of extremely minute organisms, which arc in general characterized by the terms microbes or micro- denies, and arc more specitically designated bacteria, i. e., "rod-shaped animalcules or plaiitlets." 22 HOW CROPS GROW. mainly that of diluting and tempering the affinities of oxygen. Indirectly, however, it serves other most im- portant uses, as will presently be seen. For the preparation of nitrogen we have only to remove the oxygen from a portion of atmospheric air. This may be accomplished more or less perfectly by a variety of methods. We have just learned that the process of burn- ing is a chemical union of oxygen with the combustible. If, now, we can find a body which is very combustible and one which at the same time yields by union with ox- ygen a product that may be readily removed from the air in which it is formed, the preparation of nitrogen from ordinary air becomes easy. Such a body is phosphorus, a substance to be noticed in some detail presently. EXP. 8.— The bottom of a dinner-plate is covered half an inch deep with water; a bit of chalk hollowed out into a little cup is floated on the water by means of a large flat cork or a piece of wood ; into this cup a morsel of dry phosphorus as large as a pepper- corn is placed, which is then set on fire and covered by a capacious glass bottle or bell-jar. The phosphorus burns at first with a vivid light, which is presently ob- scured by a cloud of snow-like phosphoric acid. The combustion goes on, however, until nearly all the oxy- gen is removed from the included air. The air is at first expa'nded by the heat of the flame, and a portion of it escapes from the vessel; afterward it diminishes in volume as its oxygen is removed, so that it is need- fill to pour water on the plate to prevent the external air from passing into the vessel. After some time the white fume will entirely fall, and be absorbed by the water, leaving the inclosed nitro- gen quite clear. EXP. 9.— Another instructive method of preparing nitrogen is the fol- lowing: A handful of green vitriol (protosulphate of iron or ferrous sulphate, is dissolved in half a pint of water, the solution is put into a quart bottle, a gill of ammonia-water or fresh potash-lye is added, the bottle stoppered, and the mixture vigorously agitated for some minutes ; the stopper is then lifted, to allow fresh air to enter, and the whole is again agitated as before. This is repeated occasionally for half an hour <.r nioie. until no further absorption takes place, when nearly pure nitrogen remains in the bottle. Free nitrogen, under ordinary circumstances, mani- fests no active properties, but is best characterized by its chemical indifference to most other bodies. That it is THE VOLATILE PART OF PLANTS. 23 incapable of supporting combustion is proved by the first method we have instanced for its preparation. EXP. 10. — A burning splinter is immersed in the bottle containing the nitrogen prepared by the second method, Exp. 9 ; the flame immediate- ly goes out. Nitrogen cannot maintain respiration, so that animals perish if confined in it. Vegetation also dies in an at- mosphere of this gas. For this reason it was formerly called .Azote (against life). In general it is difficult to effect direct union of nitrogen with other bodies, but at a high temperature, in presence of alkalies, it unites with carbon, forming cyanides. The atmosphere is the great store and source of nitro- gen in nature. In the mineral kingdom, especially in soils, it occurs in small relative proportion, but in large aggregate quantity as an ingredient of saltpeter and other nitrates, and of ammonia. It is a constant constituent of all plants, and in the animal it is a never-absent com- ponent of the working tissues, the muscles, tendons and nerves, and is hence an indispensable ingredient of food. Hydrogen. — Water, which is so abundant in nature, and so essential to organic existence, is a compound of two elements, viz. : oxygen, that has already been consid- ered, and hydrogen, which we now come to notice. Hydrogen, like oxygen, is a gas, destitute, when pure, of either odor, taste, or color. It does not occur nat- urally in the free state, except in small quantity in the emanations from boiling springs and volcanoes. Its most simple preparation consists in abstracting oxygen from water by means of agents which have no special affinity for hydrogen, and therefore leave it uncombined. Sodium, a metal familiar to the chemist, has such an attraction for oxygen that it decomposes water with great rapidity. EXP. 11. — Hydrogen is therefore readily procured by inverting a bot- tle full of water in a bowl, and inserting into it a bit of sodium as large as a pea. The sodium should nrst be wiped tree from the naphtha in HOW CROPS GROW. which it is kept, and then be wrapped tightly in several folds of paper. On bringing it, thus prepared, under the mouth of the bottle, it floats upward, and when the water penetrates the paper, an abundant escape of gas occurs. Metallic iron, when at a red heat, rapidly decomposes water, uniting with oxygen and setting hydrogen free, as may be shown by passing steam from boiling water through a gun-barrel filled witli iron-turnings and heated to bright redness. Certain acids which contain hydro- gen are decomposed by iron, zinc, and some other metals, their hydrogen being separated as gas, while the metal takes the place of the hydrogen with formation of a salt. Hydrochloric acid (formerly called muriatic acid) is a compound of hydrogen with chlorine, and may accord- ingly be termed hydrogen chloride. When this acid is poured upon zinc the latter takes the chlorine, forming zinc chloride, and hydrogen escapes as gas. Chemists represent such changes by the use of symbols (first letters of the names of chemical elements), as follows : =1 2 (H Cl) + Zn = Zn C12 + H, EXP. 12.— Into a bottle fitted with cork, funnel, and delivery tubes (Fig. 6) an ounce of iron tacks or zinc clippings is introduced, a gill <>t' water is poured upon them, and lastly an ounce of hydro- chloric acid is added. A brisk effervescence shortly com- mences, owing to the escape of nearly pure hydrogen gas, which may be collected in a bottle filled with water as di- rected for oxygen. The first portions that pass over are mixed with air. nml xlmn/rf In ri-ji-i-ii-gen, chlorine and a few others exeepted. The atomic weights here given are most ly whole, numbers. The actual atomic weights, as experimentally determined, differ from the above by small I'raci ions, which may be neglected. THE VOLATILE PART OF PLANTS. 33 Multiple Proportions. — When two or more bodies nnite in several proportions, their quantities, when not expressed by the atomic weights, are twice, thrice, four, or more times, these weights ; they are multiples of the atomic weights by some simple number. Thus, carbon and oxygen form two commonly occurring compounds, viz., carbon monoxide, consisting of one atom of each in- gredient, and carbon dioxide, which contains to one atom, or 12 parts by weight, of carbon, two atoms, or 32 parts by weight, of oxygen. Molecules* contain and consist of chemically-united atoms, and are the smallest particles of matter that can have an individual or physical existence. While the atoms compose and give character to the molecules, the molecules alone are sensibly known to us, and they give character to matter as we find it in masses, either solid, liquid or gaseous. In solids the molecules more or less firmly cohere together ; in liquids they have but little cohesion, and in gases they are far apart and tend to sepa- rate from each other. The so-called "elements" are, in fact, mostly compounds whose molecules consist of two or more like atoms, while all other chemical substances are compounds whose molecules are made up of two or more unlike atoms. Molecular Weights of Compounds. — The mole- cular weight of a compound is the sum of the weights of the atoms that compose it. For example, water being composed of 1 atom, or 16 parts by weight, of oxygen, and 2 atoms, or 2 parts by weight, of hydrogen, has the molecular weight of 18. f The following scheme illustrates the molecular compo- sition of a somewhat complex compound, one of the car- * Latin diminutive, signifying a little mass. t We must refer to recent treatises on chemistry for fuller informa- tion as to atoms and molecules and the methods of finding the atomic and molecular weights. 34 HOW CROPS GROW. bonates of ammonium, which consists of four elements, ten atoms, and has a molecular weight of seventy-nine. Ammonia gas results from the union of an atom of nitrogen with three atoms of hydrogen. Cue molecule of ammonia gas unites with a molecule of carbon dioxide gas and a molecule of water to produce a molecule of ammonium carbonate. Atoms. Atomic Molecular weights, weights. Ammonia _ f Hydrogen, 3 = 3 ) _ .-"I o oxide 1 mol.— \ Oxygen, 2 = 32 Water, _ ( Hydrogen, 2 = 2 i _1ft 1 mol.— I Oxygen, I = 16 — le Notation and Formulas of Compounds. — For the purpose of expressing easily and concisely the composi- tion of compounds, and the chemical changes they undergo, chemists have agreed to make the symbol of an element signify one atom of that element. Thus H implies not only the light, combustible gas 'hydrogen, but also one part of it by weight as compared with other elements, and S suggests, in addition to the idea of the body sulphur, the idea of 32 parts of it by weight. Through this association of the atomic weight with the symbol, the composition of compounds is expressed in the simplest manner by writing the symbols of their elements one after the other. Thus, carbon monoxide is represented by CO, mercuric oxide by HgO, and iron monosulphide by FeS. The symbol CO con- veys to the chemist not only the fact of the existence of carbon monoxide, but also instructs him that its mole- cule contains an atom each of carbon and of oxygen, and from his knowledge of the atomic weights he gathers the proportions by weight of the carbon and oxygen in it. "When a compound contains more than one atom of an element, this is shown by appending a small figure to-the symbol of the latter. For example : water consists of two atoms of hydrogen united to one of oxygen, and it* THE VOLATILE PART OF PLANTS. 35 symbol is H20. In like manner the symbol of carbon dioxide is C02. When it is wished to indicate that more than one mole- cule of a compound exists in combination or is concerned in a chemical change, this is done by prefixing a large figure to the symbol of the compound. For instance, two molecules of water are expressed by 2 H20. The symbol of a compound is usually termed a formula and if correct is a molecular formula and shows the com- position of one molecule of the substance. Subjoined is a table of the molecular formulas of some of the com- pounds that have been already described or employed. FORMULAS OP COMPOUNDS. Name. Formula. Molecular Weight. Water H2O 18 Hydrogen Sulphide H2S 34 Iron Moiiosulphide FeS 88 Mercuric Oxide HgO 216 Carbon Dioxide CO, 44 Calcium Chloride CaCl2 111 Sulphur Dioxide SO2 64 Sulphur Trioxide SO, 80 Phosphorus Pentoxide P265 142 Empirical and Rational Formulas. — It is obvious that many different formulas can be made for a body of complex character. Thus, the carbonate of ammonium, whose composition has already been stated (p. 33), and which contains 1 atom of Nitrogen, 1 atom of Carbon, 3 atoms of Oxygen, and 5 atoms of Hydrogen, may be most compactly expressed by the symbol NC03H5. Such a formula merely informs us what elements and how many atoms of each element enter into the compo- sition of the substance. It is an empirical formula, being the simplest expression of the facts obtained by analysis of the substance. National formulas, on the other hand, are intended to convey some notion as to the constitution, formation, or 36 HOW CROPS GROW. modes of decomposition of the body. For example, the real arrangement of the atoms in ammonium carbonate is believed to be expressed by the rational (or structural) formula -P/O-X H, °=L\o— H in which the carbon is directly united to oxygen, to which latter one hydrogen and the nitrogen are also linked, the remaining hydrogens being combined to the nitrogen. Valence. — The connecting lines or dashes in the fore- going formula show the valence of the several atoms, i. e. , their "atom-fixing power." The single dash from H indicates that hydrogen is univalent or has a valence of one. The two dashes connected with 0 express the Mvalence of oxygen or that the atom of this element can combine with two hydrogens or other univalent atoms. The nitrogen is united on one hand with 4 hydrogen atoms, and also, on the other hand, satisfies half the val- ence of oxygen ; it is accordingly quinquivalent, \. e., has five units of valence. Carbon is quadrivalent, being joined to oxygen by four units of valence. Equations of Formulas serve to explain the results of chemical reactions and changes. Thus, the breaking up by heat of potassium chlorate into potassium chloride and oxygen is expressed by the following statement: Potassium Chlorate. Potassium Chloride. Oxi/'i> H 2 KC1O, = 2 KC1 + 3 O2 The sign of equality, =, shows that what is written before it supplies and is resolved into what follows it. The sign -|- indicates and distinguishes separate com- pounds. The employment of this kind of short-hand for exhib- iting chemical changes will find frequent illustration as we proceed with our subject. Modes of Stating Composition of Chemical THE VOLATILE PART OF PLANTS. 3? Compounds. — These are two: 1, atomic or molecular statements, and 2, centesimal scatements, or proportions in one hundred parts (per cent, p. c., or %). These modes of expressing composition are very useful for com- paring together different compounds of the same ele- ments, and, while usually the atomic statement answers for substances which are comparatively simple in their composition, the statement per cent is more useful for complex bodies. The composition of the two compounds of carbon with oxygen is given below according to both methods. Atomic. Per cent. Atomic. Per cent. Carbon (C), 12 42.86 (C) 12 27.27 Oxygen (O), 16 57.14 (O2) 32 72.73 Carbon, Monoxide (CO), 28 100.00 Carbon Dioxide (CO2), 44 100.00 The conversion of one mode of statement into the other is a case of simple rule of three, which is illustrated in the following calculation of the centesimal composition of water from its molecular formula. Water, H2O, has the molecular weight 18, i. e., it consists of two atoms of hydrogen, or two parts, and one atom of oxygen, or sixteen parts by weight. The arithmetical proportions subjoined serve for the calculation, viz. : H2O Water H Hydrogen 18 ; 100 1 1 2 ' per cent sought (=11.11) H2O Water O Oxygen 18 ; 100 : : 16 : per cent sought (=88.89) By multiplying together the second and third terms of these propor- tions, and dividing by the first, we obtain the required per cent, viz., of hydrogen, 11.11 ; and of oxygen, 88.89. The reader must bear well in mind that chemical affin- ity manifests itself with very different degrees of inten- sity between different bodies, and is variously modified, excited, or annulled, by other natural agencies and forces, especially by heat, light and electricity. 8 4. VEGETABLE ORGANIC COMPOUNDS, OR PROXIMATE PRINCIPLES. We are now prepared to enter upon the study of the organic compounds, which constitute the vegetable struc- 38 HOW CROPS GROW. ture, and which are produced from the elements carbon, oxygen, hydrogen, nitrogen, sulphur, and phosphorus, by chemical agency. The number of distinct substances found in plants is practically unlimited. There are already well known to chemists hundreds of oils, acids, bitter principles, resins, coloring matters, etc. Almost every plant contains some organic body peculiar to itself, and usually the same plant in its different parts reveals to the senses of taste and smell the presence of several individual substances. In tea and coffee occurs an intensely bitter " active principle," caffeine. From tobacco an oily liquid of eminently narcotic and poison- ous properties, nicotine, can be extracted. In the orange are found no less than three oils ; one in the leaves, one in the flowers, and a third in the rind of the fruit. Notwithstanding the great number of bodies thus occurring in the vegetable kingdom, it is a few which form the bulk of all plants, and especially of those which have an agricultural importance as sources of food to man and animals. These substances, into which any plant may be resolved by simple, partly mechanical means, are conveniently termed proximate principles, and we shall notice them in some detail under eight principal classes, viz.: 1. WATER. 2. The CARBHYDRATES. 3. The VEGETABLE ACIDS. 4. The FATS and OILS. 5. The ALBUMINOIDS or PROTEIX BODIES and FER- MEXTS. 6. The AMIDES. 7. The ALKALOIDS. 8. PHOSPHORIZED SUBSTANCES. i. Water, H20, as already stated, is the most abund- ant ingredient of plants. It is itself a compound of oxygen and hydrogen, having the following centesimal composition : THE VOLATILE PAKT OF PLANTS. 39 Oxygen 88.89 Hydrogen 11.11 100.00 It exists in all parts of plants, is the immediate cause of the succulence of their tender portions, and is essen- tial to the life of the vegetable organs. In the following table are given the percentages of water in some of the more common agricultural products in the//r.s7< state, but the pro- portions are not quite constant, even in the same part of different specimens of any given plant. WATER IN FRESH PLANTS. (PER CENT.) Average, Meadow grass 71 Red clover 80 Maize, as used for fodder 82 Cabbage 85 Potato tubers 75 Sugar beets 81 Carrots 86 Turnips 91 Range. 60 to 78 68 In living plants, water is usually perceptible to the eye or feel, as sap. Bat it is not only fresh plants that contain water. When grass is made into hay, the water is by no means all dried out, but a considerable propor- tion remains in the pores, which is not recognizable by the senses. So, too, seasoned wood, flour, and starch, when seemingly dry, contain a quantity of invisible water, which can be removed by heat. EXP. 21.— Into a wide glass tube, like that shown in Fig. 2, place a spoonful of saw dust, or starch, or a little hay. Warm over a lamp, but very slowly and cautiously, so as not to burn or blacken the sub- stance. Water will be expelled from the organic matter, and will col- lect on the cold part of the tube. It is thus obvious that vegetable substances may con- tain water in at least two different conditions. Ecd clover, for example, when growing or freshly cut, contains about 80 per cent of water. "When the clover is dried, as for making hay, the greater share of this wa- ter escapes, so that the air-dry plant con- tains but about 15 per cent. On subject- ing the air-dry clover to a temperature of 212 ° for some hours, the water is completely expelled, and the substance becomes really dry, i. e., water-free. Fig. 9. 40 HOW CROPS GROW. To drive off all water from vegetable matters, the chemist usually employs a water-oven, Fig. 9, consisting of a vessel of tin or copper plate, with double walls, between which is a space that may be half lillcd with water. The substance to be dried is placed in the interior chamber, the door is closed, and the water is brought to boil by the heat of a lamp or stove. The precise quantity of water belonging to, or contained in, a substance, is ascertained by first weighing the sub- stance, then drying it until its weight is constant. The loss is water. In the subjoined table are given the average quantities, per cent, of water existing in various vegetable products when air-dry. WATER IN AIK-DRY PLANTS. PER CENT. Meadow grass (hay) 15 Red clover hay 17 Pine wood 20 Straw and chaff of wheat, rye, etc 15 Bean straw 18 Wheat (rye, oat) kernel 14 Maize kernel 12 That portion of the water which the fresh plant loses by mere exposure to the air is chiefly the water of its juices or sap, and, on crushing the fresh plant, is mani- fest to the sight and feel as a liquid. It is, properly speak- ing, the free water of vegetation. The water which remains in the air-dry plant is imperceptible to the senses while in the plant, — can only be discovered on expelling it by heat or otherwise, — and may be designated as the hygroscopic or combined water of vegetation. The amount of water contained in either fresh or air- dry vegetable matter is somewhat fluctuating, according to the temperature and the dryness of the atmosphere. 2. The Carbhydrates. This group falls into three subdivisions, viz. : a. THE AMTLOSES, comprising Cellulose, Starch, Inu- lin, Glycogen, the Dextrins and Gums, having the formula (C6H1005)n. t>. THE GLUCOSES, which include Dextrose, Levulose, Galactose and similar sugars, having the composition C6H1206. c. THE SUCROSES, viz. : Cane Sugar or Saccharose, Maltose, Lactose and other sugars, whose formula in most cases is Ci2H22On. THE VOLATILE PAKT OF PLANTS. 41 On account of their abundance and uses the Carbhy- drates rank as the most important class of vegetable sub- stances. Their name refers to the fact that they consist of Carbon, Hydrogen and Oxygen, the last two elements being always present in the same proportions that are found in water. These bodies, especially cellulose and starch, form by far the larger share — perhaps seven-eighths — of all the dry matter of vegetation, and most of them are distributed throughout all parts of plants. a. The Amy loses. Cellulose (C6H1005)n. — Every agricultural plant is an aggregate of microscopic cells, i. e., is made up of minute sacks or closed tubes, adhering to each other. Fig. 10 represents an extremely thin slice from the stem of a cabbage, magnified 230 diameters. The united walls of two cells are seen in sec- tion at a, while at b an empty space is noticed. Fig. 10. The outer coating, or wall, of the vegetable cell con- sists chiefly or entirely of cellulose. This substance is accordingly the skeleton or framework of the plant, and the material that gives toughness and solidity to its parts. Next to water it is the most abundant body in the vege- table world. 42 HOW CROPS GROW. Nearly all plants and all their parts contain cellulose, but it is relatively most abundant in stems and leaves. In seeds it forms a large portion of the husk, shell, or other outer coating, but in the interior of the seed it exists in small proportion. The fibers of cotton (Fig. 11, a], hemp, and flax (Fig. 11, V), and white cloth and unsized paper made from these materials, are nearly pure cellulose. The fibers of cotton, hemp, and flax are simply long and thick-walled cells, the appearance of •which, when highly magnified, is shown in Fig. 11, where a represents the thinner, more soft, and col- lapsed cotton fiber, and b the thicker and more dur- able fiber of linen. "Wood, or woody fiber, consists of long and slender cells of various forms and di- mensions (see p. 293), which are delicate when young (in the sap wood), but as they become older fill up interiorly by the deposition of re- peated layers of cellulose, which is more or less inter- grown with other substances.* The bard shells of nuts and stone fruits contain a basis of cellulose, which is im- pregnated with other matters. When quite pure, cellulose is a white, often silky or spongy, and translucent body, its appearance varying * Wood was formerly supposed to consist of cellulose and so-called "lignin." On this view, according to F. Schulze, ligniu Impregnates (not simply incrusts) the cell-wall, is soluble in hot alkaline solutions, and is readily oxidi/cd by nitric acid. Schulze ascribes to it the com- position Carbon 55.3 Hydrogen 5.8 Oxygen 38.9 100.0 This is, however, simply the inferred composition of what is left after the cellulose, «•!(•.. lia\ e'been removed. "L,igniii " cannot be separated in the pun- state, and has never been analy/.ed. What is thns desig- nated is a mixture of se\-era 1 i list met substances. Kremy's lignose. \\ii- none, lignin, and lignireose. as well as .1. Krdman's glycollgnose and lignose, are not established as chemically distinct substances. Fig. 11. THE VOLATILE FART OF PLANTS. 43 somewhat according to the source whence it is obtained. In the air-dry state, at common temperatures, it usually contains about 10 % of hygroscopic water. It has, in common with animal membranes, the character of swell- ing up when immersed in water, from imbibing this liquid ; on drying again, it shrinks in bulk. It is tough and elastic. Cellulose, as it naturally occurs, for the most part dif- fers remarkably from the other bodies of this group, in the fact of its slight solubility in dilute acids and alkalies. It is likewise insoluble in water, alcohol, ether, the oils, and in most ordinary solvents. It is hence prepared in a state of purity by acting upon vegetable tissues con- taining it, with successive solvents, until all other mat- ters are removed. The " skeletonized " leaves, fruit vessels, etc., which compose those beautiful objects called /i/m/i/niit, bouquets, are commonly made by dis- solving away the softer portions of fresh succulent plants by a hot solu- tion of caustic soda, and afterwards whitening the skeleton of fibers that remains by means of chloride of lime (bleaching powder). They are almost pure cellulose. Skeletons may also be prepared by steeping vegetable matters in a mixture of potassium chlorate and dilute nitric acid for a number of days. EXP. 22. — To 500 cubic centimeters* (or one pint) of nitric acid of dens- ity 1.1, add 30 grams (or one ounce) of pulverized potassium chlorate, and dissolve the latter by agitation. Suspend in this mixture a num- ber of leaves, etc.,t and let them remain undisturbed, at a temperature not above 65° F., until they are perfectly whitened, which may require from 10 to 20 days. The skeletons should be floated out from the solution on slips of paper, washed copiously in clear water, and dried under pressure between folds of unsized paper. The fibers of the whiter and softer kinds of wood are now much em- ployed in the fabrication of paper. For this purpose the wood is rasped * On subsequent pages we shall make frequent use of some of the French decimal weights and measures, for the reasons that they are much more -onvenient than the Knglish ones, and are now almost ex- clusively ei iploved in all scientific treatises and investigations. For ts, the ;f rn in, abbreviated gin. (equal to l.YV grains, nearly), iary unit. The unit of measure by volume is the ciili'n- <•/•//- reviated c. c. (30 c. c. equal one fluid ounce nearly), (iram small weigl is the eusfo timi'tr-r, abl weights and glass measures graduated into cubic centimeters are fur- nished by all dealers in chemical apparatus. + Full-grown but not old leaves of t he elm. maple, and maize, heads of unripe grain, slices of the stem and joints of mai/.e, etc., may be em- ployed to furnish skeletons that will prove valuable in the study of the structure of these organs. 44 HOW CROPS GROW. to a coarse powder by machinery, thon heated with a weak soda lye, and finally bleached with chloride of lime. Though cellulose is insoluble in, or but slightly affected by, weak or dilute acids -and alkalies, it is altered and dis- solved by these agents, when they are concentrated or hot. The result of the action of strong acids and alka- lies is various, according to their kind and the degree of strength in which they are employed. Cellulose Nitrates. — Strong nitric acid transforms cellulose into various cellulose nitrates according to its concentration. In these bodies portions of the hydrogen and oxygen of cellulose are replaced by the atomic group (radicle), N03. Cellulose hexanitrate, C12H14 (X03)60i0, is employed as an explosive under the name gun cotton. The collodion employed in photography is a solution in ether of the penta- and tetranitrates, C]2H15(N03)501o and C12H16(N03)4010. Sodium hydroxide changes these cellulose nitrates into cellulose and sodium nitrate. Hot nitric acid of ordinary strength destroys cellulose by oxidizing it with final formation of carbon dioxide gas and oxalic acid. Cellulose Sulphates. — When cold sulphuric acid acts on cellulose the latter may either remain apparently unaltered or swell up to a pasty mass, or finally dissolve to a clear liquid, according to the strength of the acid, the time of its action, and the quality (density) of the cellulose. In excess of strong oil of vitriol, cellulose (cotton) gradually dissolves with formation of various cellulose sulphates, in which OH groups of the cellulose are replaced by S04 of sulphuric acid. These sulphcites are soluble in water and alcohol, and when boiled with water easily decompose, reproducing sulphuric acid, but not cellulose. Instead of the latter, dextrin and dextrose (grape sugar) appear. Soluble Cellulose, or Amyloid. — In a cooled mix- ture of oil of vitriol, with about £ its volume of water, THE VOLATILE PAKT OF PLANTS. 45 cellulose dissolves. On adding much water to the solu- tion there separates a white substance which has the same composition as cellulose, but is readily converted into dextrin by cold dilute acid. This form of cellulose as- sumes a fine blue color when put in contact with iodine- tincture and sulphuric acid. EXP. 23.— Fill a large test-tube first with water to the depth of two or three inches. Then add gradually three t hues that bulk of oil of vitriol, and mix thoroughly. When well cooled pour a part of the liquid on a slip of unsized paper in a saucer. After some time the paper is seen to swell up and partly dissolve. Now flow it with solution of iodine,* when these dissolved portions will assume a fine and intense blue color. This deportment is characteristic of cellulose, and may be employed for its recognition under the microscope. If the experiment be re- peated, using a larger proportion of acid, and allowing the action to continue for a considerably longer time, the substance producing the blue color is itself destroyed, and addition of iodine has no effect, t Un- altered cellulose gives with iodine a i/rllntr color. Paper superficially converted into amyloid constitutes veycfu/'/i- parchment, which is tough and translucent, much resembling bladder, and very useful for various purposes, among others as a substitute for sausage " skins." EXP. 24.— Into the remainder of the cold acid of Exp.23 dip a strip of unsized paper, and let it remain for about 15 seconds ; then remove, and rinse it copiously in water. Lastly, soak some minutes in water, to which a little ammonia is added, and wash again with pure water. These washings are for the purpose of removing the acid. The success of this process for obtaining vegetable parchment depends upon the proper strength of the acid, and the time of immersion. If need be, repeat, varying these conditions slightly, until the result is obtained. The denser and more impure forms of cellulose, as they occur in wood and straw, are slowly acted upon by chem- ical agents, and are not easily digestible by most animals ; but the cellulose of young and succulent stems, leaves, and fruits is digestible to a large extent, especially by animals which naturally feed on herbage, and therefore cellulose is ranked among the nutritive ingredients of cattle-food. Chemical composition of cellulose. — This body is acom- * Dissolve a fragment of iodine as large us a wheat kernel in 20 c. c. of alcohol, and add KM) e. c. of water to the solution. t According to Crouven, cellulose prepared from rye straw iand im- pure ?) requires several hours' action of sulphuric acid before it will strike a blue color with iodine IL'/- ta'ned as a residue after removing other matters, as far as possible, by alternate treatment with dilute acids and alkalies. The methods are confessedly imperfect, because cellulose itself is dissolved to some ex- tent, and a portion of other matters often remains imattacked. The method of Henneberg, usually adopted ( J",s. >Y.,VI. 4(,»7», is as follows : 3 grams of the finely divided substance are boiled for half an hour with 200 cubic centimeters of dilute sulphuric acid (containing 1J per cent of oil of vitriol), and, after the substance has settled, the acid liquid is poured off. The residue is boiled again for half an hour with 200 c. c. of dilute potash lye (containing \\ per cent of dry caustic potash), and, after removing the alkaline liquid, it is boiled twice with water as before. What remains is brought upon a filter, and washed witli water, then •with alcohol, and, lastly, with ether, as long as these solvents take up anything. This crude cellulose contains ash and nitrogen, for wliich corrections must be made. The nitrogen is assumed to belong to some albuminoid, and from its quantity the amount of the latter is calcu- lated ; (see p. 113). Even with these corrections, .the quantity of Cellulose is not obtained with entire accuracy, as is usually indicated by its appearance and its composition. While the crude cellulose thus prepared from the pea is perfectly white, that from wheat bran is brown, and that from rape- cake is almost black in color, from impurities that cannot be removed by this method. Grouven gives the following analyses of two samples of crude cellu- lose obtained by a method essentially the same as we have described. (2ter Salzmiinder Bericht, p. 456.) Rye-*t i-d 11- fi >>rr. Flax fiber. Water 8.65 5.40 Ash 2.05 1.14 N 0.15 0.15 C 42.47 38.36 H 6.04 5.89 0 40.64 48.95 100.00 100.00 On deducting water and ash, and making proper correction for the THE VOLATILE PART OF PLANTS. 47 nitrogen, the above samples, together with one of wheat-straw fiber, analyzed by Heimeberg, exhibit the following composition, compared with pure cellulose. Bye-straw fiber. Flax fiber. Wheat-straw fiber. Pure cellulose. C 47.5 41.0 45.4 44.4 H 6.8 6.4 0.3 6.2 0 45.7 52.6 48.3 49.4 100.0 100.0 100.0 100.0 Fr. Schulze has proposed (1857) another method for estimating cellu- lose, which, though troublesome, is in most cases more correct than the one already described. Kiihn, Aronstein, and H. Schulze (Henneberg's Journal fur Land n-i rth^'huft, 18W>, pp. 289 to 297) have applied this method in the following manner : One part of the dry pulverized sub- stance (2 to 4 grams), which has been previously extracted with water, alcohol, and ether, is placed in a glass-stoppered bottle, with 0.8 part of potassium chlorate and 12 parts of nitric acid of specific gravity 1.10, and digested at a temperature not exceeding 65° F. for 14 days. At the expiration of this time, the contents of the bottle are mixed with some water, brought upon a filter, and washed, firstly, with cold and after- wards with hot water. When all the acid and soluble matters have been washed out, the contents of the filter are emptied into a beaker, and heated to 165° F. for about 45 minutes with weak ammonia (1 part commercial ammonia to 50 parts of water); the substance is then brought upon a weighed filter, and washed, tirst, with dilute ammonia, as long as this passes off colored, then with cold and hot water, then with alcohol, and, finally, with ether. The substance remaining con- tains a small quantity of ash and nitrogen, for which corrections must be made. The fiber is, however, purer than that procured by the other method, and the writers named obtained a somewhat larger quantity, by J to li per cent. The results appear to vary but about one prr '•'•/ at a /•',-- a.-:, commonly known as Jerusalem artichoke, and cultivated in Kuropc under the name /<• to saturate the mass, and let it stand 4* hours. Squeeze the acid liquid, filter it, and add alcohol, when " pectin separate. THE VOLATILE PART OF PLANTS. 61 It may be that metarabin is identical with the "pec- tose " of the sugar beet, since both yield arabin under the influence of alkalies. It is evident that the composition found for dried arabin properly belongs to metarabin, and it is probable that arabin consists of metarabin Ci2H22Ou plus one or several molecules of water, and that metara- bin is an anhydride of arabin. Arabin and metarabin, when heated with dilute sul- phuric acid, are converted into a crystallizable sugar called arabinose, C5H1005. The gums that exude from the stems of cherry, plum and peach trees appear to con- sist chiefly of a mixture of freely soluble arabates with insoluble metarabin. Gum Tragacanth is perhaps mostly metarabin. All these gums yield, by the action of hot dilute acids, the sugar arabinose. Galactin, C6H1005, discovered by Miiutz in the seeds of alfalfa and found in other legumes, has the appearance, solubility in water and general properties of arabin, and is probably the right-polarizing ingredient of gum arable. Boiled with dilute acids it is converted into the sugar galactose, C6H1206. Paragalactin, 06H1005. — In the seeds of the yellow lupin exists up to 20 per cent of a body that is insoluble in water, but dissolves by warming with alkali solutions, and when heated with dilute acids yields galactoso. Ac- cording to Steiger it probably has the composition C6Hi005. Maxwell has shown it to exist in other leguminous seeds, viz., the pea, horse-bean (Faba vulgaris) and vetch. In the "Chinese moss," an article of food prepared in China from sea-weeds, and in the similar gum agar or "vegetable gelatine" of Japan, exists a substance which is insoluble in cold water, but with that liquid swells up to a bulky jelly, and yields galactose when heated with dilute acids. This corresponds to metarabin. Xylin, or Wood Gum. — The wood of many decidu- ous trees, the vegetable ivory nut, the cob of Indian 62 HOW CROPS GROW. corn and barley husks, contain 6 to 20 per cent of a sub- stance insoluble in cold water, but readily taken up in cold solution of caustic soda. On adding to the solution an acid, and afterwards alcohol, a bulky white substance separates, which maybe obtained dry as a white powder or a translucent gum-like mass. It dissolves very slightly in boiling water, yielding an' opalescent solution. The composition of this substance was found by Thomsen to be C6H1006. Xylin differs from pararabin and pectose in not being soluble in milk of lime. It is converted by boiling with dilute sulphuric acid into a crystallizable sugar, xylose, whose properties have been but little investigated. Flax-seed Mucilage, C6H1005, resembles metarabin, but by action of hot dilute acids is resolved into cellulose and a gum, which latter is further transformed into dex- trose. The yield of cellulose is about four per cent. Quince-Seed Mucilage appears to be a compound of cellulose and a body like arabin. On boiling with dilute sulphuric acid it yields nearly one-third its weight of cel- lulose, together with a soluble gum and a sugar, the last being a result of the alteration of the gum. The sugar is similar to arabinose. The Soluble Gums in Bread-grains. — In the bread- grains, freely soluble gums occur often in considerable proportion. TABLE OF THE PROPORTIONS (jtfrcfnt.) OF CJUM* IX VAKIOfS AIR-DRY GRAINS OK MILL PKOIUTTS. (According to Von ISihr", l>i< Ciiriidinrti-n mul Barley bran c.vs Spelt Hi >ur i Tfitii-niii s/,i-/hi,.. L'.4s Oat ii'it-al :?.r>0 Wheat ]>ran 8.85 Rice Hour L'.IMI Spdt bran 12..^' Millet flour Hu;o Rye kernel 4.10 Mai/e meal 3.05 Ryefionr ~.-s> Buckwheat flour 2.85 live bran 10.40 * The "fjuni " in the above table ('which dates from 1«.")9>, includes per- haps soluble starch and dextrin in some, i! not all cases, and. accord- ing to ( >'Su!livan. barley, wheat and rye contain two distinct left-pol- anzlng giuns, which be terms a-amylan ami ii-imti/hni. These occur iit barley to the extent of 2.3 per cent. 15y action' of acids they yield dextrose. THE VOLATILE PART OF PLANTS. 63 The experiments of Grouven show that gum arabic is digestible by domestic animals. There is little reason to doubt that all the gums are digestible and serviceable as ingredients of the food of animals. b. The Glucoses, C6H1206 (or C5H1005), are a class of sugars having similar or identical composition, but dif- fering from each other in solubility, sweetness, melting point, crystal -form and action on polarized light. The glucoses, with one exception, contain in 100 parts : Carbon 40.00 Hydrogen 6.67 Oxygen 53.33 100.00 Levulose, or Fruit Sugar (Fructose), C6H1206, exists mixed with other sugars in sweet fruits, honey and molasses. Inulin and levulin are converted into this sugar by long boiling with dilute acids, or with water alone. When pure, it forms colorless crystals, which melt at 203°, but is usually obtained as a syrup. Its sweetness is equal to that of saccharose. Dextrose or Grape Sugar, C6H120G, naturally oc- curs associated with levulose in the juices of plants and in honey. Granules of dextrose separate from the juice of the grape on drying, as may be seen in old " candied " raisins. Honey often granulates, or candies, on long keeping, from the crystallization of its dextrose. Dextrose is formed from starch and dextrin by the ac- tion of hot dilute acids, in the same way that levulose is produced from inulin. In the pure state it exists as minute, colorless crystals, and is, weight for weight, but two-thirds as sweet as saccharose or cane-sugar. It fuses at 295°. Dextrose unites chemically to water. Hydrated glucose. r,,H,.,O(.lljn, occurs in commerce in an impure state as a crystalline mass. which becomes doughy at a slightly elevated temperature. This hydrate loses its crystal-water at 212°. Dissolved in water, dextrose yields a syrup, which is t>4 HOW CROPS GROW. thin, and destitute of the ropiness of cane-sugar syrup. It does not crystallize (granulate) so readily as cane- sugar. EXP. 30. — Mix 100 c. c. of water with 30 drops of strong sulphuric acid, and heat to vigorous boiling in a glass lla.sk. Stir 10 grams of starch with a little water, and pour the mixture into the hot liquid, drop by drop, so as not to interrupt the boiling. The si arch dissolves, and passes successively into amidulin, dextrin, and dextrose. Continue the ebul- lition for several hours, replacing the evaporated water from time to time. To remove the sulphuric acid, add to the liquid, which may In- still milky from impurities in the starch, powdered chalk, until the s< >m taste disappears ; filter from the calcium sulphate (gypsum) that is formed, and evaporate the solution of dextrose* at a gentle heat to a syrupy consistence. On long standing it may crystallize or granulate. By this method is prepared the so-called grape-sugar, or starch-sugar of commerce, which is added to grape-juice for making a stronger wine, and is also employed for preparing syrups and i in it at in g i no lasses. The syrups thus made from starch or corn are known in the trade as glucose.^ Imitation-molasses is a mixture of dextrose-syrup with some dextrin to make it "ropy." Even cellulose is convertible into dextrose by the pro- longed action of hot acids. If paper or cotton be first dissolved in strong sulphuric acid, and tbe solution diluted with water and boiled, the cellulose is readily transformed into dextrose. Sawdust has thus been made to yield an impure syrup, suitable for the production of alcohol. In the formation of dextrose from cellulose, starch, amidulin and dextrin, the latter substances take up the elements of water as repre- sented by the equation Starch, etc. Water. Glucose. C6H1005 + H20 C0H1206 In this process, 90 parts of starch, etc., yield 100 parts of dextrose. Trammer's Copper test. — A characteristic test for dextrose and levu- lose is found in their deportment towards an alkaline solution of cop- per, which readily yields up oxygen to these sugars, the copper being reduced to yellow cuprous hydroxide or red cuprous oxide. Kxi*. 31. — Prepare the copper test by dissolving together in 3d c. c. of warm water a pinch of sulphate of copper and one of tartaric acid: add to the liquid, solution of caustic potash until it acquires a slip- * If the boiling has been kept up but an hour or so, the dextrose will contain dextrin, as may be ascertained by mixing a small portion of the still acid liquid with 5 times its bulk of strong alcohol, which will precipitate dextrin, but not dextrose. t Under the name ft/urosp, the three sutrars levulose. dextrose and maltose were "ormerly confounded together, by chemists. THE VOLATILE PART OF PLANTS. 65 pery feel. Place in separate test tubes a few drops of solution of cane- sugar, a similar amount of the dextrin solution, obtained In Exp. 28; of solution of dextrose, from raisins, or from Exp. 30; and of molasses ; add to each a little of the copper solution, and place them in a vessel of hot water. Observe that the saccharose and dextrin suffer little or no alteration for a long time, while the dextrose and molasses shortly cause the separation of cuprous oxide. EXP. 32.— Heat to boiling a little white cane-sugar with 30 c. c. of water, and 3 drops of strong sulphuric acid, in a glass or porcelain dish, for 15 minutes, supplying the waste of water as needful, and test the liquid as in the last Exp. This treatment transforms saccharose into dextrose and levulose. The quantitative estimation of the sugars and of starch is commonly based upon the reaction just described. For this purpose the alkaline copper solution is made of a known strength by dissolving a given weight of sulphate of copper, etc., in a given volume of water, and the dextrose or levulose, or a mixture of both, being likewise made to a known volume of solution, the latter is allowed to flow slowly from a graduated tube into a measured portion of warm copper solution, until the blue color is discharged. Saccharose is first converted into dex- trose and levulose, by heating with an acid, and then examined in the same manner. Starch is transformed into dextrose by heating with hydrochloric acid or warming with saliva. The quantity of sugar stands in definite relation to the amount of copper separated, when the experiment is carried out under certain conditions. See Allihn, Jour, fur Pr. Chemie, XXII, p. 52, 1880. Galactose, C6H1206, is formed by treating right- polarizing gum arabic, galactin, or milk-sugar with dilute acids. It crystallizes, is sweet, melts at 289° and with nitric acid yields mucic acid (distinction from ara- binose, dextrose and levulose). i Mannose (Seminose?) C6H1206 is a fermentable sugar prepared artificially by oxidation of mannite (see p. 74), and, according to E. Fischer, is probably identical with the Seminose found by Reiss as a product of the action of acids on a body existing in the seeds of coffee and in palm nuts. (Berichte, XXII, p. 365). Arabinose, C5H1005, obtained from arabin (of left- polarizing gum arabic), and from cherry gum by action of hot dilute acids, appears in rhombic crystals. It is less sweet than cane sugar, and fuses at 320°. c. The Sucroses, C^H^On, are sugars which, boiled with dilute acids, undergo chemical change by taking up the 5 66 HOW CROPS GROW. elements of water and are thereby resolved into glucoses. In this decomposition one molecule of sucrose usually yields either two molecules of one glucose or a molecule each of two glucoses, doHooOu -f- H20 = C6H120G -f- C«H120,;. Saccharose, or Cane Sugar, Ci2H22Oii, so called because first and chiefly prepared from the sugar-cane, is the ordinary sugar of com- merce. When pure, it is a white solid, readily soluble in water, forming a color- Fig. LL less, ropy, and intensely sweet solution. It crystallizes in rhombic prisms (Fig. 14), which are usually small, as in granulated sugar, but in the form of rock-candy may be found an inch or more in length. The crystallized sugar obtained largely from the sugar-beet, in Europe, and that furnished in the United States by the sugar- maple and sorghum, when pure, are identical with cane- sugar. Saccharose also exists in the vernal juices of the wal- nut, birch, and other trees. It occurs in the stems of unripe maize, in the nectar of flowers, in fresh honey, in parsnips, turnips, carrots, parsley, sweet potatoes, in the stems and roots of grasses, in the seeds of the pea and bean, and in a multitude of fruits. EXP. 29. — Heat cautiously a spoonful of white sugar until it melts al 356° F.) to a clear yellow liquid. On rapid cooling, it gives :i transpar- ent mass, known as Imrh ,j *///f saccharose in the juice of various plants is given in the annexed table. It is, of course, variable, depending upon the variety of plant in case of cane, beet, and sorghum, as well as upon the stage of growth. SACCHAROSE IN PLANTS. Per f at. Sugar-cane, average 18 IVHgot. Sugar-beet, " 10 " Sorghum 13 Collier. Mai/.e. just flowered 3} Liidersdorff. Sugar-maple, sap, average 2£ Liebig. Ked maple, " " 2J " THE VOLATILE PART OF PLANTS. 67 The composition of saccharose is the same as that of arabin, and it contains in 100 parts : Carbon 42.11 Hydrogen 6.43 Oxygen 51.46 100.00 Cane-sugar, by long boiling of its concentrated aqueous solution, and under the influence of hot dilute acids (Exp. 32) and yeast, loses its property of ready crystallization, and is converted into levulose and dextrose. According to Dubrunfaut, a molecule of cane-sugar takes up the ele- ments of a molecule (5.26 per cent.) of water, yielding a mixture of equal parts of levulose and dextrose. This change is expressed in chemical symbols as follows : C12H220U + HjO = C6H]206 + C6H1206 Cane-sugar. Water, Levulose. Dextrose. This alterability on heating its solutions occasions a loss of one-third to one-half of the saccharose that is really contained in cane-juice, when this is evaporated in open pans, and is one reason why solid sugar is obtained from the sorghum in open-pan evaporation with such dif- ficulty. Molasses, sorghum syrup, and honey usually contain all three of these sugars. Honey-dew, that sometimes falls in viscid drops from the leaves of the lirne and other trees, is essentially a mix- ture of the three sugars with some gum. The mannas of Syria and Kurdistan "are of similar composition. Maltose, C12H220U.H20, is formed in the sprouting of seeds by the action of a ferment, called diastase, on starch. It is also prepared by treating starch or glycogen with saliva. In either case the starch (or glycogen) takes up the elements of water, 2 C6H1005 -j- H20 = Ci2H22On. Maltose in crystallizing unites with another molecule of water, which it loses at 212°. Maltose, thus dried, attracts moisture with great avidity. Boiled with dilute acids one molecule of maltose yields 68 HOW CROPS GROW. two molecules of dextrose, C^ILoOn -j- H20 = 2 C6Hi206= Maltose is also produced when starch and dextrin are heated with dilute acids, and thus appears to be an inter- mediate stage of their transformation into dextrose. Maltose is accordingly an ingredient of some commer- cial "grape-sugars" made from starch by boiling with diluted sulphuric acid. Lactose, or Milk Sugar, C12H22Oii -f- H20, is the sweet principle of the milk of animals. It is prepared for commerce by evaporating whey (milk from which casein and fat have been separated for making cheese). In a state of purity it forms transparent, colorless crys- tals, which crackle under the teeth, and are but slightly sweet to the taste. When dissolved to saturation in water, it forms a sweet but thin syrup. Heated to 290° the crystals become water-free. Lactose is said to occur with cane-sugar in the sapo- dilla (fruit of Achras sapota) of tropical countries. Treatment with dilute sulphuric acid converts it into galactose and dextrose. CuH^Qu + H40 = CaH12Oe + C6HJ206 Lactose. Water. Galactose. Dextrose. Raffinose, C18H32016 -f 5 H20 (?), first discovered by Loiseau in beet-sugar molasses, was afterwards found by Berthelot in eucalyptus manna, by Lippmann in beet- root, and by Boehm & Eitthausen in cotton-seed. It crystallizes in fine needles, and is but slightly sweet. It begins to melt at 190° with loss of crystal- water, which may be completely expelled at 212°. The anhydrous sugar fuses at 236°. It is more soluble in water and has higher dextrorotatory power than cane-sugar. Heated with dilute acids it yields dextrose, levulose and galactose. CuHaOu + 2 H20 = 3(C«H1206)- The Sugars in Bread- Grains. — The older observers assumed the presence of dextrose in the bread-graius. TflE VOLATILE PART OF PLANTS. 69 Thus, Vauquelin found, or thought he found, 8.5% of this sugar in Odessa wheat. More recently, Peligot, Mitscherlich, and Stein denied the presence of any sugar in these grains. In his work on the Cereals and Bread, (Die Getreidearten und das Brod, 1860, p. 163), Vpn Bibra reinvestigated this question, and found in fresh- ground wheat, etc., a sugar having some of the charac- ters of saccharose, and others of dextrose and levulose. Marcker and Kobus, in 1882, report maltose (which was unknown to the earlier observers) in sound barley, and maltose and dextrose in sprouted barley. Von Bibra found in the flour of various grains the following quanti- ties of sugar : PROPORTIONS OF SUGAR IN AIR-DRY FLOUR, BRAN, AND MEAL. Per cent. Wheat flour 2.33 Spelt flour 1.41 Wheat bran 4.30 Spelt bran 2.70 Rye flour 3.46 Rye bran 1.86 Barley meal 3.04 Barley bran 1.90 Oat nieal 2.19 Rice flour 0.39 Millet flour 1.30 Maize meal 3.71 Buckwheat meal 0.91 Glucosides. — There occur in the vegetable kingdom a large number of bodies, usually bitter in taste, which contain dextrose, or a similar sugar, chemically combined with other substances, or that yield it on decomposition. Salicin, from willow bark ; phloridzin, from the bark of the apple-tree root ; jalapin, from jalap ; aesculin, from the horse-chestnut, and amygdalin, in seeds of almond, peach, plum, apple, cherry, and in cherry-laurel leaves, are of this kind. The sugar may be obtained from these so-called glucosides by heating with dilute acids. The seeds of mustard contain the gluooside mijromc acid united to potassium. This, when the crushed seeds are wet with water, breaks up into dextrose, mustard-oil, and acid potassium sulphate, as follows : C,« Hlf K N S, 0IO = C6H1208 + C.,H5XCS + K H S O4 The cambial juice of the conifers contains runiferin, crystallizing in 70 HOW CROPS GROW. brilliant needles, which yields dextrose and a resin by action of dilute acid, and by oxidation produces vanillin, the flavoring principle of the vanilla bean. Mutual Transformations of the Carbhyd rates. — One of the most remarkable facts in the history of this group of bodies is the facility with which its members undergo mutual conversion. Some of these changes have been already noticed, but we may appropriately review them here. a. Transformations in the plant. — In germination, the starch which is largely contained in seeds is converted into amidulin, dextrin, maltose and dextrose. It thus ac- quires solubility, and passes into the embryo to feed the young plant. Here these are again solidified as cellulose, starch, or other organic principle, yielding, in fact, the chief part of the materials for the structure of the seed- ling. At spring-time, in cold climates, the starch stored up over winter in the new wood of many trees, especially the maple, appears to be converted into the sugar which is found so abundantly in the sap, and this sugar, carried upwards to the buds, nourishes the young leaves, and is there transformed into cellulose, and into starch again. The sugar-beet root, when healthy, yields a juice con- taining 10 to 14 per cent, of saccharose, and is destitute of starch. Schacht has observed that, in a certain dis- eased state of the beet, its sugar is partially converted into starch, grains of this substance making their appear- ance. (Wilda's Centralblatt, 1863, II, p. 217.) In some years the sugar-beet yields a large amount of arabin, in others but little. The analysis of the cereal grains sometimes reveals the presence of dextrin, at others of sugar or gum. Thus, Stepf found no dextrin, but both gum and sugar in maize-meal (Jour, fur I'nil.t. clu-m., ?<;. p. !IL',>: while Fresenius. in a more recent analysis < I's. .s7.. I. p. 180), obtained dextrin, but neither sugar nor gum. The sample of maize examined by Stepf contained 3.05 p. c. gum and 3.71 p. c. sugar; that analyzed by Fresenius yielded 2.33 p. c. dextrin. THE VOLATILE PART OF PLANTS. 71 Maroker & Kobns made comparative analyses of well-cured and of sprouted barley, with the following results per cent: Sottixl. Gron-,1. St arch 64.10 57.98 Soluble starch 1.76 1.17 Dextrin 1.10 0.00 Dextrose 0.00 4.92 Maltose 3.12 7.92 The various gums are a result of the transformation of cellulose, as Mohl first showed by microscopic study. b. In the animal, the substances we have been describ- ing also suffer transformation when employed as food. During the process of digestion, cellulose, so far as it is acted upon, starch, dextrin, and probably the gums, are all converted into dextrose or other sugars, and from these, in the liver especially, glycogen is formed. c. Many of these changes may also be produced apart from physiological agency, by the action of heat, acids, and ferments, operating singly or jointly. Cellulose and starch are converted, by boiling with a dilute acid, into amidulin, dextrin, maltose and dextrose. Cellulose and starch acted upon for some time by strong nitric acid give compounds from which dextrin may be separated. Cellulose nitrate sometimes yields gum (dex- trin) by its spontaneous decomposition. A kind of gum also appears in solutions of cane-sugar or in beet-juice, when they ferment under certain conditions. Inulm and the gums yield glucoses, but no dextrin, when boiled with weak acids. d. It will be noticed that while physical and chemical agencies produce these metamorphoses mostly in one di- rection, under the influence of life they go on in either direction. In the laboratory we can in general only reduce from a higher, organized, or more complex constitution to a lower and simpler one. In the vegetable, however, all these changes, take place with the greatest facility. The Chemical Composition of the Carbhydrates. — It 72 HOW f'ROPS GRO\V. has already appeared that the substances just described stand very closely related to each other in chemical coin- position. In the following table their composition is ex- pressed in formulae. CHEMICAL FORMULAE OF THE CAKBHYDRATES. Amyloses. Dried Cellulose, C6 H,,, ().-, Soluble cellulose, Amyloid, } C.H „,(),- Starch, C« H10 05 Soluble starch, Amidulin, C6 H10 Os * Amylodextrin, Dextrin, C6 H,,, ( », Inulin, 6 (C. H10 06) + Hj 0 = ^36 "f.^ * ..1 Levulin, 2(C6H1005) + HiO = C12 Hj, O,, Glycogen, C6 Hlfl 05 Pectin, (?) Arabin, ) Metarabin, } 2 (C6 H10 OB) + H2 0 Cj2 H^ On Gatoctin, C9 H10 Os Paragalactin, C9 H,0 O5 Flax-seed mucilage, C9 H,,, ()-, Quince-seed mucilage, C.H1005 + 2(C8H1005)-E [20 = CM H28 0,4 Glucoses. Crystallized Levulose, C8 H12 06 C6 H12 06 Dextrose, C6 Hu O7 and C, H12 O« C« H1S 06 Galactose, C9 H12 09 CB H,2 OB Mannose, Cg HU O9 C9 H,, <),-, Arabinose, CSH100S C6H1(("05 Kucroses. Saccharose, C,2 H»j On CM H,, (),, Maltose, C12 H24 O,2 CjJ H,, <),, Lactose, CM HM 012 Cj. HJJ O,, Rafflnose, CM H42 O2i Ci« H3, O,0 As above formulated, it is seen that all these bodies, except arabinose, contain 6 atoms of carbon, or a num- ber which is some simple multiple of 6, united to as much hydrogen and oxygen as form in most cases 5, 6 or 11 molecules of water (H20). Being thus composed of car- bon and the elements of water they are termed CarWiy- drates. The mutual convertibility of the carbhyd rates is the * These soluble bodies when dried probably lose water which is essential to their composition, as on drying they become insoluble. THE VOLATILE PART OF PLANTS. 73 easier to understand since it takes place by the loss or gain of several molecules of water. The formulae given are the simplest that accord with the results of analysis. In case of many of the amyloses it is probable that the above formulas should be multi- plied by 2, 4, or 6, or even more, in order to reach the true molecular weight. Isomerism. — Bodies which — like cellulose and dextrin, or like levu- lose and dextrose — are identical in composition, and yet are character- ized by different properties and modes of occurrence, are termed isom- eric ; they are examples of isomerism. These words are of Greek deri- vation, and signify of equal measure. We must suppose that the particles of isomeric bodies which are com- posed of the same kinds of matter, and in the same quantities, exist in different states of arrangement. The mason can build, from a given number of bricks and a certain amount of mortar, a simple wall, an aqueduct, a bridge or a castle. The composition of these unlike struc- tures may be the same, both in kind and quantity ; but the structures themselves differ immensely, from the fact of the diverse arrangement of their materials. In the same manner we may suppose starch to dif- fer from dextrin by a difference in the relative positions of the atoms of carbon, hydrogen, and oxygen in the molecules which compose them. By use of " structural formulae " it is sought to represent the different arrangement of atoms in the molecules of isomeric bodies. In case of substances so complex as the sugars, attempts of this kind have But recently met with success. The following formulae exhibit to the chemi»t the probable differences of constitution between dextrose and levuloae. Dextrose. Levulose. H H H— C— O H H— C— O H H— C— O H C— O _ C— H H— C— O H H-C-O H H C-0 H O H— C— O H H C— O H _ C— O H H C— O H To those familiar with advanced Organic Chemistry the foregoing formulae, to some extent, "account for" the chemical characters of these sugars, and explain the different products which they yield under decomposing influences. APPENDIX TO THE CABBHYDKATE8. Nearly related to the Carbhydrates are the following substances:— 74 1IOW CHOPS GRO\V. Afannite, C6H,4OB, is abundant in the so-called manna of the apoth- ecary which exudes from the bark of several species nt' ash that grow in the eastern hemisphere (t'raxintis onm* and rotti/niijniiii). It likewise exists in the sap of our fruit trees, in edible mushrooms, and sometimes is formed in the fermentation of sugar (viscous fermenta- tioii). It appears in minute colorless crystals ami lias a sweetish taste. It may be obtained from dextrose and levulose by the action of nascent hydrogen as liberated from sodium amalgam and water, CeH^O, + H2 = C,H1406. Dulcite, CBHUO0, is a crystalline substance found in the common cow- wheat (Melampyrinn nemorosum) and in Madagascar manna, li N obtained from milk-sugar by the action of sodium amalgam. The isomeres mannite and dulcite, when acted on by nitric acid, .-in- con verted into acids which are also isomeric. Mannite yields sacchar> acid, which is also formed by treating cane-sugar, dextrose, levulose, dextrin and starch with nitric acid. Dulcite yields, by the same treat- ment, mucic acid, which is likewise obtained from arabin and other gums. Milk-sugar yields both saccharic and mucic acid. Saccharic acid is very soluble in water. Mucic acid is quite insoluble. Both have the formula C6H,0O8. The Pectin-bodies. The juice of many ripe fruits, when mixed with alcohol, yields a jelly-like precipitate which has long been known under the name of pectin. When the firm flesh of acid winter-fruits is subjected to heat, as in baking or stewing, it sooner or later softens, becomes soluble in water and yields a gummy liquid from which by adding alcohol the same or a similar gelatinous substance is separated. Fremy supposes that in the pulp " pectose " exists which is transformed by acids and heat into pectin. EXP. 33. — Express, and, if turbid, filter through muslin the juice of a ripe apple, pear, or peach. Add to the clear liquid its own bulk of alcohol. Pectin is precipitated as a stringy, gelatinous mass, which. on drying, shrinks greatly in bulk, and forms, if pure, a white sub- stance that may be easily reduced to powder, and is readily soluble in cold water. Pectosic and Pectic Acids. These bodies, according to Fremy. com- pose the well-known fruit-jellies. They are both insoluble or nearly so in cold water, and remain suspended in it as a gelatinous mass. Pectosic acid is soluble in hot water, and is supposed to exist in those fruit-jellies which liquefy on heating but gelatinize on cooling. Pec- tic acid is stated to be insoluble in hot water. According to Fremy. pectin is changed into pectosic and pectic acids and finally into mrta- pectic acid by the action of heat and during the ripening process. EXP. 35.— Stew a handful of sound cranberries, covered with water, just long enough »o make them soft. Observe the speedy solution of the firm pulp or "pectose." Strain through muslin. The juice contains soluble pectin, which may be precipitated from a small portion by alcohol. Keep the remaining juice heated to near the boiling point in a water bath (i. e., by immersing the vessel containing it in a larger one of boiling water). After a time, which is variable according to the condition of the fruit, and must be ascertained by trial, the juice on cooling or standing solidifies to a jelly, that dissolves on warming. and reappears again on cooling— Fremy's pectosic acid. By further THE VOLATILE PART OF PLANTS. 75 heating, the jui°-e may form a jelly which is permanent when hot — pectic acid. Other ripe fruits, as quinces, strawberries, peaches, grapes, apples, etc., may be employed for this experiment, but in any case the time required for the juice to run through these changes cannot be pre- dicted safely, and the student may easily fail in attempting to fol- low them. Scheibler having shown that Fremy's metapectic acid of beets is arable acid, it is probable that Fremy's pectin, pectic acid and pectosic acid of fruits, are bodies similar to or identical with the gums already described. The pectin bodies of fruits have not yet been certainly ob- tained in a state of purity, since the analyses of preparations by vari- ous chemists do not closely agree. The Vegetable Acids. — Nearly every family of the vegetable kingdom, so far as investigated, contains one or more organic acids peculiar to itself. Those of more general occurrence which alone concern us here are few in number and must be noticed very concisely. The vegetable acids rarely occur in plants in the free state, but are for the most part united to metals or to organic bases in the form of salts. The vegetable acids consist of car boxy], COOH, united generally to a hydrocarbon group. They are monobasic, dibasic or tribasic, according as they contain one, two or three carboxyls. The Monobasic Acids, to be mentioned here, fall into two groups, viz. : Fatty acids and Oxyf atty acids. THE FATTY ACIDS constitute a remarkable "homolo- gous series," the names and formulae of a number of which are here given : Formic Acetic Propionic Butyric Valeric Caproic Oenanthylic Caprylic Pelargonic Capric Umbellic Laurie Tridecylic acid, H, C O O H C H, C O O H C2 H5 C O O H C3 H7 C O O H C4 H9 C O O H CK Hn C O O H (,., H13COOH 0- HI5 COOH Cs H17 COOH C., H,,,COOH CM H,, COOH C,,HMCOOH C\, H,, COOH Found in Pine needles, red ants, guano. Vinegar and many vegetable juices. Yarrow-flowers. I5utter,limburgercheese,parsnip seeds. Valerian root, old cheese. Hut tor, cocoanut oil. (Artificial.) [fusel oil. Butter, cocoanut oil, limburger cheese, Kose-geranium. Hutter, cocoanut oil. Seeds i>r California laurel. Laurel oil, butter, bayberry tallow. (Artificial.) 76 HOW CROPS GROW. Myristlc Isocetic Palmitic Margaric Stearic Nondecylic Arachic Medullic Behenic Lignoceric Hyenic Cerotic '13 HCT C O O H C18 Hj, C O O H CM H41 C O O H Cn H^ C O O H CK H45 C O O H C,4 H49 C O O H CM H31 C O O H Nutmeg oil. Seeds of Jatropha. Butter, tallow, lard, palm oiL Artificial.) Tallow, Ian I. (Unknown.) -Butter, peanut oil. Marrow of ox. Oil of Moringa oleifera. i I'n known.) Beech-wood tar. Hyena-fat. (Unknown.) Beeswax, carnauba wax, wool-fac It is to be observed that these fatty acids make a nearly complete series, the first of which contains one carbon and two hydrogen atoms, and the last 27 carbon and 54 hydrogen atoms, and that each of the intermediate acids differs from its neighbors by CH2. The first two acids in this series are thin, intensely sour, odorous liquids that mix with water in all proportions ; the third to the ninth inclusive are oily liquids whose consistency in- creases and whose sourness and solubility in water dimin- ish with their greater carbon content. The tenth and other acids are at common temperatures nearly tasteless, odorless, and fatty solids, which easily melt to oily liquids whose acid properties are but feebly manifest. Of these acids a few only require further notice. Acetic Acid, C2H402, or CH3COOH, formed in the " acetic fermentation " from cider, malt, wine and whis- ky, alcohol being in each case its immediate source, exists free in vinegar to the extent of about 5 per cent. When pure, it is a strongly acid liquid, blistering the tongue, boiling at 246°, and solidifying at about 60° to a white crystalline mass. In plants, acetic acid is said to exist in small proportion, mostly as acetate of potassium. Butyric Acid, C4H802, or CH3CH2CH2COOH, in the free state, occurs in rancid butter, whose disagreeable odor is largely due to its presence. In sweet butter it exists only as a glyceride or fat of agreeable qualities. THE VOLATILE PAKT OF PLANTS. 7? The other acids of this series are mostly found in veg- etable and animal fats or fatty oils. (See p. 85.) OXYFATTY ACIDS. — The acids of this class differ from the corresponding fatty acids by having an additional atom of oxygen, or by the substitution of OH for H in the latter. There are two acids of this class that may be briefly noticed, viz. : oxyacetic, orglycollic acid, and oxy- propionic or lactic acid. Glycollic Acid, C2H403 or HOCH2COOH, exists in the juices of plants (grape-vine), and like acetic acid may be formed by oxidizing alcohol. Lactic, C3HG03, or CH3CH (OH) COOH, is the acid that is formed in the souring of milk, where it is produced from the milk-sugar by a special organized ferment. It is also formed in the "lactic fermentation" of cane- sugar, starch and gum, and exists accordingly in sour- kraut and ensilage. The fatty and oxyfatty acids are monobasic, i.e., they contain one carboxyl, COOH, and each acid forms one salt only, with potassium, for instance, in which the hy- drogen of the carboxyl is replaced by the metal. Thus, potassium acetate is CII3COOK. The oxyfatty acids are especially prone to form anhy- drides by loss of the elements of water. Lactic acid cannot be obtained free from admixed water when its aqueous solutions are evaporated, without being partially converted into an anhydride. Gentle heat up to 270° changes it, with loss of water, into so-called lactolactic acid,* C6H1005. a solid, scarcely soluble in water, but that slowly reproduces lactic acid by contact with water, and dissolves in alkalies to form ordinary lactates. Lacto- lactic acid, heated to 290°, loses water with formation of lactide,\ C6H804, a solid nearly insoluble in water, but also convertible into lactic acid by water, and into lactates by alkalies. ~^~2 (C3H603) = CflH1005 + H,0 t C6H1006 = C6H9O4 + H,O 78 HOW CROPS GKCHV. Dibasic Acids. — The acids of this class requiring notice are COOH Oxalic acid. C,H2O4, or COOH Malonlc acid, C3H. 36. — Dissolve 5 grams of oxalic acid in 50 c. c. of hot water, add solution of ammonia orsolid carbonate of ammonium until tin- odor of the hitter slightly prevails, and allow the liquid to cool slowly. Long, needle-like crystals of .i'u!itt< separate on cooling, the compound being sparingly soluble in cold water. Preserve for future use. EXP. 37. — Add to any solution of lime, as lime-water (see note, p. 20), or hard well-water, a few drops of solution of ammonium oxalate. Secondary c'alcium oxalate immediately appears as a white, powdery precipitate, which, from its extreme insolubility, serves to indicate the presence of the minutest quantities of lime. Add a few drops of hydro- chloric or nitric acid to the calcium oxalate; it disappears. Hence ammonium oxalate is a test for lime only in solutions containing no free mineral acid. (Acetic and oxalic acids, however, have little effect upou the test.) Malonic acid and Succinic acid occur in plants in but small quantities. The former has been found in sugar-beets, the latter in lettuce and unripe grapes. Malic acid, C4H605, is the chief sour principle of ap- ples, currants, gooseberries, plums, cherries, strawberries, and most common fruits. It exists in small quantity in a multitude of plants. It is found abundantly in the gar- den rhubarb, and primary potassium malate may be ob- tained in crystals by simply evaporating the juice of the leaf-stalks of this plant. It is likewise abundant as cal- cium salt in the nearly ripe berries of the mountain ash, and in barberries. Calcium malate also occurs in con- siderable quantity in the leaves of tobacco, and is often encountered in the manufacture of maple sugar, separat- ing as a white or gray sandy powder during the evapora- tion of the sap. Pure malic acid is only seen in the chemical laboratory, and presents white, crystalline masses of an intensely sour taste. It is extremely soluble in water. 80 HOW CROPS GROW. Tartaric acid, C4H606, is abundant in the grape, from the juice of which, during fermentation, it is de- posited as argol. This, on purification, yields the cream of tartar (bitartrate of potash) of commerce. Tart rates of po- tassium and calcium exist in small quan- tities in tamarinds, in the unripe berries FiS- 16- of the mountain ash, in the berries of the sumach, in cu- cumbers, potatoes, pineapples, and many other fruits. The acid itself may be obtained in large glassy crystals (see Fig. 16), which are very sour to the taste. Of the Tribasic Acids known to occur in plants, but one need be noticed here, viz., citric acid. c HJ c o o H C6 H8 O7, or C (O H) C O O H C H, C O O H Citric acid exists in the free state in the juice of the lemon, and in unripe tomatoes. It accompanies malic acid in the currant, gooseberry, cherry, strawberry, and raspberry. It is found in small quantity in tobacco leaves, in the tubers of the artichoke (Hi'Uanthns), in the bulbs of onions, in beet-roots, in coffee-berries, in seeds of lupin, vetch, the pea and bean, and in the needles of the fir tree, mostly as potassium or calcium salt. It also exists in cows' milk. In the pure state, citric acid forms large transparent or white crystals, very sour to the taste. Relations of the Vegetable Acids to each otlnr. ami tn flic .li/ii/!oses.-~. Oxalic, malic, tartaric and citric acids usually occur together in our ordinary fruits, and some of them undergo mutual conversion in the living plant. According to Liebig, the unripe berries of the mountain ash contain much tartaric acid, wliicli. as the fruit ripens, is converted into malic acid. Tartaric acid can be artificially transformed into malic acid, and this into succinic acid. When citric, nrilic and tartaric acids arc boiled with nitric acid, or heated with ca-istic potash, they all yield oxalic acid. Cellulose, starch, dextrin, the sugars, yield oxalic acid when heated THE VOLATILE PAftT OF PLANTS. 8l With potash or nitric acid. Commercial oxalic acid is thus made from sawdust. Gum (Arabic), sugar and starch yield tartaric acid by the action of nitric acid. Definition of Acids, Bases, and Salts. — In the popular sense, an acid is any body having a sour taste. It is, in fact, true that all sour substances are acids, but all acids are not sour, some being tasteless, others bitter, and some sweet. A better characteristic of an acid is its capability of forming salts by its interaction with bases. The strong- est acids, i. e., those bodies whose acid characters are most highly developed, if soluble, so as to have any effect on the nerves of taste, are sour, viz., sulphuric acid, phos- phoric acid, nitric acid, etc. Bases are the opposite of acids. The strongest bases, when soluble, are bitter and biting to the taste, and cor- rode the skin. Potash, soda, lime, and ammonia are ex- amples. Magnesia, oxide of iron, and many other com- pounds of metals with oxygen, are insoluble bases, and hence destitute of taste. Potash, soda, and ammonia are termed alkalies ; lime and magnesia, alkali-earths. Salts are compounds that result from the mutual ac- tion of acids and bases. Thus, in Exp. 20, the salt, cal- cium phosphate, was produced by bringing together phosphoric acid, and the base, lime. In Exp. 37, cal- cium oxalate was made in a similar manner. Common salt — in chemical language, sodinm chloride — is formed when caustic soda is mixed with hydrochloric acid, water being, in this case, produced at the same time. NaOH + HCl NaCl + H,O Sodhim hydroxide. Hydrochloric acid. Sodium chloride. Water. In general, salts having a metallic base are formed by substituting the metal for the hydrogen of the acid ; or if an organic acid, for the hydrogen that is united to oxy- gen, i.e., of carboxyl, COOH. Ammonia, NH3, and many organic bases unite directly to acids in forming salts. 6 82 HOW CfiOPS GROW. NH, + HC1 XH4C1 Ammonia. Hydrochloric add. Ammonium NHS + CH3COOH CHaCOOXH4 Ammonia. Acetic aciiti;,i. or vegetable glue, is very soluble in water and aleohol. It strongly resembles animal glue and rim-fly gives to wheat dough its tenacious qualities. Munil'ni resembles gliadin, but is less soluble in strong alcohol, and is in-soluble in water. When moist, it is yellowish-white in color, has a silky luster, and slimy consistence, if exists also in gluten made from rye grain. (Ritthausen,«/oitill a subject of uncertainty. They are, in the first place, naturally mixed or associated with other matters from which it is very difficult to separate THE VOLATILE PART OF PLANTS. 105 them fully. Again, if we succeed in removing foreign substances, it must usually be done by the aid of acids, alkalies, salt-solutions, alcohol and ether, and there is reason to believe that in many cases these reagents essen- tially modify the properties and composition of the pro- teids. These bodies, in fact, as a class, are extremely susceptible to change and alter in respect to appearance, solubility, and other qualities that serve to distinguish them, without any corresponding change in chemical composition being discoverable by our methods of anal- ysis. On the other hand, the substances that have been prepared by different experimenters from the same sources, and by substantially the same methods, often show decided differences of composition. Finally, the methods of analysis used in determin- ing their composition are liable to considerable error, and, if applied to the pure substances, are scarcely delicate enough to indicate their differences with entire accuracy. In the accompanying table (p. 106) are given the most recent and trustworthy analyses of the various vegetable albuminoids, and of the corresponding substances of ani- mal origin. Eeferring to the analyses of Albumins we observe that the egg-albumin differs from serum-albumin in contain- ing about one per cent more of oxygen and one less of carbon, while hydrogen, nitrogen and sulphur are prac- tically the same. These two albumins have been very thoroughly studied, their difference of composition is well established, and they have positive differences in their properties, so that there can be little doubt that they are specifically distinct substances. Of the Vegeta- ble Albumins none offer any reasonable guarantee of purity. The composition of barley-albumin is near that of the animal albumins, but it contains one-third less sulphur. So far, then, as present data indicate, the vog- 106 HOW CROPS GROW. COMPOSITION OF ALBUMINOIDS. ALBUMINS. Egg 52. Blood serum 53.1 Wheat 53.1 Barley 52.8 .' c, FIBRINS. Blood 52. Gluten-fibrin, wheat 54. " " maize 54. Analysts. .9 15.8 1.9 23.2 Chittenden & Polton> 6.9 16.0 1.8 22.2 Hammarsten. 7.217.61.620.5 7.215.81.223.0 Ritthausen. 1.8 16.9 1.1 22.5 Hammarsten. 37.216.91.020.6 ) 67.515.50.721.7 ) Milk casein* 53.37.1 15.90.822.0 Gluten-casein, wheat 52.9 7.017.1 1.022.0 " " " 52.8:7.015.81.123.3 Gluten-casein, buckwheat*. 50.26.8 17.4 l.r. J4.1 Legumin, lupins.. GLOBULINS. 51.47.017.50.623.5 Paraglobulin ~>i . 7 7 Fibrinogen, blood :._'.:> >. Myosin, beef 52.8 7 Conglutin, lupin 50.1 hazel-nut Vitellin, squash " hemp (crystals). . . " Brazil-nut GLIADIN, wheat. .47 riiittenden & Painter Ritt hauscn. diittenden A: Siniih. Kitthausen. .015. .916. .1 16. 7.018. .118. .518 .018 .1 18 Hammarsten. 81.123.4 71.322.2 8 1.3 21 .9 Chittenden & Cummins. 7 1.1 23.0 60.622.5 10.622.5 70.822.5 10.521.9 52.77.118.00.921.3 \Veyl. Ritthausen. MUCEDIN, wheat 54.1 6.916.60.'.- ji.r, Kitlhausen. See pp. 101 and 102 for analyses of Proteoses and Peptone. etable albumins are not identical with those derived from the animal. As respects the Fibrins we have already seen that there is no similarity in properties between that of blood and those obtained from gluten. The analyses of the two gluten-fibrins show either that these substances are quite distinct or that they have not yet been obtained in the pure state. The Vegetable Caseins, as analyzed by Ritthausen, are * The analysis of milk casein should include 0.9 phosphorus. Tin- buckwheat casein contained o.'.t phosphorus, which is not included in the analysis. Whether phosphorus is an ingredient of casein, or an "impurity," is not perhaps positively established. THE VOLATILE PAKT OF PLANTS. 107 observed to contain more nitrogen by 1.2 to 1.6 per cent than exists in animal casein. Furthermore, they differ from each other so widely in carbon content (2.7 percent) as to make it highly probable that their true composition was not in all cases correctly determined. This conclusion is justified by the results of Chittenden & Smith, who have recently analyzed five different prep- arations of gluten-casein, made from wheat by Kitthau- seii's method. The average of their accordant analyses is given above.* Since nitrogen was determined by two methods (those of Dumas and Kjeldahl) these analyses would appear to establish the composition of gluten- casein, whigh accordingly closely agrees with that found by Kitthausen for "albumin" from barley, and with that of paraglobulin, and has the same nitrogen content as the casein of milk. The Animal Globulins agree in composition with each other as well as with animal fibrin which is formed from globulin (fibrinogen). The Vegetable Globulins are strik- ingly different in composition, containing 1.5 to 2 per cent more nitrogen and mostly but half as much sul- phur. The hazel-nut conglutin and the hemp-seed vitel- lin have the same composition. It is evident that the vegetable albuminoids, on the whole, are distinct from those of the animal, but their true composition and relations to each other, to a great extent, remain to be established. Some Mutual Relations of the Albuminoids. — It was formerly supposed that these bodies are identical in com- position, the differences among the analytical results being due to foreign matters, and that they differ from each other in the same way that cellulose and starch differ, viz.: on account of different arrangement of the atoms. Afterwards, Mulder advanced the notion that the albuminoids are compounds of various proportions * Kindly communicated by the authors. 108 HOW CROPS GROW. of hypothetical sulphur and phosphorus radicles with a common ingredient, which he termed protein (from the Greek signifying " to take the first place," because of the great physiological importance of such a body). Hence the designations protein-bodies and proteids. The transformations which these substances are capable of undergoing sufficiently show that they are closely related, without, however, satisfactorily indicating in what manner. In the animal organism, the albuminoids of the food, of whatever name, are dissolved in the juices of the digestive organs, and pass into the blood, where they form blood albumin and globulin. As the blood nour- ishes the muscles, they are modified into the flesh-albu- minoids ; on entering the mammary system they are converted into casein, while in the appropriate part of the circulation they are formed into the albumin of the egg, or embryo. In the living plant, similar changes of place and of character occur among these substances. The Albuminoids in Animal Nutrition. — "\Ve step aside fora moment from our proper plan to direct atten- tion to the beautiful adaptation of this group of organic substances to the nutrition of animals. Those bodies which we have just noticed as the animal albuminoids, together with others of similar composition, constitute a large share of the healthy animal organism, and espec- ially characterize its actual working machinery, being essential ingredients of the muscles and cartilages, as well as of the nerves and brain. They likewise exist largely in the nutritive fluids of the animal — in blood and milk. So far as we know, the animal body has not the power to produce a particle of albumin, or fibrin, or casein except by the transformation of similar bodies pre- sented to it from external sources. They are hence indis- pensable ingredients of the food of animals, and were THE VOLATILE PART OF PLANTS. 109 therefore designated by Liebig as the plastic elements of nutrition. They have also been termed the blood-build- ing or muscle-forming elements. It is, in all cases, the plant which originally constructs these substances, and places them at the disposal of the animal. The albuminoids are mostly capable of existing in the liquid or soluble state, and thus admit of distribution throughout the entire animal body, as in blood, etc. They likewise readily assume the solid condition, thus becom- ing more permanent parts of the living organism, as well as capable of indefinite preservation for food in the seeds and other edible parts of plants. Complexity of Constitution. — The albuminoids are highly complex in their chemical constitution. This fact is shown as well by the multiplicity of substances which may be produced from them by destructive and decom- posing processes as by the ease with which they are broken up into other and simpler compounds. Kept in the dissolved or moist state, exposed to warm air, they speedily decompose or putrefy, yielding a large variety of products. Heated with acids, alkalies, and oxidizing agents, they mostly give origin to the same or to anal- ogous products, among which no less than twenty differ- ent compounds have been distinguished. The numbers of atoms that are associated in the mole- cules of the proteids are very great, though not in most cases even approximately known. The Haemoglobin of blood, which forms red crystals that admit of preparing in a state of great purity, contains in 100 parts — C H N O S Fe 54.2 7.2 16.1 21.6 0.5 0.4 The iron (Fe) is a constant and essential ingredient, and if one atom only of this metal exist in the haemoglobin molecule, its empirical formula must be something like Cc4oH10ooN164FeS2019o, and its molecular weight over 14,- 000. Haemoglobin readily breaks up into a proteid and a 110 HOW CROPS GROW. much simpler red crystalline substance, Haemaeetin, yield- ing about 96 per cent of the former and 4 per cent of the latter. Haematin has approximately the formula CsaH^N^FeOs, so that the proteid, though simpler than haemoglobin, must have an extremely complicated mole- cule, and it is, accordingly, difficult to decide whether a few thousandths of the acids, bases or salts which may be associated with these bodies, as they exist in plants or pass through the hands of the chemist, are accidental or essential to their constitution. Occurrence in Plants. — Aleurone. — It is only in the old and virtually dead parts of a living plant that albu- minoids are ever wanting. In the young and growing organs they are abundant, and exist dissolved in the sap or juices. They are especially abundant in seeds, and here they are often deposited in an organized form, chiefly «$? Fig. 18. Fit,'. 19- in grains similar to those of starch, and mostly insoluble in water. These grains of albuminoid matter are not, in many cases at least, pure albuminoids. Hartiir, who first de- scribed them minutely, has distinguished them by the name aleurone, a term which we may conveniently em- ploy. By the word aleurone is not meant simply an THE VOLATILE PAST OF PLANTS. albuminoid, or mixture of albuminoids, but the organ- ized granules found in the plant, of which the albumin- oids are chief or characteristic ingredients. In Fig. 18 is represented a magnified slice through the outer cells (bran) of a husked oat kernel. The cavities of these outer cells, a, c, are chiefly occupied with very fine grains of aleurone. In one cell, b, are seen the much larger starch grains. In the interior of the oat kernel, and other cereal seeds, the cells are chiefly occu- pied with starch, but throughout grains of aleurone are more or less intermingled. Fig. 19 exhibits a section of the exterior part of a flax-seed. The outer cells, a, contain vegetable muci- lage ; the interior cells, e, are mostly filled with minute grains of aleurone, among which droplets of oil, /, are distributed. In Fig. 20 are shown some of the forms assumed by in- dividual albuminoid- grains ; a is aleuroue from the seed of the vetch, 5 from the castor-bean, c from flax-seed, d from the fruit of the bayberry (Myrica cerifera) and e from mace (an appendage to the nutmeg, or fruit of the Myristica moscfiata). Crystalloid aleurone. — It has been already remarked e Fig. 20. Fig. 21. that crystallized albuminoids exist in plants. This was first observed by Hartig (Eiittcickelungsgeschichte des 112 HOW CROPS GKOW. Pflanzenkeims, p. 104). In form they sometimes imitate crystals quite perfectly, Fig. 21, a; in other cases, b, they are rounded masses, having some crystalline planes or facets. They are soft, yield easily to pressure, swell up to double their bulk when soaked in weak acids or alkalies, and their angles have not the constancy peculiar to ordinary crystals. Therefore the term crystalloids, i. e. , having the likeness of crystals, has been applied to them. As Cohn first noticed (Jour, far Prakt. Chem., 80, p. 129), crystalloid aleurone may be observed in the outer portions of the potato tuber, in which it invariably pre- sents a cubical form. It is best found by examining the cells that adhere to the rind of a potato that has been boiled. In Fig. 21, a represents a cell from a boiled potato, in the center of which is seen the cube of aleurone. It is surrounded by the exfoliated remnants of starrh- grains. In the same figure, 5 exhibits the contents of a cell from the seed of the bur reed (Sparyanium ramo- sum), a plant that is common along the borders of ponds. In the center is a comparatively large mass of aleurone, having crystalloid facets. As already stated, the proteids in the crystalloid aleu- rones of hemp, castor-bean and squash have the chemical characters of globulin. The aleurone of the Brazil-nut (Berthottetia) and that of the yellow lupin contain, ac- cording to Hartig and Kubel, 9.4% of nitrogen which corresponds to some 50 or 60% of proteids. Weyl obtained from the Brazil-nut a very pure amor- phous vitellin with 18.1% of nitrogen. The vitellin of Brazil-nut, castor-bean, and of hemp and squash seeds has been recrystalized from salt solutions by Schmiedeberg, Drechsel, Griibler and Ritthausen. According to Vines, seeds of lupin and peony yield a myosin to salt-solution, and sunflower seeds, after treatment with ether to remove oil, yield a globulin with the properties of myosin, but if alcohol is used, the proteid has the character of vitellin. THE VOLATILE PART OF PLANTS. H3 Vines, who has examined the aleurone of many plants, finds it in all cases more or less soluble in water. The globulin doubtless goes into solution by help of the salts present. Vines also states that a body soluble in water, having the properties of a proteose (hemialbumose), is universally present in aleurone. Estimation of the Albuminoids. — The quantitative sep- aration of these bodies, as they occur in plants, is mostly impossible in the present state of science. In many cases their collective quantity in an organic substance may be calculated with approximate accuracy from its content of nitrogen. In calculating the nutritive value of a cattle-food the albuminoids are currently reckoned as equal to its nitro- gen multiplied by 6.25. This factor is the quotient ob- tained by dividing 100 by 16, which, some 25 years ago, when cattle-feeding science began to assume its present form, there was good reason to assume was the average per cent of nitrogen in the albuminoids. As Ritthausen has insisted, this factor is too small, since the albuminoids of the cereals and of most leguminous seeds, as well as of the various oil-cakes, contain nearer 17 than 16 per cent of nitrogen, if our analyses rightly represent their com- position, and the factor 6 (= 100 -f- 16.66) would be more nearly correct. This mode of calculation only applies with strictness where all the nitrogen exists in albuminoid form. This appears to be substantially true in most seeds, but in case of young grass and roots there is usually a considerable proportion of non-albuminoid nitrogen, for which due allowance must be made. (See Amides.) * * Ammonia, NHS, and Nitric acid, NHOS. These bodies are mineral, not organic substances, and are not, on the whole, considerable ingredients of plants. They are however t lie principal sources of I lie nitrogen of vegetation, and', serving as ]>1 ant-food, enter plants through their roots, chietly from the soil, ami exist within them in small quantity, and for a time, pending the conversion of their nitrogen into that of the amides and albuminoids, to whose production they are probably essential. In seeds and fruits, and in mature plants, growing in soil* 114 HOW CROPS GROW. AVERAGE QUANTITY OF ALBUMINOIDS IN VARIOUS VEGETABLE PRODUCTS.— ALBUMINOIDS = N X 6.25. American, Jenkins. German, Wolff Maize fodder, green 1.8 1.9 Beet tops, " 2.7 3.0 Carrot tops, " 4.3 5.1 Meadow grass, in bloom 3.1 4.8 Red clover, " 3.7 4.8 White clover, " 4.0 5.6 Turnips, fresh 1.1 1.8 Carrots, " 1.1 2.2 Potatoes, " 2.2 3.4 Corn cobs, air-dry 2.3 2.3 Straw, " 3.5 4.0 Pea straw, " 7.3 10.4 Bean straw, " 10.2 16.3 Meadow hay, in bloom 7.0 15.5 Red-clover hay, " 12.5 19.7 White-clover hay, " 14.6 23-2 Buckwheat kernel, air-dry 10.0 14.4 Barley Maize Rye Oat Wheat Pea Bean 12.4 16.0 10.6 16.0 10.6 17.6 11.4 17.6 11.8 20.8 L'2.4 35.8 24.1 40.8 THE AMIDES, AMIDOACIDS, IMIDES, AND AMINES. — Ammonia and the ammonium salts, so important as food to plants, and as ingredients of the atmosphere, of soils, and of manures, occur in so small proportions in living vegetation as to scarcely require notice in this work occupied with the composition of Plants. They are, however, important in connection with the amides now to be briefly described. Ammonia, an invisible gas of pungent odor which dissolves abundantly in water to form the aqua ammonia of spirits of hartshorn of the apothecary, is a compound of one atom of nitrogen with three atoms of hydrogen. It unites to acids, forming the ammonium salts : of moderate fertility, both ammonia and nitric acid, or strictly speak- Lng, ammonia-salts and nitrates, commonly occnx in very email pro- portions. In roots, Stems, and foliage of plants situated in soils rich ill these substances, tliey may be present in notable quantity. The dry leaves anil stems of tobacco and beets sometimes contain several per cent of nitrates. When these substances arc' presented to plants in abundance, especially in dry weather, they may accumulate in the roots and lower parts of t lie plant more rapidly than they can be assim- ilated. On the other hand, when their supply in the so'il is relatively small they are so completely and rapidly assimilated as to be scarcely detectable. Their possible presence should be taken into account when it is undertaken to calculate the albuminoids of the plant from thr amount of nitrogen found in its analysis. THE VOLATILE PART OF PLANTS. 115 CH3COOH + NHS = CHSCOONH4 Acetic acid. Ammonia. Ammonium acetate. Amides. — This term is often used as a general desig- nation for all the bodies of this section which result from the substitution of the hydrogen of ammonia by any atom or group of atoms. In a narrower sense amides are those ammonia-derivatives containing "acid-radi- cals" which are indicated in their systematic names. Acetamide, CH3CONH2. Many ammonium salts, when somewhat strongly heated, suffer decomposition into amides and water. CH3COONH4 CH3CONH2 + H,O Ammonium acetate. Acetamide. Water. The above equation shows that acetamide is ammonia, NH3, or HNH2, one of whose hydrogens has been re- placed by the group of atoms, CH3CO, the acetic acid radical, so called. Acetamide is a white crystalline body. The simple amides, like acetamide, are as yet not known to exist in plants. They readily unite with water to produce ammonium salts. Carbamide, or Urea CO(NH2)2. This substance — the amide of carbonic acid CO(OH)2 — naturally occurs in considerable proportion in the urine of man and mam- malian animals. It is a white, crystalline body, with a cooling, slightly salty taste, which readily takes up the elements of water and passes into ammonium carbonate. Urea has not been found in plants, but derivatives of it in which acid radicals replace a part of its hydrogen are of common occurrence. (Guanin, allantoin.) Amidoacids are acids containing the NH2 group as a part of the acid radical. Amidoacetic Acid, C2H5N02, or CH2(NH2)COOH, is derived from acetic acid, CH3COOH, by the replace- ment of H in CH3 by NH2. The amidoacids have not a sour, but usually a sweetish taste, and, like the amides, act both as weak acids and weak bases. Amidoacetic L16 HOW CROPS GROW. acid, also called glycocoll, has not as yet been found in plants, but exists in the scallop and probably in other shell-fish, and a compound of it, benzoylglycocoll or hip- puric acid, is a nearly constant ingredient of the urine of the horse and other domestic herbivorous animals. Betain, or trimethylglycocoll, C5HUK02, a crystalliza- ble substance found in beet-juice, stands in close chem- ical relations to amidoacetic acid. Amidovaleric acid, CgHnXOo, occurs in ox-pancreas and in young lupin plants. Amidocaproic acid, or Leucin, C6Hi3X02, first observed in animals, has lately been discovered in various plants. The same is true of Tyrosin, or oxyphenyl-amidopropionic acid, CyHnX03, and of phenyl -amidopropionic acid, C9HnN02. The above amidoacids are readily obtained as products of decomposition of animal and vegetable albuminoids by the action of hot acids. Amidoacetic acid was thus first obtained from gelatin. Leucin and Tyrosin are com- monly prepared by boiling horn shavings with dilute sul- phuric acid ; they are also formed from vegetable albu- minoids by similar treatment and are final results of the digestion of proto- and deutero-proteoses (hemialbumose) under the action of trypsin and papain. Asparagin and Glutamin. — These bodies, which are found only in plants, are amides of amidoacids, being de- rived from dibasic acids. Asparagin, the amide of amidosuccinic acid, rn MLCOOH CHjCOMIj has been found in very many plants, especially in those just sprouted, as in asparagus, peas, beans, etc. Aspara- gin forms white, rhombic crystals, and is very soluble in water. Glutamin, the amide of amidoglutaric acid, C,HY\H, THE VOLATILE PART OF PLANTS. 117 has been found, together with asparagin, in beet-juice and in squash seedlings. The amides, when heated with water alone, and more easily in presence of strong acids and alkalies, are con- verted into ammonia and the acids from which they are derived. Thus, asparagin yields ammonia and amido- succinic acid at the boiling heat under the influence of hydrochloric acid, or of potassium hydroxide, and gluta- min is broken up by the last-named reagent at common temperatures, and by water alone at the boiling point, with formation of ammonia and amidoglutaric acid. The amidoacids are not decomposed by hot water or acids with separation of ammonia. Amidosuccinic and amidoglutaric acids result from albuminoids by boiling with dilute sulphuric acid, and by the action of bromine. The latter acid as yet has been obtained from vegetable albuminoids only, and is prepared most abundantly from, gluten, and especially from mucedin. Imides, closely related to the amides, are a series of very interesting substances, into whose chemical consti- tution we cannot enter here further than to say that they contain several NH* groups, i. e., ammonia, NH3, in which two hydrogens are replaced by hydro-carbon, or oxycarbon groups or carbon atoms. These bodies are Uric acid, C5H4N403, Adenin, C5H5N5, Guanin, C5H5N50, Allantoin, C4H6"N"403, Xantldn, Hypoxanthin, C6H4N40, Theobromin, C7H80402, Caffein, C8H10N402, and Vernin, Ci6H20X808. Of these the first, so far as now known, occurs exclusively in the ani- mal. Adenin, Guanin, Allantoin, Xanthin, and Hypo- xanthin, are common to animals and plants ; the last three are exclusively vegetable. Caffein exists in coffee and tea combined with tannic acid. In the pure state it forms white, silky, fibrous crystals, and has a bitter taste. In coffee it is found to * Or its hydro-carbon derivatives. 118 HOW CROPS GROW. the extent of one-half per cent ; in tea it occurs in much larger quantity, sometimes as high as 6 per cent. Theobromin resembles caffein in its characters. It is found ii, tha cacao-bean, from which chocolate is man- ufactured. Vernin, discovered recently in various plants, young clover, vetches, squash-seedlings, etc., yields guanin by the action of hydrochloric acid. All these bodies stand in close chemical relations to each other, being complex imide derivatives of dioxymalonic (mesoxalic) acid. The amides and amidoacids, like ammonia, are able to combine directly with acids, are accordingly bases, but they are weak bases, because the basic quality of their ammonia is largely neutralized by the acid radicals already present in them. On the other hand, amides and ami- doacids often act as weak acids, for a portion of the hydro- gen of the NH2 group is easily displaced by metals. The amides thus in fact possess in a degree the quali- ties of both the acid and of the base (ammonia) from which they are derived. They also are commonly "neu- tral" in the sense of having no sharp acid or alkaline taste or corrosive character. In vegetation amides appear as intermediate stages be- tween ammonium salts and albuminoids. They are, on the one hand, formed in growing plants from ammo- nium salts by a constructive process, and from them or by their aid, probably, the albuminoids are built up. On the other hand, in animal nutrition they are stages through which the elements of the albuminoids pass in their reversion to purely mineral matters. In germinat- ing seeds and developing buds they probably combine both these offices, being first formed in the germ from the albuminoids of the seed, entering the young plant or shoot, and in it being reconstructed into albuminoids. Their free solubility in water and ability to penetrate moist membranes adapt them for this movement. They THE VOLATILE PAKT OF PLANTS. 119 temporarily accumulate in seedlings and buds, but disap- pear again as growth takes place, being converted into albuminoids, in which transformation they require the conjunction of carbhydrates. Their ability to unite with acid as well as bases further qualifies them to take part in these physiological processes. The imides are also at once weak bases and weak acids. Uric acid and allantoin, relatively rich in oxygen, have the acid qualities best developed. Guanin and caffein, with less oxygen and more hydrogen, are commonly classed among the organic bases, as in them the basic characters are most evident. Amines. — When the hydrogen of ammonia is replaced by hydrocarbon groups (radicals) such as Methyl, CH3, Ethyl, C2H5, Phenyl, C6H5, etc., compound ammonias or amines result which often resemble ammonia in physical and chemical characters, and some of them appear to be stronger bases than ammonia, being able to displace the latter from its combinations. Trimethylamine, N(CH3)3, may be regarded as ammo- nia whose hydrogens are all substituted by the methyl group, CH3, and is a very volatile liquid having a rank, fishy odor, which may be obtained from herring pickle, and exhales from some plants, as from the foliage of Chenopo- dium vulvaria, and the flowers of Crataegus oxycantha. It is produced from detain (trimethylamidoacetic acid), by heating with potash solution, just as ammonia is formed from many amides under similar treatment. Cholin, C5Hi5N02, and Neurin, C5H13NO, are organic bases related to trimethylamine, which were first ob- tained from the animal. Cholin is an ingredient of the bile, and is found also in the brain and yolk of eggs, where it exists as a component of lecithin. It has latterly b»en discovered in the hop, lupin and pumpkin plants, and in cotton seed ; by oxidation it yields betain. Neu- rin is readily formed from choliu by the action of alka- 120 HOW CROPS GROW. lies and in the process of putrefaction. It is a violent poison, and is perhaps one of the ingredients which, in the seeds of the vetch and of cotton, prove injurious, or even fatal, when these seeds are too largely eaten by ani- mals. Cholin and Neurin are syrupy, highly alkaline liquids. 7. ALKALOIDS is the general designation that has been applied to the organic bases found in many plants, which are characterized in general by their poisonous and medicinal qualities. Caffein and Theobromin, already noticed, were formerly ranked as alkaloids. We may mention the following : Nicotin, C10H14N2, is the narcotic and intensely poi- sonous principle in tobacco, where it exists in combina- tion with malic and citric acids. In the pure state it is a colorless, oily liquid, having the odor of tobacco in an extreme degree. It is inflammable and volatile, and so deadly that a single drop will kill a large dog. French tobacco contains 7 or 8 per cent ; Virginia, 6 or 7 per cent ; and Maryland and Havana, about 2 per cent of nicotin. Nicotin contains 17.3 per cent of nitrogen, but no oxygen. Lupinidin, C8H15N, Lupanin, C15H25N20, and Lu- pinin, C21H40N202, are bases existing in the seeds of the lupin. The first two are liquids ; the last is a crystal- line solid. They are poisonous and are believed to occa- sion the sickness which usually follows the use of lupin- seeds in cattle food. Sinapin, Ci6H23N05, occurs in white mustard. When boiled with an alkali it is decomposed, yielding neurin as one product. Vicin, C28H51Nn02i, and Convicin, CioH14N307, are crystalline bases that occur in the seeds of the vetch, with regard to whose nature and properties little is known. Avenin, C56H21N018, according to Sanson, is a sub- stance of alkaloidal character, existing in oats. It is said THE VOLATILE PAET OF PLANTS. 121 to be more abundant in dark than in light -colored oats, and, when present to the extent of more than nine-tenths of one per cent, to act as a decided nerve-excitant on ani- mals fed mainly on oats. Avenin is described as a gran- ular, brown, non-crystallizable substance, but neither Osborne (at the Connecticut Experiment Station) nor Wrampelmeyer ( Vs. St., XXXVI, p. 299) have been able to find any evidence of the presence of such a body in oats. Morphin, C17H19N03, occurs, together with several other alkaloids, in opium, the dried milky juice of the seed-vessels of the poppy cultivated in India. Its use in allaying pain and obtaining sleep and its abuse in the "opium habit" are well known. Piperin, Ci7H19N03, the active principle of white and black pepper, is a white crystalline body isomeric with morphin. Quinin, C20H24N202, is the most important of several bases used as anti-malarial remedies obtained from the bark of various species of cinchona growing in the forests of tropical South America, and cultivated in India. Strychnin, C2iH22N202, and Brucin, C23H26N2OH, is the intensely poisonous alkaloid of nux vomica (dog button). Atropin, CnH2SNOs, is the chief poisonous principle of the " Nightshade" or belladonna, and of stramonium or "Jamestown weed." Veratrin, CgoH^NOg, is the chief toxic ingredient of the common White Hellebore, so much used as an insecticide. Solanin, C42H87N015 (?), is a poisonous crystalline alkaloid found in many species of Solanum, especially in the black nightshade (Solanum nigrum). It occurs in the sprouted tubers and green fruit of the potato (Solanum tulerosum) and in the stems and leaves of the tomato (Solanum lycopersicum). The alkaloids, so far as investigated, appear to be more 122 HOW CEOPS GROW. or less complex derivatives of the bases Pyridin, C5H5N, and Quinolin, C9H7ST, which are colorless, volatile liquids with sharp, unpleasant odor, produced from albu- minoids at high temperatures, and existing in smoke, bone-oil and tar. The alkaloids bear to these bases simi- lar relations to those subsisting between the amines and ammonia. 8. PHOSPHORIZED SUBSTANCES. — This class of bodies are important because of their obvious relations to the nutrition of the brain and nerve tissues of the animal, which have long been known to contain phosphorus as an essential ingredient. All our knowledge goes to show that phosphorus invariably exists in both plants and ani- mals as phosphoric acid or some derivative of this acid, or, in other words, that their phosphorus is always united to oxygen as in the phosphates, and is not directly combined to carbon, hydrogen, or nitrogen. Nuclein. — This term is currently employed to desig- nate various imperfectly-studied bodies that resemble the albuminoids in many respects, but contain several per cent of phosphorus. They are easily decomposable, boiling water being able to remove from them phosphoric acid, and under the action of dilute acids they mostly yield phosphoric acid, albuminoids and hypoxanthin, C5H4N40, or similar imide bases. They are very difficult of digestion by the gastric juice. The nucleins are found in the protoplasm and especially in the cell-nuclei (see p. 245), of both plants and animals, and have been ob- tained from yeast, eggs, milk, etc. , by a process based on their indigestibility by pepsin. Chemists are far from agreed as to the nature or composition of the nucleins. Lecithin, C44H90NP09. — This name applies to a num- ber of substances that have been obtained from the brain and nerve tissue of animals, eggs and milk, as well as from yeast, and the seeds of maize, peas, and wheat. The lecithins are described as white, wax-like substances, THE VOLATILE PAKT OF PLANTS. 123 imperfectly crystallizable, similar to protagon in their deportment toward water, and readily decomposed into cholin, glyceropkosplioric acid, and one or more fatty acids. Three lecithins appear to have been identified, yielding respectively, on decomposition, stearic, palmitic, and oleic acids. The formula C44H9oNP09 is that of distearic lecithin, which is composed of glyceryl, C8H6, united to two stearic acid radicals, and also to phosphoric acid, which again is joined to cholin, as represented by the formula— Lecithin is believed to be a constant and essential in- gredient of plants and animals. Protagon, CieoHsosNsPOss, discovered by Liebreich in the brain of animals, has been further studied by Gam- gee & Blankenhorn. It is a white substance that swells up with water to a gelatinous mass and finally forms an opake solution. From solution in ether or alcohol it can be easily obtained in needle-shaped crystals, whose com- position is given below. Alkalies decompose protagon into glycero-phosphoric acid, stearic and other fatty acids, and cholin or neurin. Protagon was formerly confounded with lecithin and thought to exist in plants, but its presence in the latter has not been established. Protagon, Lecithin. Carbon ......................... 66.39 65.43 Hydrogen ...................... 10.69 11.16 Nitrogen ........................ 2.39 1.73 Phosphorus .................... 1.07 3.84 Oxygen ......................... 19.46 17.84 100.00 100.00 Knop was the first to show that the crude fat which is extracted from plants by ether contains an admixture of some substance of which phosphorus is an ingredient. In the oil obtained from the sugar-pea he found 1.25 per cent, of phosphorus. Toplor afterwards examined the 124 HOW CROPS GKOW. oils of a large number of seeds for phosphorus with the subjoined results : Source of Per cent, of Source of Per cent, of fat. phosphorus. fat. phosphorus. Lupin 0.29 Pea I-" Horse-bean 0. <2 Vetch 0-50 Winter lentil 0.39 Horse-chestnut 0.40 Chocolate-bean none Millet ' Poppy ' Walnut trace Olive none Wheat 0.25 Barley 0.28 Rye... 0.31 Oat 0.44 Flax none Colza ' Mustard " It is probable that the phosphorus in these oils existed in the seeds as lecithin, or as glycerophosphoric acid, which is produced in the decomposition of lecithin. Max- well (Constitution of the Legumes), reckoning from the phosphoric acid found in the ether-extract, estimates the pea kernel to contain 0.368 per cent, the horse-bean (Fala vulgaris) 0.600 per cent, and the vetch 0.532 per cent of lecithin. Lecithin is thus calculated to make up 19.63 per cent of the crude fat of the pea, 31.54 per cent of the crude fat of the horse-bean, and 35.24 per cent of that of the vetch. Chlorophyl, i. e., leaf -green, is the name applied to the substance which occasions the green color in vegeta- tion. It is found in all those parts of most annual plants and of the annually renewed parts of perennial plants which are exposed to light. The green parts of plants usually contain chlorophyl only near their surface, and in quantity not greater than one or two per cent of the fresh vegetable substance. Chlorophyl, being soluble in ether, accompanies fat or wax when these are removed from green vegetable mat- ters by this solvent. It is soluble in alcohol and hydro- chloric and sulphuric acids, imparting to these liquids an intense green color, but it suffers alteration and decom- position so readily that it is doubtful if the composition of chlorophyl, as it exists in the living leaf, is accurately known, especially since it is there mixed with other sub,- THE VOLATILE PART OF PLANTS. 125 stances, separation from which is difficult or imprac- ticable. Chlorophyllan, obtained by Hoppe-Seyler from grass, separates from its solution in hot alcohol in characteristic acicular crystals which are brown to transmitted light, and iii reflected light are blackish green, with a velvety, somewhat metallic lustre. This substance has the con- sistence of beeswax, adheres firmly to glass, and at about 230° melts to a brilliant black liquid. The crystallized chlorophyllan has a composition as follows : CHLOKOPHYLLAN. Carbon 73.36 Hydrogen 9.72 Nitrogen 5.68 Phosphorus 1.38 Magnesium 0.34 Oxygen 9.52 100.00 Chlorophyllan is chemically distinct from chlorophyl, as proved by its optical properties, but in what the dif- ference consists is not understood. Boiling alkali decom- poses it with formation of chlorophyllanic acid that may be obtained in blue-black crystals, and at the same time glycerophosphoric acid and cholin, the decomposi- tion-products of lecithin, are produced. Tschirch found that chlorophyllan, by treatment with zinc oxide, yields a substance whose optical properties lead to the belief that it is identical with the chlorophyl that occurs in the living plant. It was obtained as a dark-green powder, but its exact chemical composition is not known. The special interest of chlorophyl lies in the fact that it is to all appearance directly concerned in those con- structive processes by which the plant composes starch and other carbhydrates out of the mineral substances which form its food. Xanthophyl is the yellow coloring matter of leaves and of many flowers. It occurs, together with chlorophyl, in green leaves, and after disappearance of chlorophy] remains as the principal pigment of autumn foliage. 126 HOW CROPS GBOW. CHAPTER II. THE ASH OF PLANTS. §1- THE INGREDIENTS OF THE ASH. As has been stated, the volatile or destructible part of plants, i. e., the part which is converted into gases or vapors under the ordinary conditions of burning, con- sists chiefly of Carbon, Hydrogen, Oxygen and Nitro- gen, together with small quantities of Sulphur and Phos- phorus. These elements, and such of their compounds as are of general occurrence in agricultural plants, viz., the Organic Proximate Principles, have been already described in detail. The non-volatile part or ash of plants also contains, or may contain, Carbon, Oxygen, Sulphur, and Phos- phorus. It is, however, in general, chiefly made up of eight other elements, whose common compounds are permanent at the ordinary heat of burning. In the subjoined table, the names of the 12 elements of the ash of plants are given, and they are grouped under two heads, the non-metals and the metals, by rea- son of an important distinction in their chemical nature, ELEMENTS OF THE ASH OF PLANTS. Non-Metals. Metals. Oxygen. Potassium. Carbon. Sodium. Sulphur. Calcium. Phosphorus. Magnesium. Silicon. Iron. Chlorine. Manganese. If to the above be added Hydrogen and Nitrogen THE ASH OF PLANTS. 127 the list includes all the elementary substances that belong to agricultural vegetation. Hydrogen is never an ingredient of the perfectly burned and dry ash of any plant. Nitrogen may remain in the ash under certain con- ditions in the form of a Cyanide (compound of Carbon and Nitrogen), as will be noticed hereafter. Besides the above, certain other elements are found, either occasion- ally in common plants, or in some particular kind of vegetation ; these are Iodine, Bromine, Fluorine, Titanium, Boron, Arsenic, Lithium, Rubidium, Barium, Aluminum, Zinc, Copper. These elements, how- ever, so far as known, have no special importance in agricultural chemistry, and mostly require no further notice. We may now complete our study of the Composition of the Plant by attending to a description of those ele- ments that are peculiar to the ash, and of those com- pounds which may occur in it. It will be convenient also to describe in this section some substances, which, although not ingredients of the ash, may exist in the plant, or are otherwise important to be considered. The Non-metallic Elements, which we shall first notice, though differing more or less widely among them- selves, have one point of resemblance, viz., they and their compounds with each other have acid properties, i. e., they either are acids in the ordinary sense of being sour to the taste, or enact the part of acids by uniting to met- als or metallic oxides to form salts. We may, therefore, designate them as tbe acid elements. They are Oxygen, Sulphur, Phosphorus, Carbon, Silicon, and Chlorine. With the exception of Silicon, and the denser forms of Carbon, these elements by themselves are readily volatile. Their compounds with each other, which may occur in vegetation, are also volatile, with two exceptions, viz., Silicic and Phosphoric acids. In order that they may resist the high temperature at which ashes are formed, they must be combined with the metallic elements or their oxides as salts. 128 HOW CROPS GROW. Oxygen, Symbol 0, atomic weight 16, is an ingredient of the ash, since it unites with nearly all the other ele- ments of vegetation, either during the life of the plant, or in the act of combustion. It unites with Carbon, Sulphur, Phosphorus, and Silicon, forming acid bodies ; while with the metals it produces oxides, which have the characters of bases. Chlorine alone of the elements of the plant does not unite with oxygen, either in the living plant, or during its combustion. CARBON AND ITS COMPOUNDS. Carbon, Sym. C, at. wt. 12, has been noticed already with sufficient fullness (p. 14). It is often contained as charcoal in the ashes of the plant, owing to its being en- veloped in a coating of fused saline matters, which shield it from the action of oxygen. Carbon Dioxide, commonly termed Carbonic acid, Sym. C02, molecular weight 44, is the colorless gas which causes the sparkling or effervescence of beer and soda water, and the frothing of yeast. It is formed by the oxidation of carbon, when vegeta- ble matter is burned (Exp. 6). It is, therefore, found in the ash of plants, combined with those bases which in the living organism existed in union with organic acids ; the latter being destroyed by burning. It also occurs in combination with calcium in the tissues of many plants. Its compounds with bases are carbon- ates, to be noticed presently. When a carbonate, as mar- ble or limestone, is drenched with a strong acid, like vinegar or muriatic acid, the carbon dioxide is set free with effervescence. Carbonic Acid, H2C03, or CO(OH)2, mo. ivt. 62. This, the carbonic acid of modern chemistry, is not known as a distinct suostance, since, when set free from carbon- ates by the action of a stronger acid, it falls into carbon dioxide and water : THE ASH OF PLANTS. 129 CaCO3 + 2 HC1 = CaClj + H2CO3 and H,CO3 = H,O + CO,. Carbon dioxide is also termed anhydrous carbonic acid, or again, carbonic anhydride. CYANOGEN, Sym. C2NZ.— This important compound of Carbon and Ni- trogen is a gas which has an odor like that of peach-pits, and which burns on contact with a lighted taper with a fine purple flame. In its union with oxygen by combustion, carbon dioxide is formed, and nitro- gen set free : CjN, + 4 O = 2 CO2 + N2. Cyanogen may be prepared by heating an intimate mixture of two parts by weight of ferrocyanide of potassium (yellow prussiate of potash) and three parts of corrosive sublimate. The operation may be conducted in a test-tube or small flask, to the mouth of which is fitted a cork penetrated by a narrow glass tube. On applying heat, the gas issues, and may be set on fire to observe its beautiful Same. Cyanogen, combined with iron, forms the Prussian blue of com- merce, and its name, signifying the blue-producer, was given to it from that circumstance. Cyanogen unites with the metallic elements, giving rise to a series of bodies which are termed Cyanides. Some of these often occur in small quantity in the ashes of plants, being produced in the act of burning by the union of nitrogen with carbon and a metal. For this result, the temperature must be very high, carbon must be in excess, the metal is usually potassium or calcium, the nitrogen may be either free nitrogen of the atmosphere or that originally existing in the organic matter. With hydrogen, cyanogen forms the deadly poison hydrocyanic or prussic acid, HCy, which is produced from amygdalin, one of the ingre- dients of bitter almonds, peach, and cherry seeds, when these are crushed in contact with water. When a cyanide is brought in contact with steam at high tempera- tures, it is decomposed, all its nitrogen being converted into ammonia. Cyanogen is a normal ingredient of one common plant. The oil of mustard is ailylsulphocyanate, C8HBCNS. SULPHUR AND ITS COMPOUNDS. Sulphur, Sym. S, at. wt. 32. — The properties of this element have been already described (p. 25). Some of its compounds have also been briefly alluded to, but re- quire more detailed notice. HYDROGEN SULPHIDE, Sym. H,S, mo. irt. $4. This substance, familiarly known as sulphuretted hydrogen, occurs dissolved in the water of nu- merous so-called sulphur springs, as those of Avon and Sharon, N. Y., from which it escapes as a fetid gas. It is not unfrequently emitted from volcanoes and fumaroles. It is likewise produced in the decay of organic bodies which contain sulphur, especially eggs, the intolerable odor of which, when rotten, is largely due to this gas. It is evolved from manure heaps, from salt marshes, and even from the soil of moist meadows. 9 130 HOW CROPS GROW. The ashes of plants sometimes viHil this gas when they are moistened with water. In such eases. a .SK///// /'»/»• t,f j>otst plants, especially in that of clover, the bean, and other legumes. THE ASH OF PLANTS. 147 In nature, sulphate of lime is usually combined with two molecules of water, and thus constitutes Gypsum, CaS04 . 2 H20, which is a rock of frequent and exten- sive occurrence. In the cells of many plants, as for instance the bean, gypsum may be discovered by the microscope in the shape of minute crystals. It requires iOO times its weight of water to dissolve it, and being almost universally distributed in the soil, is rarely absent from the water of wells and springs. Land plaster is ground gypsum, that from Nova Scotia being white, that from Onondaga and other local- ities in New York State gray in color. THE PHOSPHATES which require special description are those of Potassium, Sodium, and Calcium. Numerous phosphates of each of these bases exist, or may be prepared artificially. But three classes of phos- phates have any immediate interest to the agriculturist. As has been stated (p 132), phosphoric acid, prepared by boiling phosphorus pentoxide with water, is represented by the symbol H3P04. The phosphates may be regarded as phosphoric acid in which one, two, or all the atoms of hydrogen are substituted by one or several metals. Potassium Phosphates or Phosphates of Potash. — There are three of these phosphates formed by replac- ing one, two, or three hydrogen atoms of phosphoric acid by potassium, viz. : KH2P04, primary or mono- potassic phosphate ; K2HP04, secondary or dipotassic phosphate, and K3P04, tertiary or tripotassic phos- phate.* Of these salts, the secondary and tertiary phos- phates exist largely (to the extent of 40 to 50 per cent) in the ash of the kernels of wheat, rye, maize, and other bread grains. The potassium phosphates do not occur in commerce ; they closely resemble the corresponding sodinm-salts in their external characters. *The primary phosphates arc often designated acid or super-phos- ptiiitrti, the secondary ncntrul jiliosphates, and the tertiary basic phos- phates. 148 HOW CROPS GROW. Sodium Phosphates, or Phosphates of Of these the disodic phosphate, Na2HP04, alone needs notice. It is found in the drug-stores in the form of glassy crystals, which contain 12 molecules (56 per cent) of water. The crystals become opaque if exposed to the air, from the loss of water. This salt has a cooling, sa- line taste, and is very soluble in water. Calcium Phosphates, or Phosphates of Lirrie. — Since one atom of calcium replaces two of hydrogen, the formulae of the calcium phosphates are written as follows : monocalcic or primary phosphate CaH4P208 ; dicalcic or secondary phosphate, CaHP04 ; tricalcic or tertiary phosphate, Ca3P208.* Both the secondary and tertiary phosphates probably occur in plants. The sec- ondary is a white crystalline powder, nearly insoluble in water, but easily soluble in acids. In nature it is found as a urinary concretion in the sturgeon of the Cas- pian Sea. It is also an ingredient of guanos, and proba- bly of animal excrements in general. The tricalcic phosphate, or, as it is sometimes termed, bone-phosphate, is a chief ingredient of the bones of ani- mals, and constitutes 90 to 95 per cent of the ash or earth of bones. It may be formed by adding a solution of lime to one of sodium phosphate, and appears as a white precipitate. It is insoluble in pure water, but dis- solves in acids and in solutions of many salts. In the mineral kingdom tricalcic phosphate is the chief ingre- dient of apatite and phosphorite. These minerals are employed in the preparation of the commercial super- phosphates now consumed to an enormous extent as a fertilizer. Plain superphosphate is essentially a mixture of sulphate of lime with the three phosphates above no- ticed ard with free phosphoric acid. The Phosphates of Magnesium, Iron, Alumin- ium and Manganese, are bodies insoluble in water, •These formulae correspond to 2 molecules of phosphoric acid, with 2 and 4 H-atonis replaced l>y fa. THE ASH OF PLANTS. 140 that occur in very small proportion in the ashes of plants and in soils, but are important ingredients of some fertilizers. THE CHLORIDES are all characterized by their ready solubility in water. The Chlorides of Calcium and Mag- nesium are deliquescent, i. e., they liquefy by absorbing moisture from the air. The Chlorides of Potassium and Sodium alone need to be described. Potassium Chloride, or Muriate of Potash, KC1, 74.5. — This body may be produced either by expos- ing metallic potassium to chlorine gas, in which case the two elements unite together directly ; or by dissolving caustic potash in hydrochloric acid. In the latter case water is also formed, as is expressed by the equation KHO -f HC1 = KC1 + H20. Potassium chloride closely resembles common salt in appearance, solubility in water, taste, etc. It is now an important article of commerce and largely consumed as a fertilizer. It is also often present in the ash and in the juices of plants, especially of sea-weeds, and is like- wise found in most fertile soils. Chloride of Sodium, Nad, 58.5. — This substance is common or culinary salt. It was formerly termed muri- ate of soda. It is scarcely necessary to speak 01 its oc- currence in immense quantities in the water of the ocean, in saline springs, and in the solid form as rock-salt, in the earth. Its properties are so familiar as to require no description. It is rarely absent from the ash of plants. Besides the salts and compounds just described, there occur in the living plant other substances, most of which have been indeed already alluded to, but may be noticed again connectedly in this place. These compounds, being destructible by heat, do not appear in the analysis of the ash of a plant. NITRATES. — Nitric acid (the compound by which ni- trogen is chiefly furnished to plants for the elaboration 150 HOW CROPS GROW. of the albuminoid principles) is not unfrequently pres- ent as a nitrate in the tissues of the plant. It usually occurs there as potassium nitrate (niter, saltpeter), KX03. The properties of this salt scarcely need description. It is a white, crystalline body, readily soluble in water, and has a cooling, saline taste. When heated with car- bonaceous matters, it yields oxygen to them, and a defla- gration, or rapid and explosive combustion, results. Touch-paper is paper soaked in solution of niter and dried. The leaves of the sugar-beet, sunflower, tobacco, and some other plants, frequently contain this salt, and, when burned, the nitric acid is decomposed, often with slight deflagration, or glowing like touch-paper, and the alkali remains in the ash as carbonate. The characters of nitric acid and the nitrates are noticed at length in " How Crops Feed." See also p OXALATES, CITRATES, MALATES, TARTRATES, and salts of other less common organic acids, are generally to be found in the tissues of living plants. On burning, the metals with which they were in combination — potassium and calcium, in most cases — remain as carbonates. Ammonium Salts exist in minute amount in some plants. What particular salts thus occur is uncertain, and special notice of them is unnecessary in this chapter. Since it is possible for each of the acids above described to unite with each of the bases in one or several propor- tions, and since we have as many oxides and chlorides as there are metals, and even more, the question at once arises — which of the 60 or more compounds that may thus be formed outside the plant do actually exist within it ? In answer, we must remark that while most or all of them may exist in the plant but few have been proved to exist as such in the vegetable organism. As to the state in which iron and manganese occur, we know little or noth- ing, and we cannot always assert positively that in a given THE ASH OF PLANTS. 151 plant potassium exists as phosphate, or sulphate, or car- bonate. We judge, indeed, from the predominance of potassium and phosphoric acid in the ash of wheat, that potassium phosphate is a large constituent of this grain, but of this we are scarcely certain, though in the absence of evidence to the contrary we are warranted in assuming these two ingredients to be united. On the other hand, calcium carbonate and calcium sulphate have been discov- ered by the microscope in the cells of various plants, in crystals whose characters are unmistakable. For most purposes it is unnecessary to know more than that certain elements are present, without paying atten- tion to their mode of combination. And yet there is choice in the manner of representing the composition of a plant as regards its ash-ingredients. We do not indeed so commonly speak of the calcium or the silicon in the plant as of lime and silica, because these rarely-seen elements are much less familiar than their oxides. Again, we do not speak of the sulphates or chlorides, when we desire to make statements which may be com- pared together, because, as has just been remarked, we cannot always, nor often, say what sulphates or what chlorides are present. In the paragraphs that follow, which are devoted to a more particular statement of the mode of occurrence, rel- ative abundance, special functions, and indispensability of the fixed ingredients of plants, will be indicated the customary methods of defining them. § 2« QUANTITY, DISTRIBUTION, AND VARIATIONS OF THE ASH- INGKEDIENTS. The Ash of plants consists of the various acids, oxides, and salts, that have been noticed in § 1, which are fixed or non-volatile at a heat near redness, 152 HOW CROPS GROW. Ash-ingredients are always present in each cell of every plant. The ash-ingredients exist partly in the cell-wall, in- crusted or imbedded in the cellulose, and partly in the plasma or contents of the cell (see p 249). One portion of the ash-ingredients is soluble in water, and occurs in the juice or sap. This is true, in general, of the salts of the alkali-metals, and of the sulphates and chlorides of magnesium and calcium. Another portion is insoluble, and exists in the tissues of the plant in the solid form. Silica, the calcium phosphates and the mag- nesium compounds, are mostly insoluble. The ash-ingredients may be separated from the volatile matter by burning or by any process of oxidation. In burning, portions of sulphur, chlorine, alkalies, and phos- phorus may be lost, under certain circumstances, by vola- tilization. The ash remains as a skeleton of the plant, and often actually retains and exhibits the microscopic form of the tissues. The Proportion of Ash is not Invariable, even ir the same kind of plant, and in the same part of the plant. Different kinds of plants often manifest very marked dif- ferences in the quantity of ash they contain. The fol- lowing table exhibits the amount of ash in 100 parts (of dry matter) of a number of plants and trees, and in theii several parts. In most cases is given an average proportion as deduced from a large number of the most trustworthy examinations. In some instances are cited the extreme proportions hitherto put on record. PROPORTIONS OF ASH IX VAHlorS VEGETABLE MATTERS.* ENTIRE PLANTS, ROOTS EXCEPTED. Avern'.ic. Average. Red clover 6.7 White Timothy 7.1 Potatoes 5.1 Sugar beet, 16.3—18.6 17.5 Field beet, 14.0— 21.8 1*.L Turnips, 10.7—19.7 15.5 Carrot, 15.0—21.3 17.1 Hops it.H Hemp 4.G Flax 4.:! H.-alh 4..J * These figures are copied unehunired from the old edition, and may differ from later averages, but are approximately correct. THE ASH OF PLANTS. 153 BOOTS AXI> TUBERS. Potatoes, 2.6—8.0 4.1 Sugar beet, 2.9—6.0 4.4 Field beet, 2.8—11.3 7.7 Turnip, 6.0— 20.9 13.0 Carrot, 5.1—10.9 8.2 Artichoke 5.2 STRAW AND STEMS. Wheat, 3.8—6.9 5.4 Rye, 4.9—5.6 5.3 Oats, 5.0—5.4 5.3 Barley 6.8 Peas, 6.5—9.4 7.9 Beans, 5.1— 7.2 6.1 Flax 3.7 Maize 5.5 GRAINS AND SEED. Wheat, 1.5—3.1 2.0 i Buckwheat, 1.1— 2.1 1.4 Rye, 1.6—2.7 2.0 Peas, 2.4—2.9 2.7 Oats, 2.5—4.0.. 3.3 Beans, 2.7— 4.3 3.7 Barley, 1.8— 2.8 2.3 Flax, 3.6 Maize, 1.3—2.1 1.5 \ Sorghum 1.9 WOOD. Beech 1.0 Birch 0.3 Grape 2.7 Apple pc. ile. Red Pine 0.3 White Pine 0.3 Fir 0.3 1.3 Larch 0.3 BARK. Birch 1.3 Red Pine 2.8 White Pine 3.3 Fir. 2.0 Walnut 6.4 Cautotree 34.4 From the above table we gather : — 1. That different plants yield different quantities of ash. It is abundant in succulent foliage, like that of the beet (18 per cent), and small in seeds, wood, and bark. 2. That different parts of the same plant yield unlike proportions of ash. Thus the wheat kernel contains 2 per cent, while the straw yields 5.4 per cent. The ash in sugar-beet tops is 17.5 ; in the roots, 4.4 per cent. In the ripe oat, Arendt found (Das Wachsthum der Haferpflanze, p. 84), In the three lower joints of the stem ... 4.6 per cent of ash. In the two middle joints of the stem .... 5.3 " " In the one upper joint of the stem 6.4 " " In the three lower leaves 10.1 " " In the two upper leaves 10.5 " " Intheear 2.6 « " 3. We further find that, in general, the upper and outer parts of the plant contain the most ash-ingredi- ents. In the oat, as we see from the above figures of Arendt, the ash increases from the lower portions to the upper, until we reach the ear. If, however, the ear be 154 HOW CROPS GROW. dissected, we shall find that its outer parts are richest in ash. Norton found In the husked kernels of brown oats 2.1 per cent of ash. In the husk of brown oats 8.2 " " In the chaff of brown oats 19.1 " " Norton also found that the top of the oat-leaf gave 16.22 per cent of ash, while the bottom yielded but 13.66 percent. (Am. Jour. Science, Vol. Ill, 1847.) From the table it is seen that wood (0.3 to 2.7 per cent) and seeds (1.5 to 3.7 per cent) — lower or inner parts of the plant — are poorest in ash. The stems of herbaceous plants (3.7 to 7.9 per cent) are next richer, while the leaves of herbaceous plants, which have such an extent of surface, are the richest of all (6 to 8 per cent). 4. Investigation has demonstrated further that the same plant in different stages of growth varies in the pro- portions of ash in dry matter, yielded both by the entire plant and by the several organs or parts. The following results, obtained by Norton, on the oat, illustrate this variation. Norton examined the various parts of the oat-plant at intervals of one week through- out its entire period of growth. He found Leaves. Stem. Knots. Chaff. Grain unhusked June 4 10.8 10.4 June 11 10.7 9.8 June 18 9.0 9.3 June25 10.9 9.1 July 2 11.3 7.8 4.9 July 9 12.2 7.8 4.3 July 16 12.6 7.9 6.0 3.3 July 23 16.4 7.9 10.0 9.1 3.6 July 30 16.4 7.4 9.6 12.2 4.2 Aug. 6 16.0 7.6 10.4 13.7 4.3 Aug. 13 20.4 6.6 10.4 18.6 4.0 Aug. 20 21.1 6.6 11.7 21.0 3.6 Aug. 27 22.1 7.7 11.2 22.4 3.5 Sept. 3 20.9 8.3 10.7 27.4 3.6 Here, in case of the leaves and chaff, we observe a con- stant increase of ash, while in the stem there is a con- THE ASH OF PLANTS. 155 stant decrease, except at the time of ripening, when these relations are reversed. The knots of the stem preserved a pretty uniform ash-content. The unhusked grain at first suffered a diminution, then an increase, and lastly a decrease again. Arendt found in the oat-plant fluctuations, not in all respects accordant with those observed by Norton. Arendt obtained the following proportions of ash : 3 lower 2 middle Upper Lower Upper Entire joints of joints of joint of leaves, leaves. Ears, plant, stem. stem. stem. June 18 4.4 9.7 7.7 8.0 June 30 2.5 2.9 3.5 9.4 7.0 3.8 5.2 July 10 3.5 4.7 5.2 10.2 6.9 3.6 5.4 July 21 4.4 5.0 5.5 10.1 9.7 2.8 5.2 July 31 6.4 5.3 6.4 10.1 10.5 2.6 5.1 Here we see that the ash increased in the stem and in each of its several parts after the first examination. The lower leaves exhibited an increase of fixed matters after the first period, while in the upper leaves the ash dimin- ished toward the third period, and thereafter increased. In the ears, and in the entire plant, the ash decreased quite regularly as the plant grew older. Pierre found that the proportion of ash of the colza (Brassica olera- cea] diminished in all parts of the plant (which was examined at five periods), except in the leaves, in which it increased. (Jahresberirht ilber Agriculturchemie, III, p. 122.) The sugar-beet (Bretschneider) and potato (Wolff) exhibit a decrease of the per cent of ash, both in tops and roots. In the turnip, examined at four periods, Anderson ( Trans. High, and Ag. Soc. , 1859-61, p. 371) found the following per cent of ash in dry matter : July 1. Aug. 11. Sept. 1. Oct. 5. Leaves 7.8 20.6 18.8 16.2 Bulbs .17.7 8.7 10.2 20.9 In this case, the ash of the leaves increased during about half the period of growth from 7.8 to 20.6, and 156 HOW CROPS GROW. thence diminished to 16.2. The ash of the bulbs fluc- tuated in the reverse manner, falling from 17. 7 to 8. 7, then rising again to 20.9. In general, the proportion of ash of the entire plant diminishes regularly as the plant grows old. 5. The influence of the soil and season in causing the proportion of ash of the same kind of plant to vary, is shown in the following results, obtained by Wunder Versuchs-Stationen, IV, p. 266) on turnip bulbs, raised during two successive years, in different soils. In sandy soil. In loamy soil. 1st year. 2d year. 1st year. 2d year. Per cent of ash 13.9 11.3 9.1 10.9 6. As might be anticipated, different varieties of the same plant, grown on the same soil, take up different quantities of non-volatile matters. In five varieties of potatoes, cultivated in the same soil and under the same conditions, Herapath (Qu. Jour, diem., Soc. II, p. 20) found the percentages of ash in dry matter of the tuber as follows : VARIETY OF POTATO. White Prince's Axbridge Forty- Apple. Beauty. Kidney. Magpie, fold. Ash per cent... 4.8 3.6 4.3 3.4 3.9 7. It has been observed further that different individ- uals of the same variety of plant, growing side by side, on the same soil (in the same field, at least), contain dif- ferent proportions of ash-ingredients, according as they are, on the one hand, healthy, vigorous plants, or, on the other, weak and stunted. Pierre (Jahresbericht iiber Agriculturchemie, III, p. 125) found in entire colza plants of various degrees of vigor the following percent- ages of ash in dry matter : In extremely feeble plants, 1856 8.0 per cent of ash In very feeble plants, 1857 9.0 " " In feeble plants, 1857 11.4 " " In strong plants, 1857 11.0 " " In extremely strong plants, 1857 14*J M " THE ASH OF PLANTS. 157 Pierre attributes the larger per cent of ash in the strong plants to the relatively greater quantity of leaves developed on them. Similar results were obtained by Arendt in case of oats. Wunder ( Versuclis-St., IV, p. 115) found that the leaves of small turnip-plants yielded somewhat more ash per cent than large plants. The former gave 19.7, the lat- ter 16.8 per cent. 8. The reader is prepared from several of the foregoing statements to understand partially the cause of the vari- ations in the proportion of ash in different specimens of the same kind of plant. The fact that different parts of the plant are unlike in their composition, the upper and outer portions being, in general, the richer in ash-ingredients, may explain in some degree why different observers have obtained differ- ent analytical results. It is well known that very many circumstances influ' ence the relative development of the organs of a plant In a dry season, plants remain stunted, are rougher on the surface, having more and harsher hairs and prickles, if these belong to them at all, and develop fruit earlier than otherwise. In moist weather, and under the influ- ence of rich manures, plants are more succulent, and the stems and foliage, or vegetative parts, grow at the ex- pense of the reproductive organs. Again, different vari- eties of the same plant, which are often quite unlike in their style of development, are of necessity classed to- gether in our table, and under the same head are also brought together plants gathered at different stages of growth. In order that the wheat plant, for example, should always have the same percentage of ash, it would be nec- essary that it should always attain the same relative de- velopment in each individual part. It must, then, always grow under the same conditions of temperature, 158 HOW CHOPS GROW. light, moisture, and soil. This is, however, as good as impossible, and if we admit the wheat plant to vary in form within certain limits without losing its proper char- acteristics, we must admit corresponding variations in composition. The difference between the Tuscan wheat, which is cultivated exclusively for its straw, of which the Leghorn hats are made, and the "pedigree wheat" of Mr. Hallett (Journal Roy. Ag. Soc. Eng., Vol. 22, p. 374), is in some respects as great as between two entirely different plants. The hat wheat has a short, loose, bearded ear containing not more than a dozen small kernels, while the pedigree wheat has shown beardless ears of 8f inches in length, closely packed with large kernels to the num- ber of 120 ! Now, the hat wheat, if cultivated and propagated in the same careful manner as has been done with the pedi- gree wheat, would, no doubt, in time become as prolific of grain as the latter, while the pedigree wheat might perhaps with greater ease be made more valuable for its straw than its grain. We easily see then, that, as circumstances are perpet- ually making new varieties, so analysis continually finds diversities of composition. 9. Of all the parts of plants, the seeds are the least lia- ble to vary in composition. Two varieties or two indi- viduals may differ enormously in their relative propor- tions of foliage, stem, chaff, and seed ; but the seeds themselves nearly agree. Thus, in the analysis of 67 specimens of the wheat kernel, collated by the author, the extreme percentages of ash were 1.35 and 3.13. In 60 specimens out of the 67, the range of variation fell between 1.4 and 2.3 per cent. In 42 the range was from 1.7 to 2.1 per cent, while the average of the whole was 2. 1 per cent. In the stems or straw of the grains, the variation is THE ASH OF PLANTS. 159 much more considerable. Wheat-straw ranges from 3.8 to 6.9 ; pea-straw, from 6.5 to 9.4 per cent. In fleshy roots, the variations are great ; thus turnips range from 6 to 21 per cent. The extremest variations in ash-con- tent are, however, found, in general, in the succulent foliage. Turnip tops range from 10.7 to 19.7; potato tops vary from 11 to near 20, and tobacco from 19 to 27 per cent. Wolff (Die Naturgesetzlichen Grundlagen des Acker- bans, 3 Aufl., p. 117) has deduced from a large number of analyses the following averages for three important classes of agricultural plants, viz. : Grain. Straw. Cereal crops 2 per cent. 5.25 per cent. Leguminous crops 3 " " 5 " " Oil-plants 4 " " 4.5 «' " More general averages are as follows (Wolff, loe. cit.) : Annual and biennial plants. Seeds 3 per cent. Stems 5 " " Rools 4 " " Leaves 15 " " Perennial plants. Seeds 3 per cent. Wood 1 " " Bark 7 " " Leaves 10 " " We may conclude this section by stating three propo- sitions which are proved in part by the facts that have been already presented, and which are a summing up of the most important points in our knowledge of this sub- ject. 1. Ash-ingredients are indispensable to the life and growth of all plants. In mold, yeast, and other plants of the simplest kind, as well as in those of the higher or- ders, analysis never fails to recognize a proportion of fixed matters. We must hence conclude that these are necessary to the primary acts of vegetation, that atmos- pheric food cannot be assimilated, that vegetable matter cannot be organized, except with the cooperation of those substances which are invariably found in the ashes of the plant. This proposition is demonstrated in the most conclusive manner by numerous synthetic experiments- 160 HOW CROPS GROW. It is, of course, impossible to attempt producing a plant at all without some ash-ingredients, for the latter are present in all seeds, and during germination are trans- ferred to the seedling. By causing seeds to sprout in a totally insoluble medium, we can observe what happens when the limited supply of fixed matters in the seeds them- selves is exhausted. Wiegmann & Polstorf (Preisschrift uber die unoryanisclien Bestandtheile der Pflanzen] plant- ed 30 seeds of cress in fine platinum wire contained in a platinum vessel. The contents of the vessel were moist- ened with distilled water, and the whole was placed under a glass shade, which served to shield from dust. Through an aperture in the shade, connection was made with a gas- ometer, by which the atmosphere in the interior could be renewed with an artificial mixture, consisting, in 100, of 21 parts oxygen, 78 parts nitrogen, and 1 part carbonic acid. In two days 28 of the seeds germinated ; afterwards they developed leaves, and grew slowly with a healthy ap- pearance during 26 days, reaching a height of two or three inches. From this time on, they refused to grow, began to turn yellow, and died down. The plants were collected and burned ; the ash from them weighed pre- cisely as much as that obtained by burning 28 seeds like those originally sown. This experiment demonstrates most conclusively that a plant cannot grow in the absence of those substances found in its ash. The development of the cresses ceased so soon as the fixed matters of the seed had served their utmost in assisting the organization of new cells. We know from other experiments that, had the ashes of cress been applied to the plants in the above experiment, just as they exhibited signs of unhealthiness, they would have recovered, and developed to a much great- er extent. II. The proportion of ash-ingredients in the plant is variable within a narrow range, but cannot fall below or exceed certain limits. The evidence of this proposition THE ASH OF PLANTS. 161 is to be gathered both from the table of ash-percentages and from experiments like that of Wiegmann & Polstorf, above described. III. We have reason to believe that each part or organ (each cell) of the plant contains a certain, nearly invaria- ble, amount of fixed matters, which is indispensable to the vegetative functions. Each part or organ may contain, besides, a variable and unessential or accidental quantity of the same. What portion of the ash of any plant is es- sential and what accidental is a question not yet brought to a satisfactory decision. By assuming the truth of this proposition, we account for those variations in the amount of ash which cannot be attributed to the causes already noticed. The evidences of this statement must be reserved for the subsequent section. SPECIAL COMPOSITION OF THE ASH OF AGBICFLTUBAL PLANTS. The result of the extended inquiries which have been made into the subject of this section may be convenient- ly presented and discussed under a series of propositions, viz. : 1. Among the substances which have been described (§ I) as the ingredients of the ash, the following are in- variably present in all agricultural plants, and in nearly all parts of them, viz. : f Potash, K,O. f Chlorine, Cl. Soda, Na,O. Sulphuric acid, SOS. Bases J. Lime, CaO. Acids J. Phosphoric acid, P,OB. Magnesia, MgO. Silicic acid, SiO,. I^Oxide of iron, Fe2O3. ^Carbonic acid, CO2. 2. Different normal specimens of the same kind of plant have a nearly constant composition. The use of the word nearly in the above statement implies what has been already intimated, viz., that some variation is noticed in the relative proportions as well as in the total quantity 11 162 HOW CROPS GROW. of ash-ingredients occurring in plants. This point will shortly be discussed in full. By taking the average of many trustworthy ash-analyses we arrive at a result which does not differ very widely from the majority of the in- dividual analyses. This is especially true of the seeds of plants, which attain nearly the same development under all ordinary circumstances. It is less true of foliage and roots, whose dimensions and character vary to a great extent. In the following tables (p. 164-170) is stated the composition of the ashes of a number of agricultural products which have been repeatedly subjected to analy- sis. In most cases, instead of quoting all the individual analyses, a series of averages is given. Of these, the first is the mean of all the analyses on record or obtainable by the writer,* while the subsequent ones represent either the results obtained in the examination of a number of samples by one analyst, or are the means of several single analyses. In this way, it is believed, the real variations of composition are pretty truly exhibited, independently of the errors of analysis. The lowest and highest percentages are likewise given. These are doubtless in many cases exaggerated by errors of analysis, or by impurity of the material analyzed. Chlo- rine and sulphuric acid are for the most part too low, be- cause they are liable to be dissipated in combustion, while silica is often too high, from the fact of sand and soil ad- hering to the plant. In two cases, single and doubtless incorrect analyses by Bichon, which give exceptionally large quantities of soda, are cited separately. A number of analyses that came to notice after making out the averages are given as additional. * At the time of preparing the first edit ion of this book, in I*»i8. More recent analyses arc comparatively few in number, excepting those of wheat (grain and straw) by La wee & Gilbert, and do not difl'cr essen- tially from those given. The numerous very incorrect ash-analyses, Bubl'lslied by Dr. K. Kmimms and Dr. J. H. Salisbury, in the Natural istory of New York, and in the Trans, of the New York State Agricul- tural Society, are not included. THE ASH OF PLANTS. 163 The following table includes both the kernel and straw of Wheat, Rye, Barley, Oats, Maize, Eice, Buckwheat, Beans, and Peas ; the tubers of Potatoes ; the roots and tops of Sugar-Beets, Field-Beets, Carrots, Turnips, and various parts of the Cotton Plant. For the average composition of other plants and vege- table products, the reader is referred to a table in the ap- pendix, p. 409, compiled by Prof. Wolff, of the Royal Agricultural Academy of Wurtemberg. That table in- cludes also the averages obtained by Prof. Wolff for most of the substances, cotton excepted, whose composition is represented in the pages immediately following. In both tables the carbonic acid, CO2, which occurs in most ashes, is excluded, from the fact that its quantity varies according to the temperature at which the ash is prepared. The following is a statement of the various Names and Symbols that are or have been currently applied to the Ash-Ingredients in Chemical Literature. The changes that have been made from time to time, both in symbols and in names, are the results of progress in knowledge or of attempts to improve nomenclature : Ol'ler Newer Symbols. Symbols. Synonyms. ' KO K,O Potash, Potassa, Potassium Oxide, Potassic Oxide. NaO Na2O Soda, Sodium Oxide, Sodic Oxide. MgO MgO Magnesia, Magnesium Oxide, Magnesic Oxide. CaO CaO Lime, Calcium Oxide, Calcic Oxide. Fe-jOa Fe2O8 Iron Oxide, Peroxide of Iron, Sesquioxide of Iron, Ferric Oxide. POg P2O5 Phosphoric Acid, Anhydrous Phosphoric Acid, Phosphoric Anhydide, Phosphorus Pentox- ide, Phosphoric Oxide. SO3 SO3 Sulphuric Acid. Anhydrous Sulphuric Acid, Sul- phuric Anhydride, Sulphur Trioxide, Sul- phuric Oxide. SiO8 SiO2 Silicic Acid, Anhydrous Silicic Acid, Silicic An- hydride, Silicon Dioxide, Silicic Oxide, Silica Silex. COa CO2 Carbonic Acid, Anhydrous Carbonic Acid, Car- bonic Anhydride, Carbon Dioxide, Carbouie Dioxide. 164 HOW CROPS GROW. «d >»o . 5^1 w ^ 0 g flfi s cJ - ^ « g C« as cS — IS 1 I II PO * § ® S * C3 •Sw Kg 2i* ^ .« >3 S <& ^ ^ • a? l>g ^ ^>j|g2<« ^ ^l^* c3^1|2« >» >% i^^Og-ga; 03 [§55? w pf^^^'S?3 ^ g ^>j 3 ; s "3 S S| ^j'cl1 fe"S " - - "3 ^ '* oj^3 s o fl*"^ S 1 ^r- ^ — 02 QJ ^J5QJ ' O ®^2 •C S O r- >> >> NN £? ^, ^i"'' *•§ 1" "51 1* SSf! k- a" "S xl ri*' fe •: g^ •*< 8 •»*«»« 8 5 ^N glOgOgOS^^OO rHOOlOOOy^ OOf^^,^ «3^~- %> "o S'o'o 0^*0 S j£J| a** 60 +i'Su)tt +^to60 *i»JS*i Jg «2Mg, «.,^ J rt r: 3 M 4> SdSSSSdSd 22325^ 22S^S235d22 2* E *r « a ce woNi--o«o=:--D eoc^^Nooo 10 rtO oci-o too: oc as co c s v ~ r. - — 2S2x'»'t'-§3:-i 5-ic^S5i"3 2i^3c-it":rfSri5^ /-- - - co 55 co « CON OOON 10t-lOCOO^>Ol~ N S-l IM O 00 CO«t-OCOCOrHCO OOOCO 100O IH COCO t-OCOrt !OO-*; 5 - •S - - tJD ' - fl o* Q O -f =~ 1 -^« tf^^S 48j?jj ^ S-7 s^ j?2 M* ||||: ^ |1l:!"1l ^ - s S3* o >>- - "3 >>.. 3 -< ^ s». < ? J-f . » o ^ o J; c r- - £ ® ^3 r „„,* ©o X ^»O 5«5^rHOO«0 5 4- O ^H oo o -f ;£ ^S C"2 f OrHH NrH p* rH rH © rH rH © » -rHCOr,©©-^ ^ rH 0,©^, ^. M u H §0 W ^ 00 O »-O Tf — . TJ "J 00 ^ 00 S5 © 13 ^ r- © f --C --C a "" i< i fc g°S° . ©©©rH©©N ^ c i c -'=,': i ^» « .~- i = -1 :f - ? co B? fe E£] •*< H E -" 's ~'3 w ^ .4 22*333 PH j,,,^,,,..,,-,^ «* e4 1^ >d rf © s> JQ jq»1--< ©©© — =: :•" — 1 © © © t-oo oo **< oo co © © N c^ CO 1O CO i; rH 1> CO C£ ^ xi lO CO CO CO oc s; a i- x i - . ^ = i-' i-' .-' ri x' -r i"r 2 1 — ^N -^ r - •„ - •' c e i-i ©' ^ •* t- oc t- • x >- ri i-liewx to 71 ?\ -i ?i = LO — i — 5 ,- — T ci ONCO rH© ?J - 55 S5 1ft -^ © =-. © 3~. t- to © 00 IM CT 1- = C X t- .jy •— •- 5 10100 © c; co CO © t- rH a © M — *" " £J ~ Xj ° rH©co©i-© ' — y: cc "" • S-H i — 1-I--T I-X — c; co LO -t co M i - lO rt< t- © X -^ -^ i- •- r- r- t--f 'f-H C ce 1- 1- 1- 00© O ^^1S^!»3:^ S CS 5 ?; = CO CO r- — — — -^ 'i ^- JS - - C._- c,^rt rHrHrH t- -t "5 tr-O CO t-fO -r x r. — '^"^.:^ (H O JiS OOCSt- MrHrH CS CS C1^ co co ^f cs ^J* 1C CO >5 53 1 * - — £« 1 t-iO THE ASH OF PLANTS. 167 mT3 • 1 (."N © 1 §5 d •T 4J • 2^ la gsSo1 •^ 2 •S a 25 too "s £ •- >, cv S "o X u "5 =0 y^'M +s CD . J . 5 o •d rt F— _;£-*— i £3 3 H C SS rt O S so 5 >'H ? o X 'a" — " ;/• •Sli a a5 cc .0 ^ li— S OS * SO 2 = | s S*3 • . •-ji^ X"° '/: S ** CJ « to *""* ^» CD ^ Sn ^* f • 7- ^ 7! ^ ^ " r' ^ 1 ~"3 93 •^'S * ° a S -^"_- 5; tjr; . .r "3 * "^ Nr*r^ ^?- .5 ai^'* cc 5 PH^ o"cj " 2 ••*•—! 2 ~ A >»- , ^ S & * o •*>- ^ ^ 2 ^*-» ^ ^ *M r^ " ^ _: u 2 5 w. Average of 5 Analyses.* Lowest percentage in 5 Highest " 5 Incomplete Anal, by He t A W. Average of 17 Analyses. " 4 " « 5 « " 8 " Lowest percentage in 9 j Higliest. " 9 ^ Average of 5 Analyses. " 3 " b « 2 " ' Lowest percentage in 5 , Highest " 5 Analysis by Henneberg L K S. 5 1 ^ X £ TRA W. | Average of 6 Analyses b W. Average of 22 Analyses. " 13 " " 6 " « 3 « Lowest percentage in 22 Highest " 22 Analysis by Baer.§ Rannnelsberg, Nit/.scli. ussingault, 15aer. Hertwi sh and Soda in tlie one a of Heintz, and in one ca ig ,J -r = -M H tOCO co c-. CO 55 CO 1C O O ***< t- ^ CO CO CO t- 0 . ~ •- z «^o.2 — _~ "~ r- O "O '!/ CO COCO rH t-^^ gH ^™ L- " CO t— C*"1 t™ O — O ;, - H H CC «5j H rHrH £.:...« 00 . fH en , , cc § 00 1C M — 3 TH t-00 (D C!1C ic n •* co co -f a 00 1-1 1C *f t- CO 00 CD •* CO £ *+-S"d ;3 S jS^Jgg ^ ?ppl? 5S H c; o oo c-i -r -H vi •* 1C t f 1C CO N s - 1C •«} 1C 1C 1C f O -H CO •2 « ^ 02 ^ OH •""• M = N ^ 0 ^3 ,»- Ci »1O ffl t-oc co c: rHCO — CCTH^M^ j B, - CO rH N CO t- 00 O CO I|l* •7^i rndli " CO'NM-* rHCO COCOW^'* 1U h_. 10 CO CO 1C t— O SO OO "". - = i — ' "i « l^Mj i.H-3 CO 001" 1C 1C O rHO o: ® - i ••> -. — p £i * CO *^ t ~. '—. ~: rHCO 0000 00 CO 1C 1C CO co CM CO CO 1C :t r: ~ t-^ t-^ oc c: co' H ?i 1*5 S rH rH - ooco rH CO 1C CO rHt- •rhCOt-Xt- 1C CM t- CO CO CO 0 r?CO C? (NO CO •rJ"^CO-* rHlO COTfC!lM-Jj CM 1C 1C 1C 00 O -f O " t "= c S (Is in 05 s rH CO CM rHrH CO Cl ?1 i; rH N •^ CO CO C^-d tNCSCOCM iCOi (N O5 CN OTJ. IO 10 OOOSrH^SJ S' = - | _; r =< lOTKCO^ COO IO *O iQ id 3 Vt-CCWrt * _- c ^ 5 168 HOW CROPS GROW. Rittcr & Knop. Way & Ogston. nalyses. not included above. V Sclml/- Kleeth, and 1 by Met/dorlV. [Wolff. \\al/.. Ilerapath. Hretsehneider. \\ a> A. Ogston. others.* \nalyses. " [above. ^ses by Heiden not included y Ritthausen. ' Hretsehneider. [berg. ' Hretsehneider \ Kiillen- iil) niann arniro . Highest " :«> Average of 4 recent Anal ROOT. Average of 40 Analyses. " 13 " I " 11 " " 14 " Additional Analysis hy 1 tt tt tt ^ Lowest pereenlage in In . Highest " 40 5 2 £ n x x c is n £_! t^«dt-^d^o CT ^« SSSSdSrf^dSS H » r: -^ — = -. r. .- x c^ ?i tt « — is' c i § O H =-. Xt-H = t-XNO.S1. pq x is rt 'C *r ^i — c 00 H PS ^ - r ~s. — < CO (NC31-O O IS ei o ri o t- ?i 0 ^D555!?55555 O ^Tf-lSI- -T -> -i X' 'H^ c; N t— t— * o t-^ 06 1- —' — ~ i x' x' i- H i- r: x' — ' — i- •-;' •t -.; :r. s: ^: ~ ri is -i^ •o« t-SO-- 53C51* est-ioa500«seoos> CXNO^- Tl " Tl II — JN^-GNN coc«o«-= = w:- t^ o ^^ ^ — ?i — ?i w s r: C ?•} 1" t- 35 ^.^•XOOOO^lSNO TfXCO 05X000 sss^-ss 04 - "• ^ " "'* "' = - "' «'s---t-«S u.2 WMt-neo « » X -J t- 0 - 3! IS SO CO IS — M M t-lS 1C X SB S t— Ci *i5 W !C t-- *fn**m**>Gf^~-* C3 O5 O O '-i 1 - T " (3 -»• ~- Xt- X OB oo^ M ~- £ r^ ~0 OOOtN«^ = £.- o = r. ri is so >o s , ^ t-- » r*5 ™f c^ o C~. — i* — '-C T- u" ?1 * • 30 0 N 0 ** ~ -r. = r. & ^-^gs §-,c 7) •- t- rc ~. c ^i n -r »»"f»i^i^»*ft'-* §S;?^g5?J5 -•-•7 — — -1 rt|, ^ ttscrt «00> ^•3- >>- rt *•«! 5 ioio » £ ?i s » 3 SC ! 1 >iQiQ 0>~ •^ (H X * I&H . by Wiinder. " Anderson. " Way & Ogston. " Gilbe " other 19 Anal, e 19 " er rs. x W al " Lo Hi o > •* «* 03 r. <0 £ a >> • ^S2 O »* g|g H^ ^S 5S H OSCOOOSCOOOO PH OSOOCSrH'* ^rHOiaini-HO>aoO ^-COOOi-li-ltO §"S ^ °>^'°' "^^ H * Pi "^ M a"° ' "" O ~ M C3 W o CN t-; rH TH CN CO pj O^IOCSOO ^5 t-;COOS OONO1O I CO »H 00 •* 30 ' ^COtN»Ow5oCS ^ CNfHC^O^ Q* Or-ioCNOi-i OCO Q CCCNCOrHCO 2 o & ^ Q H W -•„.-, trrtrt°;cl'n C5cs°?t: c^Ttitr'^e^!'?o5 t~lc1ffi'^0S'^ */. — ^ li_ ^H rH THrHrHi— tr^ iH™ rHt-t „_ - 00 CO O CO t^ i-5 M rHOc4o6lO Si^_ •uJ °Rtt5£?cJo5=5T1 =5CT?<^C5 •^ S o o o — o o co — TH o o oi 0 — 00000— — — — o — OS *P m >O CO CN N CSt-;OCOlO IH O O TO CO OS >O OJ OONCOt-;eO 5 id ei id 10 os cq o c>o — coco o to osos — 06 — 5 c»oj °2ti?'^o2a2rlr^ C1C"55^C^T^ t£?*^t^c2t^'^t^r'* "*I^OS"?0: ** oi to co to c4 <>i 10 n< o — os oi •* ^* 01 — o5 — co csoscot-cc — C? — — CO CNN?5- CO "* — — " CN 5 to ^1 Tf CO OS N CN O — O p OS to CN t- CO t- to CO CO — CO !>: O t^ sr 170 HOW CHOPS GROW. JK H'£:3 t-I Z . r T - A - X ."-' — r c '-l .- "^ ^~: § 3 "= Mtt£ - = Si § d 1 ~~ ~ ; — o._ " '~ r *+ 2 - ?'J-< - = .- ~z z ~ ~. — ."- - i - . •^ — — • * ^ ^ - - _; - X 1. c_"^ * A a ^. . . . £ • _ • x - J if. .EV ^ j XI -f •* r - •{ »« ? 22 r<^ x ~ /: ;; « z ~''~ 1 o i. 5 .fa ^> 1§ — Zf) i-^33 in (— -— ^ — , . ^ n a 1 ^ 1, ||s '« ^2 — " -f p -^ " ;". •_ 3 •_ ' > e> CM 0 /. - u Dg« i. - :! E . - _ •/. iJt- x ^ g|| C Jt* & -.i 12.2 5.1 4.7 2.4 THE ASH OF PLANTS. 173 Ripe Fruit. * Stamens. Petals. Green Fruit. Kernel. Green Brown Shell. Shell. Potash 60.7 61.2 58.7 61.7 75.9 54.6 Lime 13.8 13.6 9.8 11.5 8.6 16.4 Magnesia 3.1 3.8 2.4 0.6 1.1 2.4 Sulphuric acid — trace trace 3.7 1.7 1.0 3.6 Phosphoric acid... 19.5 17.0 20.8 22.8 5.3 18.6 Silica 0.7 1.5 0.9 0.2 0.6 0.8 Chlorine 2.8 3-8 4.8 2.0 7.6 5.2 4. Similar kinds of plants, and especially the same parts of similar plants, exhibit a close general agreement in the composition of their ashes ; while plants which are un- like in their botanical characters are also unlike in the proportions of their fixed ingredients. The three plants, wheat, rye, and maize, belong, botan- ically speaking, to the same natural order, graminece, and the ripe kernels yield ashes almost identical in composi- tion. Barley and the oat are also graminaceous plants, and their seeds should give ashes of similar composition. That such is not the case is chiefly due to the fact, that, unlike the wheat, rye, and maize-kernel, the grains of barley and oats are closely invested with a husk, which forms a part of the kernel as ordinarily seen. This husk yields an ash which is rich in silica, and we can only prop- erly compare barley and oats with wheat and rye, when the former are hulled, or the ash of the hulls is taken out of the account. There are varieties of both oats and bar- ley, whose husks separate from the kernel — the so-called naked or skinless oats and naked or skinless barley — and the ashes of these grains agree quite nearly in composi- tion with those of wheat, rye, and maize, as may be seen from the table on page 174. By reference to the table (p. 166), it will be observed that the pea and bean kernel, together with the allied vetch and lentil (p. 171), also nearly agree in ash-com-i position. So, too, the ashes of the root-crops, turnips, carrots, 174 HOW CEOPS GROW. and beets, exhibit a general similarity of composition, as may be seen in the table (p. 168-9). Wheat. Rye. Maize. Skinless Stinles Average Average Average oats. barley*. of of of Analysis Analysis seventy-nine twenty-one seven by Fr. by Fr. Analyses. Analyses. Analyses. Sci.ulze. Schulze. Potash 31.3 28.8 27.7 33.4 35.9 Soda 3.2 4.3 4.0 1.0 Magnesia 12.3 11.6 15.0 11.8 13.7 Lime 3.2 3.9 1.9 3.6 2.9 Oxide of Iron 0.7 0.8 1.0 0.8 0.7 Phosphoric acid 46.1 45.6 47.1 46.9 45.0 Sulphuric acid 1.2 1.9 1.7 Silica 1.9 2.6 2.1 2.4 0.7 Chlorine 0.2 0.7 0.1 The seeds of the oil-bearing plants likewise constitute a group whose members agree in this respect (p. 170). 5. The ash of the same species of plant is more or less variable in composition, according to circumstances. The conditions that have already been noticed as in- fluencing the proportion of ash are in general the same that affect its quality. Of these we may specially notice : a. The stage of growth of the plant. b. The vigor of its development. c. The variety of the plant or the relative development of its parts, and d. The soil or the supplies of food. a. TJie stage of growth. The facts that the different parts of a plant yield ashes of different composition, and that the different stages of growth are marked by the development of new organs or the unequal expansion of those already formed, are sufficient to sustain the point now in question, and render it needless to cite analytical evidence. In a subsequent chapter, wherein we shall at- tempt to trace some of the various steps in the progress- ive development of the plant, numerous illustrations will be adduced (p. 241). b. Vigor of development. Arendt (Die Haferpflanze, p. 18) selected from an oat-field a number of plants in blossom, and divided them into three parcels : 1, com- THE ASH OF PLANTS. 1^5 posed of very vigorous plants ; 2, of medium ; and, 3, of very weak plants. He analyzed the ashes of each parcel, with results as below : 123 Silica 27.0 39.9 42.0 Sulphuric acid 4.8 4.1 5.6 Phosphoric acid 8.2 8.5 8.8 Chlorine 6.7 5.8 4.7 Oxide of Iron 0.4 0.5 1.0 Lime 6.1 5.4 5.1 Magnesia, Potash and Soda. 45.3 34.3 30.4 Here we notice that the ash of the weak plants con- tains 15 per cent less of alkalies, and 15 per cent more of silica, than that of the vigorous ones, while the propor- tion of the other ingredients is not greatly different. Zoeller (LieMg's Ernahrung der Vegetdbilien, p. 340) examined the ash of two specimens of clover which grew on the same soil and under similar circumstances, save that one, from being shaded by a tree, was less fully de- veloped than the other. Six weeks after the sowing of the seed, the clover was cut, and gave the following results on partial analysis : Shaded clover. Unshaded clover. Alkalies 54.9 36.2 Lime 14.2 22.8 Silica 5.5 12.4 c. The variety of the plant or the relative development of its parts must obviously influence the composition of the ash taken as a whole, since the parts themselves are unlike in composition. Herapath (Qu. Jour. Chem. Soc., II, p. 20) analyzed the ashes of the tubers of five varieties of potatoes, raised on the same soil and under precisely similar circum- stances. His results are as follows : White Prince's Axbridge Apple. Beauty. Kidney. Magpie. Forty-fold. Potash 69.7 65.2 70.6 70.0 62.1 Chloride of Sodium . . 2.5 Lime 3.0 1.8 5.0 5.0 3.3 Magnesia 6.5 5.5 5.0 2.1 3.5 Phosphoric acid 17.2 20.8 14.9 14.4 30.7 Sulphuric acid 3.6 6.0 4.3 7.5 7.9 Silica 0.2 — 176 HOW CROPS GROW. d. The soil, or the supplies of food, manures included, have the greatest influence in varying the proportions of the ash -ingredients of the plant. It is to a considerable degree the character of the soil which determines the vigor of the plant and the relative development of its parts. This condition, then, to a certain extent, in- cludes those already noticed. It is well known that oats have a great range of weight per bushel, being nearly twice as heavy, when grown on rich land, as when gathered from a sandy, inferior soil. According to the agricultural statistics of Scotland, for the year 1857 (Trans. Highland and Ag. Soc., 1857-9, p. 213), the bushel of oats produced in some districts weighed 44 pounds per bushel, while in other districts it was as low as 35 pounds, and in one instance but 24 pounds per bushel. Light oats have a thick and bulky husk, and an ash-analysis gives a result quite unlike that of good oats. Herapath (Jour. Roy. Ag. Society, XI, p. 107) has published analyses of light oats from sandy soil, the yield being six bushels per acre, and of heavy oats from the same soil, after "warping,"* where the produce was 64 bushels per acre. Some of his results, per cent, are as follows : Light oats. Heavy oats. Potash 9.8 13.1 Soda 4.6 7.2 Lime 6.8 4.2 Phosphoric acid 9.7 17.6 Silica 56.5 45.6 Wolff (Jour, fiir Prakt. Chem., 52, p, 103) has anal- ysed the ashes of several plants, cultivated in a poor soil, with the addition of various mineral fertilizers. The in- fluence of the added substances on the composition of the plant is very striking. The following figures comprise his results on the ash of buckwheat straw, which grew •Thickly covering with sediment from muddy tide-water. THE ASH OF PLANTS. 17? on the unmanured soil, and on the same, after applica- tion of the substances specified below : 1234 56 Unma- Chloride Nitrate Carbonate Su'phate Carbonate nured. of of of of of sodium, potash, potash, magnesia. lime. Chloride of potassium . . .. 7.4 ... 4.6 26.9 3.0 0.8 3.2 3.1 3.8 6.9 3.4 9.7 1.7 Lime . .15.7 14.0 12.8 11.6 14.1 18.6 Magnesia .. 1.7 1.9 3.3 1.4 4.7 4.2 Sulphuric acid ... 4.7 2.8 2.7 4.3 7.1 3.5 10.3 9.5 6 5 8.9 10.9 10.0 Carbonic acid . .20.4 16.1 27.1 22.2 20.0 23.2 Silica ... 3.6 4.2 4.2 4.2 4.8 5.2 100.0 100.0 100.0 100.0 100.0 100.0 It is seen from these figures that all the applications employed in this experiment exerted a manifest influ- ence, and, in general, the substance added, or at least one of its ingredients, is found in the plant in increased quantity. In 2, chlorine, but not sodium ; in 3 and 4, potash ; in 5, sulphuric acid and magnesia, and in 6, lime, are present in larger proportion than in the ash from the unmanured soil. 6. What is the normal composition of the ash of a plant ? It is evident from the foregoing facts and con- siderations that to pronounce upon the normal composi- tion of the ash of a plant, or, in other words, to ascer- tain what ash-ingredients and what proportions of them are proper to any species of plant or to any of its parts, is a matter of much difficulty and uncertainty. The best that can be done is to adopt the average of a great number of trustworthy analyses as the approximate expression of ash-composition. From such data, how- ever, we are still unable to decide what are the abso- lutely essential, and what are really accidental, ingredi- ents, or what amount of any given ingredient is essential, and to what extent it is accidental. Wolff, who appears to have first suggested that a part of the ash of plants 178 HOW CROPS GROW. may be accidental, endeavored to approach a solution of this question by comparing together the ashes of sanb- pies of the same plant, cultivated under the same circum- stances in all respects, save that they were supplied with unequal quantities of readily-available ash-ingredients. The analyses of the ashes of buckwheat-stems, just quoted, belong to this investigation. Wolff showed that, by assuming the presence in each specimen of buckwheat- straw of a certain excess of certain ingredients, and de- ducting the same from the total ash, the residuary ingre- dients closely approximated in their proportions to those observed in the crop which grew in an unmanured soil. The analyses just quoted (p. 163) are here "corrected" in this manner, by the subtraction of a certain per cent of those ingredients which in each case were furnished to the plant by the fertilizer applied to it. The num- bers of the analyses correspond with those on the previ- ous page. 1 234 5 6 20 p c. 20 p. c, 25 p. c. 8.5 p. c. 16.6 p. c. Chloride Carbonate Carbonate Sulphate Carbonates After deduction if of of of ofcalc'mani of Nothing, potas- potas- potas- marine- magne- sium, sium. sium. sium. sium. Potash 31.7 27.0 32.5 33.5 30.6 28.0 Chloride of potassium. 7.4 9.1 1.0 3.9 7.4 11.3 Chloride of sodium. . 4.6 3.8 4.0 4.7 3.7 1.9 Lime 15.7 17.3 16.0 14.5 15.3 14.6 Magnesia 1.7 2.4 4.1 1.7 2.3 2.9 Sulphuric acid 4.7 3.5 3.4 5.4 2.1 4.1 Phosphoric acid 10.3 11.7 8.1 11.2 11.8 11.7 Carbonic acid 20.4 20.1 25.9 19.8 21.6 19.3 Silica 3.6 5.2 5.2 5.3 5.2 6.1 100.0 100.0 100.0 100.0 100.0 100.0 The correspondence in the above analyses thus " cor- rected," already tolerably close, might, as "Wolff remarks (loc. cit.), be made much more exact by a further correc- tion, in which the quantities of the two most variable in- gredients, viz., chlorine and sulphuric acid, should be reduced to uniformity, and the analyses then be recalcu- lated to per cent. THE ASH OF PLANTS. 179 In the first place, however, we are not warranted in assuming that the "excess" of potassium chloride, potassium carbonate, etc., deducted in the above analyses respectively, was all accidental and unnecessary to the plant, for, under the influence of an increased amount of a nutritive ingredient, the plant may not only mechani- cally contain more, but may chemically employ more in the vegetative processes. It is well proved that vegeta- tion, grown under the influence of large supplies of nitro- genous manures, contains an increased proportion of truly assimilated nitrogen as albuminoids, amido-acids, etc. The same may be equally true of the various ash- ingredients. Again, in the second place, we cannot say that in any instance the minimum quantity of any ingredient neces- sary to the vegetative acts is present, and no more. It must be remarked that these great variations are only seen when we compare together plants produced on poor soils, i. e., on those which are relatively deficient in some one or several ingredients. If a fertile soil had been employed to support the buckwheat plants in these trials, we should doubtless have had a very different result. In 1859, Metzdorf (Wilda's CentralUatt, 1862, II, p. 367) analysed the ashes of eight samples of the red- onion potato, grown on the same field in Silesia, but dif- ferently manured. Without copying the analyses, we may state some of the most striking results. The extreme range of varia- tion in potash was 5£ per cent. The ash containing the highest percentage of potash was not, however, obtained from potatoes that had been manured with 50 pounds of this substance, but from a parcel to which had been ap- plied a poudrette containing less than three pounds of potash for the quantity used. The unmanured potatoes were relatively the richest in 180 HOW CHOPS G&OW. lime, phosphoric acid, and sulphuric aeid, although sev- eral parcels were copiously treated with mauures contain- ing considerable quantities of these substances. These facts are of great interest in reference to the theory of the action of manures. 7. To what extent is each ash-ingredient essential, and how far may it be accidental ? Before chemical analysis had arrived at much perfection, it was believed that the ashes of the plant were either unessential to growth, or else were the products of growth — were gener- ated by the plant. Since the substances found in ashes are universally dis- tributed over the earth's surface, and are invariably pres- ent in all soils, it is not possible, by analysis of the ash of plants growing under natural conditions, to decide whether any or several of their ingredients are indispen- sable to vegetative life. For this purpose it is necessary to institute experimental inquiries, and these have been prosecuted with great painstaking, and with highly val- uable results. Experiments in Artificial Soils. — The Prince Salm- Horstmar, of Germany, was one of the first and most laborious students of this question. His plan of experi- ment was the following : The seeds of a plant were sown in a soil-like medium (sugar-charcoal, pulverized quartz, purified sand) which was as thoroughly as possible freed from the substance whose special influence on growth was the subject of study. All other substances presum- ably necessary, and all the usual external conditions of growth (light, warmth, moisture, etc.), were supplied. The results of 195 trials thus made with oats, wheat, barley, and colza, subjected to the influence of a great variety of artificial mixtures, have been described, the most important of which will shortly be given. Experiments in Solutions. — Water-Culture. — - Sachs, W. Kuop, Stohmaun, Nobbe, Siegert, and others THE ASH OP PLAKTS. 181 have likewise studied this subject. Their method was like that of Prince Salm-Horstmar, except that the plants were made to germinate and grow independently of any soil; and, throughout the experiment, had their roots im- mersed in water, containing in solution or suspension the substances whose action was to be observed. Water-Culture has recently contributed so much to our knowledge of the conditions of vegetable growth, that some account of the mode of conducting it may be prop- erly given in this place. Cause a num- ber of seeds of the plant it is desired to experiment upon to germinate in moist blotting-paper, and, when the roots have become an inch or two in length, select the strongest seedlings, and support them so that the roots shall be immersed in water, while the seeds themselves shall be just above the surface of the liquid.- For this purpose, in case of a single jp maize plant, for example, provide a quart cylinder or bottle with a wide mouth, to which a cork is fitted, as in Pig. 22. Cut a vertical notch in the cork to its center, and fix therein the stem of the seedling by packing with cotton. The cork thus serves as a sup- port of the plant. Fill the jar with pure water to such a height that when the cork is brought to its place, the seed, S, shall be a little above the liquid. If the endosperm or cotyledons dip into the water, they will speedily mould and rot ; they require, however, to be kept in a moist atmosphere. Thus arranged, suitable warmth, ventilation, and illumination alone are requi- site to continue the growth until the nutriment of the seed Fig. 22. 182 HOW CROPS GROW. is nearly exhausted. As regards illumination, this should be as full as possible, for the foliage ; but the roots should be protected from it, by enclosing the vessel in a shield of black paper, as, otherwise, minute parasitic algae would in time develop upon the roots, and disturb their functions. For the first days of growth, pure distilled water may ad- vantageously surround the roots, but, when the first green leaf appears, they should be placed in the solution whose nutritive power is to be tested. The temperature should be properly proportioned to the light, in imitation of what is observed in the skillful management of conservatory or house-plants. The experimenter should first learn how to produce large and well-developed plants by aid of an appropriate liquid, before attempting the investigation of other prob- lems. For this purpose, a solution or mixture must be prepared, containing in proper proportions all that the plant requires, save what it can derive from the atmos- phere. The experience of Nobbe and Siegert, Knop, Wolff, and others,* supplies valuable information on this point. Wolff has obtained striking results with a variety of plants in using a solution made essentially as follows: Place 20 grams of the fine powder of well-burned bones with a half pint of water in a large glass flask, heat to boil- ing, and add nitric acid cautiously in quantity just suffi- cient to dissolve the bone-ash. In order to remove any injurious excess of nitric acid, pour into the boiling liq- uid a solution of pure potassium carbonate until a slight permanent turbidity is produced; then add 11 grams of potassium nitrate, 7 grams of crystallized magnesium sul- phate, and 3 grams of potassium chloride, with water enough to make the solution up to the bulk of one liter. Wolff's solution, thus prepared, contains in 1000 parts as follows, exclusive of iron: r.filr Landtvlrthschaft,\8&2, p. 637) for full and concise instructions. THE ASH OF PLANTS. 183 Phosphoric acid 8.2 Lime 10.5 Potash 9.1 Magnesia 1.4 Sulphuric acid 2.2 Chlorine 0.9 Nitric acid 29.7 Solid Matters 62 Water 938 1000 For use, dilute 15 or 20 c. c. of the above solution with water to the bulk of a liter and add one or two drops of strong solution of ferric chloride. The solution should be changed at first every week, and, as the plants acquire greater size, their roots should be transferred to a larger vessel filled with solution of the same strength, and the latter changed every 5 or 3 days. It is important that the water which escapes from the jar by evaporation and by transpiration through the plant should be daily or oftener replaced, by filling it with pure water up to the original level. The solution, whose prep- aration has been described, may be turbid from the sepa- ration of a little calcium sulphate before the last dilution, as well as from the precipitation of phosphate of iron on adding ferric chloride. The former deposit may be dis- solved, though this is not needful; the latter will not dis- solve, and should be occasionally put into suspension by stirring the liquid. When the plant is half grown, fur- ther addition of iron is unnecessary. In this manner, and with this solution, Wolff produced a maize plant five and three quarters feet high, and equal in every respect, as regards size, to plants from similar seed, cultivated in the field. The ears were not, however, fully developed when the experiment was interrupted by the plant becoming unhealthy. With the oat his success was better. Four plants were brought to maturity, having 46 stems and 1535 well-de- veloped seeds. (Fa. St., VIII, pp.190-215.) 184 HOW CKOPS GROW. In similar experiments, Nobbe obtained buckwheat plants, six to seven feet high, bearing three hundred plump and perfect seeds, and barley stools with twenty grain-bearing stalks. (Vs. St., VII, p. 72.) In water -culture the composition of the solution is suf- fering continual alteration, from the fact that the plant makes, to a certain extent, a selection of the matters pre- sented to it, and does not necessarily absorb them in the proportions in which they originally existed. In this way, disturbances arise which impede or become fatal to growth. In the early experiments of Sachs and Knop, in 1860, they frequently observed that their solutions suddenly acquired the odor of hydrogen sulphide, and black iron sulphide formed upon the roots, in consequence of which they were shortly destroyed. This reduction of a sulphate to a sulphide takes place only in an alkaline liquid, and Stohmann was the first to notice that an acid liquid might be made alkaline by the action of living roots. The plant, in fact, has the power to decompose salts, and by appropriating the acids more abundantly than the bases, the latter accumulate in the solution in the free state, or as carbonates with alkaline properties. To prevent the reduction of sulphates, the solution must be kept slightly acid, if needful, by addition of a very little free nitric acid, and, if the roots blacken, they must be washed with a dilute acid, and, after rinsing with water, must be transferred to a fresh solution. On the other hand, Kiihn has shown that when am- monium chloride is employed to supply maize with nitro- gen, this salt is decomposed, its ammonia assimilated, and its chlorine, which the plant cannot use, accumulates in the solution in the form of hydrochloric acid to such an extent as to prove fatal to the plant (Henneberg's Journal, 1864, pp. 116 and 135). Such disturbances are avoided by employing large volumes of solution, and by frequently renewing them, THE ASH OF PLANTS. 185 The concentration of the solution is by no means a matter of indifference. While certain aquatic plants, as sea-weeds, are naturally adapted to strong saline solutions, agricultural land-plants rarely succeed well in water cul- ture, when the liquid contains more than T^^ of solid matters, and will thrive in considerably weaker solutions. Simple well-water is often rich enough in plant-food to nourish vegetation perfectly, provided it be renewed suffi- ciently often. Sachs's earliest experiments were made with well-water. Birner and Lucanus, in 1864 ( Vs. $£.,VIII, 154), raised oat-plants in well-water, which in respect to entire weight were more than half as heavy as plants that grew simul- taneously in garden soil, and, as regards seed-production, fully equalled the latter. The well-water employed con- tained but ^^^ of dissolved matters, or in 100,000 parts: Potash 2.10 Lime 15.10 Magnesia 1.50 Phosphoric acid 0.16 Sulphuric acid 7.50 Nitric acid 6.00 Silica, Chlorine, Oxide of iron traces Solid Matters 32.36 Water 99,967.64 100,000 On the other hand, too great dilution is fatal to growth. Nobbe ( Vs. St., VIII, 337) found that in a solution con- taining but TTT^OTT °f solid matters, which was continually renewed, barley made no progress beyond germination, and a buckwheat plant, which at first grew rapidly, was soon arrested in its development, and yielded but a few ripe seeds, and but 1.746 grm. of total dry matter. While water-culture does not provide all the normal conditions for the growth of land plants — the soil having important functions that cannot be enacted by any liquid medium — it is a method of producing highly-developed plants, under circumstances which admit of accurate con- 186 HOW CROPS GROW. trol and great variety of alteration, and is, therefore, oi the utmost value in vegetable physiology. It has taught important facts which no other means of study could re- veal, and promises to enrich our knowledge in a still more eminent degree. Potassium, Calcium, and Magnesium as soluble Salts, Phosphorus as Phosphates and Sulphur as Sulphates, are absolutely necessary for the life of- Agricultural Plants, as is demonstrated by all the ex- periments hitherto made for studying their influence. It is impossible to recount here in detail the evidence to this effect that is furnished by the investigations of Salm-Horstmar, Sachs, Knop, Nobbe, Birner and Luca- nus, and others ( Vs. St., VIII, p. 128-161). Some of the experimental proof of this statement is strikingly exhibited by the figures on Plate I, copied from Kobbe, showing results of the water-culture of buckwheat in normal nutritive solutions and in solutions variously deficient. Is Sodium Essential for Agricultural Plants? This question has occasioned much discussion. A glance at the table of ash-analyses (pp. 164-170) will show that the range of variation is very great as regards this alkali- metal. The older analysts often reported a considerable proportion of sodium oxide, even 20% or more, in the ash of seeds and grains. In most of the analyses, however, sodium oxide is given in much smaller quantity. The average in the ashes of the grains is less than 3 per cent, and in not a few of the analyses it is entirely wanting. In the older analyses of other classes of agricultural plants, especially in root crops, similarly great variations occur. Some uncertainty exists as to these older data, for the reason that the estimation of sodium by the processes customarily employed is liable to great inaccuracy, espe- cially with the inexperienced analyst. On the one hand, it is not or was not easy to detect, much less to estimate, THE ASH OF PLANTS. 187 minute traces of sodium when mixed with much potassi- um ; while, on the other hand, sodium, if present to the extent of a per cent or more, is very liable to be estimated too high. It has therefore been doubted if these high percentages in the ash of grains are correct. Again, the processes formerly employed for preparing the ash of plants for analysis were such as, by too elevated and prolonged heating, might easily occasion a partial or total expulsion of sodium from a material which prop- erly should contain it, and we may hence be in doubt whether the older analyses, in which sodium is not men- tioned, are to be altogether depended upon. The later analyses, especially those by Bibra, Zoeller, Arendt, Bretschneider, Ritthausen, and others, who have employed well-selected and carefully-cleaned materials for their investigations, and who have been aware of all the various sources of error incident to such analyses, must therefore be appealed to in this discussion. From these recent analyses we are led to precisely the same conclu- sions as were warranted by the older investigations. Here follows a statement of the range of percentages of sodium oxide in the ash of several field crops, according to the newest analyses: SODIUM OXIDE (SODA) IX LATER ASH-ANALYSES. Ash of Wheat kernel, none, Bibra, to 5% Bibra. 0.28% Lawes& Gilbert," 1.18% Potato tuber, none, J ^fzdorff, " 4% Wolff- TCirlpv Vprnpl I l% Bibra, „ ,„„ ( Bibra. Barley kernel, j ^ Zoeller> 6%{veltmann. " 7% Zoeller. Q,,,,o,-Ko«t / 4% Ritthausen, " 29.8% Ritthausen. 1 7% Bretschneider, " 16.6% Bretschneider. Turnip root, 7.7% Anderson, " 17.1% Anderson. Although, as just indicated, sodium in some instances Las been found wanting in the wheat kernel and in po- tato tubers, it is not certain that it was absent from other parts of the same plants, nor has it been proved that sodium is wanting in any entire plant which has grown on a natural soil. 188 HOW CROPS GROW. "Weinhold found in the ash of the stem and leaves of the common live-for-ever (Sedum telephium) no trace of sodium detectable by ordinary means ; while in the ash of the roots of the same plant there occurred 1.8 per cent of its oxide ( Vs. St., IV, p. 190). It is possible then that, in the above instances, so- dium really existed in the plants, though not in those parts which were subjected to analysis. It should be added that in ordinary analyses, where sodium is stated to be absent, it is simply implied that it is present, if at all, in too small a quantity to admit of determining by the usual method, while in reality a minute amount may be present in all such cases.* The final result of all the analytical investigations hitherto made, with regard to cultivated agricultural plants, then, is that sodium is an extremely variable in- gredient of the ash of plants, and though generally pres- ent in some proportion, and often in large proportion, has been observed to be absent in weighable quantity in the seeds of grains and in the tubers of potatoes. Salm-Horstmar, Stohmann, Knop, and Xobbe & Sie- gert have contributed experimental evidence bearing on this question. The investigations of Salm-Horstmar were made with great nicety, and especial attention was bestowed on the influence of very minute quantities of the various sub- stances employed. He gives as the result of numerous experiments, that, for wheat, oats, and barley, in the early vegetative stages of growth, Sodium, while advan- tageous, is not essential, but that for the perfection of fruit an appreciable though minute quantity of this ele- ment is indispensable. ( Versuche und Resultate iiber die Nalirung der Pflanzen, pp. 12, 27, 29, 36.) •The methods of spectral analysis, by which ssnoj^nn of a pram of sodium oxide may lie detected. < lemons) rate t his "element to lie so uni- versally distributee" that it is next to impossible to find or to prepare anything that is free from it. THE ASH OF PLANTS. 189 Stohmann's single experiment led to the similar con- clusion, that maize may dispense with sodium in the earlier stages of its growth, but requires it for a full development. (Henneberg's Jour, filr Landwirtliscliaft, 1862, p. 25.) Knop, on the other hand, succeeded in bringing the ,naize plant to full perfection of parts, if not of size, in a solution which was intended and asserted to contain no sodium. (Vs. St., Ill, p. 301.) Nobbe & Siegert came to the same results in similar trials with buckwheat. Vs. St., IV, p. 339.) Later trials by Nobbe, Schroder and Erdmann, and by others, confirm the conclusion that sodium may be nearly or altogether dispensed with by plants. The buckwheat represented in Plate I vegetated for 3 months in solutions as free as possible from sodium, with the exception of VI, in which sodium was substituted for potassium. The experiments of Knop, Nobbe, Siegert and others, while they prove that much sodium is not needful to maize and buckwheat, do not, however, satisfactorily demonstrate that a little sodium is not necessary, because the solutions in which the roots of the plants were im mersed stood for months in glass vessels, and coul-i scarcely fail to dissolve some sodium from the glass. Again, slight impurity of the substances which were em- ployed in making the solution could scarcely be avoided without extraordinary precautions, and, finally, the seeds of these plants might originally have contained enough sodium to supply this substance to the plants in appre- ciable quantity. To sum up, it appears from all the facts before us : 1. That sodium is never totally absent from plants, and that, 2. If indispensable, but a minute amount of it is requisite. 190 HOW CHOPS GROW. 3. That the foliage and succulent portions of the plant may include a considerable amount of sodium that is not necessary to the plant ; that is, in other words, accidental. Can Sodium replace Potassium? — The close simi- larity of potassium and sodium, and the variable quanti- ties in which the latter especially is met with in plants, have led to the assumption that one of these alkali-metals can take the place of the other. Salm-Horstmar and Knop & Schreber firit demon- etrated that sodium cannot entirely take the place of potassium — that, in other words, potassium is indispen- sable to plant life. Plate I, VI, shows the development of buckwheat during 3 months, in Nobbe, Schroder & Erdmann's water-cultures, when, in a normal nutritive solution, potassium is substituted by sodium, as com- pletely as is practicable. Cameron concluded, from a series of experiments which it is unnecessary to describe, that, under natural condi- tions, sodium may partially replace potassium. A partial replacement of this kind would appear to be indicated by many facts. Thus, Herapath has made two analyses of asparagus, one of the wild, the other of the culti- vated plant, both gathered in flower. The former was rich in sodium, the latter almost destitute of this sub- stance, but contained correspondingly more potassium. Two analyses of the ash of the beet, one by Wolff (1), the other by Way (2), exhibit similar differences : Atparatjus. Field Beet. Wild. Cultivated. 1. 2. Potassium oxide 18.8 50.5 57.0 • 25.1 Sodium oxide 16.2 trace 7.3 34.1 Calcium oxide 28.1 21.3 5.8 2.2 Magnesium oxifle 1.5 4.0 2.1 Chlorine 16.5 8.3 4.9 34.8 Sulphur trioxide 9.2 4.5 3.5 3.6 Phosphorus pentoxide 12.8 12.4 12.9 1.9 Sili.-a 1.0 3.7 3.7 1.7 These results go to show — it being assumed that only a very minute amount of sodium, if any, is absolutely nee- THE ASH OF PLANTS. 191 essary to plant-life — that the sodium which appears to replace potassium is accidental, and that the replaced potassium is accidental also, or in excess above what is really needed by the plant, and leaves us to infer that the quantity of these bodies absorbed depends to some ex- tent on the composition of the soil, and is to the same degree independent of the wants of vegetation. Alkalies in Strand and Marine Plants. — The above conclusions apply also to plants which most com- monly grow near or in salt water. Asparagus, the beet and carrot, though native to saline shores, are easily ca- pable of inland cultivation, and indeed grow wild in com- parative absence of sodium compounds. The common saltworts, Salsola, and the samphire, Salicornia, are plants which, unlike those just men- tioned, seldom stray inland. Gobel, who has analyzed these plants as occurring on the Caspian steppes, found in the soluble part of the ash of the Salsola brachiata 4.8 per cent of potassium oxide, and 30.3 per cent of sodium oxide, and in the Salicornia herbacea 2.6 per cent of potassium oxide and 36.4 per cent of sodium oxide, the sodium oxide constituting in the first instance no less than -fa and in the latter ^ of the entire weight, not of the ash, but of the air-dry plant. Potas- sium is never absent from these forms of vegetation. (Agricultur-Chemie, 3te Auf., p. 66.) According to Cadet (Liebig's Ernahrung der Veg., p. 100), the seeds of the Salsola kali, sown in common garden soil, gave a plant which contained both sodium and potassium ; from the seeds of this, sown also in garden soil, grew plants in which only potassium-salts with traces of sodium could be found. These strand- plants are occasionally found at a distance from salt- shores, and their growth as strand-plants appears to be due to their capacity for flourishing in spite of salt, and not from their requiring it. (Hoffmann, Vs. St., XIII, p. 295.) 192 HOW CROPS GROW. Another class of plants — the sea- weeds (algce) — de- rive their nutriment exclusively from the sea-water in which they are immersed. Though the quantity of po- tassium in sea-water is but ^ that of the sodium, it is yet a fact, as shown by the analyses of Forchhammer (Jour, fur Prakt. Chem., 36, p. 391) and Anderson (Trans. High, and Ag. Soc., 1855-7, p. 349) that the ash of sea-weeds is, in general, as rich, or even richer, in potassium than in sodium. In 14 analyses, by Forch- hammer, the average amount of sodium in the dry weed was 3.1 per cent; that of potassium 2.5 per cent. In Anderson's results the percentage of potassium is inva- riably higher than that of sodium.* Analogy with land-plants would lead to the inference that the sodium of the sea-weeds is in a great degree ac- cidental. In fact, Fucus vesiculosis and Zygogonium sal- inum have been observed to flourish in fresh water. (Vs. St., XIII, p. 295.) Iron is Essential to Plants. — It is abundantly proved that a minute quantity of ferric oxide, Fe208, is essential to growth, though the agricultural plant may be perfect if provided with so little as to be discoverable in its ash only by sensitive tests. According to Salm- Horstmar, ferrous oxide, FeO, is indispensable to the colza plant. (Versuche, etc., p. 35.) Knop asserts that maize, which refuses to grow in entire absence of iron, flourishes when ferric phosphate, which is exceedingly insoluble, is simply suspended in the solution that bathes its roots for the first four weeks only of the growth of the plant. ( Vs. St., V, p. 101.) We find that the quantity of ferric oxide given in the analyses of the ashes of agricultural plants is small, being usually less than one per cent. Here, too, considerable variations are observed. In * Doubtless iluc to the fact that ilie material used by Anderson was freed by washing from adhering common salt. THE ASH OF PLANTS. 193 the analyses of the seeds of cereals, ferric oxide ranges from an unweighable trace to 2 and even 3%. In root crops it has been found as high as 5%. Kekule found in the ash of gluten from wheat 7.1% of ferric oxide. (Jahresbericht der Ohem., 1851, p. 715.) Schulz-Meeth found 17.5% in the ash of the albumin from the juice of the potato tuber. The proportion of ash is, however, so small that in case of potato-albumin the ferric oxide amounts to but 0.12 per cent of the dry substance. (Der Rationelle Ackerbau, p. 82.) In the ash of v^ood, and especially in that of bark, ferric oxide often exists to the extent of 5 to 10%. The largest percentages have been found in aquatic plants. In the ash of the duckweed (Lemna trisulca) Liebig found 7.4%. Gorup-Besanez found in the ash of the leaves of the Trapa natans 29.6%, and in the ash of the fruit- envelope of the same plant 68.6%. (Ann. Cli. Ph., 118, p. 223.) Probably much of the iron of agricultural and land plants is occidental In case of the Trapa natans, we cannot suppose all the iron to be essential, because the larger share of it exists in the tissues as a brown powdery oxide which may be extracted by acids, and has the ap- pearance of having accumulated there mechanically. Doubtless a portion of the iron encountered in anal- yses of agricultural vegetation has never once existed within the vegetable tissues, but comes from the soil, which adheres with great tenacity to all parts of plants. Manganese is Unessential to Agricultural Plants. Manganese is commonly much less abundant than iron, and is often, if not usually, as good as wanting in agri- cultural plants. It generally accompanies iron where the latter occurs in considerable quantity. Thus, in the ash of Trapa, the oxide Mn304 was found to the extent of 7.5-14.7%. Sometimes it is found in much larger quantity than oxide of iron ; e. g., Ct Ifresenms found 13 194 HOW CROPS GROW. 11.2% of oxide of manganese in ash of leaves of the red beech (Fagus sylvaticd) that contained but 1% of oxide of iron. In the ash of oak leaves (Quercus robur) Xeu- bauer found, of the former 6.6, of the latter but 1.2%. In ash of the wood of the larch (Larix Europcea), Bot- tinger found 33.5% Mn304 and 4.2% Fe203, and in ash of wood of Pinus sylvestris 18.2% Mu304, and 3.5% Fe203. In ash of the seed of colza, Nitzsch found 16.1% Mn304, and 5.5 Fe203. In case of land plants, these high percentages are accidental, and specimens of most of the plants just named have been analyzed, which were free from all but traces of oxide of manganese. Salm-Horstmar concluded from his experiments that oxide of manganese is indispensable to vegetation. Sachs, Knop, and most other experimenters in water- culture, make no mention of this substance in the mix- tures, which in their hands have served for the more or less perfect development of a variety of agricultural plants. Birner & Lucanus have demonstrated that man- ganese is not needful to the oat-plant, and cannot take the place of iron. ( Vs. St., VIII, p. 43.) Is Chlorine Indispensable to Crops ? — What has been written of the occurrence of sodium in plants ap- pears to apply in most respects equally well to chlorine. In nature, sodium is generally associated with chlorine as common salt. It is most probably in this form that the two substances usually enter the plant, and in the majority of cases, when one of them is present in large quantity, the other exists in corresponding quantity. Less commonly, the chlorine of plants is in combination with potassium exclusively. Chlorine is doubtless never absent from the perfect agricultural plant, as produced under natural conditions, though its quantity is liable to great variation, and is often very small — so small as to be overlooked, except by the careful analyst. In many analyses of grain, chlorine THE ASH OF PLANTS. 195 is not mentioned. Its absence, in many cases, is due, without doubt, to the fact that chlorine is readily dissi- pated from the ash of substances rich in phosphates or silica, on prolonged exposure to a high temperature. In some of the later analyses, in which the vegetable sub- stance, instead of being at once burned to ashes, at a high red heat, is first charred at a heat of low redness, and then leached with water, which dissolves the chlo- rides, and separates them from the unburned carbon and other matters, chlorine is invariably mentioned. In the tables of analyses, the averages of chlorine are undeni- ably too low. This is especially true of the grains. The average of chlorine in the 26 analyses of wheat by Way and Ogston, p. 150, is but 0.08%, it not being found at all in the ash of 21 samples. In Zoeller's later anal- yses chlorine is found in every instance, and averages 0.7%. In Lawes and Gilbert's numerous analyses of wheat-grain ash chlorine ranges from 0 to 1.14%, the average being 0.1%. In wheat-straw ash they found from 1.08 to 2.06%. The ash was in all cases prepared by burning at a low red heat. Like sodium, chlorine is particularly abundant in the stems and leaves of those kinds of vegetation which grow in soils or other media containing much common salt. It accompanies sodium in strand and marine plants, and, in general, the content of chlorine of any plant may be large- ly increased or diminished by supplying it to or withhold- ing it from the roots. As to the indispensableness of chlorine, we have some- what conflicting data. Salm-Horstmar believed that a trace of it is needful to the wheat plant, though many of his experiments in reference to this element were unsatis- factory to himself. Nobbe and Siegert, who have made an elaborate investigation on the nutritive relations of chlorine to buckwheat, were led to conclude that while the stems and foliage of this plant are able to attain a 196 HOW CROPS GROW. considerable development in the absence of chlorine (the minute amount in the seed itself excepted), presence of chlorine is essential to the perfection of the fruit. Leydhecker came to the same conclusions as Nobbe and Siegert regarding the indispensableness of chlorine to the perfection of buckwheat. ( Vs. St., VIII, p. 177.) On the other hand, Knop excludes chlorine from the list of necessary ingredients of maize, buckwheat, cress, and Psamma arenaria, having obtained a maize plant 3 feet high, bearing 4 ripe seeds, harvested 23 " chlorine- free seeds" from 5 buckwheat-plants, and raised 40 to 50 ripe seeds from more than one cress-plant, all grown without chlorine. (Vs. St., XIII, p. 219.) Wagner also obtained, in absence of chlorine, maize- plants 40 inches high, of 20 grams dry-weight. One of these ripened 5 small seeds, of which two were proved capable of germination ; but none of these plants produced any pollen and they were fertilized with pollen from garden-plants. (Vs. St., XIII, pp. 218-222.) From a series of experiments in water-culture, Birner and Lucanus (Vs. St., VIII, p. 160) conclude that chlo- rine is not indispensable to the oat-plant, and has no spe- cific effect on the production of its fruit. Chloride of potassium increased the weight of the crop, chloride of sodium gave a larger development of foliage and stem, chloride of magnesium was positively deleterious, under the conditions of their trials. Lucanus ( Vs. St., VII, pp. 363-71) raised clover by water-culture without chlorine, the crop (dry) weigh- ing in the most successful experiments 240 times as much as the seed. Addition of chlorine gave no better result. Nobbe (Vs. St., VIII, p. 187) has produced normally developed vetch and pea plants, but only in solutions containing chlorine. Beyer (Vs. St., XI, p. 262) found exclusion of chlorine in water-culture to prevent forma- tion of seed in case of peas ; the plants, after a month's !THE ASH OF PLANTS. 197 healthy growth, produced new shoots only at the expense of the older leaves. In similar trials oats gave a small crop of ripe seeds when chlorine was not supplied. When, however, the seeds thus obtained nearly free from chlorine were vegetated in a solution destitute of this element they failed to produce seed again, though their growth and reproduction were normal when chlorine was furnished them in the nutritive solution. In Plate I, X shows the extent to which, in Nobbe's cultures, buckwheat developed when vegetating for 3 months in a solution destitute of chlorine, but otherwise fully adapted to nourish plants. In view of all the evidence, then, it would appear probable that chlorine is needful for the cereals, and that when the seed and nutritive media (soil or solution and air) are entirely destitute of this element fruit cannot be perfected. It is probable that in the cases where fruit was produced in supposed absence of chlorine this substance in some way gained access to the plants. Until further more decisive results are reached, we are warranted in adopting, with regard to chlorine as related to agricultural plants, the following conclu- sions, viz. : 1. Chlorine is never totally absent. 2. If indispensable, but a minute amount is requisite for a very considerable vegetative development. 3. Some plants, as vetches and peas, require a not in- considerable amount of chlorine for full development, especially of seed. 4. The foliage and succulent parts may include a large quantity of chlorine that is not indispensable to the life of the plant. Silica is not indispensable to Plants. — The numer- ous analyses we now possess indicate that this substance is always present in the ash of all parts of agricultural plants, when they grow in natural soils. 198 HOW CROPS GROW. In the ash of the wood of trees, it usually ranges from 1-3%, but is often found to the extent of 10-20%, or even 30%, especially in the pine. In leaves, it is usually more abundant than in stems. The ash of turnip leaves contains 3-10% ; of tobacco leaves, 5-18% ; of the oat, 11-58%. (Arendt, Norton.) In ash of lettuce, 20% ; of beech leaves, 26% ; in those of oak, 31% have been observed. (Wicke, Henneberg's Jour., 1862, p. 156.) The bark or cuticle of many plants contains an extra- ordinary amount of silica. The canto tree of South America (Hirtella silicea) is most remarkable in this respect. Its bark is very firm and harsh, and is difficult to cut, having the texture of soft sandstone. It yields 34% of ash, and of this 96% is silica. (Wicke, loc. cit., p. 143.) Another plant, remarkable for its content of silica, is the bamboo. The ash of the rind contains 70%, and in the joints of the stem are often found concretions of hydrated silica, the so-called Tabashir. The ash of the common scouring rush (Equisetum hye- male) has been found to contain 97.5% of silica. The straw of the cereal grains, and the stems and leaves of grasses, both belonging to the botanical family Grami- nacce, are specially characterized by a large content of silica, ranging from 40-70% of the ash. The sedge and rush families likewise contain much of this substance. The position of silica in the plant would thus appear to be, in general, at the surface. Although it is present in other parts of the plant, yet the cuticle is usually rich- est, especially where the content of silica is large. Daw. in 1799, drew attention to the deposition of silica in the cuticle of the grasses and cereals, and advanced the idea that it serves these plants an office of support similar to that enacted in animals by the bones. In case of the pine (Finns sylvestris), "Wittstein has obtained results which indicate that the age of wood or THE ASH OF PLANTS. 199 bark greatly influences the content of silica. He found in ash of the — And in — Wood of a tree, 220 years old, 32.5% " " 170 " 24.1 " " 135 " 15.1 Bark " 220 " 30.3 " " 170 " 14.4 " " 135 " 11.9 In the ash of the straw of the oat, Arendt found the percentage of silica to increase as the plant approached maturity. So the leaves of forest trees, which in autumn are rich in silica, are nearly destitute of this substance in spring time. Silica accumulates then, in general, in the older and less active parts of the plant, whether these be external or internal, and is relatively deficient in the younger and really growing portions. This rule is not without excep- tions. Thus, the chaff of wheat, rye and oats is richer in silica than any other part of these plants, and Bo'ttin- ger found the seeds of the pine richer in silica than the wood. In numerous instances, silica is deposited in or upon the cell-wall in such abundance that when the organic matters are destroyed by burning, or removed by sol- vents, the form of the cell is preserved in a silicious skeleton. This has long been known in case of the Equisetums and Deutzias. Here the peculiar rough- nesses of the stems or leaves are fully incrusted or inter- penetrated by silica, and the ashes of the cuticle present the same appearance under the microscope as the cuticle itself. The hairs of nettles, hemp, hops, and other rough- leaved plants, are highly silicious. According to Wicke, the beecli owes the smooth and undecayed surface which its trunk presents, to the silica of the bark. The best textile materials, which are bast- 200 HOW CROPS GROW. fibers of various plants, viz., common hemp, Manila hemp (Musa textilis), aloe-hemp (Agave Americana), common flax, and New Zealand flax (PJiormium tenets) are incrusted with silica. In jute (Corchorus textilis) some cells are partially incrusted. The cotton fiber is free from silica. Wicke (loc. cit.) suggests that the du- rability of textile fibers is to a degree dependent on their conteni of silica. Sachs, in 1862, was the first to publish evidence that silica is not a necessary ingredient of maize. He ob- tained in his early essays in water-culture a maize plant of considerable development, whose ashes contained but 0.7% of silica. Shortly afterwards, Knop produced a maize plant with 140 ripe seeds, and a dry-weight of 50 grammes (nearly 2 oz. av.) so free from silica that a mere trace of this substance could be found in the root, but half a milligramme in the stem, and 22 milligrammes in the 15 leaves and sheaths. It was altogether absent from the seeds. The ash of the leaves of this plant thus contained but 0.54 per cent of silica, and the stem but 0.07 per cent. Way & Ogston had found in the ash of field-grown maize, leaf and stem together, 27.98 per cent of silica. In the numerous experiments that have been made more recently upon the growth of plants in aqueous solu- tions, by Sachs, Knop, Nobbe & Sieger t, Stohmann, Kautenberg & Kiihn, Birner & Lucanus, Leydhecker, Wolff, and Harnpe, silica, in nearly all cases, has been excluded, so far as it is possible to do so, in the use of glass vessels. This has been done without prejudice to the development of the plants. Nobbe & Siegert and Wolff especially have succeeded in producing buckwheat, maize, and the oat, in full perfection of size and parts, with this exclusion of silica. Wolff (Vs. St., VIII, p. 200) obtained in the ash of maize thus cultivated, 2 to 3% of silica, while the same THE ASH OF PLANTS. 201 two varieties from the field contained in their ash 11£ to 13%. The proportion of ash was essentially the same in both cases, viz., about 6%. Wolff's results with the oat plant were entirely similar. Birner & Lucanus ( Vs. St., VIII, p. 141) found that the supply of soluble silicates to the oat made its ash very rich in silica (40%) but diminished the growth of straw, without affecting that of the seed, as compared with plants nearly destitute of silica. It is thus made certain that plants ordinarily rich in silica may attain a high development in absence of this substance. We shall see later, however (p. ), that silica is probably not altogether useless to plants when they grow under ordinary conditions. Jodin reports having bred maize by water-culture, with the utmost practicable exclusion of silica, for four gener- ations— whereby this substance was reduced to the merest traces — without interference with the normal develop- ment of the plant. (Ann. Agron., IX, p. 385.) The Ash-Ingredients, which are Indispensable to Crops, may be taken up in Larger Quantity than is Essential. — More than eighty years ago, Saussure de- scribed a simple experiment which is conclusive on this point. He gathered a number of peppermint plants, and in some determined the amount of dry matter, which was 40.3 per cent. The roots of others were then im- mersed in pure water, and the plants were allowed to veg- etate 2£ months in a place exposed to air and light, but sheltered from rain. At the termination of the experiment, the plants, which originally weighed 100, had increased to 216 parts, and the dry matter of these plants, which at first was 40.3, had become 62 parts. The plants could have acquired from the glass vessels and pure water no con- siderable quantity of mineral matters. It is plain, then, that the ash-ingredients which were contained in two 202 HOW CROPS GROW. parts of the peppermint were sufficient for the produc- tion and existence of three parts. We may assume, therefore, that at least one-third of the ash of the origi- nal plants was in excess, and accidental. The fact of excessive absorption of essential ash-ingre- dients is also demonstrated by the precise experiments of Wolff on buckwheat, already described (see p. 164), where the point in question is incidentally alluded to, and the difficulties of deciding how much excess may occur, are brought to notice. (See also pp. 192 arid 194 n regard to potassium and iron.) As further striking instances of the influence of the nourishing medium on the quantity of ash-ingredients in the plant, the following are adduced, which may serve to put in still stronger light the fact that a plant does not always require what it contains. Nobbe & Siegert have made a comparative study of the composition of buckwheat, grown on the one hand in garden soil, and on the other in an aqueous solution of saline matters. (The solution contained magnesium sulphate, calcium chloride, phosphate and nitrate of potassium, with phosphate of iron, which together con- stituted 0.316% of the liquid.) The ash-percentage was much higher in the water-plants than in the garden- plants, as shown by the subjoined figures. ( Vs. St., V, p. 132.) Per cent of ash in Stems and leaves. Roots. Seeds. Entire plant. Water-plant 18.6 15.3 2.6 16.7 Garden-plant 8.7 6.8 2.4 7.1 We have seen that well-developed plants contain a larger proportion of ash than feeble ones, when they grow side by side in the same medium. In disregard of this general rule, the water-plant in the present instance has an ash-percentage double that of the land-plant, although the former was a dwarf compared with the lat- ter, yielding but £ as much dry matter. The seeds, how- ever, are scarcely different in composition. THE ASH OF PLANTS. 203 Similar results were obtained by Councler with the leaves of Acer negundo (Vs. St., XXIX, p. 242), 1,000 parts of the perfectly dry leaves contained : Water-plant. Soil-plant. Silica, SiO2, 8.51 23.72 Sulphuric oxide, SO3, 38.97 9.69 Phosphoric oxide, P2O6)... 26.00 4.56 Iron oxide, Fe2Os, 1.94 1.22 Magnesium oxide, MgO,. .. 7.56 6.25 Calcium oxide, CaO 31.77 36.17 Sodium oxide, Na2O, 1.23 0.88 Potassium oxide, K,O, 96.92 45.05 212.90 127.54 Leaves of the water-plant are much richer in ash-ingre- dients, especially in sulphate and phosphate of potassium. Those of the soil-plant contain more silica and lime. Disposition by the Plant of Excessive or Super- fluous Ash-ingredients — The ash-ingredients taken up by a plant in excess beyond its actual wants may be disposed of in three ways. The soluble matters — those soluble by themselves, and also incapable of forming in- soluble combinations with other ingredients of the plant — viz., the alkali chlorides, sulphates, carbonates, and phosphates, the chlorides of calcium and magnesium, may— 1. Eemain dissolved in, and diffused 'throughout, the juices of the plant ; or, 2. May exude upon the surface as an efflorescence, and be washed off by rains. Exudation to the surface has been repeatedly observed in case of cucumbers and other kitchen vegetables, grow- ing in the garden, as well as with buckwheat and barley in water-culture. (Vs. St., VI, p. 37.) Saussure found in the white incrustations upon cucum- ber leaves, besides an organic body insoluble in water and alcohol, calcium chloride with a trace of magnesium chloride. The organic substance so enveloped the cal- cium chloride as to prevent deliquescence of the latter. (Recherches sur la Veg., p. 265.) 204 HOW CROPS GROW. Saussure proved that foliage readily yields up saline matters to water. He placed hazel leaves eight success- ive times in renewed portions of pure water, leaving them therein 15 minutes each time, and found that by this treatment they lost ^ of their ash-ingredients. The portion thus dissolved was chiefly alkaline salts ; but con- sisted in part of earthy phosphates, silica, and oxide of iron. (Recherches, p. 287.) Ritthausen has shown that clover which lies exposed to rain after being cut may lose by washing more than one- half of its ash-ingredients. Mulder (Chemie der AcTcerlcrume, II, p. 305) attributes to loss by rain a considerable share of the variations in percentage and composition of the fixed ingredients of plants. We must not, however, forget that all the exper- iments which indicate great loss in this way have been made on the cut plant, and their results may not hold good to the same extent for uninjured vegetation. 3. The insoluble matters, or those which become so in the plant, viz., the calcium sulphate, the oxalates, phos- phates, and carbonates of calcium and magnesium, the oxides of iron and manganese, and silica, may be depos- ited as crystals or concretions in the cells, or may incrust the cell-walls, and thus be set aside from the sphere of vital action. In the denser and comparatively juiceless tissues, as in bark, old wood, and ripe seeds, we find little variation in the amount of soluble matters. These are present in large and variable quantity only in the succulent organs. In bark (cuticle), wood, and seed envelopes (husks, shells, chaff) we often find silica, the oxides of iron and manganese, and calcium carbonate — all insoluble substances — accumulated in considerable amount. In bran, phosphate of magnesium exists in comparatively large quantity. In the dense teak wood, concretions of calcium phosphate have been noticed. Of a certain THE ASH OF PLANTS. 205 species of cactus (Cactus senilis) 80% of the dry matter consists of crystals of calcium oxalate and phos- phate. That the quantity of matters thus segregated is in some degree proportionate to the excess of them in the nourish- ing medium in which the plant grows has been observed by Nobbe & Siegert, who remark that the two portions of buckwheat, cultivated by them in solutions and in gar- den-soil respectively (p. 203), both contained crystals and globular crystalline masses, consisting probably of calcium and magnesium oxalates, and phosphates, depos- ited in the rind and pith ; but that these were by far most abundant in the water-plants whose ash-percentage was twice as great as that of the garden-plants. These insoluble substances may be either entirely unes- sential, or, having once served the wants of the plant, may be rejected as no longer useful, and by assuming the in- soluble form, are removed from the sphere of vital action, and become in reality dead matter. They are, in fact, excreted, though not, in general, formally expelled beyond the limits of the plant. They are, to some extent, thrown off into the bark or into the older wood or pith, or else are encysted in the living cells. The occurrence of crystallized salts thus segregated in the cells of plants is illustrated by the following cuts. Fig. 23 represents a crystallized con- cretion of calcium oxalate, having a basis or skeleton of cellulose, from a leaf of the walnut. (Payen, Chimie In- dxstrielle, PL XII. ) Fig. 24 shows a mass of crystals of the same salt, from the leaf stem of rhubarb. Fig. 25 illus- trates similar crystals from the beet root. In the root of the young bean? Sachs found a ring of cells., containing Fig. 23. 206 HOW CROPS GROW. crystals of sulphate of lime. (Sitzungsberichte der Wien. Akad., 37, p. 106.) Bailey ob- served in certain parts of the in- ner bark of the locust a series of cells, each of which contained a crystal. In the onion-bulb, and many other plants, crystals are Fig. 24. Fig. 25. abimdant. (Gray's Botanical Text-Book, 6th ed., Vol. II, p. 52.) Instances are not wanting in which there is an obvious excretion of mineral matters, or at least a throwing of them off to the surface. Silica, as we have seen, is often found in the cuticle, but is usually imbedded in the cell- wall. In certain plants, other substances accumulate in considerable quantity without the cuticle. A striking ex- ample is furnished by Saxifraga crustata, a low European plant, which is found in lime soils. The leaves of this saxifrage are en- tirely coated with a scaly incrusta tion of calcium and magnesium carbonates. At the edges of the leaf this incrustation acquires a considerable thickness, as is illus- trated by figure 26, a. In an anal- ysis made by linger, to whom these facts are due, the fresh (undried) leaves yielded to a dilute acid 4.14% of calcium carbonate, and 0.82% of magnesium carbonate. linger learned by microscopic investigation that this excretion of carbonates proceeds mostly from a series of granular expansions at the margin of the leaf, which are directly connected with the sap-ducts of the plant. (Sitzungsbe- richte der Wien. Akad., 43, p. 519.) In figure 26, « represents the appearance of a leaf, magnified 4J cliam- •D Fig. 26. THE ASS OF PLANTS. 207 Cters. Around the borders are seen the scales of carbonates ; some of these have been detached, leaving round pits on the surface of the leaf : c, d exhibit the scales themselves, e in profile : ft shows a leaf, freed from its incrustation by an acid, and from its cuticle by potash-solution, so as to exhibit the veins (ducts) and glands, whose course the carbon- ates chiefly take, in their passage through the plant. Further as to the state of ash-ingredients. — It ia by no means true that the ash-ingredients always exist in plants in the forms under which they are otherwise famil- iar to us. Arendt and Hellriegel have studied the proportions of soluble and insoluble matters, the former in the ripe oat plant, and the latter in clover at various stages of growth. Arendt extracted from the leaves and stems of the oat plant, after thorough grinding, the whole of the soluble matters by repeated washings in water.* He found that all the sulphuric acid and all the chlorine were soluble. Nearly all the phosphoric acid was removed by water. The larger share of the calcium, magnesium, sodium and potassium compounds was soluble, though portions of each escaped solution. Iron was found in both the soluble and insoluble state. In the leaves, iron was found among the insoluble matters after all phosphoric acid had been re- moved. Finally, silica was mostly insoluble, though in all cases a small quantity occurred in the soluble condi- tion, viz., 3-8 parts in 10,000 of the dry plant. (Wach- sthum der Haferpflanze, pp. 168, 183-4. See, also, table on p. 171). Weiss and Wiesner discovered by microchemical in- vestigation that iron exists as insoluble ferrous and ferric compounds both in the cell-membrane and in the cell- contents. (Sitzungsberichte der Wiener Akad., 40, 278.) Hellriegel found that in young clover a larger propor- tion of the various bases was soluble than in the mature plant. As a rule, the leaves gave most soluble matters, the leaf stalks less, and the stems least. He obtained, *To extract the soluble parts of the grain in this way was impossible. 208 SOW CROPS GROW. among others, the following results (Vs. St., IV, p. 59) : Of 100 parts of the following fixed ingredients of clover, were dissolved in the sap, and not dissolved — In young leaves. In full-grown leaves. (dissolved 75.2 37.3 \ uiidissolved 24.8 62.7 i dissol ved 69.5 72.4 I uiidissolved 30.5 27.6 i dissolved 43.6 78.3 .. I undtagolved 56.4 21.7 Phosphoric (dissolved 20.9 19.9 oxide, P2OS ( uiidissolved 79.1 80.1 eHi™ (dissolved 26-8 16.1 ca fundissolved 73.2 83.9 These researches demonstrate that potassium and sodi- um— bodies, all of whose commonly-occurring compounds, silicates excepted, are readily soluble in water — enter into insoluble combinations in the plant ; while phosphoric acid, which forms insoluble salts with calcium, magnesi- um, and iron, is freely soluble in connection with these bases in the sap. It should be added that sulphates may be absent from the plant or some parts of it, although they are found in the ashes. Thus, Arendt discovered no sulphates in the lower joints of the stem of oats after blossom, though in the upper leaves, at the same period, sulphuric oxide (S03) formed nearly 7% of the sum of the fixed ingre- dients. (Waclisthum der Haferpf., p. 157.) Ulbricht found that sulphates were totally absent from the lower leaves and stems of red clover, at a time when they were present in the upper leaves and blossom. "( Vs. St. , IV. , p. 30 Tabclle. ) Both Arendt and Ulbricht observed that sul- phur existed in all parts of the plants they experimented upon ; in the parts just specified, it was, however, no longer combined to oxygen, but had, doubtless, become an integral part of some albuminoid or other complex or- ganic body. Thus the oat stem, at the period above cited, contained a quantity of sulphur, which, had it been con- verted into sulphuric oxide, would have amounted to fHE ASH OS1 PLANTS. 209 of the fixed ingredients. In the clover leaf, at a time when it was totally destitute of sulphates, there existed an amount of sulphur which, in the form of sulphuric- oxide, would have made 13.7% of the fixed ingredients, or one per cent of the dry leaf itself.* Other ash-ingredients. — Salm-Horstmarhas describ- ed some experiments, from which he infers that a minute amount of Lithium and Fluorine (the latter as fluoride of potassium) are indispensable to the fruiting of barley. (Jour, fiir prakt. Chem., 84. p. 140.) The same observer, some years ago, was led to conclude that a trace of Titan- ium is a necessary ingredient of plants. The later re- sults of water-culture would appear to demonstrate that these conclusions are erroneous. The rare alkali-metal, Rubidium, has been found in the sugar-beet, in tobacco, coffee, tea, and the grape. It doubt- less occurs, perhaps together with the similar Caesium in many other plants, though always in very minute quan- tity. Birner and Lucanus found that these bodies, in the absence of potassium, acted as poisons to the oat. ( Vs. St., VIII, p. 147.) According to Nobbe, Schroeder and Erdmann, Lith- ium is very injurious to buckwheat, even in presence of potassium. When lithium was substituted for two- thirds of the potassium of a normal nutritive solution, buckwheat vegetated indeed for 3 months, the stem reaching a length of 18 inches, but the plant was small and unhealthy, the leaves were pale and the older ones dropped away, as shown by VIII, plate I. (Vs. St., XIII, p. 356). *Arendtvrua the first to estimate sulphuric oxide (SO3) in vegetable matters with accuracy, and to discriminate it from the sulphur of or- ganic compounds. This chemist separated the sulphates of the oat- plant by extracting the pulverized material with acidulated water. He likewise estimated the total sulphur by a special method, and by sub- tract ing the sulphur of the sulphuric oxide from the total he obtained as a difference that portion of sulphur which belonged to the albuminoids, etc. In his analysis of clover, I'lln-ichl followed a similar plan. ( f's. St., Ill, p. 147.) As has already been stated, many of the older analyses are Wholly untrustworthy as regards sulphur and sulphuric oxide. 14 210 HOW CROPS GROW. The investigations of A. Braun and of Risse (Sachs, Exp. Physiologic, 153) show that Zinc is a usual ingredi- ent of plants growing about zinc-mines, where the soil contains carbonate or silicate of this metal. Certain marked varieties of plants are peculiar to, and appear to have been produced by, such soils, viz., a violet ( Viola tricolor, var. calaminaris), and a shepherd's purse ( Thlaspi alpestre, var. calaminaris). In the ash of the leaves of the latter plant, Risse found 13% of oxide of zinc ; in other plants he found from 0.3 to 3.3%. These plants, however, grow equally well in absence of zinc, which may slightly modify their appearance, but is unes- sential to their nutrition. Boron as boric acid has recently been found in many wines of California and Europe. Copper is often or commonly found in the ashes of plants ; and other elements, viz., Arsenic, Barium and Lead, have been discovered therein, but as yet we are not warranted in assuming that any of these substances are of importance to agricultural vegetation. The soluble compounds of copper, arsenic and lead are in fact very injurious to plant life, unless very highly diluted. Iodine, an invariable and probably a necessary constit- uent of many algae, is not known to exist to any consid- erable extent or to be essential in any cultivated plants. 8 4. FUNCTIONS OP THE ASH-INGREDIEXTS. Although much has been written, little is certainly known, with reference to the subject of this section. Sulphates. — The albuminoids, which contain sulphur as an essential ingredient, obviously cannot be produced in absence of sulphates, which, so far as we know, are the exclusive source of sulphur to plants. The sulphurized THE ASH OF PLANTS. 211 oils of the onion, mustard, horse-radish, turnip, etc., like- wise require sulphates for their organization. Phosphates. — The phosphorized substances (prota- gon, lecithin, chlorophyl] require to their elaboration that phosphates be at the disposal of the plant. Knop has shown that hypophosphites cannot take the place of phosphates. The albuminoids which are probably formed in the foliage must pass thence through the cells and ducts of the stem into growing parts of the plant, and into the seed, where they accumulate in large quantity. But the albuminoids penetrate membranes with great difficulty and slowness when in the pure state. The di- and tri-potassic phosphates dissolve or form water-soluble compounds with many albuminoids, and, according to Schumacher (Physik der Pflanze, p. 128), considerably increase the diffusive rate of these bodies, and thus facilitate their translocation in the plant. Potassium. — The organic acids, viz., oxalic, malic, tartaric, citric, etc., require potassium to form the salts of this metal, which exist abundantly in plants, e. g. , potassium oxalate in sorrel, potassium bitartrate in the grape, potassium malate in garden rhubarb ; and without potassium it is in most cases probably impossible for {he acids to accumulate or to be formed. Mercadante culti- vated sorrel (Oxalis acetosella and Rumex acetosa), in ab- sence of potassium-salts; sodium, calcium, and magnesium being supplied. The plants failed to fructify, and their juices contained but one-eighth as much free acid (or acid salts?) as exists in the sap of the same kind of plants veg- etating under normal conditions. The acids — oxalic, with a little tartaric — were united to calcium (Berichte, 1875, II, p. 1200). The organic acids may result from the de- composition of carbhydrates (starch or sugar), or they may be preliminary stages in the production of the carb- hydrates. In either case their formation is an index to the constructive processes by which the plant originates 212 HOW CROPS GROW. new vegetable substance and increases in dry weight. Mercadaute's observations are therefore in accord with the results of the investigations next to be considered. In 1869, Nobbe, Schroder, and Erdmann employed the method of water-culture to make an elaborate study of the influence of potassium on the vegetative processes, and found that, all other needful conditions of growth being supplied, in absence of potassium buckwheat plants vegetated for three months without any increase in weight — that is to say, without producing new vegetable matter. Examination of these miniature plants demon- strated that (in absence of potassium) the first evident stage in the production of vegetable substance, viz., the appearance of starch in the chlorophyl granules of the leaf, could not be attained. The experimenters therefore drew the conclusion that potassium is an essential factor in the assimilation of carbon and the formation of starch. They found that the plants were able to produce starch when potassium was supplied either as .chloride, nitrate, phosphate or sulphate. The transfer of the starch from the leaves to the fruit, or its conversion into a soluble form, appeared to require the presence of chlorine ; ac- cordingly, potassium chloride gave the best developed plants, especially at the period of fructification. This conclusion was greatly 'strengthened by the observation, repeatedly made, that the miniature plants which had vegetated for three or four weeks without increase of weight, or growth other than that which the seedling can make at the expense of the seed, began at once, on suit- able addition of potassium chloride to the nutritive solu- tion, to form starch, discoverable in all the chlorophyl granules, and thenceforward developed new stems and leaves and grew in quite the normal manner. In Plate I the appearance of some of the plants produced in these trials is shown. la represents the average plant raised in the normal solution containing abundance of potus- PLATE I. EXPLANATION. (See p. 212.) Water-cultures of Japanese Buckwheat, supplied with the inprre dieuts of a Normal Solution, viz. : Sulphates, Nitrates, Phosphates and Chlorides of Potassium, Magnesium, Calcium and Iron, except as stated below. I and la. Solution normal. Potassium as Chloride. II. Solution without Potassium. II3. Without Potassium for 4 weeks, thereafter Potassium Chloride. III. Potassium as Nitrate. Chlorine as in Normal. IV. Potassium as Sulphate. Chlorine one-fourth of Normal. V. Potassium as Phosphate. Chlorine one-fifth of Normal. VI. Sodium but not Potassium. VIII. Lithium. IX. Without Calcium. X. Without Chlorine. XI. Without Nitrogen. The meter-scale (3!>3 inches) serves to measure the dimensions of the plants. +K.— Cot. b. EXPLANATION. (See p. 213.) Water-cultures of Flower •)£ Hoan after vegetating 38 days. a. In normal solution, seed with eotyledons. b. In normal solution, seed without eotyledons. c. In potassium-free solution, seed with cotyledons. d. In potassium-free solution, seed without cotyledons. sium chloride. II was deprived of potassium save that contained in the seed. In IV and V, respectively, the chlorine of the solution was reduced to one-fourth and one-fifth the amounts contained in the normal solution and replaced by sulphuric acid in IV and by phosphoric acid in V. In case of II3, the plant vegetated without potassium for four weeks with a result similar to II, and then for two months was supplied with potassium chlo- ride. For numerous interesting details reference must be made to the original paper ( Vs. St., XIII, pp. 321-424). Liipke, from water-cultures with the flowering bean Phaseolus multiflorus, and common bean P. vulyaris, has recently arrived at different conclusions. He finds that these plants are able, under the utmost possible ex- clusion of potassium, to assimilate carbon and produce starch, in fact to grow and to carry on all the vegetative functions that belong to the fully-nourished plant, though on a diminished scale. In order to limit the supply of potassium to the utmost, the cotyledons of some of the plants were cut away when the plumule began to appear above them. In this way 90% of the potassium of the seed was removed* and while the plants were thereby reduced in dimensions, their power to vegetate in a healthy manner was not suppressed. After 65 days of vegetation one of these plants yielded a crop of dry- substance 4.8 times as much as was contained in the newly sprouted seedling after excision of the cotyledons. Some results of these cultures are shown in Plate II. The stem of the unmutilated flowering bean in normal solution I, a, reached a final length of 80 inches, that de- prived of potassium grew to 40 inches. Nobbe's conclusion that potassium is specifically essen- tial or concerned in starch-production is accordingly erro- * Liipke found tliat one seed of P. multtflortU contained 23 milligrams of potassium oxide; the seedling, after cutting off the cotyledons, con- tains '-'..'i nun. HOW CROPS GROW. neons. As Liipke remarks, potassium is rather like nitro- gen, phosphorus, sulphur, etc., one of the elements of which probably a cercain quantity is indispensable to the formation of every vegetable cell. Nobbe's results per- haps indicate that buckwheat requires relatively more potassium than the bean for its processes of growth. (Land. Jahrbiicher, 1888, pp. 887-913.) Calcium. — Bohm (Jaliresbericht uber Ag. Chemie, 1875-6, Bd. I, p. 255) and Von Raumer ( Vs. St., XXIX, 251) have furnished evidence that calcium (lime) is di- rectly necessary to the formation of cell-tissue, that is to say, of cellulose. This evidence rests upon observations made with seed- lings of the flowering bean (scarlet-ruriner), Phaseolus multiflorus. When a seed sprouts, the young plant at first is nourished exclusively by the nutritive matters contained in the seed. When its roots enter the soil it begins to de- rive water, nitrogen, and ash-ingredients from the earth. When its leaves unfold in the light it begins to gather carbon from the air and to increase in weight. If its roots are placed in pure water it can acquire no ash-in- gredients ; if its leaves are kept in darkness it can gain nothing from the air. Thus circumstanced, it may live and vegetate for a time, but constantly loses in total dry weight, and its apparent growth is only the formation of new parts at the expense of the old. For some days the young stem shoots upward without green color, but per- fectly formed, and then (in case of the flowering bean) suddenly, at a little space below the terminal bud, a dis- coloration appears, the stem wilts, withers, and dies away. The growth of stem that thus occurs is accom- panied by and depends upon the solution of starch in the seed-lobes and its transfer to the points of growth where it is made over into cellulose — the frame-work of the stem. In absence of any external source of ash-ingredi- ents the young stem dies long before the starch of the THE ASH OF PLANTS. 215 cotyledons is consumed. But if the roots be placed in a nutritive solution suited to water-culture, the stem grows on without injury until the cotyledons are com- pletely emptied of starch, and afterwards continues to de- velop at the expense of the lower leaves. The arrest of growth in the stem evidently is due to the absence of some one or more ash-ingredients, and Bohm found in fact that, by withholding lime-salts from the roots, this characteristic malady was invariably pro- duced. Hence he concludes that calcium compounds are immediately concerned in the conversion of starch into cellulose. Magnesium. — Von Eaumer,in the paper just referred to ( Vs. St., XXIX, pp. 263 and 273), gives his observa- tions on the relations of the magnesium salts to the veg- etative processes. He states that, all other conditions being favorable, the exclusion of magnesium from a nu- tritive solution in which the scarlet-runner vegetates is followed by cessation of chlorophyl-production and of that enlargement of the new-formed cells wherein the act of growth largely consists. Accordingly, in absence of magnesium-supply, the plants, which at first grew nor- mally, after reaching a height of forty inches, began to show signs of disturbed nutrition. The uppermost in- ternodes (joints) of the stems almost ceased to lengthen and became exceptionally thick and hard, their leaves failed to open, and both joints and leaves were white in color with but the faintest tint of green. Soon new up- ward growth ceased altogether, the terminal bud and unfolded leaves dried away, and, while the lower, first- formed and green leaves remained fresh for weeks and the lower stem threw out new shoots, healthy growth was at a stand-still, and the plants gradually withered and perished. The normal growth of the bean plants for a month or more in nutritive solutions containing no magnesium is accounted for by the supply of this ele- 216 HOW CROPS GROW. ment existing in the seed,* which evidently was enough for the necessities of growth until the stem was forty inches high. From that point on the plants almost ceased to grow, and gradually died from want of food and inability to assimilate. We have already seen that, according to Hoppe-Seyler, magnesium is a constant and presumably an essential in- gredient of chlorophyllan, a crystallized derivative of chlorophyl. This makes evident that magnesium is di- rectly concerned in and needful to the formation of the chlorophyl granules which, so far as observation as yet has gone, are the seat of those operations which first construct organic substance from inorganic matter. Magnesium and calcium occur in the aleurone of seeds and, according to Griibler, form soluble, crystallizable compounds with certain albuminoids, so that these ele- ments, like potassium, may be concerned in the transport of protein-bodies. Silica. — Humphrey Davy was the first to suggest that the function of silica might be, in case of the grasses, sedges, and equisetums, to give rigidity to the slender stems of these plants, and enable them to sustain the often heavy weight of the fruit. The results of the many experiments in water-culture by Sachs, Knop, Wolff, and others (see p. 200), in which the supply of silica has been reduced to an extremely small amount, without detriment to the development of plants, commonly rich in this substance, prove in the most conclusive manner, however, that silica does not essentially contribute to the stiffness of the stem. Wolff distinctly informs us that the maize and oat plants produced by him, in solutions nearly free from silica, were as firm in stalk, and as little inclined to lodge or "lay," as those which grew in the field. •Common beans contain about one-fourth of one per cent of mag- THE ASH OF PLANTS. 217 The " lodging " of cereal crops is demonstrated to re- sult from too close a stand and too little light, which occasion a slender and delicate growth, and is not per- ceptibly influenced by presence or absence of silica. Silica, however, if not necessary to the life of the cereals, appears to have an important office in their perfect de- velopment under ordinary circumstances. Kreuzhage and Wolff have carefully studied the relations of silica to the oat plant, using the method of water-culture. In a series of nine trials in 1880, where, other things being equal, much silica, little silica, and no silica were sup- plied, the numbers of seeds produced were 1,423, 1,039, and 715 respectively, the corresponding weights being 46, 34, and 23 grams. The total crops weighed 196, 172, and 168 grams respectively, so that while the yield of seed was doubled in presence of abundant silica, the total crop (dry) was increased in weight but one-sixth. The supply of silica was accompanied with an absolutely diminished root-formation as well as by a relatively in- creased seed-production. Similar trials in 1881 and 1882 gave like results (Vs. St., XXX, p. 161). Wolff con- cludes that silica ensures the timely and uniform ripen- ing of the crop as well as favors the maximum develop- ment of seed. The natural supply of silica appears to be always suf- ficient. Application of this substance in fertilizers has never proved remunerative. In those water-cultures where large seed-production has been obtained in ab- sence of silica, it is probable that lime-salts, phosphates, or other ash-ingredients, which are commonly taken up more abundantly than in field culture, have brought about the same result that silica usually effects. This action of the ash-ingredients is apparently due to a clog- ging of the cell-tissues and consequent check of the pro- cesses of growth and would seem to be caused either by the otherwise unessential silica or by an excess of the 218 HO\V C.ROPS GROW. ingredients essential to growth. The hard, dense coat of the seed of the common weed "stone-crop" (Litliosper- mum) usually contains some 13 to 20 per cent of silica and twice that amount of calcium carbonate. Hohnel produced these seeds in water-culture from well-grown plants deprived of silica and found them quite normally developed. The seed-coat was permeated with calcium carbonate, which appears to have fully replaced silica without detriment to the plant (Haberlandt, Unter- suchungen, II, p. 160). Chlorine. — As has been mentioned, both Nobbe and Leydhecker found that buckwheat grew quite well up to the time of blossom without chlorides. From that period on, in absence of chlorides, remarkable anomalies appeared in the development of the plant. In the ordi- nary course of growth, starch, which is organized in the mature leaves, does not remain in them to much extent, but is transferred to the newer organs, and especially to the fruit, where it often accumulates in large quantities. In absence of chlorides in the experiments of Nobbe and Leydhecker, the terminal leaves becam. thick and fleshy, from extraordinary development of cell-tissue, at the same time they curled together and finally fell off, upon slight disturbance. The stem became knotty, transpira- tion of water was suppressed, the blossoms withered without fructification, and the plant prematurely died. The fleshy leaves were full of starch-grains, and it ap- peared that in absence of chlorine the transfer of starch from the foliage to the flower and fruit was rendered im- possible ; in other words, chlorine (in combination with potassium or calcium) was concluded to be necessary to —was, in fact, the agent of — this transfer. Knop believes, however, that these phenomena are due to some other cause, and that chlorine is not essential to the perfection of the fruit of buckwheat (see p. 196). Knop (CJiem. Centralblatt, 1869, p. 189) obtained some THE ASH OF PLANTS. 219 ripe, well-developed buckwheat seeds in chlorine-free water-cultures, while in the same solutions, with addition of chlorides, other buckwheat plants remained sterile, the flowers withering without setting seed. Knop states that in other trials maize and bean plants grew better without than with chlorides. In either case starch did not accumulate in the stem or leaves of maize, while all the organs of the bean were overloaded with starch both in presence and absence of chlorides. The experiments of Nobbe and Leydhecker are very circumstantially described and have been confirmed by the later work of Nobbe, Schroder, and Erdmann ( Vs St., XIII, pp. 302-6). See p. 196. Iron. — We are in possession of some interesting facts, which throw light upon the function of this metal in the plant. In case of the deficiency of iron, foliage loses its natural green color, and becomes pale or white even in the full sunshine. In absence of iron a plant may un- fold its buds at the expense of already organized matters, as a potato-sprout lengthens in a dark cellar, or in the manner of fungi and white vegetable parasites ; but the leaves thus developed are incapable of assimilating carbon, and actual growth or increase of total weight is impossi- ble. Sulm-Horstmar showed (1849) that plants which grow in soils or media destitute of iron are very pale in color, and that addition of iron-salts very speedily gives them a healthy green. Sachs found that maize-seed- lings, vegetating in solutions free from iron, had their first three or four leaves green ; several following were white at the base, the tips being green, and afterward perfectly white leaves unfolded. On adding a few drops of sulphate or chloride of iron to the nourishing medium, the foliage was plainly altered within twenty-four hours, and in three to four days the plant acquired a deep, lively green. Being afterwards transferred to a solution desti- tute of iron, perfectly white leaves were again developed, 220 HOW CROPS GROW. and these were brought to a normal color by addition of iron. E. Gris was the first to trace the reason of these effects, and first found (in 1843) that watering the roots of plants with solutions of iron, or applying such solutions externally to the leaves, shortly developed a green color where it was previously wanting. By microscopic stud- ies he found that, in the absence of iron, the protoplasm of the leaf-cells remains a colorless or yellow mass, desti- tute of visible organization. Under the influence of iron, grains of chlorophyl begin at once to appear, and pass through the various stages of normal development. We know that the power of the leaf to decompose carbon dioxide and assimilate carbon resides in the cells that contain chlorophyl, or, we may say, in the chlorophyl- grains themselves. We understand at once, then, that in the absence of iron, which is essential to the forma- tion of chlorophyl, there can be no proper growth, no increase at the expense of the external atmospheric food of vegetation. Risse, under Sachs' s direction (Exp. Physiologic, p. 143), demonstrated that manganese cannot take the plac^ of iron in the office just described. CHAPTER III. §1. QUANTITATIVE RELATIONS AMONG THE LSGREDIENI - OF PLANTS. Various attempts have been made to exhibit definite numerical relations between certain different ingredients of plants. Equivalent Replacement of Bases. — In 1840, Lie- big, in his Chemistry applied to Agriculture, suggested QUANTITATIVE RELATIONS. 221 that the various bases or basic metals might displace each other in equivalent quantities, i. e. , in the ratio of their molecular or atomic weights, and that, were such the case, the discrepancies to be observed among analyses should disappear, if the latter were interpreted on this view. Liebig instanced two analyses of the ashes of fir- wood and two of pine- wood made by Berthier and Saus- sure, as illustrations of the correctness of this theory. In the fir of Mont Breven, carbonate of magnesium was present ; in that of Mont La Salle, it was absent. In the former existed but half as much carbonate of potas- sium as in the latter. In both, however, the same total percentage of carbonates was found, and the amount of oxygen in the bases was the same in both instances. Since the unlike but equivalent quantities of potash, lime, and magnesia contain the same quantity of oxy- gen, these oxides, in the case in question, really replaced each other in equivalent proportions. The same was true for the ash of pine-wood, from Allevard and from Norway. On applying this principle to other cases it has, however, signally failed. The fact that the plant can contain accidental or unessential ingredients ren- ders it obvious that, however truly such a law as that of Liebig may in any case apply to those substances which are really concerned in the vital actions, it will be impos- sible to read the law in the results of analyses. Relation of Phosphates to Albuminoids. — Liebig likewise considered that a definite relation exists be- tween the phosphoric acid and the albuminoids of the ripe grains. That this relation is not constant is evi- dent from the following statement of data bearing on the question. In the table, the amount of nitrogen (N), representing the albuminoids (see p. 113), found in vari- ous analyses of rye and wheat grain, is compared with that of phosphoric acid (P205), the latter being taken as unity. The ratios of P205 to N were found to range as follows : 223 HOW CROPS GROW. In 7 Samples of Rye-kernel by Fehling & Faiszt . . .......... 1 : 1.97—3.06 » Mayer ......................... 1 : 2.04— :>.:« » Bibra .......................... 1:1.68—2.81 " Siegert ........................ 1:2.35—2.96 " the extreme range was from — 1 : 1.68 — 3.06 Wheat-kernel by Fehling & Faiszt ........... 1 : 2.71—2.86 " Mayer ...................... 1:1.83—2.19 " Zoeller ..................... 1:2.02—2.16 " Bibra ....................... 1:1.87—3.55 " Siegert ..................... 1 : 2.30—3.33 " the extreme range was from — 1 : 1.83 — 3.55 11 5 6 28 2 11 2 30 6 51 Siegert, who collected these data ( Vs. St., Ill, p. and who experimented on the influence of phospjiatic and nitrogenous fertilizers upon the composition of wheat and rye, gives as the general result of his special inquiries that Phosphoric acid and Nitrogen stand iti no constant rela- tion to each other. Nitrogenous manures increase the per cent of nitrogen and diminish that of phosphoric acid. Other Relations. — All attempts to trace simple and constant relations between other ingredients of plants, viz., between starch and alkalies, cellulose and silica, etc., have proved fruitless. It is ranch rather demonstrated that the proportion of the constituents is constantly changing from day to day as the relative mass of the individual organs themselves un- dergoes perpetual variation. In adopting the above conclusions it is not asserted that such genetic relations between phosphates and albumin- oids, or between starch and alkalies, as Liebig first sug- gested and as various observers have labored to show, do not exist, but simply that they do not appear from the analyses of plants. §2. THE COMPOSITION OF THE PLANT IN SUCCESSIVE STAGES OF GROWTH. We have hitherto regarded the composition of the plant mostly in a relative sense, and have instituted no compar- COMPOSITION IN SUCCESSIVE STAGES. 223 isons between the absolute quantities of its ingredients at different stages of growth. We have obtained a series of isolated views of the chemistry of the entire plant, or of its parts at some certain period of its life, or when placed under certain conditions, and have thus sought to ascer- tain the peculiarities of these periods, and to estimate the influence of these conditions. It now remains to attempt in some degree the combination of these sketches into a panoramic picture — to give an idea of the composition of the plant at the successive steps of its development. We shall thus gain some insight into the rate and manner of its growth, and acquire data that have an important bearing on the requisites for its perfect nutrition. For this purpose we need to study not only the relative (percentage) composition of the plant and of its parts at various stages of its existence, but we must also inform ourselves as to the total quantities of each ingredient at these periods. We shall select from the data at hand those which illustrate the composition of the oat-plant. Not only the ash-ingredients, but also the organic constituents, will be noticed so far as our information and space permit. The Composition and Growth of the Oat-Plant may be studied as a type of an important class of agricul- tural plants, viz. : the annual cereals — plants which com- plete their existence in one summer, and which yield a large quantity of nutritious seeds — the most valuable re- sult of culture. The oat-plant was first studied in its various parts and at different times of development by Prof. John Pitkin Norton, of Yale College. His labori- ous research published in 1846 ( Trans. Highland and Ag. Soc., 1845-7, also Am. Jour. ofSci. and Arts,Vol. 3, 1847) was the first step in advance of the single and disconnected analyses which had previously been the only data of the agricultural physiologist. For several reasons, however, the work of Norton was imperfect. The analytic meth- 224 HOW CROPS GROW. ods employed by him, though the best in use at that day, and handled by him with great skill, were not adapted to furnish results trustworthy in all particulars. Fourteen years later, Arendt* at Moeckern, and Bretschneiderf at Saarau, in Germany, at the same time, but independently of each other, resumed the subject, and to their labors the subjoined figures and conclusions are due. Here follows a statement of the Periods at which the plants were taken for analysis : [still closed. i«.t T»»i-i«H 1 JTine 18, Arendt— Three lower leaves unfolded, two upper ) " 19, Bretschneider— Four to five leaves developed. 9/1 T>O -nA i June 30, (12 days), Arendt — Shortly before full heading. "M " 29, (10 days), Bn-tsHincidrr— Tin- plants were headed. Q/I i> ,.i 1 1 July 10, (10 days), Arendt— Immediately after bloom. )aj " 8, ( 9days), Bivisclm.-icl.-r— Full l.loom. 4th Pprirwl 1 July 21, (11 days), Arendt— Beginning to ripen. "M " 28, (20 days), Bn-tsclmoider— " fith Ppriorlljuly 31' (10 days), Arendt— Fully ripe. M ] Aug. 6, ( 9 days), Bretschneider— Fully ripe. It will be seen that the periods, though differing some- what as to time, correspond almost perfectly in regard to the development of the plants. It must be mentioned that Arendt carefully selected luxuriant plants of equal size, so as to analyze a uniform material (see p. 171), and took no account of the yield of a given surface of soil. Bretschneider, on the other hand, examined the entire produce of a square rod. The former procedure is best adapted to study the composition of the well-nourished individual plant; the latter gives a truer view of the crop. The unlike character of the material as just indicated is but one of the various causes which might render the two series of observations discrepant. Thus, differences in soil, weather and seeding, would necessarily influence the relative as well as the absolute development of the two crops. The results are, notwithstanding, strikingly ac- cofdant in many particulars. In all cases the roots were not and could not be included in the investigation, as it is impossible to free them from adhering soil. • 1 1,1* Jl'nrlistiiiiin ili'f llilf< I'll ll"i i-.i . /.7 372 Amounts of Carbon, Hydrogen, Oxygen, Nitro- gen, and Ash-ingredients assimilated by the oat-crop during the several periods. Water of vegetation is not included (ll>s. per acre) : TABLE \l.—Bretschnriii< /•. Ifitrogen. Ath-iwriredients. 46 110 76 153 L's 28 17 81 *ln P.n-tsehncicler's analyses. " ash " signifies the residue left after can-fully burning the plant. In Aivii'lfs investigation the sulphur and chlorine were determined in the uuliurned plant. Carbon. Hydrogen. Oxj/ge 1st Period, 593 80 455 2.•{ 35.96 2.79 94.04 5.96 4th " 47.91 6.33 37.65 2.78 94.67 5.33 Mil " 4<>.s!t 5.88 39.40 2.43 94.60 5.40 Relative Quantities of Carbon, Hydrogen, Oxy- gen, and Nitrogen, in dry substance, after deducting the somewhat variable amount of ash (per cent) : TABLE \IlI.—Bret$chneider. Carbon. Hydrogen. Oxygen. Nitrogen. 1st Period, 50.55 6.81 38.71 3.93 2d & 3d " 51.85 6.95 38.24 2.86 4th " 50.55 6.96 39.83 2.93 5th " 49.59 6.21 41.64 2.56 5. The Tables V, VI, VII, and VIII, demonstrate that while the absolute quantities of the elements of the dry oat-plant continually increase to the time of ripening, they do not increase in the same proportion. In other words, the plant requires, so to speak, a change of diet as it advances in growth. They further show that nitro- gen and ash are relatively more abundant in the young than in the mature plant ; in other words, the rate of assimilation of Nitrogen and fixed ingredients falls be- hind that of Carbon, Hydrogen, and Oxygen. Still oth- erwise expressed, the plant as it approaches maturity organizes relatively more carbhydrates and less albu- minoids. The relations just indicated appear more plainly when we compare the (Jinintiti<>x of Xitrogen, Hydrogen, and Oxygen, assimilated during each period, calculated upon the amount of Carbon assimilated in the same time and assumed at 100. TABLE IX.— 7 Cartiuii. Miriujfii. Hydrogen. O.rt/gen. 1st Period, 100 J£ 13.4 73.6 2d&3d" 100 4.9 13.3 72.5 4th " 100 6.1 12.3 100.8 5th " 100 2.6 10.6 100.5 228 Sow CROPS GROW. From Table IX we see that the ratio of Hydrogen to Carbon regularly diminishes as the plant matures ; that of Nitrogen falls greatly from the infancy of the plant to the period of full bloom, then strikingly increases during the first stages of ripening, but falls off at last to mini- mum. The ratio of Oxygen to Carbon is the same during the 1st, 3d, and 3d Periods, but increases remarkably from the time of full blossom until the plant is ripe. As already stated, the largest absolute assimilation of all ingredients — most rapid growth — takes place at the time of heading out, or blossom. At this period all the volatile elements are assimilated at a nearly equal rate, and at a rate similar to that at which the fixed matters (ash) are absorbed. In the first period Nitrogen and Ash ; in the 4th Period, Nitrogen and Oxygen ; in the 5th Period, Oxygen and Ash are assimilated in largest proportion. This is made evident by calculating for each period the relative average daily increase of each ingredient, the amount of the ingredients in the ripe plant being assumed at 100, as a point of comparison. The figures resulting from such a calculation are given in TABLE K.—Bretschneider. Carbon. Hydrogen. Oxygen. Nitrogen. Ash. 1st Period, 0.31 0.33 0.28 0.47 0.50 2d and 3d " 2.51 2.68 2.1T 2.39 2.13 4th " 0.89 0.88 1.07 1.06 0.47 5th " 1.49 1.16 1.89 0.75 1.70 The increased assimilation of the 5th over the 4th Period is, in all probability, only apparent. The results of analysis, as before mentioned, refer only to those parts of the plant that are above ground. The activity of the foliage in gathering food from the atmosphere is doubt- less greatly diminished before the plant ripens, as evi- denced by the leaves turning yellow and losing water of vegetation. The increase of weight in the plant above ground probably proceeds from matters previously stored COMPOSITION IN SUCCESSIVE STAGES. 229 in the roots, which now are transferred to the fruit and foliage, and maintain the growth of these parts after their power of assimilating inorganic food (C02, H20, :NH3, N205) is lost. The following statement exhibits the absolute average daily increase of Carbon, Hydrogen, Oxygen, Nitrogen, and Ash, during the several periods (Ibs. per acre) : TABLE Xl.—Bretschneider. Carbon. Hydrogen. Oxygen. Nitrogen. Ash. 1st Period, 10.0 1.4 7.8 0.8 1.9 2dand3d " 81.0 10.8 83.0 4.0 8.0 4th " 22.6 2.9 23.4 1.4 1.4 5th " 70.0 6.9 74.4 1.9 9.0 Turning now to Arendt's results, which are carried more into detail than those of Bretschueider, we will notice: A. — The Relative (percentage) Composition of the Entire Plant and of its Parts* during the several periods of vegetation. 1. Fiber \ is found in greatest proportion — 40 per cent — in the lower joints of the stem, and from the time when the grain "heads out," to the period of bloom. Relatively considered, there occur great variations in the same part of the plant at different stages of growth. Thus, in the ear, which contains the least fiber, the quantity of this substance regularly diminishes, not absolutely, but only relatively, as the plant becomes older, sinking from 27 per cent at heading to 12 per cent at maturity. In the leaves, which, as regards fiber, stand intermediate between the stem and ear, this * Arendt selected large and well-developed plants, divided them into six parts, and analyzed each part separately. His divisions of the plants were : 1, the three lowest joints of the stein; 2, the two middle joints; 3, the upper joint ; 4, the three lowest leaves; 5, the two upper jea ves; li. I he ear. The stems were cut just above the nodes. 1 he lea vrs included the sheaths, the ears were Stripped from the stem. Arendt rejected all plants which were not perfect when gathered. When nearly ripe, the eereals, as is well known, often lose one or more of their lower leaves. Kor the numerous analyses on which these conclu- sions are based we must refer to the original. tl. e., Crude cellulose; see p. 45. 230 HOW CROPS GRO\V. substance ranges from 22 to 38 per cent. Previous to blossom, the upper leaves, afterwards the lower leaves, are the richest in fiber. In the lower leaves the maxi- mum (33 per cent) is found in the fourth ; in the upper leaves (38 per cent), in the second period. The apparent diminution in amount of fiber is due in all cases to increased production of other ingredients. 2. Fat and Wax are least abundant in the stem. Their proportion increases, in general, in the upper parts of the stem as well as during the latter stages of its growth. The range is from 0.2 to 3 per cent. In the ear the propor- tion increases from 2 to 3.7 per cent. In the leaves the quantity is much larger and is mostly wax with little fat. The smallest proportion is 4. 8 per cent, which is found in the upper leaves when the plant is ripe. The largest proportion, 10 per cent, exists in the lower leaves, at the time of blossom. The relative quantities found in the leaves undergo considerable variation from one stage of growth to another. 3. Non-nitrogenous matters, other than fiber, viz., starch, sugars, gums, etc.,* undergo great and irregular variation. In the stem the largest percentage (57 per cent) is found in the young lower joints; the smallest (43 per cent) in ripe upper straw. Only in the ear occurs a regular in- crease, viz., from 54 to 63 per cent. 4. TJie albuminoids, f in Arendt's investigation, exhibit a somewhat different relation to the vegetable substance from what was observed by Bretschneider, as seen from the subjoined comparison of the percentages found at the different periods : PERIODS. i. ii. in. rv. v. Arendt 20.93 11.65 10.86 13.67 14.30 Bretschneider 22.73 17.07 17.01 15.39 * What remains after deducting fat and wax, albuminoids, fiber and ash, from the dry substance, is here included. t Calculated by multiplying the pciveiitage of nitrogen by 6.33. These differences may be variously accounted for. They COMPOSITION 1$ SUCCESSIVE STAGES. 231 are due, in part, to the fart that Arendt analyzed only large and perfect plants. Bretschneider, on the other hand, examined all the plants of a given plot, large and small, perfect and injured. The differences illustrate what has been already insisted on, viz., that the develop- ment of the plant is greatly modified by the circum- stances of its growth, not only in reference to its exter- nal figure, but also as regards its chemical composition. The relative distribution of nitrogen in the parts of the plant at the end of the several periods is exhibited by the following table, simple inspection of which shows the fluctuations (relative) in the content of this element. The percentages are arranged for each period separately, pro- ceeding from the highest to the lowest : I. II. III. IV. V. Upper leaves. Lower leaves. Upper leaves. Ears. Ears. 3.74 2.39 2.27 2.85 3.04 Lower leaves. Upper leaves, bovver leaves. Upper leaves. Upper leaves. 3.38 2.19 2.18 1.91 1.74 Lower leaves. Ears. Ears. Lower leaves. Upper stem. 2.15 2.06 1.85 1.62 1.56 Middle stem. Upper stem. Upper stem. Lower leaves. l..",i> 1.34 1.60 1.43 Upper stein. Middle sirm. .Middle stem. Middle stem. 0.87 0.98 1.20 1.17 Lower stem. Lower stem. Lower stem. Lower stem. 0.80 0.88 0.83 0.79 5. Ash. — The agreement of the percentages of ash in the entire plant, in corresponding periods of the growth of the oat, in the independent examinations of Bret- schneider and Arendt, is remarkably close, as appears from the figures below : Bretschneider 8.57 Arendt 8.03 II. 5.24 PERIODS. III. 5.96 5.44 IV. V. 5.33 5.40 5.20 5.17 As regards the several parts of the plant, it was found by Arendt that, of the stem, the upper portion was richest in ash throughout the whole period of growth. Of the leaves, on the contrary, the lower contained most fixed matters. In the ear there occurred a continual decrease 232 HOW CROPS GROW. from its first appearance to its maturity, while in the stem and leaves there was, in general, a progressive increase towards the time of ripening. The greatest percentage (10.5 per cent) was found in the ripe leaves; the smallest (0.78 per cent) in the ripe lower straw. Far more interesting and instructive than the relative proportions are B. — The Absolute Quantities of the Ingredients found in the Plant at the conclusion of the sev- eral periods of growth. — These absolute quantities, as found by Arendt, in a given number of carefully- selected and vigorous plants, do not accord with those obtained by Bretschneider from a given area of ground, nor could it be expected that they should, because it is next to impossible to cause the same amount of vegeta- tion to develop on a number of distinct plots. Though the results of Bretschneider more nearly rep- resent the crop as obtained in farming, those of Arendt give a truer idea of the plant when situated in the best possible conditions, and attaining a uniformly high development. We shall not attempt to compare the two sets of observations, since, strictly speaking, in most points they do not admit of comparison. From a knowledge of the absolute quantities of the substances contained in the plant at the ends of the several periods, we may at once estimate the rate of growth, i. e., the rapidity idth which the constituents of the plant are either taken up or organized. The accompanying table, which gives in alternate col- umns the total weights of 1,000 plants at the end of the several periods, and (by subtracting .the first from the second, the second from the third, etc.) the gain from matters absorbed or produced during each period, will serve to justify the deductions that follow, which are taken from the treatise of Arendt, and which apply, of course, only to the plants examined by this investigator. COMPOSITION SUCCESSIVE STAGES. . 233 f 1 9 i '£ <~-r s^ *-H CC ^ ^1 " 'f. 'f. V. — ~r^tyi^i— 'f. 'f. f. X *.. § rn : ^3~ "M »-. C r4 S C — = = =, tj HMH 0 3 V i - 2 1 ==»=>--= » c§^ggj,.cgS5g E >, ts ^ •S cj -C PH -6 s 6-gS * o 10 -* o ^< «o la o « S 1 ! •5 1 -_'• •f. SSSagf=3S2 1 « C3 QC C ^ *H r**" "*"* ^ O 3 HH fcJC'^- •^ * 'C ~ S J » fi •= -„ ' 0^00^0^ i S to O 1 ! . » 1 r §««5 o SSiS^^gS!? r- 00 9 C3 ^ — PH J2 6 § |Sp ?! ^ -»• « 0 rh 10 10 11 3; § ' 1 1 e -«-3 8o??Soso2g g? o 'S X Q ^ M £3 'C ^ p-"3 o I s^s- O5 •* O CO r-n-l O C5 8 ' 1 = • g | OOC5 t-^00 r. S38SSS8SS 5 tc 3 tS c3 "3 p^ 3 a § 3 OC ^-i O r- S«Soa«M«s i IB X S o n s 5 . CT ^00«N>0 0 ^gc.gg^^^g X X 1 ,S = o S S § -- R. "S § c-i ?i ;o i rt S '• irf II S^H 22 *3 « ^ ° w S ^««« i gsg^gnSS- i -. P^» I18 1 a 1 a * IJS iCdlOCOOiMCCi— « l-H r- 1 C CD d (D • Q S -§ £? fi ° «Or-l-*Tf N gg8gssa88 X V/H/S. ( is unne( "I'll 8 vble are f/ standard I il *2 ; is 2 u ; ol ; ! 1 i i i « £^ 1<3 i d • • •— • • ^ i 1 flR = = ijl Organic m til if L - - "S- - - = 'C "7 7. -7. El i !Z ~, ^ 7. ^ ~. c c 1 Tlin woif reduction 234 HOW CROPS GROW. 1. The plant increases in total iceiglit (dry matter) through all its growth, but to unequal degrees in differ- ent periods. The greatest growth occurs at the time of heading out ; the slowest, within ten days of maturity. "\Ve may add that the increase of the oat after blossom takes place mostly in the seed, the other organs gaining but little. The lower leaves almost cease to grow after the 2d Period. 2. Fiber is produced most largely at the time of head- ing out (2d Period). "When the plant has finished blos- soming (end of 3d Period), the formation of fiber entirely ceases. Afterward there appears to occur a slight diminution of this substance, more probably due to unavoidable loss of lower leaves than to a resorption or metamorphosis in the plant. 3. Fat is formed most largely at the time of blossom. It ceases to be produced some weeks before ripening. 4. Albuminoids are very irregular in their formation. The greatest amount is organized during the 4th Period (after blossoming). The gain in albuminoids within this period is two-fifths of the total amount found in the ripe plant, and also is nearly two-fifths of the entire gain of organic substance in the same period. The absolute amount organized in the 1st Period is not much less than in the 4th, but in the 2d, 3d and 5th Periods the quantities are considerably smaller. Bretschneider gives the data for comparing the pro- duction of albuminoids in the oat crop examined by him with Arendt's results. Taking the quantity found at the conclusion of the 1st Period as 100, the amounts gained during the subsequent periods are related as follows: PERIODS. i. ii. in. (ii. & in.) iv. (ii., in. & iv.) v. Arendt 100 67 46 (113) 120 (233) 36 Bretschiii-idcr .100 ? ? (165) 62 35 \\Q perceive striking differences in the comparison. In COMPOSITION IN SUCCESSIVE STAGES. £3o Bretschneider's crop the increase of albuminoids goes on most rapidly in the 2d and 3d Periods, and sinks rapidly during the time when in Arendt's plants it attained the maximum. Curiously enough, the gain in the 2d, 3d and 4th Periods, taken together, is in both cases as good as identical (233 and 227), and the gain during the last period is also equal. This coincidence is doubtless, how- ever, merely accidental. Comparisons with other crops of oats examined, though much less completely, by Stockhardt (Chemischer Ackersmann, 1855) and Wolff (Die Erscliopfiuig des Bodens darcli die Cultur, 1856) demonstrate that the rate of assimilation is not related to any special times or periods of development, but depends upon the stores of food accessible to the plant and the favor of the weather, or other external conditions. The following figures, which exhibit for each period of both crops a comparison of the gain in albuminoids with the increase of the other organic matters, further strikingly demonstrate that, in the act of organization, the nitrogenous principles have no close quantitative relations to the non-nitrogenous bodies (carbhydrates and fats). The quantities of albuminoids gained during each period being represented by 10, the amounts of carbhy- drates, etc., are seen from the subjoined ratios : PERIODS. UK l'ii} hi I. U&III. IV. V. /?/>•/•/,/„/. Arendt 10 : Si 10:114 10:28 10 : 25 10:66 Bret8Chneider..lO : 30 10 : 50 10 : 46 10 : 120 10 : :>l 5. The Ash-ingredients of the oat are absorbed through- out its entire growth, but in regularly diminishing quan- tity. The gain during the 1st Period being taken at 10, that in the 3d Period is 9, in the 3d, 8, in the 4th, 5£, in the 5th, 2 nearly. The ratios of gain in ash-ingredients to that in entire dry substance, are as follows, ash-ingredients being assumed as 1 , in the successive periods ; 236 HOW CROPS GROW. 1 : 12J, 1 : 27, 1 : 16, 1 : 23, 1 : 19. Accordingly, the absorption of ash-ingredients is not proportional to the growth of the plant, but is to some degree accidental, and independent of the wants of vegetation. Recapitulation. — Assuming the quantity of each proxi- mate element in the ripe plant as 100, it contained at the end of the several periods the following amounts (per cent) : Fiber. Fat. Carbhydrates.* Albuminoids. Ash. I. Period, 18 20 15 27 29 II. " 81 50 47 45 55 III. •« 100 85 70 57 79 IV. " 100 100 92 90 95 V. " 100 100 100 100 100 Taking the total gain as 100, the gain during each period was accordingly as follows (per cent) : Fiber. Fat. Carbhydrates.* Albuminoids. Ash. I. Period, 18 20 15 27 29 II. " 63 30 32 18 26 III. " 19 35 23 12 24 IV. " 0 15 22 33 16 V. " 00 8 10 5 100 100 100 100 100 6. — As regards the individual ingredients of the ash, the plant contained at the end of each period the follow- ing amounts, — the total quantity in the ripe plant being taken at 100. Corresponding results from Bretschneider enclosed in ( ) are given for comparison: Sulphuric Phosphoric Silica. Ofide Oxide Lime. Magnesia. Potash. Percent. Percent. Percent. Percent. Percent. Per<-r:ii. I. Period, 18 ( 22) 20 ( 42) 23 ( 23) 30 ( 31) 24 ( 31) 39 ( 42) 41 \ ( 57) 52 ) ( 44) 42 \ ( 63) ^ 1 ( 83) ^ } ( 73) 70 } ( 89) III. " 70' 52< 78 > TO » 88 > 91 ^ IV. " 93 ( 72) 90 ( 39) 91 ( 74) 99 ( 74) 84 ( 77) 100 (100) V. " 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) 100 (95») The gain (or loss, indicated by the minus sign — ) in these ash-ingredients during each period is given below: * Exclusive of Fiber- COMPOSITION IN SUCCESSIVE STAGES. 237 Silica. Sulphuric Oxide. Ptioiphoric Oxide. Lime. Magnesia. Potash. Per cent, , Per cent. Per cent. Per cent. Per cent. Per cent. I. Period, II. " ILL " is •2:; 901 (22) [(35) 20 32 0 (42) |( 2) 23 ( 23) 19 \ ( 40) 31 J 30 28 21 (31 ) |(52) 24 18 16 (31) [(42) 39 311 21) (42) |(47) IV. " V. " L'.'i 7 ( 15) (28) 38 10 (-5*) (56 ) 18 ( 10) 9 (27) L'O 1 (-9*) (17) 26 16 (4) (23) 9 0 (11 ) (-5*) 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) 100 (100) These two independent investigations could hardly give all the discordant results observed on comparing the above figures, as the simple consequence of the unlike mode of conducting them. We observe, for example, that in the last period Arendt's plants gathered less silica than in any other — only 7 per cent of the whole. On the other hand, Bretschneider's crop gained more silica in this than in any other single period, viz. : 28 per cent. A similar statement is true of phosphoric oxide, f It is obvious that Bretschneider's crop was tak- ing up fixed matters much more vigorously in its last stages of growth than were Arendt's plants. As to potash, we observe that its accumulation ceased in the 4th Period in both cases. C. — Translocation of Substances in the Plant. — The transfer of certain matters from one part of the plant to another during its growth is revealed by the analyses of Arendt, and since such changes are of inter- est from a physiological point of view, we may recount them here briefly. It has been mentioned already that the growth of the stem, leaves, and ear of the oat plant in its later stages probably takes place to a great degree at the expense of the roots. It is also probable that a transfer of carbhy- *In these instances Bretschneider's later crops appear to contain less sulphuric oxide, lime and potash, than tlie earlier. This result may be due to the washing of the crop by rains, but is probably caused by unequal development of the several plots. t Phosphoric oxide is the " phosphoric acid," P2O5, of older and to a great degree of current usage. See p. 163. 238 HOW CROPS GROW. drates, and certain that one of albuminoids, goes on from the leaves through the stem into the ear. Silica appears not to be subject to any change of posi- tion after it has once been fixed by the plant. Chlorine likewise reveals no noticeable mobility. On the other hand, phosphoric oxide passes rapidly from the leaves and stem towards or into the fruit in the ear- lier as well as in the- later stages of growth, as shown by the following figures : One thousand plants contained in the various periods quantities (grams) of phosphoric oxide as follows : 1st 2d Zd 4th 5th Period. Period. Period. Period. Period. 3 lower joints of stem, 0.47 0.20 0.21 0.20 0.19 2 middle " " 0.39 1.14 0.46 0.18 Upper joint " 0.66 1.73 0.31 0.39 3 lower leaves " 1.05 0.70 0.69 0.51 0.35 2 upper leaves " 1.75 1.67 1.18 0.74 0.59 Ear, 2.36 5.36 10.67 12.52 Observe that these absolute quantities diminish in the stem and leaves after the 1st or 3d Period in all cases, and increase very rapidly in the ear. Arendt found that sulphuric oxide existed to a much greater degree in the leaves than in the stem through- out the entire growth of the oat plant, and that, after blossoming, the lower stem no longer contained sulphur in the form of sulphates at all, though its total in the plant considerably increased. It is almost certain, then, that sulphuric oxide originates, either partially or wholly, by oxidation of sulphur or some sulphurized compound, in the upper organs of the oat. Magnesium is translated from the lower stem into the upper organs, and in the fruit, especially, it constantly increases in quantity. There is no evidence that Calcium moves upward in the plant. On the contrary, Arendt's analyses go to show that in the ear, during the last period of growth, it COMPOSITION ttf SUCCESSIVE STAGES. 239 diminishes in quantity, being, perhaps, replaced by magnesium. As to potassium, no transfer is fairly indicated, except from the ears. These contained at blossoming (Period III) a maximum of potassium. During their subsequent growth the amount of this element diminished, being probably displaced by magnesium. The data furnished by Arendt's analyses, while they indicate a transfer of matters in the cases just named, and in most of them with great certainty, do not and cannot from their nature disprove the fact of other simi- lar changes, and cannot fix the real limits of the move- ments which they point out. DIVISION II. THE STRUCTURE OF THE PLANT AND OFFICES OF ITS ORGANS. CHAPTER I. GENERALITIES. We have given a brief description of those elements and compounds which constitute the plant in a chemical sense. They are the materials — the stones and timbers, so to speak — out of which the vegetable edifice is built. It is important, in the next place, to learn how these building materials are put together, what positions they occupy, what purposes they serve, and on what plan the edifice is constructed. It is impossible for the builder to do his work until he has mastered the plans and specifications of the archi- tect. So it is hardly possible for the farmer with cer- tainty to contribute in any great, especially in any new, degree, to the upbuilding of the plant, unless he is acquainted with the mode of its structure and the ele- ments that form it. It is the happy province of science to add to the vague and general information which the observation and experience of generations have taught, a more definite and particular knowledge, — a knowledge acquired by study purposely and carefully directed to special ends. An acquaintance with the parts and structure of the plant is indispensable for understanding the mode by which it derives its food from external sources, while the 16 241 HOW CROPS GROW. ingenious methods of propagation practiced in fruit- and flower-culture are only intelligible by the help of this knowledge. ORGANISM OF THE PLANT. — We have at the outset spoken of organic matter, of organs and organization, It is in the world of life that these terms have their fit- test application. The vegetable and animal consist of numerous parts, differing greatly from each other, but each essential to the whole. The root, stem, leaf, flower and seed are each instruments or organs whose co-oper- ation is needful to the perfection of the plant. The plant (or animal) being thus an assemblage of organs, is called an Organism; it is an Organized or Organic Structure. The atmosphere, the waters, the rocks and soils of the earth, do not possess distinct co-operating parts ; they are Inorganic matter. In inorganic nature, chemical affinity rules over the transformations of matter. A plant or animal that is dead, under ordinary circumstances, soon loses its form and characters ; it is gradually consumed, and, at the ex- pense of atmospheric oxygen, is virtually burned up to air and ashes. In the organic world a something, which we call Vitality, resists and overcomes or modifies the affinities of oxygen, and insures the existence of a continuous and perpetual succession of living forms. An Organism or Organized Structure is characterized and distinguished from inorganic matter by two par- ticulars : 1. It builds up and increases its own mass by appro- priating external matter. It absorbs and assimilates food. It grows by the enlargement of all its parts. 2. It reproduces itself. It develops from a germ, and in turn gives origin to new germs. ULTIMATE AND COMPLEX ORGANS. — In our account of the Structure of the Plant we shall first consider the ELEMENTS OF ORGANIZED STRUCTURE. 243 elements of that structure — the Ceils — which cannot be divided or wounded without extinguishing their life, and by whose expansion or multiplication all growth takes place. Then will follow an account of the com- plex parts of the plant — its Organs — which are built up by the juxtaposition of numerous cells. Of these we have one class, viz., the Koots, Stems and Leaves, whose office is to sustain and nourish the Individual Plant. These may be distinguished as the Vegetative Organs. The other class, comprising the Flower and Fruit, are not essential to the existence of the individual, but their function is to maintain the Race. They are the Repro- ductive Organs. CHAPTER II. PRIMARY ELEMENTS OF ORGANIZED STRUCTURE. THE VEGETABLE CELL. One of the most interesting discoveries that the micro- scope has revealed, is that all organized matter originates in the form of minute vesicles or cells. If we examine by the microscope a seed or an egg, we find nothing but a cell-structure — a mass of rounded or many-sided bags lying closely together, and more or less filled with solid or liquid matters. From these cells, then, comes the frame or structure of the plant or of the animal. In the process of maturing, the original vesicles are vastly mul- tiplied and often greatly modified in shape and appear- ance, to suit various purposes ; but still it is always easy, especially in the plant, to find cells of the same essential characters as those occurring in the seed. 244 HOW CROPS GROW. Cellular Plants. — In the simpler forms or lower orders* of vegetation, we find plants which, throughout all the stages of their life, consist entirely of similar cells, and indeed many are known which are but a single cell. The phenomenon of red snow, frequently observed in Alpine and Arctic regions, is due to a microscopic one-celled plant which propagates with great rapidity, and gives its color to the surface of the snow. In the chemist's laboratory it is often observed that in the clear- est solutions of salts, like the sulphates of sodium and magnesium, a flocculent mold, sometimes red, some- times green, most often white, is formed, which, under the microscope, is seen to be a vegetation consisting of single cells. Brewers' yeast, Fig. 27, is nothing more than a mass of one or few-celled plants. In sea-weeds, mushrooms, the molds that grow on damp walls, or upon bread, cheese, etc., and in the blights which infest many of the farmer's crops, we have examples of plants formed exclusively of cells. o Fi, the blade ; e, roots covered with hairs and enveloped in soil. Only the growing tips of the roots, w, which have not put forth hairs, come out clean of soil. Fig. 41 represents the roots of a wheat-plant one month older than those of the previous figure. In this instance not only the root-tips are naked as before, but the older parts of the primary roots, e, and of the secondary roots, n, no longer retain the particles of soil ; the hairs upon them being, in fact, dead and decom- posed. The newer parts of the root alone are clothed with active hairs, and to these the soil is firmly attached as before. The next illustration, Fig. 42, exhibits the appearance of root-hairs with ad- hering particles of earth, when mag- nified 800 diameters : A, root-hairs of wheat-seedling, like Fig. 40; B, of oat-plant, both from loamy soil. Here is plainly seen the intimate attachment of the soil and root- hairs. The latter, in forcing their way against considerable pressure, often expand around, and partially envelop, the particles of earth. (Sachs's Exp. Phys. d. Pflanzen.) Imbibition of water by the root. — The force with which active roots imbibe the water of the soil is sufficient to force the liquid upward into the stem and to exert a continu- al pressure on all parts of the plant. When the stem of a plant in vigor- ous growth is cut off near the root, and a pressure-gauge is attached to it, as in Fig. 43, we have the means of observing and pleasuring the force with which the roots absorb water. Fig. 43. 270 HOW CROPS GROW. The pressure-gauge contains a quantity of mercury in the middle reservoir, b, and the tube, c. It is attached to the stem of the plant, p, by a stout india-rubber pipe, q.* For accurate measurements, the space a and b should be filled with water. Thus arranged, it is found that water will enter a through the stem, and the mer- cury will rise in the tube, e, until its pressure becomes sufficient to balarce the absorptive power of the roots. Stephen Hales, who first experimented in this manner (1721) found in one instance that the pressure exerted on a gauge, attached in spring time to the stump of a grape-vine, supported a column of mercury 32^- inches high, which is equal to a column of water of 36| feet. Hofmeister obtained on other plants, rooted in pots, the following results : Bean (Phaseolw multiflorus) 6 inches of mercury. Nettle 14 " " Vine 29 " " The seat of absorption Dutrochet demonstrated to be the surface of the young and active roots. At least, he found that absorption was exerted with as much force when the gauge was applied to near the lower extremity of a root as when attached in the vicinity of the stem. In fact, when other conditions are alike, the column of liquid sustained by the roots of a plant is greater the less the length of stem that remains attached to them. The stem thus resists the rise of liquid in the plant. While the seat of absorptive power in the root lies near the extremities, it appears from the experiments of Ohlerts that the extremities themselves are incapable of imbibing water. In trials with young pea, flax, lupine and horseradish plants with nnbranched roots, he found that they withered speedily when the tips of the roots were immersed for about one-fourth of an inch in water, *For experimenting on small plants, a simple tube of glass may be adjusted to the stump vertically by help of a rubber connector. the remaining parts being in moist air. Ohlerts like, wise proved that these plants flourish when only the middle part of their roots is immersed in water. Keep- ing the root-tips, the so-called spongioles, in the air, or cutting them away altogether, was without apparent effect on the freshness and vigor of the plants. The absorbing surface would thus appear to be confined to those portions of the root upon which the development of root-hairs is noticed. The absorbent force is manifested by the active root- lets, and most vigorously when these are in the state of most rapid development. For this reason we find, in case of the vine, for example, that during the autumn, when the plant is entering upon a period of repose from growth, the absorbent power is trifling. Sometimes water is absorbed at the roots so forcibly as not only to distend the plant to the utmost, but to cause the sap of the plant to exude in drops upon the foliage. This may be noticed upon newly-sprouted maize, or other cereal plants, where the water escapes from the leaves at their extreme tips, especially when the germination has pro- ceeded under the most favorable conditions for rapid development. The bleeding of the vine, when severed in the spring- time, the abundant flow of sap from the sugar-maple and the water-elm, are striking illustrations of this imbibition of water from the soil by the roots. These examples are, indeed, exceptional in degree, but not in kind. Hofmeister has shown that the bleeding of a sev- ered stump is a general fact, and occurs with all plants when the roots are active, when the soil can supply them abundantly with water, and when the tissues above the absorbent parts are full of this liquid. When it is other- wise, water may be absorbed from the gauge into the stem and large roots, until the conditions of activity are renewed. 272 HOW CROPS GKOW. Of the external circumstances that affect this absorp- tive power, heat and light would appear to be influential. By observing a gauge attached to the stump of a plant during a clear summer day, it will be usually noticed that the mercury begins to rise in the morning as the sun warms the soil, and continues to ascend for a num- ber of hours, but falls again as the sun declines. Sachs found in some of his experiments that, in case of potted tobacco and squash plants, absorption was nearly or entirely suppressed by cooling the roots to 41° F., but was at once renewed by plunging the pots into warm water. The external supplies of water, — in case a plant is stationed in the soil, the degree of moisture contained in this medium, — obviously must influence any manifesta- tion of the imbibing force. But full investigation shows that this regular daily fluctuation is a habit of the plant which is independent of small changes of temperature and even of considerable variation in the amount of mois- ture of the soil. The rate of absorption is subject to changes depend- ent on causes not well understood. Sachs observed that the amount of liquid which issued from potato stalks cut off just above the ground underwent great and continual variation from hour to hour (during rainy weather) when the soil was saturated with water and when the thermometer indicated a constant temperature. Ilofmeister states that the formation of new roots and buds on the stump is accompanied by a sinking of the water in the pressure-gauge. Absorption of Nutriment from the Soil. — The food of the plant, so far as it is derived from the soil, enters it in a state of solution, and is absorbed with the water which is taken up by the rootlets. The absorption of the matters dissolved in water is in some degree inde- pendent of the absorption of the water itself, the plant VEGETATIVE OBGAJfS Of PLANTS. 273 having apparently, to a certain extent, a selective power. See p. 401. 3. The Root as a Magazine. — In Fleshy Tap- Roots, like those of the carrot, beet, and turnip, the absorption of nutriment from the soil takes place princi- pally, if not entirely, by means of the slender rootlets which proceed abundantly from all their surface, and especially from their lower extremities, while the older fleshy part serves as a magazine in which large quantities of carbhydrates, etc., are stored up during the first year's growth of these biennial plants, to supply the wants of the flowers and seed which are developed the second year. When one of these roots, put into the ground for a sec- ond year, has produced seed, it is found to be quite exhausted of the nutritive matters which it previously contained in so large quantity. Root Tubers, like those of the dahlia and sweet potato, are fleshy enlargements of lateral or secondary roots filled with reserve material, from which buds and new stems may develop. Small tubers (Tubercles) are fre- quently formed on the roots of the garden bean (PJiaseolus). In cultivation, the farmer not only greatly increases the size of these roots and the stores of organic nutritive materials they contain, but, by removing them from the ground in autumn, he employs to feed himself and his cattle the substances that nature primarily designed to nourish the growth of flowers and seeds during another summer. Soil-Roots ; Water-Roots ; Air-Roots. — We may distinguish, according to the medium in which they are formed and grow, three kinds of roots, viz.: soil-roots, 'water-roots, and air-roots. Most agricultural plants, and indeed by far the greater number of all plants found in temperate climates, have roots adapted especially to the soil, and which perish by 18 XJ74 HOW CROPS GROW. short exposure to dry air, or rot, if long immersed in water. Many aquatic plants, on the other hand, speed- ily die when their roots are removed from water, or from earth saturated with water, and exposed to the atmos- phere or stationed in earth of the usual dryness. Air-roots are not common except among tropical plants or under tropical conditions of heat and moisture. In- dian corn, when thickly planted and of rank growth, often throws out roots from the lower joints of the stem, which extend through the air several inches before they reach the soil. The same may be observed of many com- mon plants, as the oat, grape, potato, and buckwheat, when they long remain in hot, moist air. The Banyan- tree of India sends out from its branches, vertically, pendants several yards long which penetrate the earth and there become soil-roots. On the other hand, various tropical plants, especially Orchids, emit roots which hang free in the air and never reach the earth. In the humid forest ravines of Madeira and Teneriffe, the Laurus Canariensis, a large tree, sends out from its stem, during the autumn rains, a pro- fusion of fleshy air-roots, which cover the trunk with their interlacing branches and grow to an inch in thick- ness. The following summer they dry away and fall to the ground, to be replaced by new ones in the ensuing autumn. (Schacht, Der Baum, p. 172.) A plant, known to botanists as the Zamia spiralis, not only throws out air-roots, c c, Fig. 44, from the crown of the main soil-root, but the side rootlets, 5, after extend- ing some distance horizontally in the soil, send, from the same point, roots downward and upward, the latter of which, d, pass into and remain permanently in the air. a is the stem of the plant. (Schacht, Anatomie tier Gewiichse, Bd. II, p. 151.) The formation of air-roots may be very easily observed by placing water to the depth of half an inch in a tall VEGETATIVE OEGANS OF PLANTS. 275 vial, inserting a sprig of the common greenhouse-plant Tradescantia zebrina, so that the cut end of the stem shall stand in the water, and finally corking the vial air- tight. The plant, which is very tenacious of life, and usually grows well in spite of all neglect, is not checked in its vegetative development by the treatment just de- scribed, but immediately begins to adapt itself to its new circumstances. In a few days, if the temperature be 70° or thereabout, air-roots will be seen to issue from the joints of the stem. These are fringed with a profu- sion of delicate hairs, and rapidly extend to a length of from one to two inches. The lower ones, if they chance Fig. 41 to penetrate the water, become discolored and decay ; the others, however, remain for a long time fresh, and of a white color. Some plants have roots which are equally able to exist and perform their functions, whether in the soil or sub- 276 HOW CROPS GROW. merged in water. Many forms of vegetation found in our swamps and marshes are of this kind. Of agricul- tural plants, rice is an example in point. Rice will grow in a soil of ordinary character, in respect of moisture, as the upland cotton-soils, or even the pine-barrens of the Carolinas. It flourishes admirably in the tide-swamps of the coast, where the land is laid under water for weeks at a time during its growth, and it succeeds equally well in fields which are flowed from the time of planting to that of harvesting. (Russell, North America, its Agri- culture and Climate, p. 176.) The willow and alder, trees which grow on the margins of streams, send a part of their roots into soil that is constantly saturated with water, or into the water itself ; while others occupy the merely moist or even dry earth. Plants that customarily confine their growth to the soil occasionally throw out roots as if in search of water, and sometimes choke up drain-pipes or even wells by the profusion of water-roots which they emit. At Welbeck, England, a drain was completely stopped by roots of horse-radish plants at a depth of 7 feet. At Thornsby Park, a drain 16 feet deep was stopped entirely by the roots of gorse, growing at a distance of 6 feet from the drain. (Jour. Roy. Ag. Soc., I, p. 364.) In New Haven, Connecticut, certain wells are so obstructed by the aquatic roots of the elm trees as to require cleaning out every two or three years. This aquatic tendency has been repeatedly observed in the poplar, cypress, laurel, turnip, mangel-wurzel, and various grasses. Henrici surmised that the roots which most cultivated plants send down deep into the soil, even when the latter is by no means porous or inviting, are designed especially to bring up water from the subsoil for the use of the plant. He devised the following experiment, which ap- pears to prove the truth of this view. On the 13th of May, 1862, a young raspberry plant, having but two VEGETATIVE ORGANS OF PLAHTS. ^IJ"? leaves, was transplanted into a large glass funnel filled with garden soil, the throat of the funnel being closed with a paper filter. The funnel was supported in the mouth of a large glass jar, and its neck reached nearly to the bottom of the latter, where it just dipped into a quantity of water. The soil in the fuonel was at first kept moderately moist by occasional waterings. The plant remained fresh and slowly grew, putting forth new leaves. After the lapse of several weeks, four strong roots penetrated the filter and extended down the empty funnel-neck, through which they emerged, on the 21st of June, and thenceforward spread rapidly in the water of the jar. From this time on, the soil was not watered any more, but care was taken to maintain the supply in the jar. The plant continued to develop slowly ; its leaves, however, did not acquire a vivid green color, but remained pale and yellowish ; they did not wither until the usual time, late in autumn. The roots continued to grow, and filled the water more and more. Near the end of December the plant had seven or eight leaves, and a height of eight inches. The water-roots were vigorous, very long, and beset with numerous fibrils and buds. In the funnel tube the roots made a perfect tissue of fibers. In the dry earth of the funnel they were less extensively developed, yet exhibited some juicy buds. The stem and the young axillary leaf-buds were also full of sap. The water-roots being cut away, the plant was put into garden soil and placed in a conservatory, where it grew vigorously, and in May bore two offshoots. (Henneberg*8 Jour, fiir Landwirtlischaft, 1863, p. 280.) This growth towards water must be accounted for on the principles asserted in the paragraph, Apparent Search for Food (p. 263). The seeds of many ordinary land plants — of plants, indeed, that customarily grow in a dry soil, such as the bean, squash, maize, etc. — will readily germinate in 278 HOW CHOPS GROW. moist cotton or sawdust, and if, when fairly sprouted, the young plants have their roots suspended in water, taking care that the seed and stem are kept above the liquid, they will continue to grow, and with due supplies of nutriment will run through all the customary stages of development, produce abundant foliage, blossoms, and perfect seeds, without a moment's contact of their roots with soil. (See Water Culture, p. 181.) In plants thus growing with their roots in a liquid medium, after they have formed several large leaves, be carefully transplanted to the soil, they wilt and perish, unless frequently watered ; whereas similar plants, started in the soil, may be transplanted without suffering in the slightest degree, though the soil be of the usual dryness, and receive no water. The water-bred seedlings, if abundantly watered as often as the foliage wilts, recover themselves after a time, and thenceforward continue to grow without the need of watering. It might appear that the first-formed water-roots are incapable of feeding the plant from a dry soil, and hence the soil must be at first profusely watered ; after a time, however, new roots are thrown out, which are adapted to the altered situation of the plant, and then the growth proceeds in the usual manner. The reverse experiment would seem to confirm this view. If a seedling that has grown for a short time only in the soil, so that its roots are but twice or thrice branched, have these immersed in water, the roots already formed mostly or entirely perish in a short time. They indeed absorb water, and the plant is sustained by them, but immediately new roots grow from the crown with great rapidity, and take the place of the original roots, which become disorganized and useless. It is, however, only the young and active rootlets, and those covered with hairs, which thus refuse to live in water. VEGETATIVE OKGANS OF PLANTS. 279 The older parts of the roots, which are destitute of fibrils and which have nearly ceased to be active in the work of absorption, are not affected by the change of circum- stance. These facts, which are due to the researches of Dr. Sachs ( Vs. St., II, p. 13), would naturally lead to the conclusion that the absorbent surface of the root un- dergoes some structural change, or produces new roots witli modified characters, in order to adapt itself to the medium in which it is placed. It would appear that when this adaptation proceeds rapidly the plant is not permanently retarded in its growth by a gradual change in the character of the medium Avhich surrounds its roots, as may happen in case of rice and marsh-plants, when the saturated soil in which they may be situated at one time is slowly dried. Sudden changes of medium about the roots of plants slow to adapt themselves would be fatal to their existence. Nobbe has, however, carefully compared the roots of buckwheat, as developed in the soil, with those emitted in water, without being able to observe any structural differences. The facts above detailed admit of partial, if not complete, explanation, without recourse to the suppo- sition that soil- and water-roots are essentially diverse in nature. When a plant which is rooted in the soil is taken up so that the fibrils are not broken or injured, and set into water, it does not suffer any hindrance in growth, as Sachs found by his later experiments. (Ex- perimental Physiologic, p. 177.) Ordinarily, the suspen- sion of growth and decay of fibrils and rootlets is due, doubtless, to the mechanical injury they suffer in remov- ing from the soil. Again, when a plant that has been reared in water is planted in earth, similar injury occurs in packing the soil about the roots, and moreover the fibrils cannot be brought into that close contact with the soil which is necessary for them to supply the foliage with water j hence the plant wilts, and may easily perish 280 HOW CROPS GROW. unless profusely watered or shielded from evaporation. The air-roots of Orchids, which never reach the soil, have a peculiar spongy texture and take up the water which exists as vapor in the air, as shown by the experi- ments of linger, Chatin, and Sachs. Duchartre's inves- tigations led him to deny their absorptive power. (Ele- ments de Botanique, p. 216.) In his experiments made on entire plants, the air-roots failed to make good the loss by evaporation from the other parts of the plant. It is evident from common observation that moisture is the condition that chiefly determines root-develop- ment. Not only do all seeds sprout and send forth roots when provided with abundant moisture at suitable tem- peratures, but generally older roots and stems, and fleshy leaves, or cuttings from these, will produce new rootlets when properly circumstanced as regards moisture, whether that moisture be supplied by aid of a covering of damp soil, wet sand or paper, by stationing in humid air, or by immersion in water itself. Root-Excretions. — It was formerly supposed that the roots of plants perform a function of excretion, the reverse of absorption — that plants, like animals, reject matters which are no longer of use in their organism, and that the rejected matters are poisonous to the kind of vegetation from which they originated. De Candolle, an eminent French botanist, who first advanced this doc- trine, founded it upon the observation that certain plants exude drops of liquid from their roots when these are placed in dry sand, and that odors exhale from the roots of other plants. Numerous experiments have been in- stituted at various times for the purpose of testing this question. Noteworthy are those of Dr. Alfred (iydr (Trans. Highland and Ayr. Soc., 1845-47, pp. 273-92). This experimenter planted a variety of agricultural plants, viz., wheat, barley, oats, rye, beans, peas, vetches, cab- bage, mustard, and turnips, in pots filled either with VEGETATIVE ORGANS OF PLANTS. 281 garden soil, sand, moss, or charcoal, and after they had attained considerable growth, removed the earth, etc., from their roots by washing with water, using care not to injure or wound them, and then immersed the roots in vessels of pure water. The plants were allowed to re- main in these circumstances, their roots being kept in darkness, but their foliage exposed to light, from three to seventeen days. In most cases they continued appa- rently in a good state of health. At the expiration of the time of experiment, the water which had been in contact with the roots was evaporated, and was found to leave a very minute amount of yellowish or brown mat- ter, a portion of which was of organic and the remainder of mineral origin. Dr. Gvde concluded that plants do throw off organic and inorganic excretions similar in composition to their sap ; but that the quantity is ex- ceedingly small, and is not injurious to the plants which furnish them. In the light of newer investigations touching the structure of roots and their adaptation to the medium which happens to invest them, we may well doubt whether agricultural plants in the healthy state excrete any solid or liquid matters whatever from their roots. The familiar excretion of gum, resin, and sugar* from the stems of trees appears to result from wounds or dis- ease, and the matters which in the experiments of Gyde and others were observed to be communicated by the roots of plants to pure water probably came either from the continual pushing off of the tips of the rootlets by the interior growing point — a process always naturally accompanying the growth of roots — or from the disor- ganization of the absorbent root-hairs. Under certain circumstances, small quantities of sol- uble salts or free acids may indeed diffuse out of the *From the wounded bark of the sugar-pine (Pinus Lambertiana) of California. 282 HOW CROPS GKO\V. root-cells into the water of the soil. This is, however, no physiological action, but a purely physical process. Vitality of Roots. — It appears that in case of most plants the roots cannot long continue their vitality if their connection with the leaves be interrupted, unless, indeed, they be kept at a winter temperature. Hence weeds may be effectually destroyed by cutting down their tops ; although, in many cases, the process must be several times repeated before the result is attained. The roots of our root-crops, properly so-called, viz., beets, turnips, carrots, and parsnips, when harvested in autumn, contain the elements of a second year's growth of stem, etc., in the form of a bud at the crown of the root. If the crown be cut away from the root, the latter cannot vegetate, while the growth of the crown itself is not thereby prevented. As regards internal structure, the root closely resem- bles the stem, and what is stated of the latter, on subse- quent pages, applies in all essential points to the former. THE STEM. Shortly after the protrusion of the rootlet from a ger- minating seed; the STEM makes its appearance. It has, in general, an upward direction, which in many plants is permanent, while in others it shortly falls to the ground and grows thereafter horizontally. All plants of the higher orders have stems, though in many instances they do not appear above ground, but extend beneath the surface of the soil, and are usually considered to be roots. While the root, save in exceptional cases, does not develop other organs, it is the special function of the stem to bear the leaves, flowers, and seed of the plant, VEGETATIVE OKGANS OF PLANTS. 283 and even in certain tribes of vegetation, like the cacti, which have no leaves, to perform the offices of these organs. In general, the functions of the stem are sub- ordinate to those of the organs which it bears — the leaves and flowers. It is the support of these organs, and, it would appear, only extends in length or thickness with the purpose of sustaining them mechanically or provid- ing them with nutriment. Buds. — In the seed the stem exists in a rudimentary state, associated with undeveloped leaves, forming a bud. The stem always proceeds at first from a bud, during all its growth is terminated by a bud at every growing point, and only ceases to be thus tipped when it fully accom- plishes its growth by the production of seed, or dies from injury or disease. In the leaf-bud we find a number of embryo leaves and leaf-like scales, in close contact and within each other, but all at- tached at the base to a central conical axis, Fig. 45. The opening of the bud consists in the lengthening of this axis, which is the stem, and the con- sequent separation from each other as well as expansion of Fig. 45. the leaves. If the rudimentary leaves of a bud be represented by a nest of flower-pots, the smaller placed within the larger, the stem may be signified by a rope of India-rubber passed through the holes in the bottom of the pots. The growth of the stem may now be shown by stretching the rope, whereby the pots are brought away from each 284 HOW CROPS GROW. other, and the whole combination is made to assume the character of a fully-developed stem, bearing its leaves at regular intervals ; with these important differences, that the portions of stem nearest the root extend more rap- idly than those above them, and the stem has within it the material and the mechanism for the continual for- mation of new buds, which unfold in successive order. In Fig. 45, which represents the two terminal buds of a lilac twig, is shown not only the external appearance of the buds, which are covered with leaf-like scales, imbricated like shingles on a roof ; but, in the section, are seen the edges of the undeveloped leaves attached to the conical axis. All the leaves and the whole stem of a twig of one summer's growth thus exist in the bud, in plan and in miniature. Subsequent growth is but the development of the plan. In the flower-bud the same structure is manifest, save that the rudimentary flowers and fruit are enclosed within the leaves, and may often be seen plainly on cut- ting the bud open. Nodes; Internodes. — Xodes are those knots or parts of the stem where the leaves are attached. The portions of the stem between the nodes are termed internodes. It is from the nodes that roots most freely develop when stems (layers or cuttings) are surrounded by moist air or soil. Culms. — The grasses and the common cereal grains have single, unbranched stems, termed culms in botani- cal language. The leaves of these plants clasp the stem entirely at their base, and rest upon a well-defined, thick- ened node. Branching Stems. — Other agricultural plants besides those just mentioned, and all the trees of temperate cli- mates, have branching stems. As the principal or main stem elongates, so that the leaves arranged upon it sepa- rate from each other, we find one or more buds at the VEGETATIVE ORGANS OF PLANTS. 285 point where the base of the leaf or of the leaf-stalk unites with the stem. From these axillary buds, in case their growth is not checked, side-stems or branches issue, which again subdivide in the same manner into branchlets. In perennial plants, when young, or in their young shoots, it is easy to trace the nodes and internodes, or the points where the leaves are attached and the inter- vening spaces, even for some time after the leaves, which only endure for one year, are fallen away. The nodes are manifest by the enlargement of the stem, or by the scar, covered with corky matter, which marks the spot where the leaf-stalk was attached. As the stem grows older these indications of its early development are grad- ually obliterated. In a forest where the trees are thickly crowded, the lower branches die away from want of light; the scars resulting from their removal, or short stumps of the limbs themselves, are covered with a new growth of wood, so that the trunk finally appears as if it had always been destitute of branches, to a great height. When all the buds develop normally and in due pro- portion, the plant, thus regularly built up, has a sym- metrical appearance, as frequently happens with many herbs, and also with some of the cone-bearing trees, especially the balsam-fir. Latent Buds. — Often, however, many of the buds remain undeveloped, either permanently or for a time. Many of the side-buds of most of our forest and fruit trees fail entirely to grow, while others make no progress until the summer succeeding their first appearance. When the active buds are destroyed, either by frosts or by pinching off, other buds that would else remain latent are pushed into growth. In this way trees whose young leaves are destroyed by spring frosts cover themselves again, after a time, with foliage. In this way, 286 HOW CROPS GROW. too, the gardener molds a straggling, ill-shaped shrub or plant into almost any form he chooses ; for, by removing branches and buds where they have grown in undue pro- portion, he not only checks excess, but also calls forth development in the parts before suppressed. Close pruning or breaking the young twigs causes abundant development of flower-buds on fruit trees that otherwise "run to wood." Adventitious or irregular Buds are produced from the stems as well as older roots of many plants, when they are mechanically injured during the growing season. The soft or red maple and the chestnut, when cut down, habitually throw out buds and new stems from the stump, and the basket-willow is annually polled, or pol- larded, to induce the growth of slender shoots from an old trunk. Elongation of Stems. — While roots extend chiefly at their extremities, we find the stem elongates equally, or nearly so, in all its contiguous parts, as is manifest from what has already been stated in illustration of its development from the bud. Besides the upright stem, there are a variety of pros- trate and in part subterranean stems, which may be briefly noticed. Runners and Layers are stems that are sent out hor- izontally just above the soil, and, coming in contact with the earth, take root, forming new plants, which may thenceforward grow independently. The gardener takes advantage of these stems to propagate certain plants. The strawberry furnishes the most familiar example of runners, while many of the young shoots of the currant fall to the ground and become layers. The runner is a somewhat peculiar stem. It issues horizontally, and usually bears but few or no leaves. The layer does not differ from an ordinary stem, except by the circum- stance, often accidental, of becoming prostrate. Many VEGETATIVE ORGAHS OF PLANTS. 287 plants which usually send out no layers are nevertheless artificially layered by bending their stems or branches to the ground, or by attaching to them a ball or pot of earth. The striking out of roots from the layer is in many cases facilitated by cutting half through, twisting, or otherwise wounding the stem at the point where it is buried in the soil. The tillering of wheat and other cereals, and of many grasses, is the spreading of the plant by layers. The first stems that appear from these plants ascend vertically, but, subsequently, other stems issue, whose growth is, for a time, nearly horizontal. They thus come in con- tact with the soil, and emit roots from their lower joints. From these again grow new stems and new roots in rapid succession, so that a stool produced from a single kernel of winter wheat, having perfect freedom of growth, has been known to carry 50 or 60 grain-bearing culms. (Hallet, Jour. Roy. Soc. of Eng.< 22, p. 372.) Suckers. — When branches ariso from the stem below the surface of the soil, so that they are partly subter- ranean and partly aerial, as in the Rose and Raspberry, they are termed Suckers. These leafy shoots put out roots from their buried nodes, and may be separated artificially and used for propagating the plant. Subterranean Stems. — Of these there are three forms. They are usually taken to be roots, from the fact of existing below the surface of the soil. This cir- cumstance is, however, quite accidental. The pods of the peanut (Arachis hypogced) ripen beneath the ground — the flower-stems lengthening and penetrating the earth as soon as the blossom falls ; but these stems are not by any means to be confounded with roots. Root-stocks, or Rhizomes. — True roots are desti- tute of leaves. This fact easily distinguishes them from the rhizome, which is a stem that extends below the sur- face of the ground. At the nodes of these root-stocks, 288 HOW CROPS GROW. as they are appropriately named, scales or rudimentary leaves are seen, and thence roots proper are emitted. In the axils of the scales may be traced the buds from which aerial and fruit-bearing stems proceed. Examples of the root-stock are very common. Among them we mav mention the blood-root and pepper-root as abundant in the woods of the Northern and Middle States, various mints, asparagus, and the quack-grass (Agropyrum* repens) represented in Fig. 46, which infests so many farms. Each node of the root-stock, being usually sup- plied with roots, and having latent buds, is ready to become an independent growth the moment it is detached Fig. 46. from its parent plant. In this way quack-grass becomes especially troublesome, for the more the fields where it has obtained a footing are tilled the more does it com- monly spread and multiply; only oft-repeated harrow- ing in a season of prolonged dryness suffices for its extirpation. Corms are enlargements of the base of the stem, bear- ing leaf-buds either at the summit or side, and may be regarded as much-shortened rhizomes, with only a few slightly-developed internodes. Externally they resemble bulbs. The garden crocus furnishes an example. Tubers of many plants are fleshy enlargements of the •Formerly Triticwn. VEGETATIVE ORGANS Of PLANTS. 2&9 extremities of subterranean stems. Their eyes are the points where the buds exist, usually three together, and where minute scales — rudimentary leaves — may be observed. The common potato and artichoke (Helian- tlms tuberosus) are instances of this kind of tubers. Tubers serve excellently for propagation. Each eye, or bud, may become a new plant. From the quantity of starch, etc., accumulated in them, they are of great importance as food. The number of tubers produced by a potato-plant appears to be increased by planting orig- inally at a considerable depth, or by "hilling up" earth around the base of the aerial stems during the early stages of its growth. Bulbs are greatly thickened stems, whose leaves — usually having the form of fleshy scales or concentric coats — are in close contact with each other, and arise from nearly a common base, the internodes being undeveloped. The bulb is, in fact, a permanent bud, usually in part or entirely subterranean. From its apex, the proper stem, the foliage, etc., proceed; while from its base roots are sent out. The structural identity of the bulb with a bud is shown by the fact that the onion, which furnishes the commonest example of the bulb, often bears bulblets at the top of its stem, in place of flowers. In like manner, the axillary buds of the tiger-lily are thickened and fleshy, and fall off as bulblets to the ground, where they produce new plants. STRUCTURE OF THE STEM. — The stem is so compli- cated that to discuss it fully would occupy a volume. For our immediate purposes it is, however, only neces- sary to notice its structural composition very concisely. The rudimentary stem, as found in the seed, or the new-formed part of the maturer stem at the growing points just below the terminal buds, consists of cellular tissue, or is an aggregate of rounded and cohering cells, which rapidly multiply during the vigorous growth of the plant. 19 290 HOW CROPS GROW. In some of the lower orders of vegetation, as in mush- rooms and lichens, the stem, if any exist, always pre- serves a purely cellular character ; but in all flowering plants the original cellular tissue of the stem, as well as of the root, is shortly penetrated by vascular tissue, consisting of ducts or tubes, which result from the obliteration of the horizontal partitions of cell-tissue, and by wood-cells, which are many times longer than wide, and the walls of which are much thickened by internal deposition. These ducts and wood-cells, together with some other forms of cells, are usually found in close connection, and are arranged in bundles, which constitute the fibers of the stem. They are always disposed lengthwise in the stem and branches. They are found to some extent in the softest herbaceous stems, while they constitute a large share of the trunks of most shrubs and trees. From the toughness which they possess, and the manner in which they are woven through the original cellular tissue, they give to the stem its solidity and strength. Flowering plants may be divided into two great classes, in consequence of important and obvious differences in the structure of their stems and seeds. These are : 1, Monocotyledons, or Endogens ; and 2, Dicotyledons, or Exo- gens. As regards their stems, these two classes of plants differ in the arrangement of the vascular or woody tissue. Endogenous Plants are those whose stems enlarge by the formation of new wood in the interior, and not by the external growth of concentric layers. The embryos in the seeds of endogenous plants consist of a single piece — do not readily split into halves — or, in botanical lan- guage, have but one cotyledon; hence are called monoco- tyledonous. Indian corn, sugar-cane, sorghum, wheat, oats, rye, barley, the onion, asparagus, and all the grasses, belong to this tribe of plants. If a stalk of maize, asparagus, or bamboo be cut VEGETATIVE ORGANS OF PLANTS. 291 across, the fiber-like bundles of ducts and wood-cells arc seen disposed somewhat uniformly throughout the sec- tion, though less abundantly towards the center. On splitting the fresh stalk lengthwise, these vascular bun- dles may be torn out like strings. At the nodes, where the stem is branched, or where leaf-stalks are attached, the vascular bundles likewise divide and form a net-u-orl-. In a ripe maize-stalk which is exposed to circumstances favoring decay, the soft cell-tissue first suffers change and often quite disappears, leaving the firmer vascular bundles unaltered in form. A portion of the base of such a stalk, cut lengthwise, is represented in Fig. 47, where the vascular bundles are seen arranged parallel to each other in the internodes, and curiously interwoven and branched at the nodes, both at those (a and b) from which roots issued, or at that (c) which was clasped by the base of a leaf. The endogenous stem, as represented in the maize- stalk, has no well-defined bark that admits of being stripped off externally, and no separate central pith of soft cell-tissue free from vascular bundles. It, like the aerial portions of all flowering plants, is covered with a skin, or epidermis, composed usually of one or several layers of flattened cells, whose walls are thick, and far less penetrable to fluid than the delicate texture of the interior cell-tissue. The stem is denser and harder at the circumference than towards the center. This is due to the fact that the bundles are more numerous and older towards the outside of the stem. The newer bun- dles, as they continually form at the base of the growing terminal bud, pass to the inside of the stem, aM after- 292 no\v CROPS GROW. wards outwards and downwards, and hence the designa- tion endogenous, which in plain English means inside- In consequence of this inner growth, the stems of most woody endogens, as the palms, after a time become so indurated externally that all lateral expansion ceases, and the stem increases only in height. In some cases, the tree dies because its interior is so closely packed with bundles that the descent of new ones, and the accom- panying vital processes, become impossible. In herbaceous endogens the soft stem admits the indefinite growth of new vascular tissue. 293 The stems of the grasses are hollow, except at the nodes. Those of the rushes have a central pith free from vascular tissue. The Minute Structure of the Endogenous Stem is exhibited in the accompanying cuts, which represent highly magnified sectioas of a Vascular Bundle or fiber from the maize-stalk. As before remarked, the stem is composed of a groundwork of delicate cell-tissue, in which bundles of vascular-tissue are distributed. Fig. 48 represents a cross section of one of these bundles, c, g, h, as well as of a portion of the surrounding cell-tis- Fig. 49. sue, a, a. The latter consists of quite large cells, which have between them considerable inter-cellular spaces, i. The vascular bundle itself is composed externally of narrow, thick-walled cells, of which those nearest the exterior of the stem, li, are termed bast-cells, as they correspond in character and position to the cells of the bast or inner bark of our common trees ; those nearest the center of the stem, c, are wood-cells. In the maize stem, bast-cells and wood-cells are quite alike, and are 294 HOW CHOPS GROW. distinguished only by their position. In other plants, they are often unlike as regards length, thickness, and pliability, though still, for the most part, similar in form. Among the wood-cells we observe a number of ducts, d, e, f, and between these and the bast-cells is a delicate and transparent tissue, g, which is the cambium, in which all the growth of the bundle goes on until it is complete. On either hand is seen a remarkably large duct, 1), b, while the residue of the bundle is composed of long and rather thick-walled wood-cells. Fig. 49 represents a section made vertically through the bundle from c to li. In this the letters refer to the same parts as in the former cut : a, a is the cell-tissue, enveloping the vascular bundle ; the cells are observed to be much longer than wide, but are separated from each other at the ends as well as sides by an imperforate membrane. The wood and bast-cells, c, h, are seen to be long, narrow, thick-walled cells running obliquely to a point at either end. The wood-cells of oak, hickory, and the toughest woods, as well as the bast-cells of flax and hemp, are quite similar in form and appearance. The proper ducts of the stem are next in the order of our section. Of these there are several varieties, as riug- ducts, d; spiral ducts, e; dotted ducts, f. These are continuous tubes produced by the absorption of the transverse membranes that once divided them into such cells as a, a, and they are thickened internally by ring- like, spiral, or punctate depositions of cellulose (see Fig. 32, p. 248). Wood or bast-cells that consist mainly of cellulose are pliant and elastic. It is the deposition of other matters (so-called ligniii) in their walls which ren- ders them stiff and brittle. At g, the cambial tissue is observed to consist of del- icate cylindrical cells. Among these, partial absorption of the separating membrane often occurs, so that they communicate directly with each other through sieve-like VEGETATIVE OEGANS OF PLANTS. 295 partitions, and become continuous channels or ducts. (Sieve-cells, p. 303.) The cambium is the seat of growth by cell-formation. Accordingly, when a vascular bun- dle has attained maturity, it no longer possesses a cam- bium. To complete our view of the vascular bundle, Fig. 50 represents a vertical section made at right angles to the last, cutting two large ducts, Z>, 5; a, a is cell-tissue; ft a M 1 Fig. 50. c, c are bast or wood-cells less thickened by interior deposition than those of Fig. 49 ; d is a ring and spiral duct; T), b are large dotted ducts, which exhibit at g, g the places where they were once crossed by the double membrane composing the ends of two adhering cells, by whose absorption and removal an uninterrupted tube has been formed. In these large dotted ducts there appears to be no direct communication with the sur- rounding cells through their sides. The dots or pits are simply very thin points in the cell-wall, through which sap may soak or diffuse laterally, but not flow. 296 HOW CBOPS GROW. When the cells become mature and cease growth, the pits often become pores by absorption of the membrane, so that the ducts thus enter into direct communication with each other. Exogenous Plants are those whose stems contin- ually enlarge in diameter by the formation of new tissue near the outside of the stem. They are outside-growers. Their seeds are usually made up of two loosely-united parts, or cotyledons^ wherefore they are designated dicotyledonous. All the forest trees of temperate cli- mates, and, among agricultural plants, the bean, pea, clover, potato, beet, turnip, flax, etc., are exogens. In the exogenous stem the bundles of ducts and fibers that appear in the cell-tissue are always formed just within the rind. They occur at first separately, as in the endogens, but, instead of being scattered throughout the cell-tissue, are disposed in a circle. As they grow, they usually close up to a ring or zone of wood, which incloses unaltered cell-tissue — the pith. As the stem enlarges, new rings of fibers may be formed, but always outside the older ones. In hard stems of slow growth the rings are close together and chiefly consist of very firm wood-cells. In the soft stems of herbs the cellular tissue preponderates, and the ducts and cells of the vascular zones are delicate. The harden- ing of herbaceous stems which takes place as they become mature is due to the increase and induration of the wood-cells and ducts. The circular disposition of the fibers in the exogenous stem may be readily seen in a multitude of common plants. The potato tuber is a form of stem always accessible for observation. If a potato be cut across near the stem- end with a sharp knife, it is usually easy to identify upon the section a ring of vascular-tissue, the general course of which is parallel to the circumference of the tuber VEGETATIVE OEGAKS OF PLANTS. 297 except where it runs out to the surface in the eyes or buds, and in the narrow stem at whose extremity it grows. If a slice across a potato be soaked in solution of iodine for a few minutes, the vascular ring becomes strikingly apparent. In its active cambial cells, albu- minoids are abundant, which assume a yellow tinge with iodine. The starch of the cell-tissue, on the other hand, becomes intensely blue, making the vascular tissue all the more evident. Since the structure of the root is quite similar to that of the stem, a section of the common beet as well as one of a branch from any tree of temperate latitudes may serve to illustrate the concentric arrangement of the vas- cular zones when they are multipled in number. Pith is the cell-tissue of the center of the stem. In young stems it is charged with juices; in older ones it often becomes dead and sapless. In many cases, espec- ially when growth is active, it becomes broken and nearly obliterated, leaving a hollow stem, as in a rank pea-vine, or clover-stalk, or in a hollow potato. In the potato tuber the pith-cells are occupied throughout with starch, although, as the coloration by iodine makes evident, the quantity of starch diminishes from the vascular zone towards the center of the tuber. The Rind, which, at first, consists of mere epidermis, or short, thick-Availed cells, overlying soft cellular tissue, becomes penetrated with cells of unusual length and tenacity, which, from their position in the plant, are termed bast-cells. These, together with ducts of various kinds, constitute the so-called bast, which grows chiefly upon the interior of the rind, in successive annual layers, in close proximity to the wood. With their abundant development and with age, the rind becomes bark as it occurs on shrubs and trees. The bast-cells give to the bark its peculiar toughness, and cause it to come off the stem in long and pliant strips. 298 HOW CEOPS GROW. All the vegetable textile materials employed in the man- ufacture of cloth and cordage, with the exception of cot- ton, as flax, hemp, New Zealand flax> etc., are bast-fibers- (See p. 248.) In some plants the annual layers of bast are so sepa- rated by cellular tissue that in old stems they may be split from one another. Various kinds of matting are made by weaving together strips of bast layers, especially those of the Linden (Bass-wood or Bast-wood) tree. The leather-wood or moose- wood bark, often employed for tying flour-bags, has bast-fibers of extraordinary tenacity. The bast of the grape-vine separates from the stem in long shreds a year or two after its formation. The epidermis of young stems is replaced, after a cer- tain age, by the corky layer. This differs much in dif- ferent plants. In the Birch it is formed of alternate layers of large- and small-celled tissue, and splits and curls up. From the Plane-tree it is thrown off period- ically in large plates by the expansion of the cellular tis- sue underneath. In the Maple, Elm, and Oak, especially in the Cork-Oak, it receives annual additions on its inner side and does not separate : after a time it conse- quently acquires considerable thickness, the growth of the stem furrows it with deep rifts, and it gradually decays or drops away exteriorly as the newer bark forms within. Pith Rays. — Those portions of the first-formed cell- tissue which were interposed between the young and originally ununited wood-fibers remain, and connect the pith with the cellular tissue of the bark. They inter- rupt the straight course of the bast-cells, producing the netted appearance often seen in bast layers, as in the Lace-bark. In hard stems they become flattened by the pressure of the fibers, and are readily seen in most kinds of wood when split lengthwise. They are espe- cially conspicuous in the Oak and Maple, and form what VEGETATIVE ORGANS OF PLANTS. 299 is commonly known as the silver-grain. The botanist terms them pith-rays, or medullary rays. Fig. 51 exhibits a section of spruce wood, magnified 200 di- ameters. The section is made lengthwise of the wood-cells, four of which are in part represented, and cuts across the pith-rays, whose cell-structure and position in the wood are seen at m, n. Branches have the same struct- ure as the stems from which they spring. Their tissues traverse those of the stem to its center, \ \lll'//\ wnere they connect with the pith V/<^ and its sheath of spiral ducts. ™ ' Cambium of JExogens.—The Fig- 51- growing part of the exogenous stem is between the fully formed wood and the ma- ture bark. There is, in fact, no definite limit where wood ceases and bark begins, for they are connected by the cambial or formative zone, from which, on the one hand, wood-fibers, and on the other, bast-fibers, rapidly develop. In the cambium, likewise, the pith-rays which connect the inner and outer parts of the stem continue their outward growth. In spring-time the new cells that form in the cambial region are very delicate and easily broken. For this reason the rind or bark may be stripped from the wood without difficulty. In autumn these cells become thick- ened and indurated — become, in fact, full-grown bast and wood-cells — so that to peel the bark off smoothly is im- possible. Minute Structure of Exogenous Stems. — The ac- companying figure (52) will serve to convey an idea of 300 :ow CROPS GROW. the minute structure of the elements of the exogenous stem. It exhibits a section lengthwise, through a young potato tuber magnified 200 diameters ; a, b is the rind ; e the vascular ring ; f the pith. The outer cells of the rind are converted into cork. They have become empty of sap and are nearly impervious to air and moisture. This corky-layer, a, constitutes the thin coat or skin that may be so readily peeled off from a boiled potato. When- ever a potato is superficially wounded, even in winter time, the exposed part heals over by the formation of Fig. 53. cork-cells. The cell tissue of the rind consists at its center, b, of full-formed cells with delicate membranes which contain numerous and large starch grains. On either hand, as the rind approaches the corky-layer or the vascular ring, the cells are smaller, and contain smaller starch grains ; at either side of these are noticed cells containing no starch, but having nuclei, c, y. These nucleated cells are capable of multiplication, and they are situated where the growth of the tuber takes place. The rind,* which makes a large part of the flesh of the potato, increases in thickness by the formation of new cells within and without. Without, where it joins the corky skin, the latter likewise grows. Within, contigu- *The word riml is lien- used in its Ixitunical (not in the ordinary' sense, to denote thsit part of the tuber which corresponds to the rind of the stem. VEGETATIVE OBGAXS OF PLANTS. 301 ous to the vascular zone, new ducts are formed. In a similar manner, the pith expands by formation of new cells, where it joins the vascular tissue. The latter consists, in our figure, of ring, spiral, and dotted ducts, like those already described as occurring in the maize-stalk. The deli- cate cambial cells, c, are in the region of most active growth. At this point new cells rapidly develop, those to the right, in the figure, remaining plain cells and becoming loosely filled with starch ; those to the left developing new ducts. In the slender, overground potato- stem, as in all the stems of most agri- cultural plants, the same relation of parts is to be observed, although the vascular and woody tissues often pre- ponderate. Wood -cells are especially abundant in those stems that need strength for the fulfilment of their offices, and in them, especially in those of our trees, the structure is commonly more complicated. Pitted Wood-Cells of the Coni- fers.— In the wood of cone-bearing trees there are no proper ducts, such as have been described. The large wood-cells which constitute the concentric rings of the wood are constructed in a spe- cial manner, being provided laterally with pits, or, accord- ing to Schacht, with visible pores, through which the fluid contents of one cell may easily diffuse (by osmose), or even pass directly into those of its neighbors. Fig. 53, B represents a portion of an isolated wood-cell of the Scotch Fir (Pinussylvestris) magnified 200 diam- eters. Upon it are seen nearly circular disks, x, y, the Fig. 53. 302 HOW CROPS GROW. structure of which, while the cell is young, is shown by a section through them lengthwise. A exhibits such a section through the thickened walls of two contiguous and adhering cells, x, in both A and B, shows a cavity between the two primary cell-walls ; y is the narrow part of the channel, that remains while the mem- brane thickens around it. This is seen at y, as a pit in each cell-wall, or, as Schacht believed, a pore or opening from cell to cell. In A it appears closed because the section passes a little to one side «d! the pore. (Schacht.) In the next figure (54), representing a transverse section of the spring wood of the same tree magnified 300 diameters, the struct- ure and the gradual form- ation of these pore-disks is made evident. The sec- tion, likewise, gives an in- structive illustration of the general character of the simplest kind of wood. R -. are the young cells of the " rind ; C is the cambium, where cell-multiplication goes on; W is the wood, whose cells are more developed the older they are, i. e., the more distant from the cam- bium, as is seen from their figure and the thickness of their walls. At a is shown the disk in its earliest stage ; I and c exhibit it in a more advanced growth. At d the VEGETATIVE OKGANS OF PLANTS. 303 disk has become a pore, the primary membrane has been absorbed, and a free channel made between the two cells. The dotted lines at d lead out laterally to two concentric circles, which represent the disk-pore seen flatwise, as in Fig. 53. At e the section passes through the new annual ring into the autumn wood of the preceding year. Sieve-cells, or Sieve-ducts. — The spiral, ring, and dotted ducts and pitted wood-cells already noticed, ap- pear only in the older parts of the vascular bundles, and, although they may be occupied with sap at times when the stem is surcharged with water, they are ordinarily filled with air alone. The real transmission of the nutritive juices of the growing plant, so far as it goes on through actual tubes, is now admitted to proceed in an independ- ent set of ducts, the so-called sieve-tubes, which are usu- ally near to and originate from the cambium. These are extremely delicate, elongated cells, whose transverse or lateral walls are perforated, sieve-fashion (by absorp- tion of the original membrane) so as to establish direct communication from one to another, and this occurs while they are yet charged with juices and at a time when the other ducts are occupied with air alone. These sieve-ducts are believed to be the channels through which the organic matters that are formed in the foliage mostly pass in their downward movement to nourish the stem and root. Fig. 55 represents the sieve-cells in the over- ground stem of the potato ; A, B, cross-section of parts of vascular bundle ; A, exterior part towards rind ; B, interior portion next to pith ; a, a, cell-tissue inclosing the smaller sieve-cells, A, B, which contain sap turbid with minute granules ; b, cambium cells ; c, wood-cells (which are absent in the potato tuber) ; d, ducts inter- mingled with wood-cells. C represents a section length- wise of the sieve-ducts ; and D, more highly magnified, exhibits the finely perforated, transverse partitions, through which the liquid contents more or less freely 304 HOW CROPS GROW. Milk Ducts. — Besides the ducts already described, there is, in many plants, a system of irregularly branched channels containing a milky juice (latex) as in the sweet potato, dande- lion, milk-weed, etc. These milk - ducts a occur in all parts of the plants, but most abundantly in the pith and inner bark of stems and in the cellular tissue of ,, roots. They often so completely permeate all the organs of the plant that the slight- est wound breaks some of them and causes a flow of latex. The latter, like ani-«T mal milk, is a watery fluid holding in sus- pension minute gran- ules or drops which make it opaque.a The latex often con- tains the organic substances peculiar to the plant, acquires a sticky, viscid char- acter, and hardens on exposure to the air. Fig. 55. Opium, India-rubber, gutta- percha, and various resins are dried latex. Alkaloids frequently occur, and ferments like papain (p. 104) are probably not uncommon in this secretion. Herbaceous Stems. — Annual stems of the exogenous VEGETATIVE ORGANS Of PLANTS. 305 kind, whose growth is entirely arrested by winter, consist usually of a single ring of woody tissue with interior pith and surrounding bark. Often, however, the zone of wood is thin, and possesses but little solidity, while the chief part of the stem is made up of cell-tissue, so that the stem is herbaceous. Woody Stems. — Perennial exogenous stems consist, in temperate climates, of a series of rings or zones, cor- responding in number with that of the years during which their growth has been progressing. The stems of our shrubs and trees, especially after the first few years of growth, consist, for the most part, of woody tissue, the proportion of cell-tissue being very small. The annual cessation of growth which occurs at the approach of winter is marked by the formation of smaller or finer wood-cells, as shown in Fig. 54, e, while ths vigorous renewal of activity in the cambium at spring- time is exhibited by the growth of larger cells, and in many kinds of wood in the production of ducts, which, as in the oak, are visible to the eye at the interior of the annual layers. Sap-wood and Heart-wood. — The living processes in perennial stems, while proceeding with most force in the cambium, are not confined to that locality, but go on to a considerable depth in the wood. Except at the cambial layer, however, these processes consist not in the formation of new cells, nor the enlargement of those once formed — not properly in growth — but in the trans- mission of sap and the deposition of organized matter on the interior of the wood-cells. In consequence of this deposition the inner or heart- wood of many of our forest trees becomes much denser in texture and more durable for industrial purposes. It then acquires a color differ- ent from the outer or sap-wood (alburnum), becomes brown in most cases, though it is yellow in the barberry and red in the red cedar. 20 306 fiow CROPS GROW. The final result of the filling up of the cell of £he heart-wood is to make this part of the stem almost or quite impassable to sap, so that the interior wood may be removed by decay without disturbing the vigor of the tree. Passage of Sap through the Stem. — The stem, besides supporting the foliage, flowers and fruit, has also a most important office in admitting the passage upward to these organs of the water and mineral matters which enter the plant by the roots. Similarly, it allows the downward transfer to the roots of substances gathered by the foliage from the atmosphere. To this and other topics connected with the ascent and descent of the sap we shall hereafter recur. The stem constitutes the chief part by weight of many plants, especially of forest trees, and serves the most im- portant uses in agriculture, as well as in a thousand other industries. §o O. LEAVES. These most important organs issue from the stem, are at first folded curiously together in the bud, and after- wards expand so as to present a great amount of surface to the air and light. The leaf consists of a thin membrane of cell-tissue directly connected with the cellular layer of the bark, arranged upon a skeleton or net-work of fibers and ducts continuous with those of the inner bark and wood. In certain plants, as cactuses, there scarcely exist any leaves, or, if any occur, they do not differ, except in external form, from the stems. Many of these plants, above ground, are in form all stem, while in structure and function they are all leaf. In the grasses, although the stem and leaf are distin- VEGETATIVE ORGANS OF PLANTS. 307 guishable in shape, they are but little unlike in other external characters. In forest trees, we find the most obvious and striking differences between the stem and leaves. Color of Leaves. — A peculiarity most character- istic of the leaves of the higher orders of plants, so long as they are in vigorous discharge of their proper vegeta- tive activities, is the possession of a green color, due to the presence of Chlorophyl. (See p. 124.) This color is also proper in most cases to the young bark of the stem, a fact further indicating the connection between these parts, or rather demonstrating their identity of origin and function, for it is true, not only in the case of the cactuses, but also in that of all other young plants, that the green (young) stems perform, to some extent, the same offices as the leaves, the latter being, in fact, growths from and extensions of the bark. The loss of green color that occurs in autumn, in the foliage of our deciduous trees, or on the maturing of the plant, as with the cereal grains, is related to the cessa- tion of growth and death of the leaf, and results from chemical changes in the chlorophyl-pigment. Plants naturally destitute of chlorophyl, like Indian pipe (Monotropa), Dodder (Cuscuta), Mushrooms, Toadstools, and fungi generally, are parasites on living or dead organisms, from which they derive their nour- ishment. Such plants cannot construct organic sub- stances out of inorganic matters, as do the plants having chlorophyl. When leaves, ordinarily green, are totally excluded from light, or develop at a low temperature, they have a pale yellow color; on exposure to light and warmth they become green. In both cases the Chlorophyl-gramiles are formed, but the chlorophyl-pigment appears only in the latter. In absence of iron, leaves are white, contain no chlorophyl granules, and growth is arrested. 308 HOW CROPS GROW. There are many leafy plants cultivated for ornamental purposes with more or less brown, red, yellow, white, or variegated foliage, which are by no means destitute of chlorophyl, as is shown by micro- scopic examination, though this substance is associated with other coloring matters which mask its green tint. Structure of Leaves. — While in shape, size, modes of arrangement upon and attachment to the stem, we find among leaves no end of diversity, there is great sim- plicity in the matter of their internal structure. The whole surface of the leaf, on both sides, is cov- ered with epidermis, & coating which, in many cases, may be readily stripped off the leaf, and consists of thick- walled cells, which are, for the most part, devoid of liq- uid contents, except when very young. (E, E, Fig. 56.) Fig. 56 represents the appearance of a bit of bean-leaf as seen on a section from the upper to the lower surface, and highly magnified. Below the upper epidermis, there often occur one or more layers of oblong cells, whose sides are in close con- tact, and which are arranged endwise, with reference to the flat of the leaf. Below these, down to the lower epi- dermis, for one-half to three-quarters of the thickness of the leaf, the cells are commonly spherical or irregular in figure and arrangement, and more loosely disposed, with numerous and large interspaces. The interspaces among the leaf-cells are occupied with air, which is also, in most cases, the i nily content of the epidermal cells. The interior cells of the leaf are filled with sap and contain the chloropJiyl- granules. Under the microscope, these are commonly seen attached to the walls of the cells, as in Fig. 50, or coating grains of starch, or else floating free in the cell-sap. The structure of the reins or ribs of the leaf is similar to that of the vascular 56 bundles of the stem, of which they are branches. At a, Fig. 56, is seen the cross section of a vein in the bean-leaf. VEGETATIVE ORGANS OF PLANTS. 309 The epidermis, while often smooth, is frequently beset with hairs or glands, as seen in the figure^ These are variously shaped cells, sometimes empty, sometimes, as in the nettle, filled with an irritating liquid. Leaf-Pores. — The epidermis of the mature leaf is pro- vided with a vast number of " breathing pores," or stomata, by means of which the intercellular spaces in the interior of the leaf are brought into direct communication with the outer atmosphere. Each of these stomata consists usually of two curved guard-cells, which are disposed toward each other like the halves of an elliptical car- riage-spring. (Figs. 52 and 53.) The opening between them is an actual orifice in the skin of the leaf. The size of the orifice is, how- ever, constantly changing, as the atmosphere becomes drier or more moist, and as Flg> 57' the sunlight acts more or less intensely on its surface. In strong light they curve outwards, and the aperture is enlarged ; in darkness they straighten and shut together, like the springs of a heavily- loaded carriage, and nearly or entirely close the entrance. The effect of water usually is to close their orifices. In Fig. 56 is represented a section^ through the shorter diameter of a pore on the under surfaee of a bean-leaf. The air-space within it is shaded black. , Unlike the other epidermal cells, those of the leaf-pores contain chlorophyll granules. Fig. 57 represents a portion of the epi- dermis of the upper surface of a potato- leaf, and Fig. 58 a similar portion of the Fig. 58. under surface of the same leaf, magnified 200 diameters. In both figures are seen the open stomata between the semi-elliptical cells. The outlines of the other epidermal cells are 310 HOW CROPS GROW. marked by irregular double lines. The round bodies in the guard- cells of the pores are starch-grains, often present in these cells, when not existing in any other part of the leaf. The stomata are, with few exceptions, altogether want- ing on the submerged leaves of aquatic plants. On floating leaves they occur, but only on the upper surface. Thus, as a rule, they are not found in contact with liquid water. On the other hand, they are either absent from, or comparatively few in number upon, the upper surfaces of the foliage of land plants, which are exposed to the heat of the sun, while they occur abundantly on the lower sides of all green leaves. In number and size they vary remarkably. Some leaves possess but 800 to the square inch, while others have as many as 170,000 to that amount of surface. About 100,000 may be counted on an average-sized apple-leaf. In general, they are largest and most numerous on plants which belong to damp and shaded situations, and then exist on both sides of the leaf. The epidermis itself is most dense — consists of thick- walled cells and several layers of them — in case of leaves which belong to the vegetation of sandy soils in hot cli- mates. Often it is impregnated with wax on its upper surface, and is thereby made almost impenetrable to moisture. On the other hand, in rapidly-growing plants adapted to moist situations, the epidermis is thin and delicate. Exhalation of Water-Vapor. — A considerable loss of water goes on from the leaves of growing plants when they are freely exposed to the atmosphere. The water thus lost exhales in the form of invisible vapor. The quantity of water exhaled from any plant may be easily ascertained, provided it is growing in a pot of glazed earthen or other impervious material. A metal or glass cover is cemented air-tight to the rim of the vessel, and around the stem of the plant. The cover has an open- VEGETATIVE ORGANS OF PLAXTS. 311 ing with a cork, through which weighed quantities of water are added from time to time, as required. The amount of exhalation during any given interval of time is learned with a close approach to accuracy by simply noting the loss of weight which the plant and pot together suffer. Hales, who first experimented in this manner, found that a vigorous sunflower, three and a half feet high, whose foliage had an aggregate surface of 39 square feet, gave off 30 ounces av. of water in a space of 12 hours, during a very warm, dry day. The average "rate of perspiration" for 15 days, in July and August, was 20 ounces av. At night, with "any sensible, though small dew, the perspiration was nothing." Knop observed a maize-plant to exhale, between May 22d and September 4th, no less than 36 times its weight of water. Hellriegel (at Uahme, Prussia) found that summer wheat and rye, oats, beans, peas, buckwheat, red clover, yellow lupine and summer colza, on the average exhaled 300 grams of water for 1 gram of dry matter produced above ground, during the entire season of growth, when stationed in a sandy soil. (Die Metliode der Sandkultur, p. 662.) Exhalation is not a regular or uniform process, but varies with a number of circumstances and conditions. It depends largely upon the dryness and temperature of the air. When the air is in the state most favorable to evaporation, the loss from the plant is rapid and large. "When the air is loaded with moisture, as during dewy nights or rainy weather, then exhalation is nearly or totally checked. The temperature of the soil, and even its chemical composition, the condition of the leaf as to its texture, age, and number of stomata, likewise affect the rate of exhalation. Exhalation is rather incidental than necessary to the life of many plants, since it may be suppressed or reduced 312 HOW CHOPS GROW. to a minimum, as in a Wardian case or fernery, without evident influence on growth ; but plants of parentage naturally accustomed to copious exhalation of water flourish best where the conditions are favorable to this process. Exhalation is not injurious, unless the loss be greater than the supply. If water escapes from the leaves faster than it enters the roots, the succulent organs soon wilt, and if t h i s disturbance goes on too far the plant dies. Exhalation ordinarily proceeds to a large extent from the surface of the epidermal cells. Although the cavities of these cells are chiefly oc- cupied with air, their thickened walls transmit outward the water which is supplied to the interior of the leaf. Otherwise the escape of vapor occurs through the stomata. These pores appear to have the function of facil- itating exhalation, by their property of opening when exposed to sunlight. Thus evaporation from the leaves is favored at the time when root-action is most vigorous, and the plant is to the greatest degree surcharged with water. Access of Air to the Interior of the Plant. — Not only does the Fig. 59. leaf allow the escape of vapor of water, but it admits of the entrance and exit of gaseous bodies. The particles of atmospheric air have easy access to the interior of all leaves, however dense and close their epidermis may be, however few or small their stomata. All leaves are actively engaged in absorbing or exhaling certain gaseous ingredients of the atmosphere during the whole of their healthy existence. REPRODUCTIVE ORGANS OF PLANTS. 313 The entire plant is, often, pervious to air through the stomata of the leaves. These communicate with the intercellular spaces of the leaf, which are, in general, occupied exclusively with air, and these again connect with the ducts which ramify throughout the veins of the leaf and branch from the vascular bundles of the stem. In the bark or epidermis of woody stems, as Hales long ago discovered, pores or cracks exist, through which the air has communication with the longitudinal ducts. These facts admit of demonstration by simple means. Sachs employs for this purpose an apparatus consisting of a short, wide tube of glass, B, Fig. 59, to which is adapted, below, by a tightly-fitting cork, a bent glass tube. The stem of a leaf is passed through a cork which is then secured air-tight in the other opening of the wide tube, the leaf itself being included in the latter, and the joints are made air-tight by smear- ing with tallow. The whole is then placed in a glass jar containing enough water to cover the projecting leaf -stem, and mercury is quickly poured into the open end of the bent tube, so as nearly to fill the lat ter. The pressure of the column of this dense liquid immediately forces air into the stomata of the leaf, and a corresponding quantity is forced on through the intercellular spaces and through the vein ducts into the ducts of the leaf-stem, whence it issues in fine bubbles at S. It is even easy in many cases to demonstrate the permeability of the leaf to air by immersing it in water, and, taking the leaf -stem between the lips, produce a current by blowing. In this case the air escapes from the stomata. The air-passages of the stem may be shown by a similar arrange- ment, or in many instances, as, for example, with a stalk of maize, by simply immersing one end in water and blowing into the other. On the contrary, roots are destitute of any visible external pores, and are not pervious to air or vapor in the sense that leaves and young stems are. The air passages in the plant correspond roughly to the mouth, throat, and breathing cavities of the animal. "We have, as yet, merely noticed the direct communica- tion of these passages with the external air by means of microscopically visible openings. But the cells which are not visibly porous readily allow the access and egress of water and of gases by osmose. To the mode in which this is effected we shall recur on subsequent pages. The Offices of Foliage are to put the plant in com- munication with the atmosphere and with the sun. On 314 HOW CROPS GROW. the one hand it permits, and to a certain degree facili- tates, the escape of the water which is continually pumped into the plant by its roots, and on the other hand it absorbs, from the air that freely penetrates it, certain gases which furnish the principal materials for the construction of vegetable matter. We have seen that the plant consists of elements, some of which are volatile at the heat of ordinary fires, while others are fixed at this temperature. When a plant is burned, the former, to the extent of 90 to 99 per cent of the plant, are con- verted into gases, the latter remain as ashes. The reorganization of vegetation from the products of its combustion (or decay) is, in its simplest phase, the gathering by a new plant of the ashes from the soil through its roots, and of these gases from the air by its leaves, and the compounding of these comparatively sim- ple substances into the highly complex ingredients of the vegetable organism. Of this work the leaves have by far the larger share to perform ; hence the extent of their surface and their indispensability to the welfare of the plant. CHAPTER IV. REPRODUCTIVE ORGANS OF PLANTS. §-| J^ i MODES OF REPRODUCTION. Plants are reproduced in various ways. The simplest cellular plants have no evident special organs of repro- duction, but propagate themselves solely by a process of division which begins in the protoplasm, as already de- scribed in case of Yeast, p. 253. The lower so-called flowerless plants (Cryptogams), including molds, blights, mildews, mushrooms, toadstools (Fungi), mosses, lichens, REPRODUCTIVE ORGANS OF PLANTS. 315 etc., reproduce themselves in part by spores, each of which is a single minute cell that is capable of develop- ing into a plant like that from which it was thrown off. In very many cases a portion or " cutting "of root, stem or leaf, from herb or tree, placed in moist, warm earth, will grow and develop into a new plant in all respects similar to the original. The potato, grape, banana, and sugar-cane plants are almost exclusively propagated in this manner/ In budding and grafting a portion of stem, carrying a single bud or a number of buds (scion), is planted, not in the soil, but in the cam- bial layer of a living root or stem with which it unites and thenceforward grows. The higher orders of plants (Phanerogams) have spe- cial reproductive organs, constituting or contained in their flowers, whose office it is to produce seed, the essen- tial part of which is the embryo, a ready-formed minia- ture plant which may grow into the full likeness of its parent. 8 2 THE FLOWER. In the higher plants the onward growth of the stem or of its branches is not necessarily limited, until from the terminal buds, instead of leaves, only flowers unfold. When this happens, as is the case with most annual and biennial plants, raised on the farm or in the garden, the vegetative energy has usually attained its fullest develop- ment, and the reproductive function begins to prepare for the death of the individual by providing seeds which shall perpetuate the species. There is often at first no apparent difference between the leaf-buds and flower-buds, but commonly, in the later stages of their growth, the latter are to be readily dis- tinguished from the former by their greater size, and by peculiar shape or color. 316 HOW CHOPS GROW. st The Flower is a short branch, bearing a collection of organs, which, though usually having little resemblance to foliage, may be considered as leaves, more or less mod- ified in form, color, and office. The flower commonly presents four different sets of organs, viz., Calyx, Corolla, Stamens, and Pistils, and is then said to be complete, as in case of the apple, potato, and many common plants. Fig. 60 represents the com- plete flower of the Fuchsia, or ladies' ear-drop, now uni- versally cultivated. In Fig. 61 the same is shown in section. The Calyx (cup) ex, is the outermost floral envelope. Its color is red or white in the Fuchsia, though generally it is green. When it consists of several distinct leaves, they are called sepals. The calyx is frequently small and inconspicu- ous. In some cases it falls away> as the flower opens. In the Fuchsia it firmly adheres at its base \to the seed-vessel, |and is divided into 'four lobes. The Corolla (crown), c, or ca, is one or several series of leaves which are situated within the calyx. It is usually of some other than a green color (in the Fuchsia, purple, etc.), often has marked peculiarities of form and great delicacy of struc- ture, and thus chiefly gives beauty to the flower. When st Fig. 80. Fig. 61. BEPRODUCTIVE ORGANS OF PLANTS. 317 the corolla is divided into separate leaves, these are termed petals. The Fuchsia has four petals, which are attached to the calyx-tube. The Stamens, s, in Figs. 60 and 61, are generally slender, thread-like organs, terminated by an oblong sack, the anther, which, when the flower attains its full growth, discharges a fine yellow or brown dust, the so- called pollen. The anthers, as well as the grains of pollen, vary in form with nearly every kind of plant. The yellow pollen of Pine and Spruce is not in- frequently transported by the wind to a great distance, and when brought clown by rain in considerable quantities, has been mistaken for sulphur. The Pistil, p, in Figs. 60 and 61, or pistils, occupy the center of the perfect flower. They are exceedingly various in form, but always have at their base the seed- vessels, or ovaries, ov, in which are found the ovules or rudimentary seeds. The summit of the pistil is desti- tute of the epidermis which covers all other parts of the plant, and is termed the stigma, st. As has been remarked, the floral organs may be consid- ered to be modified leaves ; or rather, all the appendages of the stem — the leaves and the parts of the flower to- gether— are different developments of one fundamental structure. The justness of this idea is sustained by the transform- ations which are often observed. The Rose in its natural state has a corolla consisting of five petals, but has a multitude of stamens and pistils. In a rich soil, or as the effect of those agencies which are united in " cultivation," nearly all the stamens lose their reproductive function and proper structure, and revert to petals ; the flower becoming "double." The tulip, poppy, and numerous garden-flowers, illustrate this in- teresting metamorphosis, and in these flowers we may often see the various stages intermediate between the perfect petal and the unaltered stamen. 318 HOW CROPS GROW. On the other hand, the reversion of all the floral organs into ordinary green leaves 1ms been observed not infrequently, in case of the rose, white clover, and other plants. While the complete flower consists of the four sets of organs above described, only the stamens and pistils are essential to the production of seed. The latter, accord- ingly, constitute a perfect flower, even in the absence of calyx and corolla. The flower of buckwheat has no corolla, but a white or pinkish calyx. The grasses have flowers in which calyx and corolla are represented by scale-like leaves, which, as the plants ma- ture, become chaff. In various plants the stamens and pistils are borne on separate flowers. Such are called moncecious plants, of which the birch and oak, maize, melon, squash, cucum- ber, and often the strawberry, are examples. In case of maize, the staminate flowers are the "tas- sels "at the summit of the stalk; the pistillate flowers are the young ears, the pistils themselves being the " silk," each fiber of which has an ovary at its base, that, if fertilized, develops to a kernel. Dioecious plants are those which bear the staminate (male, or sterile) flowers and the pistillate (female, or fertile) flowers on different individuals ; the willow, the hop-vine, and hemp, are of this kind. Nectaries are special organs — glands or tubes — secret- ing a sugary juice or nectar, which serves as food to insects. The clovers and honeysuckles furnish familiar examples. Fertilization and Fructification. — The grand func- tion of the flower is fructification. For this purpose pollen must fall upon or be carried by wind, insects, or other agencies, to the naked tip of the pistil. Thus sit- uated, each pollen-grain sends out a slender microscopic EEPKODUCTIVE ORGANS OF PLANTS. 319 tube which penetrates the interior of the pistil until it enters the seed-vessel and comes in contact with the ovule or rudimentary seed. This contact being established, the ovule is fertilized and begins to grow. Thencefor- ward the corolla and stamens usually wither, while the base of the pistil and the included ovules rapidly increase in size until the seeds are ripe, when the seed-vessel falls to the ground or else opens and releases its contents. Fig. 62 exhibits the process of fertilization as observed in a plant allied to buckwheat, viz., the Polygonum con- volvulus. The cut represents a magnified section length- wise through the short pistil ; a is the stigma or summit of the pistil ; I are grains of pollen ; c are pollen tubes that have penetrated into the seed-vessel which forms the base of the pistil ; one has entered the mouth of the rudimentary seed, g, and reached the embryo sack, e, within which it causes the development of a germ ; d represents the interior wall of the seed-vessel ; h, the base of the seed and its attachment to the seed- vessel. Self-Fertilization occurs when ovules are impregnated by pollen from the same flower. In many plants self-fertilization is favored by the posi- tion of the organs concerned. In the pendent flower of the Fuchsia as well Fi#- 63- as in the upright one of the strawberry the stigma is just below and surrounded by the anthers, so that when the mature pollen is discharged it cannot fail to fall upon the stigma. Some flowers, as' those of the closed gentian (Gentiana Andrewsii] and the small subterranean blos- soms of sheep-sorrel (Oxali* acetosella), touch-me-not (Impatiens), and of many violets, never open, and not 320 HOW CROPS GROW. only are self-fertile but cannot well be otherwise. Some plants which carry these closed and inconspicuous subter- ranean flowers depend upon them for reproduction by seed, their large and showy aerial flowers being often bar- ren, as in violets, or totally infertile ( Voandzeia.) Flax and turnips are self-fertilizing. Cross-Fertilization results from the contact of the pollen of one flower with the ovules of another. In many plants remarkable arrangements exist that hinder or totally prevent self-fertilization and favor or ensure cross- fertilization. In moncecious plants, as hazel or squash, flowers of one sort yield pollen, others, different, contain the ovules ; so that two distinct and more or less distant blossoms of the same plant are necessary for seed-production. In the dioecious poplar and hops, the plant that pro- duces pollen never carries ovules and that which bears the latter is destitute of the former, so that two distinct plants must co-operate to form seeds. It often happens that the pollen of a flower cannot fer- tilize the ovules of the same flower. This may be either because the stigma is behind the pollen in development, as in case of various species of geranium, or because the stigma has passed its receptive period before the pollen is mature, as in Sweet Vernal Grass (Antltoxanthum odo- ratitm). In both instances the ripened pollen may reach stigmas that are ready in other flowers and fertilize their ovules, insects being often the means of transportation. In a large number of flowers, whose pollen and stigmas are simultaneously prepared, the position of the organs is such that self-fertilization is difficult or impossible. The Iris, Crocus. Pansy, Milk-weed (Asrtepias), and many Orchids, are of this class. The offices of insects in search of nectar, or attracted by odors, are here indispensable. The common red clover cannot produce seed without insect aid, and the bumblebee customarily performs this REPRODUCTIVE OHGANS OF PLANTS. 321 service. The insect, in exploring a flower for nectar, leaves upon its stigma pollen taken from the flower last visited, and in emerging renews its burden of pollen to bestow it in turn upon the stigma of a third flower. Cross-fertilization is doubtless often effected by insects in case of flowers which are in all respects adapted for self-fertilization, while flowers that casual examination would pronounce self-fertile are in fact of themselves sterile. The flowers of rye open singly, the long stamens shortly mature and discharge their pollen, which falls on the stigmas of flowers standing lower in the same head, or on neighboring heads. According to Kimepare, the individual rye-flower can fertilize neither itself nor the different flowers of an ear, nor can the different ears of one and the same plant pollinate one another with suc- cess, although no mechanical hindrance exists. (Sachs, Physiology of Plants, p. 790.) Results of Self-Fertilization and Cross-Fertili- zation.— Spreugel, one of the early students of Plant- Eeproduction, wrote in 1793, " Nature appears to be unwilling that any flower shall be fertilized by its own pollen." Extensive observation indicates decidedly that cross-fertilization is far more general than self- fertilization, especially among the higher plants. Dar- win has shown that, in many cases, the pollen of a flower is incapable of fertilizing its own ovules, and that the pollen from another flower of the same plant is scarcely more potent. In these cases the pollen from a flower borne by another plant of the same kind is potent, and the more so the more unlike the two plants are. In Darwin's trials on the reproduction of the Morning Glory, Ipomea purpurea, carried out through ten gener- ations, the average height of 73 self-fertilized plants was 66 inches, while that of the same number of crossed plants was 85.8 inches, or in the ratio of 77 to 100. The relative number of seeds produced by the self-fertil* 21 322 SOW CROPS GROW. ized and cross-fertilized plants in the 1st, 3d, and 9th generations were respectively as 64 to 100; 35 to 100, and 26 to 100. In other cases, but, so far as observed, mnch less com- monly, self-fertilization gives the best results both as regards numbers and vigor of offspring. In Darwin's ex- periments a variety of Mimulus luteus originated, of which the self-fertilized progeny surpassed the cross-fer- tilized, during several generations. In the seventh gen- eration the ratio of superiority of the self-fertilized, as regards numbers of fruit, was as 137 to 100, and in respect to size of plants as 126 to 100. Continued self-fertilization, is thus limited by its ten- dency, as statistically determined, to reduce both the vegetative and reproductive vigor of the plant. On the other hand, cross-fertilization is possible or practicable only within very narrow bounds, and the increased pro- ductiveness that follows it soon reaches a limit, as is shown by the history of vegetable hybrids. That neither mode of fertilization is exclusively or speci- ally adapted to the highest development of plants in gen- eral, or of particular kinds of plants, is shown by the fact that in the course of Darwin's researches on the Ipomea purpurea, just referred to, in the sixth generation a self- fertilized plant (variety) appeared, which was superior to its crossed collateral, and was able to transmit its vigor and fertility to its descendants. It is evident, therefore, that the causes which lead to higher development co-operate most fully, sometimes in the one, sometimes in the other, mode of impregnation and do not necessarily belong to either. We must be- lieve that excellence in offspring is the result of excel- lence in the parents, no matter what lines their heredity may have followed, except as these lines have influenced their individual excellence. That crossing commonly gives better offspring than in-and-in breeding is due to EEPRODUOTIVE ORGANS OF PLANTS. 323 the fact that in the latter both parents are likely to pos- sess by inheritance the same imperfections, which are thus intensified in the progeny, while in cross-breeding the parents more usually have different imperfections which often, more or less, compensate each other in the immediate descendants. Hybridizing. — As the sexual union of quite different kinds of animals sometimes results in the birth of a hybrid, so, among plants, the ovules of one kind (spe- cies, or even genus) may be fertilized by the pollen of another different kind, and the seed thus developed, in its growth produces a hybrid plant. As in the animal, so in the vegetable kingdom, the range within which hybridization is possible appears to be very narrow. It is only between rather closely allied plants that fecunda- tion can take place, and the more close the resemblance the more ready and fruitful the result. Wheat, rye, and barley, in ordinary cultivation, show no tendency to " mix ; " the pollen of one of these similar plants rarely fertilizing* the ovules of the others. But external sim- ilarity is no certain mark of capacity for hybridization. The apple and pear have never yet been crossed, while the almond and nectarine readily form hybrids. (Sachs.) Hybrids are usually less productive of seeds than the parent plants, and sometimes are entirely sterile, but, on the other hand, they are often more vigorous in their vegetative development — produce larger and more numer- ous leaves, flowers, roots, and shoots, and are longer- *In the first edition was written, "being incapable of fertilizing." The experiments of Mr. Carman have lately shown that wheat ami rye may be made to produce fertile hybrids. A beardless wheat was Fertilized by rye-pollen and produced nine seeds, eight of which were fully fertile, one nearly sterile. The last yielded 20 heads, which bore only a few grains. The plants from the nine fertile seeds were polli. nated again with rye and produced but a few fertile seeds. A few plants, seven-eighths rye. were finally produced, which were, however. totally sterile. Of the three-fourths cross, fertile progeny has been raised for several years, and the characters of this genus-hybrid ap- pear to be nearly fixed, though occasionally a sterile head appears.— Rural Xew Yorker, 1883, p. 044. 324 HOW CROPS GROW. lived than their progenitors. For this reason hybrids are much valued in fruit- and flower-culture. Some genera of plants have great capacity for produc- ing hybrids. The Vine and the Willow are striking examples. The cultivated Vine of Europe and Western Asia is Vitis vinifera. In the United States some twelve distinct species are found, of which three, Vitis riparia, Vitis cestivalis, and Vitis labrusca, are native to New England. Nearly all these kinds of grape cross with such readiness that scores of new hybrids have been brought into cultivation. "The kinds now known as Clinton, Taylor, Elvira, Franklin, are hybrids of V. riparia and V. labrusca. York-Madeira, Eumelan, Alvey, Morton's Virginia, Cynthiana, are crosses of V. labrusca and V. cestivalis. Delaware is a hybrid of V. labrusca, V. vinifera, and V. cestivalis. Herbemont, Rulander, and Cunningham are hybrids of V. cestivalis, V. cinerea, and V. vinifera. The vine known in France as " Gaston-Bazille " is a hybrid of V. labrusca, V. cesti- valis, V. rupestris, and V. riparia."* The foregoing are "spontaneous wild hybrids." The "Rogers Seed- lings," including Salem, Wilder, Barry, Agawam, Mas- msoit, etc., are examples of artificial hybrids of V. vin- ifera and V. labrusca. Hybridization between plants is effected, if at all, by removing from the flower of one kind the stamens before they shed their pollen, and dusting the summit of the properly-matured pistil with pollen from another kind. Commonly, when two plants hybridize, the pollen of either will fertilize the ovules of the other. In some cases, however, two plants yield hybrids by only one order of connection. The mixing of different Varieties, as commonly hap- pens among maize, melons, etc., is not hybridization, •Millarclet in >>»<•;<*•* L> <•!«,•<* on tin: I'l ij*\'>ln|tr;ir. is difficult to explain. Varieties may often be perpetuated for a long time by REPRODUCTIVE ORGANS OF PLANTS. 327 the seed. This is true of our cereal and leguminous plants, which commonly reproduce their kind with strik- ing regularity. Varieties of some plants cannot, with certainty, be reproduced unaltered by tbe seed, but are continued in the possession of their peculiarities by cut- tings, layers, and grafts. The fact that .the seeds of a potato, a grape, an apple, or pear cannot be depended upon to reproduce the variety, may perhaps be more common]^ due to unavoidable contact of pollen from other varieties (variety-hybridization) than to inability of the mother plant to perpetuate its peculiarities. That such inability often exists is, however, well estab- lished, and is, in general, most obvious in case of varie- ties that have, to the greatest degree, departed from the original specific type and of course, in sterile hybrids. The sports which originate in the processes of propa- gating from buds (grafts, tubers, cuttings) are perpet- uated by the same processes. Species and Varieties, as established in our botanical literature, are exemplified by the Vine, whose species are vinifera, riparia, labrusca, etc., and some of whose North American Varieties, the results of hybridization, have already been enumerated. Genus (plural Genera). — Species which resemble each other in most important points of structure are grouped together by botanists into a genus. Thus the various species of oaks, — white, red, black, scrub, live, etc., — taken together, form the Oak-genus Quercus, which has a series of characters common to all oaks (generic characters), that distinguishes them from every other kind of tree or plant. Families, or Orders, in botanical language, are groups of genera that agree in certain particulars. Thus the several plants well-known as mallows, hollyhock, okra, and cotton, are representatives of as many different genera. They all agree in a number of points, especially 328 HOW CHOPS GROW. as regards the structure of their fruit. They are accord- ingly grouped together into a natural family or order, which differs from all others. Classes, Series, and Classification. — Classes are groups of orders, and Series are groups of classes. In botanical classification, as now universally employed— classification after the Natural System — all plants are separated into two series, as follows : 1'. Flowering Plants (Phanerogams), which produce flowers and seeds with embryos, and 2. Flowerless Plants (Cryptogams), that have no proper flowers nor seeds, and are reproduced, in part, by spores which are in most cases single cells. This series includes Ferns, Horse-tails, Mosses, Liverworts, Lichens, Sea-weeds, Mushrooms, and Molds. It was believed, until recently, that there exist-; a sharp and abso- lute distinction between flowering and flowerless plants, but our /arger knowledge now recognizes that here, as among genera, speeh-s, and varieties, kinds merge or shade into each other. The use of Classification is to give precision to our notions and distinctions, and to facilitate the using and acquisition of knowledge. Series, classes, orders, genera, species, and varieties are as valuable to the naturalist as pigeon-holes are to the accountant, or shelves and draw- ers to the merchant. Botanical Nomenclature. — The Latin or Greek names which botanists employ are essential for the dis- crimination of plants, being equally received in all coun- tries, and belonging to all languages where science has a home. They are made necessary, not only by the confu- sion of tongues, but by confusions in each vernacular. Botanical usage requires for each plant two names, one to specify the genus, another to indicate the species. Thus all oaks are designated by the Latin word Quercus, while the red oak is Quercus rubra, the white oak is Quercus alba, the live oak is Quercus virens, etc. REPRODUCTIVE ORGANS OF PLANTS. 329 The designation of certain important families of plants is derived from a peculiarity in the form or arrangement of the flower. Thus the pulse family, comprising the bean, pea, and vetch, as well as alfalfa and clover, are called Papilionaceous plants, from the resemblance of their flowers to a butterfly (Latin, papilio). Again, the mustard family, including the radish, turnip, cabbage, water-cress, etc., are termed Cruciferous plants, because their flowers have four petals arranged like the four arms of a cross (Latin, crux). The flowers of a large natural order of plants are arranged side by side, often in great numbers, on the expanded extremity of the flower stem. Examples are the thistle, dandelion, sunflower, artichoke, China-aster, etc., which, from bearing such compound heads, are called Composite plants. The Coniferous (cone-bearing) plants comprise the pines, spruces, larches, hemlocks, etc., whose flowers are arranged in conical receptacles. The flowers of the carrot, parsnip, and caraway are stationed at the extremities of stalks which radiate from a central stem like the arms of an umbrella ; hence they are called Umbelliferous plants (from umbel, Latin for little screen). §2. THE FRUIT. THE FRUIT comprises the seed-vessel and the seeds, to- gether with their various appendages. Fruits are either dehiscent when the seed-vessel opens and sheds the seed or are indehiscent when it remains closed. The seed-vessel, consisting of the base of the pistil in its matured state, exhibits a great variety of forms and characters, which serve, chiefly, to define the different 330 HOW CROPS GROW. kinds of Fruits. Of these we shall only adduce such as are of common occurrence and belong to the farm. The Nut has a hard, leathery or bony indehiscent shell, that usually contains a single seed. Examples are the acorn, chestnut, beech-nut, and hazel-nut. The cup of the acorn and the bur or shuck of the others is a sort of fleshy calyx. The Stone-fruit, or Drupe, is a nut enveloped by a fleshy or leathery coating, like the peach, cherry, and plum, also the butternut and hickory-nut. Raspberries and blackberries are clusters of small drupes. Pome is a term applied to fruits like the apple and pear, the core of which is the true seed-vessel, originally belonging to the pistil, while the often edible flesh is the enormously enlarged and thickened calyx, whose with- ered tips are always to be found at the end opposite the stem. The Berry is a many-seeded fruit of which the entire seed-vessel becomes thick and soft, as the grape, currant, tomato, and huckleberry. Gourd fruits have externally a hard rind, but are fleshy in the interior. The melon, squash, and cucum- ber are of this kind. The Akene is a fruit containing a single seed which does not separate from its dry envelop. The so-called seeds of the composite plants — for example, the sunflower, thistle, and dandelion — are akenes. On removing the outer husk or seed-vessel we find within the true seed. Many akenes are furnished with a pappus, a downy or hairy appendage, the remains of the calyx, as seen in the thistle, which enables the seed to float and be carried about in the wind. The fruit or grain of buckwheat is akene-like. The Grains are properly fruits. Wheat, rye, and maize consist of the seed and the seed-vessel closely united. When these grains are ground, the bran that REPRODUCTIVE ORGANS OF PLANTS. 331 comes off is the seed-vessel together with the outer coat- ings of the seed. Barley-grain, in addition to the seed- vessel, has the petals of the flower or inner chaff, and oats have, besides these, the calyx or outer chaff adher- ing to the seed. Pod is the name properly applied to any dry seed-ves- sel which opens and scatters its seeds when ripe. Sev- eral kinds have received special designations ; of these we need only notice one. The Legume is a pod, like that of the bean, which splits into two halves, along whose inner edges seeds are borne. The pulse family, or papilionaceous plants, are also termed leguminous, from the form of their fruit. THE SEED, or ripened ovule, is borne on a stalk which connects it with the seed-vessel. Through this stalk it is supplied with nutriment while growing. When ma- tured and detached, a scar commonly indicates the point of former connection. The seed has usually two distinct coats or integuments. The outer one is often hard, and is generally smooth. In the case of cotton-seed it is covered with the valuable cotton fiber. The second coat is commonly thin and delicate. The Kernel lies within the integuments. In many cases it consists exclusively of the embryo, or rudimen- tary plant. In others it contains, besides the embryo, what has received the name of endosperm. The Endosperm forms the chief bulk of all the grains. If we cut a seed of maize in two lengthwise, we observe, extending from the point where it was attached to the cob, the soft " chit," b, Fig. 63, which is the em- bryo, to be presently noticed. The remainder of the kernel, a, is endosperm ; the latter, therefore, yields in great part the flour or meal which is so important a part of the food of man and animals. The endosperm is intended for the support of the 332 HOW CBOPS GROW. young plant as it develops from the embryo, before it is capable of depending on the soil and atmosphere for sus- tenance. It is not, however, an indispensable part of the seed, and may be entirely removed from it, without thereby preventing the growth of a new plant. The Embryo, or Germ, is the essential and most important portion of the seed. It is, in fact, a ready- formed plant in miniature, and has its root, stem, leaves, and a bud, although these organs are often as undevel- oped in form as they are in size. As above mentioned, the chit of the seeds of maize and the other grains is the embryo. Its form is with diffi- culty distinguishable in the 'dry seeds, but when they have been soaked for several days in water, it is readily removed from the accompanying endosperm, and plainly exhibits its three parts, viz., the Radicle, the Plumule, and the Cotyledon. In Fig. 63 is represented the embryo of maize. In A and B it is seen in section imbedded in the endosperm. C exhibits the detached embryo. The Radicle, r, is the stem of the seed-plant, its lower extremity is the point from which downward growth proceeds, and from which the first true roots are produced. The Plumule, c, is the central bud, out of which the stem, with new leaves, flowers, etc., is developed. The Cotyledon, I, is in structure a ready-formed leaf, which clasps the plumule in the embryo, as the proper leaves clasp the stem in the mature maize-plant. The coty- ledon of maize does not, however, perform the functions of a leaf ; on the contrary, it remains in the soil during the act of sprouting, and its contents, like those of the endosperm, are absorbed by the seedling. The first leaves which ap- REPRODUCTIVE ORGANS OF PLANTS. 333 pear above-ground, in the case of maize and the other grains (buckwheat excepted), are those which in the embryo were wrapped together in the plumule, where they can be plainly distinguished by the aid of a mag- nifier. It will be noticed that the true grains (which have sheathing leaves and hollow jointed stems) are monocot- yledonous (one-cotyledoned) in the seed. As has been mentioned, this is characteristic of plants with endoge- nous or inside-growing stems (p. 290). The seeds of the Exogens (outside-growers — p. 296) are dicotyledonous, i. e., have two cotyledons. Those of buckwheat, flax, and tobacco contain an endosperm. The seeds of nearly all other exogenous agricultural plants are destitute of an endosperm, and, exclusive of the coats, consist entirely of embryo. Such are the seeds of the Leguminosse, viz., the bean, pea, and clover; of the Cruciferae, viz., turnip, radish, and cabbage ; of ordi- nary fruits, the apple, pear, cherry, plum, and peach ; of the Gourd family, viz., the pumpkin, melon and cucum- ber ; and finally of many hard-wooded trees, viz., the oak, maple, elm, birch, and beech. We may best observe the structure of the two-cotyle- doned embryo in the ordinary garden- or kidney-bean. After a bean has been soaked in warm water for several hours, the coats may be easily removed, and the two fleshy cotyledons, c, c, in Fig. 64, are found separated from each other save at the point where the radicle, a, is seen projecting like a blunt spur. On carefully breaking away one of the coty- ledons, we get a side view of the radicle, a, and plumule, b, the former of which la was partially and the latter entirely im- bedded between the cotyledons. The Fig. 64. plumule plainly exhibits two delicate leaves, on which the unaided eye may note the veins. 334 HOW CKOPS GROW. These leaves are folded together along their mid-ribs, and may be opened and spread out with help of a needle. When the kidney-bean (Phaseohis) germinates, the cotyledons are carried up into the air, where they become green and constitute the first pair of leaves of the new plant. The second pair are the tiny leaves of the plum- ule just described, between which is the bud, whence all the subsequent aerial organs develop in succession. In the horse-bean ( Vicia faba), as in the pea, the cot- yledons never assume the office of leaves, but remain in the soil and gradually yield a large share of their con- tents to the growing plant, shriveling and shrinking greatly in bulk, and finally falling away and passing into decay. VITALITY OF SEEDS AND THEIR INFLUENCE ON THE PLANTS THEY PRODUCE. Duration of Vitality. — In the mature seed the em- bryo lies dormant. The duration of its vitality is very various. The seeds of the willow, it is asserted, will not grow after having once become dry, but must be sown when fresh ; they lose their germiuative power in two weeks after ripening. On the other hand, single seeds of various plants, as of sorrel (Oxalis strictd), shepherd's purse (Thlaspi arv- ense), and especially of trees like the oak, beech, and cherry, remain with moist embryos many months or sev- eral years before sprouting. (Xobbe & Haenlein, I".-. St., XX, p. 70.) Among the seeds of various plants, clover for example, which, under favorable circumstances, mostly germinate within one or two weeks, may often be found a number which remain unchanged, sound and dry within, for months or years, though constantly wet externally. The REPRODUCTIVE ORGANS OF PLANTS. 335 outer coat of these seeds is exceptionally thick, dense, and resistant to moisture. If this coat be broken by the scratch of a needle the seed will shortly germinate. In a collection of such seeds, kept in water, individuals sprout from time to time. In case of common sorrel (Rumex acetosella], Nobbe & Haenlein found that 10 per cent of the seeds germinated between the 400th and 500th day of keeping in the sprouting apparatus. The appearance of strange plants in earth newly thrown out of excavations may be due to the presence of such resistant seed, which, scratched by the friction of the soil in digging, are brought to germination after a long period of rest. Lyell states that seeds of the yellow Nelumbo (water lily) have sprouted after being in the ground for a century, and K. Brown is authentically said to have germinated seeds of a Nelumbo taken by him from Hans Sloane's herbarium, where they had been kept dry for at least 150 years. The seeds of wheat usually, for the most part, lose their power of growth after having been kept from three to seven years. Count Steinberg and others are said to have succeeded in germinating wheat taken from an Egyptian mummy, but only after soaking it in oil, Sternberg relates that this ancient wheat manifested no vitality when placed in the soil under ordinary circum- stances, nor even when submitted to the action of acids or other substances which gardeners sometimes employ with a view to promote sprouting. Girardin claims to have sprouted beans that were over a century old. It is said that Grimstone with great pains raised peas from a seed taken from a sealed vase found in the sarcophagus of an Egyptian mummy, presented to the British Museum by Sir G. Wilkinson, and estimated to be near 3,000 years old. Vilmorin, from his own trials, doubts altogether the authenticity of the " mummy wheat," and it is probable 336 HOW CROPS GftOW. that those who have raised mummy wheat or mummy peas were deceived either by an admixture of fresh seed with the ancient, or by planting in ordinary soil, which commonly contains a variety of recent seeds that come to light under favorable conditions. Dietrich (Hoff. Jahr., 1862-3, p. 77) experimented with seeds of wheat, rye, and a species of Bromns, which were 185 years old. Nearly every means reputed to favor germination was employed, but without success. After proper exposure to moisture, the place of the germ was usually found to be occupied by a slimy, putrefying liq- uid. Commonly, among the freshest seeds, when put to the sprouting trial, some will mold or putrefy. The fact appears to be that the circumstances under which the seed is kept greatly influence the duration of its vitality. If seeds, when first gathered, be thoroughly dried, and then sealed up in air-tight vessels, there is no evident reason why their vitality should not endure for long periods. Moisture and the microbes that flourish where it is present, not to mention insects, are the agen- cies that usually put a speedy limit to the duration of the germinative power of seeds. In agriculture it is a general rule that the newer the seed the better the results of its use. Experiments have proved that the older the seed the more numerous the failures to germinate, and the weaker the plants it pro- duces. Londet made trials in 1856-7 with seed-wheat of the years 1856, '55, '54, and '53. The following table exhib- its the results : Dumber of stalks Per cent of seeds Length of Jeares four days andearsper sprouted. after coming up. hundred seeds. Seed of 1853 none " " 1854 51 0.4 to 0.8 inches. 269 " " 1855 73 1.2 " 365 " " 1856 74 1.6 " 404 The results of similar experiments made by Haberlandt on various grains are contained in the following table : ORCHIS Otf PLANTS. Per cent of seeds that germinated in 1861 from the years : "Wheat 1850 0 1851 0 1854 8 1855 4 1 857 73 1858 60 1859 84 1860 96 Rye 0 0 0 0 0 0 48 100 0 0 24 0 48 33 92 89 Oats. . 60 0 56 48 72 32 80 96 Maize... .. 0 not tried 76 56 not tried 77 100 97 Results of the Use of Long-kept Seeds The fact that old seeds yield weak plants is taken advantage of by the florist in producing new varieties. It is said that while the one-year-old seeds of Ten-weeks Stocks yield single flowers, those which have been kept four years give mostly double flowers. In case of melons, the experience of gardeners goes to show that seeds which have been kept several, even seven years, though less certain to come up, yield plants that give the greatest returns of fruit ; while plantings of new seeds run excessively to vines. Unripe Seeds. — Experiments by Lucanus prove that seeds gathered while still unripe, — when the kernel is soft and milky, or, in case of cereals, even before starch has formed, and when the juice of the kernel is like water in appearance, — are nevertheless capable of germi- nation, especially if they be allowed to dry in connection with the stem (after-ripening). Such immature seeds, however, have less vigorous germinative power than those which are allowed to mature perfectly ; when sown, many of them fail to come up, and those which do, yield comparatively weak plants at first and in poor soil give a poorer harvest than well-ripened seed. In rich soil, however, the plants which do appear from unripe seed, may, in time, become as vigorous as any. (Lucanus, Vs. St., IV, p. 253.) According to Siegert, the sowing of unripe peas tends to produce earlier varieties. Liebig says : " The gar- dener is aware that the flat and shining seeds in the pod of the Stock Gillyflower will give tall plants with single flowers, while the shriveled seeds will furnish low plants with double flowers throughout. 22 338 HOW CHOPS GROW. Cohn found that seeds not fully ripe germinate some- what sooner than those which are more mature, and he believes that seeds in a medium stage of ripeness germi- nate most readily. Quick- and Slow-Sprouting Seeds. — When a con- siderable number of agricultural or garden seeds, fresh and of uniform appearance, are placed under favorable circumstances for germinating, it is usually observed that sprouting begins within two to ten days, and con- tinues for one or several weeks before all or nearly all the living embryos have manifestly commenced to grow. Nbbbe (in 1886 and 1887) found in extensive trials with 12 varieties of. stocks, Matthiola annua, that the quick- sprouting seeds, which germinated in three to four days, yielded earlier and larger plants, which blossomed with greater regularity and certainty, and produced a pre- ponderance (82 per cent) of sterile double flowers, while the slow-sprouting seeds, that were ten to twelve days in germinating, gave smaller plants that came later to bloom, and yielded 73 per cent of fertile single flowers. Should continued trials prove these results to be of constant occurrence, it is evident that by breeding exclu- sively from the quick-sprouting seeds, the double-flower- ing varieties should soon become extinct, from failure to produce seed. On the other hand, exclusive use of the slow-sprouting seeds would extinguish the tendency to variation and double-blooming, which gives this plant its value to the florist. Dwarfed or Light Seeds. — Miiller, as well as Hell- riegel, found in case of the cereals that light or small grain sprouts quicker but yields weaker plants, and is not so sure of germinating as heavy grain. Liebig asserts (Xatnrul Laivs of Husbandry, Am. Ed., 1863, p. 24) that "poor and sickly seeds will pro- duce stunted plants, which will again yield seeds bearing in a great measure the same character." This is true "in the long run," i. e., small or light seeds, the result REPRODUCTIVE GROANS OF PLANTS. 333 of unfavorable conditions, will, under the continuance of those conditions, produce stunted plants (varieties), whose seeds will be small and light. (Compare Tuscan and pedigree wheat, p. 158.) Schubart, whose observations on the roots of agricul- tural plants are detailed in a former chapter (p. 263), says, as the result of much investigation, "the vigorous development of plants depends far less upon the size and weight of the seed than upon the depth to which it is covered with earth, and upon the stores of nourishment which it finds in its first period of life." Eeference is here had to the immediate produce under ordinary agri- cultural conditions. Value of Seed as Related to its Density. — From a series of experiments made at the Royal Agricultural College at Cirencester, in 1863-6, Church concludes that the value of seed-wheat stands in a certain connection with its specific gravity (Practice with Science, pp. 107, 342, 345, London, 1867). He found:— 1. That seed-wheat of the greatest density produces the densest seed. 2. The seed-wheat of the greatest density yields the greatest amount of dressed corn. 3. The seed-wheat of medium density generally gives the largest number of ears, but the ears are poorer than those of the densest seed. 4. The seed-wheat of medium density generally pro- duces the largest number of fruiting plants. 5. The seed- wheats which sink in water, but float in a liquid having the specific gravity 1.247, are of very low value, yielding, on an average, but 34.4 Ibs. of dressed grain for every 100 yielded by the densest seed. 6. The densest wheat-seeds are the most translucent or horny, and contain about one-fourth more proteids (or 3 per cent more) than the opake or starchy grains from the same kind of wheat, or even from the same individual plant, or even from the same ear. 340 HOW CROPS GROW. 7. The weight of wheat per bushel depends upon many circumstances, and bears no constant relation to the density of the seed. The densest grains are not, according to Church, always the largest. The seeds he experimented with ranged from sp. gr. 1.354 to 1.401. Marek has shown that specific gravity is no universal test of the quality of seed, for while, in case of wheat, flax, and colza, the large seeds are generally the denser, the reverse is true of horse-beans ( Vicia faba) and peas (F*. St., XIX, 40). The Absolute Weight of Seeds from different varieties of the same species is known to vary greatly, as is well exemplified by comparing the kernels of com- mon field maize with those of "pop corn." Similar dif- ferences are also observable in different single seeds from the same plant, or even from the same pod or ear. Thus, Harz obtained what were, to all appearance, normally developed seeds that varied in weight as follows : FROM SINGLE PLANTS. MiJli(/rnm8. Wheat, Triticum vulgare, from 15 to 37 Wheat, Triticum polonicum, «« 21 to 55 Barley, ffordeum distichon, « 31 to 41 Oats, Avena safim, u 19 to 30 Maize, Zen .Vni/* < infjuaiitiiio, «« 1G9 to 201 Pea, Pisum, satir,/,,*, « 143 to 502 FROM SINGLE FRUIT (PODS). Pea> from 309 to 473 Vetch. « 33 to 66 LuPIn' " 486 to 639 Differences often no less marked are found among the seeds in any considerable sample, gathered from a large number of plants and representing a crop. Nobbe, with great painstaking, has ascertained the average, maxi- mum and minimum weights, of 180 kinds of seeds, such as are found in commerce or are used in Agriculture, Horticulture, and Forestry. The following table gives some of his results : REPRODUCTIVE ORGANS OF PLANTS. 341 Absolute Weight of Commercial Seeds. Number of Weight of one Seed in Samples Milligrams. Examined. Average. Maximum. Minimum Oats, 84 28.8 54.1 14.7 Barley, 66 41.0 48.9 27.7 Rye , 119 23.3 47.9 13.0 ' Wheat 95 37.6 45.8 15.2 Maize,. 22 282.7 382.9 114.5 Beet, 39 22.0 42.4 14.2 Turnip, Brass-lea rapifera,.. 23 2.2 3.0 1.4 Carrot, 35 1.2 1.7 0.8 Pea, 43 185.8 564.6 46.1 Kidney Bean, Phaseolus,.... 5 585.6 926.3 367.3 Horse Bean, Vicia 7 676.0 2061.0 256.4 Potato 3 0.6 0.7 0.5 Tomato, 5 2.5 2.7 2.4 Spinage, 4 6.9 9.0 2.4 Radish, 5 7.1 9.7 5.7 Lettuce, 18 1.1 1.7 0.8 Parsnip, 3 3.1 3.8 2.3 Squash 5 173.0 322.0 106.7 Musk Melon, 3 32.9 35.5 28.2 Cucumber, 6 25.4 27.0 21.0 Timothy, I'ltleum pratense,. 73 0.41 0.59 0.34 Blue Grass, Poo prafetwi*,.. 28 0.15 0.21 o.io Red (lover, 355 1.60 2.08 1.14 White Clover, 53 0.61 0.69 0.47 Ten -weeks-stocks, Alatthi- designated this body tn.Mr\n,\i\\\ this term being established as Die name of the characteristic ingredient of animal mucus, Ritthau- sen has replaced it by inucedin. GERMINATION". 361 idity of the action and the amount of effect are usually far less than that exhibited by the so-called diastase. It must not be forgotten, however, that in all cases in. which the conversion of starch into dextrin and sugar is accomplished artificially, an elevated temperature is re- quired, whereas, in the natural process, as shown in the germinating seed, the change goes on at ordinary or even low temperatures. It is generally taught that oxygen, acting on the albu- minoids in presence of water, and within a certain range of temperature, induces the decomposition which confers on them the power in question. The necessity for oxygen in the act of germination has been thus accounted for, as needful to the solution of the starch, etc., of the cotyledons. This may be true at first, but, as we shall presently see, the chief action of oxygen is probably of another kind. How diastase or other similar substances accomplish the change in question is not certainly known. Soluble Starch. — The conversion of starch into sugar and dextrin is thus in a sense explained. This is not, however, the only change of which starch is suscepti- ble. In the bean (Phaseol- us multiftorus) Sachs (Sitz- ungsberichte der Wi ener Akad., XXXVII, 57) in- forms us that the starch of the cotyledons is dissolved, passes into the seedling, and reappears (in part, at least) as starch, without conver- sion into dextrin or sugar, as these substances do not appear in the cotyledons during any period of germination, except in small quantity near the joining of the seedling. Compare p. 52, Amidulin. Fig. 65. 362 HOW CROPS GROW. The same authority gives the following account of the microscopic changes observed in the starch-grains them- selves, as they undergo solution. The starch-grains of the bean have a narrow interior cavity (as seen in Fig. 65, 1). This at first becomes filled with a liquid. Next, the cavity appears enlarged (2), its borders assume a corroded appearance (3, 4), aud frequently channels are seen extending to the surface (4, 5, 6). Finally, the cavity becomes so large, and the channels so extended, that the starch-grain falls to pieces (7, 8). Solution continues on the fragments until they have completely disappeared. Soluble Albuminoids. — The insoluble proteids of the seed are gradually transferred to the young plant, probably by ferment-actions similar to those referred to under the heading " Proteoses and Peptones," p. 100. The production of small quantities of acetic and lactic acids (the acids of vinegar and of sour milk) has been observed in germination. These acids perhaps assist in the solution of the albuminoids. Gaseous Products of Germination. — Before leav- ing this part of our subject, it is proper to notice some other results of germination which have been thought to belong to the process of solution. On refemng to the table of the composition of malt, we find that 100 parts of dry barley yield 92 parts of malt and 2% of sprouts, leaving 5£ parts unaccounted for. In the malting pro- cess, 1^ parts of the grain are dissolved in the water in which it is soaked. The remaining 4 parts escape into the atmosphere in the gaseous form. Of the elements that assume the gaseous condition, carbon does so to the greatest extent. It unites with atmospheric oxygen (partly with the oxygen of the seed, according to Oudemans), producing carbonic acid gas (C02). Hydrogen is likewise separated, partly in union with oxygen, as water (H20), but to some degree GEBMINATION. 363 in the free state. Free nitrogen appears in considerable amount (Scliulz, Jour, far Prakt. Chem., 87, p. 163). while very minute quantities of Hydrogen and of Nitro- gen combine to gaseous ammonia (NH3). Heat developed in Germination. — These chemica-1 changes, like all processes of oxidation, are accompanied with the production of heat. The elevation of temper- ature may be imperceptible in the germination of a sin- gle seed, but the heaps of sprouting grain seen in the malt-house, warm so rapidly and to such an extent that much care is requisite to regulate the process ; otherwise the malt is damaged by over-heating. 2. The Transfer of the Nutriment of the Seed- ling from the cotyledons or endosperm where it has un- dergone solution, takes place through the medium of the water which the seed absorbs so largely at first. This water fills the cells of the seed, and, dissolving their con- tents, carries them into the young plant as rapidly as they are required. The path of their transfer lies through the point where the embryo is attached to the cotyle- dons ; thence they are distributed at first chiefly down- wards into the extending radicles, after a little while both downwards and upwards toward the extremities of the seedling. Sachs has observed that the carbhydrates (sugar and dextrin) occupy the cellular tissue of the rind and pith, which are penetrated by numerous air-passages ; while at first the albuminoids chiefly diffuse themselves through the intermediate cambial tissue, which is destitute of air-passages, and are present in largest relative quantity at the extreme ends of the rootlets and of the plumule. In another chapter we shall notice at length the phe- nomena and physical laws which govern the diffusion of liquids into each other and through membranes similar to those which constitute the Avails of the cells of plants, and there shall be able to gather some idea of the causes 3G4: HOW CEOPS GROW. which set up and maintain the transfer of the materials of the seed into the infant plant. 3. Assimilation is the conversion of the transferred nutriment into the substance of the plant itself. This process involves two stages, the first being a chemical, the second, a structural transformation. The chemical changes in the embryo are, in part, simply the reverse of those which occur in the cotyle- dons ; viz., the soluble and structureless proximate prin- ciples are metamorphosed into the insoluble and organ- ized ones of the same or similar chemical composition. Thus, dextrin may pass into cellulose, and the soluble albuminoids may revert in part to the insoluble condi- tion in which they existed in the ripe seed. But many other and more intricate changes proceed in the act of assimilation. With regard to a few of these we have some imperfect knowledge. Dr. Sachs informs us that when the embryo begins to grow, its expansion at first consists in the enlargement of the ready-formed cells. As a part elongates, the starch which it contains (or which is formed in the early stages of this extension) disappears, and sugar is found in its stead, dissolved in the juices of the cells. When the organ has attained its full size, sugar can no longer be detected ; while the walls of the cells are found to have grown both in circumference and thickness, thus indicating the accumulation of cellulose. Oxygen Gas needful to Assimilation. — Traube has made some experiments, which prove conclusively that the process of assimilation requires free oxygen to surround and to be absorbed by the growing parts of the germ. This observer found that newly-sprouted pea- seedlings continued to develop in a normal manner when the cotyledons, radicles, and lower part of the stem were withdrawn from the influence of oxygen by coat- ing with varnish or oil. On the other hand, when the GERMINATION". 365 tip of the plumule, for the length of about an inch, was coated with oil thickened with chalk, or when by any means this part of the plant was withdrawn from contact with free oxygen, the seedling ceased to grow, withered, and shortly perished. Traube observed the elongation of the stem by the following expedient. A young pea-plant was fastened by the cotyledons to a rod, and the stem and rod were both graduated by deli- cate cross-lines, laid on at equal intervals, by means of a brush dipped in a mixture of oil and indigo. The growth of the stem was now manifest by the widening of the spaces between the lines ; and, by comparison with those on the rod, Traube remarked that no growth took place at a distance of more than ten to twelve lines from the base of the terminal bud. Here, then, is a coincidence which appears to demon- strate that free oxygen must have access to a growing part. The fact is further shown by varnishing one side of the stem of a young pea. The varnished side ceases to extend, the uncoated portion continues enlarging, which results in a curvature of the stem. Traube further indicates in what manner the elabora- tion of cellulose from sugar may require the co-operation of oxygen and evolution of carbon dioxide, as expressed by the subjoined equation. Glucose. Oxygen. Carbon dioxide. "Water. Cellulose. + 240 = 12 (CO,) + 14 (H,O) + C^H^O^. When the act of germination is finished, which occurs as soon as the cotyledons and endosperm are exhausted of all their soluble matters, the plant begins a fully inde- pendent life. Previously, however, to being thus thrown upon its own resources, it has developed all the organs needful to collect its food from without ; it has unfolded its perfect leaves into the atmosphere, and pervaded a portion of soil with its rootlets. 366 HOW CEOPS GKOW. During the latter stages of germination it gathers its nutriment both from the parent seed and from the exter- nal sources which afterward serve exclusively for its support. Being fully provided with the apparatus of nutrition, its development suffers no check from the exhaustion of the mother seed, unless it has germinated in a sterile soil, or under other conditions adverse to vegetative life. CHAPTER II. THE FOOD OF THE PLANT WHEN INDEPENDENT OF THE SEED. This subject will be sketched in this place in but the briefest outlines. To present it fully would necessitate entering into a detailed consideration of the Atmosphere and of the Soil, whose relations to the Plant, those of the soil especially, are very numerous and complicated. A separate volume is therefore required for the adequate treatment of these topics. The Eoots of a plant, which are in intimate contact with the soil, absorb thence the water that fills the active cells ; they also imbibe such salts as the water of the soil holds in solution ; they likewise act directly on the soil, and dissolve substances, which are thus first made of avail to them. The compounds that the plant must derive from the soil are those which are found in its ash, since these are not volatile, and cannot, therefore, exist in the atmosphere. The root, however, commonly takes FOOD AFTER GERMINATIOH. 367 up some other elements of its nutrition to which it has immediate access. Leaving out of view, for the present, those matters which, though found in the plant, appear to be unessential to its growth, viz., silica and sodium salts, the roots absorb the following substances, viz. : Sulphates ~l f Potassium, Phosphates - | Calcium, Nitrates and Magnesium and Chlorides J ^ Iron. These salts enter the plant by the absorbent surfaces of the younger rootlets, and pass upwards, through the stem, to the leaves and to the new-forming buds. The Leaves, which are unfolded to the air, gather from it Carbon dioxide Gas. This compound suffers decomposition in the plant ; its Carbon remains there, its Oxygen or an equivalent quantity, very nearly, is thrown off into the air again. The decomposition of carbon dioxide takes place only by day and under the influence of the sun's light. From the carbon thus acquired and the elements of water with the co-operation of the ash-ingredients, the plant organizes the Carbhydrates. Probably some of the glucoses are the first products of this synthesis. Starch, in the form of granules, is the first product that is recognizable by help of the microscope. The formation of carbhydrates appears to proceed in the chlorophyl-cells of the leaf, where starch-granules first make their appearance. The Albuminoids require for their production the presence of a compound of Nitrogen. The salts of Nitric Acid (nitrates) are commonly the chief, and may be the only, supply of this element. The other proximate principles, the fats, the alkaloids, and the acids, are built up from the same food-elements. In most cases the steps in the construction of organic matters are unknown to us, or subjects of uncertain con- jecture. 368 HOW CROPS GKOW. The carbhydrates, albuminoids, etc., that are organ- ized in the foliage, are not only transformed into the solid tissues of the leaf, but descend and diffuse to every active organ of the plant. The plant has, within certain limits, a power of select- ting its food. The sea-weed, as has been remarked, contains more potash than soda, altbough the latter is 30 times more abundant than the former in the water of the ocean. Vegetation cannot, however, entirely? shut out either excess of nutritive matters or bodies that are of no use or even poisonous to it. The functions of the Atmosphere are essentially the same towards plants, whether growing under the con- ditions of water-culture or under those of agriculture. The Soil, on the other hand, has offices which are pe- culiar to itself. We have seen that the roots of a plant have the power to decompose salts, e. g., potassium nitrate and ammonium chloride (p. 184), in order to appropriate one of their ingredients, the other being rejected. In water-culture, the experimenter must have a care to remove the substance which would thus accu- mulate to the detriment of the plant. In agriculture, the soil, by virtue of its chemical and physical qualities, commonly renders such rejected matters comparatively insoluble, and therefore innocuous. The Atmosphere is nearly invariable in its composi- tion at all times and over all parts of the earth's surface. Its power of directly feeding crops has, therefore, a nat- ural limit, which cannot be increased by art. The Soil, on the other hand, is very variable in com- position and quality, and may be enriched and improved, or deteriorated and exhausted. From the Atmosphere the crop can derive no appreci- able quantity of those elements that are found in its Ash. In the Soil, however, from the waste of both plants MOTION OF THE JUICES. 360 and animals, may accumulate large supplies of all the elements of the Volatile part of Plants. Carbon, cer- tainly in the form of carbon dioxide, probably or possi- bly in the condition of Humus (Vegetable Mold, Swamp Muck), may thus be put as food, at the disposition of the plant. Nitrogen is chiefly furnished to crops by the soil. Nitrates are formed in the latter from various sources, and ammonia-salts, together with certain proxi- mate animal principles, viz., urea, guanin, tyrosin, uric acid and hippuric acid, likewise serve to supply nitrogen to vegetation and are often ingredients of the best ma- nures. It is, too, from the soil that the crop gathers all the Water it requires, which not only serves as the fluid medium of its chemical and structural metamorphoses, but likewise must be regarded as the material from which it mostly appropriates the Hydrogen and Oxygen of its solid components. §2. THE JUICES OP THE PLANT, THEIR NATURE AND MOVEMENTS. "Very erroneous notions have been entertained with regard to the nature and motion of sap. It was formerly taught that there are two regular and opposite currents of sap circulating in the plant. It was stated that the "crude sap" is taken up from the soil by the roots, ascends through the vessels (ducts) of the wood, to the leaves, there is concentrated by evaporation, "elabor- ated" by the processes that go on in the foliage, and thence descends through the vessels of the inner bark, nourishing these tissues in its way down. The facts from which this theory of the sap naturally arose admit of a very different interpretation ; while numerous con- 370 HOW CROPS GROW. siderations demonstrate the essential falsity of the theory itself. Flow of Sap in the Plant — not Constant or Necessary. — We speak of the Flow of Sap as if a rapid current were incessantly streaming through the plant, as the blood circulates in the arteries and veins cf an ani- mal. This is an erroneous conception. A maple in early March, without foliage, with its whole stem enveloped in a nearly impervious bark, its buds wrapped up in horny scales, and its roots sur- rounded by cold or frozen soil, cannot be supposed to have its sap in motion. Its juices must be nearly or abso- lutely at rest, and when sap runs copiously from an ori- fice made in the trunk, it is simply because the tissues are charged with water under pressure, which escapes at any outlet that may be opened for it. The sap is at rest until motion is caused by a perforation of the bark and new wood. So, too, when a plant in early leaf is situa- ted in an atmosphere charged witli moisture, as happens on a rainy day, there is little motion of its sap, although, if wounded, motion may be established, and water may stream more or less from all parts of the plant towards the cut. Sap does move in the plant when evaporation of water goes on from the surface of the foliage. This always happens whenever the air is not saturated with vapor. When a wet cloth hung out, dries rapidly by giving up its moisture to the air, then the leaves of plants lose their water more or less readily, according to the nature of the foliage. Mr. Lawes found that in the moist climate of England common plants (Wheat, Barley, Beans. Peas, and Clover) exhaled, during five months of growth, more than 200 times their (dry) weight of water. Hellriegel, in the drier climate of Dahme, Prussia, observed exhalation to average 300 times the dry weight of various common MOTION" OF THE JUICES. 371 crops (p. 312). The water that thus evaporates from the leaves is supplied by the soil, and, entering the roots, more or less rapidly streams upwards through the stem as long as a waste is to be supplied, but this flow ceases when evaporation from the foliage is suppressed. The upward motion of sap is therefore to a great de- great independent of the vital processes, and compara- tively unessential to the welfare of the plant. Flow of Sap from the Plant; "Bleeding." — It is a familiar fact, that from a maple tree "tapped" in spring-time, or from a grape-vine wounded at the same season, a copious flow of sap takes place, which continues for a number of weeks. The escape of liquid from the vine is commonly termed " bleeding," and while this rapid issue of sap is thus strikingly exhibited in compar- atively few cases, bleeding appears to be a universal phe- nomenon, one that may occur, at least, to some- degree, under certain conditions with very many plants. The conditions under which sap flows are various, according to the character of the plant. Our perennial trees have their annual period of active growth in the warm season, and their vegetative functions are nearly suppressed during cold weather. As spring approaches the tree renews its growth, and the first evidence of change within is furnished by its bleeding when an open- ing is made through the bark into the young wood. A maple, tapped for making sugar, loses nothing until the spring warmth attains a certain intensity, and then sap begins to flow from the wounds in its trunk. The flow is not constant, but fluctuates with the thermometer, being more copious when the weather is warm, and fall- ing off or suffering check altogether as it is colder. The stem of the living maple is always charged with water, and never more so than in winter.* This water * Experiments made in Tharand, Saxony, under direction of Stoeck- hardt, show that the proportion of water, both in the bark and wood 372 HOW CROPS GROW. is either pumped into the plant, so to speak, by the root- power already noticed (p. 269), or it is generated in the trunk itself. The water contained in the stem in winter is undoubtedly that raised from the soil in the autumn. That which first flows from an auger-hole, in March, may be simply what was thus stored in the trunk ; but, as the escape of sap goes on for 14 to 20 days at the rate of several gallons per day from a single tree, new quantities of water must be continually supplied. That these are pumped in from the root is, at first thought, difficult to understand, because, as we have seen (p. 272), the root-power is suspended by a certain low tempera- ture (unknown in case of the maple), and the flow of sap often begins when the ground is covered with one or two feet of snow, and when we cannot suppose the soil to have a higher temperature than it had during the pre- vious winter months. Nevertheless, it must be that the deeper roots are warm enough to be active all the winter through, and that they begin their action as soon as the trunk acquires a temperature sufficiently high to admit the movement of water in it. That water may be pro- duced in the trunk itself to a slight extent is by no means impossible, for chemical changes go on there in spring-time with much rapidity, whereby the sugar of the sap is formed. These changes have not been suffi- ciently investigated, however, to prove or disprove the generation of water, and we must, in any case, assume that it is the root-power which chiefly maintains a pres- sure of liquid in the tree. The issue of sap from the maple tree in the sugar- season is closely connected with the changes of tempera- ture that take place above ground. The sap begins to of trees, varies considerably in different seasons of the year, ranging, in case of the beech, from 3D to 4!i per cent of tlie fresh-felled tree. The greatest proportion of water in the wood was found in the months of December and January; in the bark, in March to May. The minimum of water in the. wood 'occurred in May. June, and J'uly: in the. bark, much irregularity was observed. Chvni. Ai-kcrsmann, 1866, p. 159. MOTION OP THE JUICES. 373 flow from a cut when the trunk itself is warmed to a cer- tain point and, in general, the flow appears to be the more rapid the warmer the trunk. During warm, clear days, the radiant heat of the sun is absorbed by the dark, rough surface of the tree most abundantly ; then the temperature of the latter rises most speedily and acquires the greatest elevation — even surpasses that of the atmos- phere by several degrees ; then, too, the yield of sap is most copious. On clear nights, cooling of the tree takes place with corresponding rapidity ; then the snow or surface of the ground is frozen, and the flow of sap is checked altogether. From trees that have a sunny ex- posure, sap runs earlier and faster than from those hav- ing a cold northern aspect. Sap starts sooner from the spiles on the south side of a tree than from those towards the north. Duchartre (Comptes Rendus, IX, 754) passed a vine situated in a grapery, out of doors, and back again, through holes, so that a middle portion of the stem was exposed to a steady winter temperature ranging from 18° to 10° F., while the remainder of the vine, in the house, was surrounded by an atmosphere of 70° F. Under these circumstances the buds within developed vigor- ously, but those without remained dormant and opened not a day sooner than buds upon an adjacent vine whose stem was all out of doors. That sap passed through the cold part of the stem was shown by the fact that the interior shoots sometimes wilted, but again recovered their turgor, which could only happen from the partial suppression and renewal of a supply of water through the stem. Pay en examined the wood of the vine at the con- clusion of the experiment, and found the starch which it originally contained to have been equally removed from the warm and the exposed parts. That the rate at which sap passed through the stem was influenced by its temperature is a plain deduction 374 HOW CROPS GBOW. from the fact that the leaves within were found wilted in the morning, while they recovered toward noon, al- though the temperature of the air without remained below freezing. The wilting was no doubt chiefly due to the diminished power of the stem to transmit water ; the return of the leaves to their normal condition was probably the consequence of the warming of the stem by the sun's radiant heat.* One mode in which changes of temperature in the trunk influence the flow of sap is very obvious. The wood-cells contain, not only water, but air. Both are expanded by heat, and both contract by cold. Air, especially, undergoes a decided change of bulk in this way. Water expands nearly one-twentieth in being warmed from 32° to 212°, and air increases in volume more than one-third by the same change of temperature. "When, therefore, the trunk of a tree is warmed by the sun's heat, the air is expanded, exerts a pressure on the sap, and forces it out of any wound made through the bark and wood-cells. It only requires a rise of tempera- ture to the extent of a few degrees to occasion from this cause alone a considerable flow of sap from a large tree. (Hartig.) If we admit that water continuously enters the deep- lying roots whose temperature and absorbent power must remain, for the most part, invariable from day to day, we should have a constant slow escape of sap from the trunk were the temperature of the latter uniform and sufficiently high. This really happens at times during every sugar-season. When the trunk is cooled down to the freezing point, or near it, the contraction of air and water in the tree makes a vacuum there, sap ceases to flow, and air is sucked in through the spile ; as the trunk * The temperature of the nir is not always a sure indication of that of the solid bodies which it surrounds. A thermometer will often rise by exposure of the bulb to the direct rays of the sun, 30 or 40° above its indications when in the shade. MOTION OF THE JUICES. 375 becomes heated again, the gaseous and liquid contents of the ducts expand, the flow of sap is renewed, and pro- ceeds with increased rapidity until the internal pressure passes its maximum. As the season advances and the soil becomes heated, the root-power undoubtedly acts with increased vigor and larger quantities of water are forced into the trunk, but at a certain time the escape of sap from a wound suddenly ceases. At this period a new phenomenon supervenes. The buds which were formed the previous summer begin to expand as the vessels are distended with sap, and finally, when the temperature attains the proper range, they unfold into leaves. At this point we have a proper motion of sap in the tree, whereas before there was little motion at all in the sound trunk, and in the tapped stem the motion was towards the orifice and thence out of the tree. The cessation of flow from a cut results from two cir- cumstances : first, the vigorous cambial growth, where- by incisions in the bark and wood rapidly heal up ; and, second, the extensive evaporation that goes on from foliage. That evaporation of water from the leaves often pro- ceeds more rapidly than it can be supplied by the roots is shown by the facts that the delicate leaves of many plants wilt when the soil about their roots becomes dry, that water is often rapidly sucked into wounds on the stems of trees which are covered with foliage, and that the proportion of water in the wood of the trees of tem- perate latitudes is least in the months of May, June, and July. Evergreens do not bleed in the spring-time. The oak loses little or no sap, and among other trees great diver- sity is noticed as to the amount of water that escapes at a wound on the stem. In case of evergreens we have a stem destitute of all proper vascular tissue, and admit- 376 HOW CROPS GROW. ting a flow of liquid only through perforations of the wood-cells, if these really exist (which Sachs denies). Again, the leaves admit of continual evaporation, and furnish an outlet to the water. The colored heart-wood existing in many trees is impervious to water, as shown by the experiments of Boucherie and Hartig. Sap can only flow through the white, so-called sap-wood. In early June, the new shoots of the vine do not bleed when cut, nor does sap flow from the wounds made by break- ing them off close to the older stem, although a gash in the latter bleeds profusely. In the young branches, there are no channels that permit the rapid efflux of water. Composition of Sap. — The sap in all cases consists chiefly of water. This liquid, as it is absorbed, brings in from the soil a small proportion of certain saline mat- ters— the phosphates, sulphates, nitrates, etc., of potas- sium, calcium, and magnesium. It finds in the plant itself its organic ingredients. These may be derived from matters stored in reserve during a previous year, as in the spring sap of trees ; or may be newly formed, as in summer growth. The sugar of maple-sap, in spring, is undoubtedly pro- duced by the transformation of starch which is found abundantly in the wood in winter. According to Hartig (Jour, far Prakt. Ch., 5, p. 217, 1835), all deciduous trees contain starch in their wood and yield a sweet spring sap, while evergreens contain little or no starch. Hartig reports having been able to procure from the root- wood of the horse-chestnut in one instance no less than 26 per cent of starch. This is deposited in the tissues during summer and autumn, to be dissolved for the use of the plant in developing new foliage. In evergreens and annual plants the organic matters of the sap are derived more directly from the foliage itself. The leaves absorb carbon dioxide and unite its carbon to the ele- MOTION OF THE JUICES. 37 7 ments of water, with the production of sugar and other carbhydrates. In the leaves, also, probably nitrogen from the nitrates and ammonia-salts gathered by the roots, is united to carbon, hydrogen, and oxygen, in the formation of albuminoids. Besides sugar, malic acid and minute quantities of proteids exist in maple sap. Towards the close of the sugar-season the sap appears to contain other organic substances which render the sugar impure, brown in color, and of diiferent flavor. It is a matter of observation that maple-sugar is whiter, purer, and "grains " or crystallizes more readily in those years when spring-rains or thaws are least frequent. This fact would appear to indicate that the brown or- ganic matters which water extracts from leaf-mold may enter the roots of the trees, as is the belief of practical men. The spring-sap of many other deciduous trees of tem- perate climates contains sugar, but while it is cane sugar in the maple, in other trees it appears to consist mostly or entirely of dextrose. Sugar is the chief organic ingredient in the juice of the sugar cane, Indian corn, beet, carrot, turnip, and parsnip. The sap that flows from the vine and from many cul- tivated herbaceous plants contains little or no sugar-; in that of the vine, gum or dextrin is found in its stead. What has already been stated makes evident that we cannot infer the quantity of sap in a plant from what may run out of an incision, for the sap that thus issues is for the most part water forced up from the soil. It is equally plain that the sap, thus collected, has not the normal composition of the juices of the plant ; it must be diluted, and must be the more diluted the longer and the more rapidly it flows. TJlbricht has made partial analyses of the sap obtained 378 HOW CROPS GROW. from the stumps of potato, tobacco, and sun-flower plants. He found that successive portions, collected separately, exhibited a decreasing concentration. In sunflower sap, gathered in five successive portions, the liter contained the following quantities (grams) of solid matter : 1. 2. 3. 4. 5. Volatile substance,... 1.45 0.60 0.30 0.25 0.21 Ash, 1.58 1.56 1.18 0.70 0.60 Total, 3.03 2.1G 1.48 0.95 0.81 The water which streams from a wound dissolves and carries forward with it matters that, in the uninjured plant,, would probably suffer a much less rapid and ex- tensive translocation. From the stump of a potato-stalk would issue, by the mere mechanical effect of the flow of water, substances generated in the leaves, whose proper movement in the uninjured plant would be downwards into the tubers. Different Kinds of Sap. — It is necessary at this point in our discussion to give prominence to the fact that there are different kinds of sap in the plant. As we have seen (p. 289), the cross section of the plant pre- sents two kinds of tissue, the cellular and vascular. These carry different juices, as is shown by their chemi- cal reactions. In the cell-tissues exist chiefly the non- nitrogenous principles, sugar, starch, oil, etc. The liquid in these cells, as Sachs has shown, commonly con- tains also organic acids and acid-salts, and hence gives a red color to blue litmus. In the vascular tissue albumin- oids preponderate, and the sap of the ducts commonly has an alkaline reaction towards test papers. These dif- ferent kinds of sap are not, however, always strictly con- fined to either tissue. In the root-tips and buds of many plants (maize, squash, onion), the young (new- formed) cell-tissue is alkaline from the preponderance of MOTION" OF THE JUICES. 379 albuminoids, while the spring sap flowing from the ducts and wood of the maple is faintly acid. In many plants is found a system of channels (milk- ducts, p. 304), independent of the vascular bundles, which contain an opaque, white, or yellow juice. This liquid is seen to exude from the broken stem of the milk- weed (Asdepias), of lettuce, or of celandine (Chelidon- inm], and may be noticed to gather in drops upon a fresh-cut slice of the sweet potato. The milky juice often differs, not more strikingly in appearance than it does in taste, from the transparent sap of the cell-tissue and vascular bundles. The former is commonly acrid and bitter, while the latter is sweet or simply insipid to the tongue. Motion of the Nutrient Matters of the Plant. — The occasional rapid passage of a current of water up- wards through the plant must not be confounded with the normal, necessary, and often contrary motion of the nutrient matters out of which new growth is organized, but is an independent or highly subordinate process by which the plant adapts itself to the constant changes that are taking place in the soil and atmosphere as re- gards their content of moisture. A plant supplied with enough moisture to keep its tis- sues turgid is in a normal state, no matter whether the water within it is nearly free from upward flow or ascends rapidly to compensate the waste by evaporation. In both cases the motion of the matters dissolved in the sap is nearly the same. In both cases the plant develops nearly alike. In both cases the nutritive matters gath- ered at the root-tips ascend, and those gathered by the leaves descend, being distributed to every growing cell ; and these motions are comparatively independent of, and but little influenced by, the motion of the water in which they are dissolved. The upward flow of sap in the plant is confined to the 380 HOW CROPS GROW. vascular bundles, whether these are arranged symmetri- cally and compactly, as in exogenous plants, or distrib- uted singly through the stem, as in the endogens. This is not only seen upon a bleeding stump, but is made evi- dent by the oft-observed fact that colored liquids, when absorbed into a plant or cutting, visibly follow the course of the vessels, though they do not commonly penetrate the spiral ducts, but ascend in the sieve-cells of the cam- bium. * The rapid supply of water to the foliage of a plant, either from the roots or from a vessel in which the cut stem is immersed, goes on when the cellular tissues of the bark and pith are removed or interrupted, but is at once checked by severing the vascular bundles. The proper motion of the nutritive matters in the plant — of the salts disssolved from the soil and of the organic principles compounded from carbonic acid, water, and nitric acid or ammonia in the leaves — is one of slow diffusion, mostly through the walls of imperforate cells, and goes on in all directions. Xew growth is the forma- tion and expansion of new cells into which nutritive substances are imbibed, but not poured through visible passages. When closed cells are converted into ducts or visibly communicate with each other by pores, their ex- pansion has ceased. Henceforth they merely become thickened by interior deposition. Movements of Nutrient Matters in the Bark or Rind. — The ancient observation of what ordinarily ensues when a ring of bark is removed from the stem of an exo- genous tree, led to the erroneous assumption of a form- al downward current of " elaborated " sap in the bark. When a cutting from one of our common trees is girdled at its middle and then placed in circumstances favorable * As in T'nger's experiment of placing a hyacinth in the iuiee of the poke weed < Phytolacca\ or in Ilallicr's observations on cuttings dipped in cherry-juice. (.;*. .«., IX, p. 1.; MOTION OF THE JUICES. 381 Fig. 66. for growth, as in moist, warm air, with its lower extremity in water, roots form chiefly at the edge of the bark just above the removed ring. The twisting, or half-breaking, as well as ringing of a layer, promotes the development of roots. Latent buds are often called forth on the stems of fruit trees, and branches grow more vigorously, by making a transverse incision through the bark just below the point of their issue. Girdling a fruit-bearing branch of the grape-vine near its junction with the older wood has the effect of greatly enlarging the fruit. It is well known that a wide wound made on the stem of a tree heals up by the formation of new wood, and commonly the growth is most rapid and abundant above the cut. From these facts it was concluded that sap descends in the bark, and, not being able to pass below a wound, leads to the organization of new roots or wood just above it. The accompanying illustration, Fig. 66, represents the base of a cut- ting from an exogenous stem (pear or currant), girdled at />' and kept for some days immersed in water to the depth indicated by the line L. 382 HOW CROPS GROW. The first maifestation of growth is the formation of a protuberance at the lower edge of the bark, which is known to gardeners as a callous, C. This is an extension of the eellular tissue. From t lie callous shortly appear rootlets, Ji, which originate from the vascular tissue. Rootlets also break from the stem above the eallous and also above the water. if the air be moist. They appear, likewise, though in less number, below the girdled place. Nearly all the organic substances (carbhydrates, al- buminoids, acids, etc.) that are formed in a plant are produced in the leaves, and must necessarily find their way down to nourish the stem and roots. The facts just mentioned demonstrate, indeed, that they do go down in the bark. We have, however, no proof that there is a downward flow of sap. Such a flow is not indicated by a single fact, for, as we have before seen, the only current of water in the uninjured plant is the upward one which results from root-action and evapora- tion, and that is variable and mainly independent of the distribution of nutritive matters. Closer investigation has shown that the most abundant downward movement of the nutrient matters generated in the leaves proceeds in the thin-walled sieve-cells of the cambium, which, in exogens, is young tissue common to the outer wood and the inner bark — which, in fact, unites bark and wood. The tissues of the leaves communicate directly with, and are a continuation of, the cambium, and hence matters formed by the leaves must move most rapidly in the cambium. If they pass with greatest freedom through the sieve-cells, the fact is simply demonstration that the latter communicate most directly with those parts of the leaf in which the matters they conduct are organized. In endogenous plants and in some exogens (Pijjer me- dium, Amaranthu* sanyuineus], the vascular bundles containing sieve-cells pass into the pith and are not con- fined to the exterior of the stem. Girdling such plants does not give the result above described. With them, roots are formed chiefly or entirely at the base of the cutting (Hanstein), and not above the girdled place. MOTION OF THE JUICES. 383 In all cases, without exception, the matters organized in the leaves, though most readily and abundantly mov- ino1 downwards in the vascular tissues, are not confined O * to them exclusively. When a ring of bark is removed from a tree, the new cell-tissues, as well as the vascular, are interrupted. Notwithstanding, matters are trans- mitted downwards, through the older wood. When but a narrow ring of bark is removed from a cutting, roots often appear below the incision, though in less number, and the new growth at the edges of a wound on the trunk of a tree, though most copious above, is still de- cided below — goes on, in fact, all around the gash. Both the cell-tissue and the vascular thus admit of the transport of the nutritive matters downwards. In the former, the carbhydrates — starch, sugar, inulin — the fats, and acids, chiefly occur and move. In the large ducts, air is contained, except when by vigorous root- action the stem is surcharged with wacer. In the sieve- ducts (cambium) are found the albuminoids, though not unmixed with curbhydrates. If a tree have a deep gash cut into its stem (but not reaching to the colored heart- wood), growth is not suppressed on either side of the cut, but the nutritive matters of all kinds pass out of a vertical direction around the incision, to nourish the new wood above and below. Girdling a tree is not fatal, if done in the spring or early summer when growth is rapid, provided that the young cells, which form externally, are protected from dryness and other destructive influ- ences. An artificial bark, i. e., a covering of cloth or clay to keep the exposed wood moist and away from air, saves the tree until the wound heals over.* In these cases it is obvious that the substances which commonly preponderate in the sieve-ducts must pass through the * If the freshly exposed wood be nibbed or wiped with a cloth. whereby the moist eambial layer (of eells containing nuclei and capa- ble of multiplying) is removed, no growth can occur. Ratzeburg. 384 Sow CHOPS GROW. cell-tissue in order to reach the point where they nourish the growing organs. Evidence that nutrient matters also pass upwards in the bnrk is furnished, not only by tracing the course of colored liquids in the stem, but also by the fact that undeveloped buds perish in most cases when the stem is girdled between them and active leaves. In the excep- tions to this rule, the vascular bundles penetrate the pith, and thereby demonstrate that they are the chan- nels of this movement. A minority of these exceptions again makes evident that the sieve-cells are the path of transfer, for, as Hanstein has shown, in certain plants (Solanaceas, Asclepiadeas, etc.), sieve-cells penetrate the pith unaccompanied by any other elements of the vascu- lar bundle, and girdled twigs of these plants grow above as well as beneath the wound, although all leaves above the girdled place be cut off, so that the nutriment of the buds must come from below the incision. The substances which are organized in the foliage of a plant, as well as those which are imbibed by the roots, move to any point where they can supply a want. Garb- hydrates pass from the leaves, not only downwards, to nourish new roots, but upwards, to feed the buds, flow- ers, and fruit. In case of cereals, the power of the leaves to gather and organize atmospheric food nearly or altogether ceases as they approach maturity. The seed grows at the expense of matters previously stored in the foliage and stems (p. 237), to such an extent that it may ripen quite perfectly although the plant be cut when the kernel is in the milk, or even earlier, while the juice of the seeds is still watery and before starch-grains have begun to form. In biennial root-crops, the root is the focus of motion for the matters organized by growth during the first year ; but in the second year the stores of the root are completely exhausted for the support of flowers and seed, CAUSES OF THE MOTIOX OF JUICES. 385 so that the direction of the movement of these organized matters is reversed. In both years the motion of water is always the same, viz., from the soil upwards to the leaves. * The summing up of the whole matter is that the nutri- ent substances in the plant are not absolutely confined to any path, and may move in any direction. The fact that they chiefly follow certain channels, and move in this or that direction, is plainly dependent upon the structure and arrangement of the tissues, on the sources of nutriment, and on the seat of growth or other action. §3. THE CAUSES OF MOTION OF THE VEGETABLE JUICES. Porosity of Vegetable Tissues. — Porosity is a property of all the vegetable tissues and implies that the molecules or smallest particles of matter composing the tis- sues are separated from each other by a certain space. In a multitude of cases bodies are visibly porous. In many more we can see no pores, even by the aid of the highest magnifying powers of the microscope ; nevertheless the fact of porosity is a necessary inference from another fact which may be observed, viz., that of absorption. A fiber of linen, to the unassisted eye, has no pores. Under the microscope we find that it is a tubular cell, the bore being much less than the thickness of the walls. By immersing it in water it swells, becomes more trans- parent, and increases in weight. If the water be colored by solution of indigo or cochineal, the fiber is visibly * The motion of water is always upwards, because the soil always contains more water than the air. If a plant were so situated that its roots si ion Id steadily lack water while its foliage had an excess of this liquid, it cannot be doubted that then the "sap" would pass down in a regular How. In this case, nevertheless, the nutrient matters would take their normal course. 25 386 HOW CROPS GROW. penetrated by the dye. It is therefore porous, not only in the sense of having an interior cavity which becomes visible by a high magnifying power, but likewise in hav- ing throughout its apparently imperf orate substance in- numerable channels in which liquids can freely pass. In like manner, all the vegetable tissues are more or less penetrable to water. Imbibition of Liquids by Porous Bodies. — Xot onlv do the tissues of the plant admit of the access of water into their pores, but they forcibly drink in or aosoro tnis liquid, when it is presented to them in excess, until their pores are full. "When the molecules of a porous body have freedom of motion, they separate from each other on imbibing a liquid ; the body itself swells. Even powdered glass or fine sand perceptibly increases in bulk by imbibing water. Clay swells much more. Gelatinous silica, pectin, gum tragacanth, and boiled starch hold a vastly greater amount of water in their pores or among their molecules. In case of vegetable and animal tissues, or membranes, we find a greater ar less degree of expansibility from the same cause, but here the structural connection of the molecules puts a limit to their separation, and the result of saturating them with a liquid is a state of turgidity and tension, which subsides to one of yielding flabbiness when the liquid is partially removed. The energy with which vegetable matters imbibe water may be gathered from a well-known fact. In granite quarries, long blocks of stone are split out by driving plugs of dry wood into holes drilled along the desired line of fracture and pouring water over the plugs. The liquid penetrates the wood with immense force, and the toughest rock is easily broken apart. The imbibing power of different tissues and vegetable matters is widely diverse. In general, the younger or- gans or parts take up water most readily and freely. The CAUSES OF THE MOTION OF JUICES. 387 sap-wood of trees is far more absorbent than the heart- wood and bark. The cuticle of the leaf is often com- paratively impervious to water. Of the proximate ele- ments we have cellulose and starch-grains able to retain, even when air-dry, 10 to 15% of water. Wax and the solid fats, as well as resins, on the contrary, do not greatly attract water, and cannot easily be wetted with it. They render cellulose, which has been impregnated with them, unabsorbeut. Those vegetable substances which ordinarily manifest the greatest absorbent power for water, are the gummy carbhydrates and the albuminoids. In the living plant the protoplasmic membrane exhibits great absorbent power. Of mineral matters, gelatinous silica (Exp. 58, p. 137) is remarkable on account of its attraction for water. Not only do different substances thus exhibit unlike adhesion to water, but the same substance deports itself variously towards different liquids. One hundred parts of dry ox-bladder were found by Liebig to absorb during 24 hours : — 268 parts of pure Water. 133 " " saturated Brine. 38 " " Alcohol (84%). 17 " " Bone-oil. A piece of dry leather will absorb either oil or water, and apparently with equal avidity. If, however, oiled leather be immersed in water, the oil is gradually and perfectly displaced, as the farmer well knows from his experience with greased boots. India-rubber, on the other hand, is impenetrable to water, while oil of tur- pentine is imbibed by it in large quantity, causing the caoutchouc to swell up to a pasty mass many times its original bulk. The absorbent power is influenced by the size of the pores. Other things being equal, the finer these are, the greater the force with which a liquid is imbibed. This 388 HOW CROPS GROW. is shown by what has been learned from the study of a kind of pores whose effect admits of accurate measure- ment. A tube of glass, with a narrow, uniform caliber, is such a pore. In a tube of I millimeter (about ^ of an inch), in diameter, water rises 30 mm. In a tube of Jy millimeter, the liquid ascends 300 mm. (about 11 inches) ; and, in a tube of TJo mm., a column of 3,000 mm. is sustained. In porous bodies, like chalk, plaster stucco, closely packed ashes or starch, Jam in found that water was absorbed with force enough to overcome the pressure of the atmosphere from three to six times ; in other words, to sustain a column of water in a wide tube 100 to 200 ft. high. (Comptes Rendus, 50, p. 311.) Absorbent power is influenced by temperature. Warm water is absorbed by wood more quickly and abundantly than cold. In cold water starch does not swell to any striking or even perceptible degree, although consider- able liquid is imbibed. In hot water, however, the case is remarkably altered. The starch-grains are forcibly burst open, and a paste or jelly is formed that holds many times its weight of water. (Exp. 27, p. 51.) On freezing, the particles of water are mostly withdrawn from their adhesion to the starch. The ascent of liquids in narrow tubes whose walls are unabsorbent, is, on the contrary, diminished by a rise of temperature. Adhesive Attraction.— The absorption of a liquid into the cavities of a porous body, as well as its rise in a narrow tube, are expressions of the general fact that there is an attraction between the molecules of the liquid and the solid. In its simplest manifestation this attrac- tion exhibits itself as Adhesion, and this term we shall employ to designate the kind of force under considera- tion. If a clean plate of glass be dipped in water, the liquid touches, and sticks to, the glass. On withdraw- ing the glass, a film of water comes away with it — the adhesive force of water to glass being greater than the cohesive force among the water molecules. CAUSES OF THE MOTION OF JUICES. 389 Capillary Attraction. — If two squares of glass be Bet up together iipon a plate, so that they shall be in contact at their vertical edges on one side, and one- eighth of an inch apart on the other, it will be seen, on pouring a little water upon the plate, that this liquid rises in the space between them to a hight of several inches where they are in very near proximity, and curves downwards to their base where the interval is large. Capillary attraction, which thus causes liquids to rise in narrow channels or fine tubes, involves indeed the adhesion of the liqiiid to the walls of the tube, but also depends on a tension of the surface of the liquid, due to the fact that the molecules at the surface only attract and are only attracted by underlying molecules, so that they exert a pressure on the mass of liquid beneath them. "Where the liquid adheres to the sides of a containing tube or cavity, this pressure is diminished and there the liquid rises. Adhesion may be a Cause of Continual Move- ment under certain circumstances. When a new cotton wick is dipped into oil, the motion of the oil may be fol- lowed by the eye, as it slowly ascends, until the pores are filled and motion ceases. Any cause which removes oil from the pores at the apex of the wick will disturb the equilibrium which had been established between the solid and the liquid. A burning match held to the wick, by its heat destroys the oil, molecule after mole- cule, and this process becomes permanent when the wick is lighted. As the pores at the base of the flame give up oil to the latter, they fill themselves again from the pores beneath, and the motion thus set up propagates itself to the oil in the vessel below and continues as long as the flame burns or the oil holds out. We get a further insight into the nature of this motion when we consider what happens after the oil has all been sucked up into the wick. Shortly thereafter the dimen- 390 HOW CROPS GROW. sions of the flame are seen to diminish. It does not, however, go out. but burns on for a time with continually decreasing vigor. When the supply of liquid in the por- ous body is insufficient to saturate the latter, there is still the same tendency to equalization and equilibrium. If, at last, when the flame expires, because the combus- tion of the oil falls below that rate which is needful to generate heat sufficient to decompose it, the wick be placed in contact at a single point, with another dry wick of equal mass and porosity, the oil remaining in the first will enter again into motion, will pass into the second wick, from pore to pore, until the oil has been shared nearly equally between them. In case of water contained in the cavities of a porous body, evaporation from the surface of the latter becomes remotely the cause of a continual upward motion of the liquid. The exhalation of water as vapor from the foliage of a plant thus necessitates the entrance of water as liquid at the roots, and maintains a flow of it in the sap-ducts, or causes it to pass by absorption from cell to cell. Liquid Diffusion. — The movements that proceed in plants, when exhalation is out of the question, viz., such as are manifested in the stump of a vine cemented into a gauge (Fig. 43, p. 248), are not to be accounted for by capillarity or mere absorptive force under the conditions a? yet noticed. To approach their elucidation we require to attend to other considerations. The particles of many different kinds of liquids attract each other. Water and alcohol may be mixed together in all proportions in virtue of their adhe ive attraction. If we fill a vial with water to the rim and carefully lower it to the bottom of a tall jar of alcohol, we shall find after some hours that alcohol has penetrated the vial, and water has passed out into the jar, notwithstanding the latter liquid is considerably heavier than the former. CAUSES OF THE MOTION OF JUICES. 391 If the water be colored by indigo or cherry juice, its motion may be followed by the eye, and after a certain lapse of time the water and alcohol will be seen to have become uniformly mixed throughout the two vessels. This manifestation of adhesive attraction is termed Liq- uid Diffusion. What is true of two liquids likewise holds for two solutions, i. e., for two solids made liquid by the action of a solvent. A vial filled with colored brine, or syrup, and placed in a vessel of water, will discharge its con- tents into the latter, itself receiving water in return ; and this motion of the liquids will not cease until the whole is uniform in composition, i. e., until every mole- cule of salt or sugar is equally attracted by all the moje- cules of water. When several or a large number of soluble substances are placed together in water, the diffusion of each one throughout the entire liquid will go on in the same way until the mixture is homogeneous. Liquid Diffusion may be a Cause of Continual Movement whenever circumstances produce continual disturbances in the composition of a solution or in that of a mixture of liquids. f If into a mixture of two liquids we introduce a solid body which is able to combine chemically with, and solidify one of the liquids, the molecules of this liquid will begin to move toward the solid body from all points, and this motion will cease only when the solid is able to combine with no more of the one liquid, or no more remains for it to unite with. Thus, when quicklime is placed in a mixture of alcohol and water, the water is in time completely condensed in the lime, and the alcohol is rendered anhydrous. Rate of Diffusion. — The rate of diffusion varies with the nature of the liquids ; if solutions, with their degree of concentration and with the temperature. 392 HOW CROPS GROW. Colloids and Crystalloids. — There is a class of bodies whose molecules are singularly inactive in many respects, and have, when dissolved in water or other liquid, a very low capacity for diffusive motion. These bodies are termed Colloids,* and are characterized by swelling up or uniting with water to bulky masses (hydrates) of gelatinous consistence, by inability to crystallize, and by feeble and poorly-defined chemical affinities. Starch, dextrin, the gums, the albuminoids, pectin and pectic acid, gelatin (glue), tannin, the hydroxides of iron and aluminium and gelatinous silica, are colloids. Opposed to these, in the properties just specified, are those bodies Avhich crystallize, such as saccharose, glucose, oxalic, citric, and tartaric acids, and the ordinary salts. Other bodies which have never been seen to crystallize have the same high diffusive rate ; hence the class is termed by Graham Crystalloids.} Colloidal bodies, when insoluble, are capable of imbib- ing liquids, and admit of liquid diffusion through their molecular interspaces. Insoluble crystalloids are, on the other hand, impenetrable to liquids in this sense. The colloids swell up more or less, often to a great bulk, from absorbing a liquid ; the volume of a crystalloid admits of no such change. In his study of the rates of diffusion of various sub- stances, dissolved in water to the extent of one per cent of the liquid, Graham found the following APPKOXIMATE TIMES OF EQUAL DIFFUSION. Hydrochloric acid, Crystalloid. 1. Sodium Chloride, " 2J. fane Sugar, " 7. Magnesium Sulphate, " 7. Albumin, Colloid, 49. Caramel, " 98. * From two Greek words which signify glue-like. t Wo have already employed the word ('ri/.*f7>. This use of the word was proposed bv Xageli, in 1862. Graham had employed it, as opposed to colloid, in 1861. CAUSES OF THE MOTION OF JUICES. 393 The table shows that the diffusive activity of hydro- chloric acid through water is 98 times as great as that of caramel (see p. G6, Exp. 29). In other words, a mole- cule of the acid will travel 98 times as far in a given time as the molecule of caramel. Osmose,* or Membrane Diffusion. — When two miscible liquids or solutions are separated by a porous diaphragm, the phenomena of diffusion (which depend upon the mutual attraction of the molecules of the dif- ferent liquids or dissolved substances) are complicated with those of imbibition or capillarity, and of chemical affinity. The adhesive or other force which the septum is able to exert upon the liquid molecules supervenes upon the mere diffusive tendency, and the movements may suffer remarkable modifications. If we should separate pure water and a solution of common salt by a membrane upon whose substance these liquids could exert no action, the diffusion would pro- ceed to the same result as were the membrane absent. Molecules of water would penetrate the membrane on one side and molecules of salt on the other, until the liquid should become alike on both. Should the water move faster than the salt, the volume of the brine would increase, and that of the water would correspondingly diminish. Were the membrane fixed in its place, a change of level of the liquids would occur. Graham has observed that common salt actually diffuses into water, through a thin membrane of ox-bladder deprived of its outer muscular coating, at very nearly the same rate as when no membrane is interposed. Dutrochet was the first to study the phenomena of membrane diffusion. He took a glass funnel with a long and slender neck, tied a piece of bladder over the wide opening, inverted it, poured in brine until the funnel was filled to the neck, and immersed the bladder in a * From a Greek word meaning impulsion. 394 HOW CROPS GROW. vessel of water. He saw the liquid rise in the narrow tube and fall in the outer vessel. He designated the passage of water into the funnel as endosmose, or inward propulsion. At the same time he found the water sur- rounding the funnel to acquire the taste of salt. The outward transfer of salt was his exosmose. The more general word, Osmose, expresses both phenomena ; we may, however, employ Dutrochet's terms to designate the direction of osmose. Osmometer. — When the apparatus employed by Dutrochet is so con- structed that the diameter of the nar- row tube has a known relation to, is, for example, exactly one-tenth that of the membrane, and the narrow tube itself is provided with a millimeter scale, we have the Osmometer of Grah- am, Fig 67. The ascent or descent of the liquid in the tube gives a measure of the amount of osmose, provided the hydrostatic pressure is counterpoised by making the level of the liquid with- in and without equal, for which pur- pose water is poured into or removed from the outer ves- sel. Graham designates the increase of volume in the osmometer as 'positive osmose, or simply osmose, and dis- tinguishes the fall of liquid in the narrow tube as nega- tive osmose. In the figure, the external vessel is intended for the reception of \vater. The funnel-shaped interior vessel is closed below with mem- bran^, and stands upon a shelf of perforated zinc for support. The graduated tube fits the neck of the funnel by a ground joint. Action of the Membrane. — When an attraction exists the membrane itself and one or more of the substances between which it is interposed, then the rate, amount, and even direction, of diffusion may be greatly changed, CAUSES OF THE MOTIOX OF JUICES. 395 Water is imbibed by the membrane of bladder much more freely than alcohol ; on the other hand, a film of collodion (cellulose nitrate left from the evaporation of its solution in ether) is penetrated much more easily by alcohol than by water. If, now, these liquids be sepa- rated by bladder, the apparent flow will be towards the alcohol ; but if a membrane of collodion divide them, the more rapid motion will be into the water. When a vigorous chemical action is exerted upon the membrane by the liquid or the dissolved matters, osmose is greatly heightened. In experiments with a septum of porous earthenware (porcelain biscuit), Graham found that in case of neutral organic bodies, as sugar and alco- hol, or neutral salts, like the alkali-chlorides and nitrates, very little osmose is exhibited, i. e., the diffusion is not perceptibly greater than it would be in absence of the porous diaphragm. The acids, — oxalic, nitric, and hydrochloric, — mani- fest a sensible but still moderate osmose. Sulphuric and phosphoric acids, and salts having a decided alka- line or acid reaction, viz., acid potassium oxalate, sodi- um phosphate, and carbonates of potassium and sodium, exhibit a still more vigorous osmose. For example, a solution of one part of potassium carbonate in 1,000 parts of water gains volume rapidly, and to one part of the salt that passes into the water 500 parts of water enter the solution. In all cases where diffusion is greatly modified by a membrane, the membrane itself is strongly attacked and altered, or dissolved, by the liquids. When animal membrane is used, it constantly undergoes decomposi- tion and its osmotic action is exhaustible. In case earthenware is employed as a diaphragm, portions of its calcium and aluminium are always attacked and dis- solved by the solutions upon which it exerts osmose. Graham asserts that to induce osmose in bladder, the 396 HOW CROPS GROW. chemical action on the membrane must be different on the two sides, and apparently not in degree only, but also in kind, viz., an alkaline action on the albuminoid substance of the membrane on the one side, and an acid action on the other. The water appears always to accu- mulate on the alkaline or basic side of the membrane. Hence, with an alkaline salt, like potassium carbonate, in the osmometer, and water outside, the flow is inwards ; but with an acid in the osmometer, there is negative osmose, or the flow is outwards, the liquid then falling in the tube. •Osmotic activity is most highly manifested in such salts as easily admit of decomposition with the setting free of a part of their acid, or alkali. Hydration of the membrane. — It is remarkable that the rapid osmose of potassium carbonate and other alkali-salts is greatly interfered with by common salt, is, in fact, reduced to almost nothing by an equal quantity of this substance. In this case it is probable that the physical effect of the salt, in diminishing the power of the membrane to imbibe water (p. 393), operates in a sense inverse to, and neutralizes the chemical action of, the carbonate. In fact, the osmose of the carbonate, as well as of all other salts, acid or alkaline, may be due to their effect in modifying the hydration* or power of the membrane, to imbibe the liquid, which is the vehicle of /their motion. Graham suggests this view as an explana- tion of the osmotic influence of colloid membranes, and it is not unlikely that in case of earthenware, the chem- ical action may exert its effect indirectly, viz., by pro- ducing hydrated silicates from the burned clay, which are truly colloid and analogous to animal membranes in respect of imbibition. Graham has shown a connection between the hydrating effect of acids and alkalies on colloid membranes and their osmotic rate» * In case water is employed as the liquid. CAUSES OF THE MOTION OF JUICES. 397 "It is well known that fibrin, albumin, and animal membrane swell much more in very dilute acids and alkalies than in pure water. On the other hand, when the proportion of acid or alkali is carried beyond a point peculiar to each substance, contraction of the colloid takes place. The colloids just named acquire the power of combining with an increased proportion of water and of forming higher gelatinous hydrates in conse- quence of contact with dilute acid or alkaline reagents. Even parchment-paper is more elongated in an alkaline solution than in pure water. When thus hyd rated and dilated, the colloids present an extreme osmotic sensibility." An illustration of membrane-diffusion which is highly instructive and easy to produce, is the following : A cavity is scooped out in a carrot, as in Fig. 68, so that the sides remain £ inch or so thick, and a quantity of dry, crushed sugar is introduced ; after some time, the previ- ously dry sugar will be converted into a syrup by withdrawing water from the flesh of the carrot. At the same time the latter will visibly shrink from the loss of a por- tion of its liquid contents. In this case Fig. 68. ^ne sma]i portions of juice moistening the cavity form a strong solution with the sugar in contact with them, into which water diffuses from the adjoining cells. Doubtless, also, sugar penetrates the parenchyma of the carrot. In the same manner, sugar, when sprinkled over thin- skinned fruits, shortly forms a syrup with the water which ib thus withdraws from them, and salt packed with fresh meat runs to brine by the exosmose of the juices of the flesh. In these cases the fruit and the meat shrink as a result of the loss of water. Graham observed gum tragacanth, which is insoluble 398 HOW CEOPS GROW. in water, to cause a rapid passage of water through a membrane in the same manner from its power of imbibi- tion, although here there could be no exosmose or out- ward movement. The application of these facts and principles to explain- ing the movements of the liquids of the plant is obvioiu. The cells and the tissues composed of cells furnish pre- cisely the conditions for the manifestation of motion by the imbibition of liquids and by simple diffusion, as well as by osmose. The disturbances needful to maintain motion are to be found in the chemical changes that accompany the processes of nutrition. The substances that normally exist in the vegetable cells are numerous, and they suffer remarkable transformations, both in chemical constitution and in physical properties. The rapidly-diffusible salts that are presented to the plant by the soil, and the equally diffusible sugar and organic acids that are generated in the leaf-cells, are, in part, converted into the sluggish, soluble colloids, soluble starch, dextrin, albumin, etc., or are deposited as solid matters in the cells or upon their walls. Thus the dif- fusible contents of the plant not only, but the mem- branes which occasion and direct osmose, are subject to perpetual alterations in their nature. More than this, the plant grows ; new cells, new membranes, new pro- portions of soluble and diffusible matters, are unceas- ingly brought into existence. Imbibition in the cell- membranes and their solid, colloid contents, Diffusion in the liquid contents of the individual cells, and Osmose between the liquids and dissolved matters and the mem- branes, or colloid contents of the cells, must unavoid- ably take place. That we cannot follow the details of these kinds of action in the plant does not invalidate the fact of their operation. The plant is so complicated and presents such a number and variety of changes in its growth, CAUSES OF THE MOTION OF JUICES. 399 that we can never expect to understand all its mysteries. From what has been briefly explained, we can compre- hend some of the more striking or obvious movements that proceed in the vegetable organism. Absorption and Osmose in Germination. — The absorption of water by the seed is the first step in Ger- mination. The coats of the dry seed, when put into the moist soil, imbibe this liquid which follows the cell-walls, from cell to cell, until these membranes are saturated and swollen. At the same time these membranes occa- sion or permit osmose into the cell-cavities, which, dry before, become distended with liquid. The soluble con- tents of the cells, or the soluble results of the transforma- tion of their organized matters, diffuse from cell to cell in their passage to the expanding embryo. The quantity of water imbibed by the air-dry seed commonly amounts to 50 and may exceed 100 per cent. R. Hoffmann has made observations on this subject (Vs. St.,\II, p. 50). The absorption was usually complete in 48 or 72 hours, and was as follows in case of certain agricultural plants : — Per cent. Per cent. Mustard 8.0 Millet 25.0 Maize 44.0 Wheat 45.5 Buckwheat 46.8 Barley 48.2 Turnip 51 .0 Rye 57.7 Oats 59.8 Hemp 60.0 Kidney Bean 96.1 Horse Bean 104.0 Pea 106.8 Clover 117.5 Beet 120.5 White Clover 126.7 Root-Action. — Absorption at the roots is unquestion- ably an osmotic action exercised by the membrane that bounds the young rootlets and root-hairs externally. In principle it does not differ from the absorption of water by the seed. The mode in which it occasions the sur- prising phenomena of bleeding or rapid flow of sap from a wound on the trunk or larger roots is doubtless essen- tially as Hofmeister first elucidated by experiment. This flow proceeds in the ducts and wood-cells. Between these and the soil intervenes loose cell- tissue 400 HOW CROPS GRO\V. A surrounded by a compacter epidermis. Osmose takes place in the epidermis with such energy as not only to distend to its utmost the cell-tissue, but to cause the water of the cells to filter through their walls, and thus gain access to the ducts. The latter are formed in young cambial tissue, and, when new, are very delicate in their walls. Fig. 69 represents a simple apparatus by Sachs for imitating the supposed mechanism and process of Eoot- action. In the Fig., g g represents a short, wide, open glass tube ; at a, the tube is tied over and se- curely closed by a piece of pig's bladder ; it is then filled with solution of sugar, and the other end, b, is closed in similar manner by a piece of parch- ment-paper (p. 59). Finally a cap of India-rub- ber, K, into whose neck a narrow, bent glass tube, r, is fixed, is tied on over b. (These join- ings must be made very carefully and firmly.) The space within r K is left empty of liquid, and r the combination is placed in a vessel of water, as in the figure. C represents a root-cell whose exterior wall (cuticle), a, is less penetrable under pressure than its interior, b; r corres- ponds to a duct of vas- cular tissue, and the surrounding water takes the place of that Fig. 69. existing in the pores of the soil. The water shortly penetrates the cell, C, dis- tends the previously flabby membranes, under the accu- mulating tension filters through b into r, and rises in the tube ; where in Sachs's experiment it attained a height of 4 or 5 inches in 24 to 48 hours, the tube, r, being about 5 millimeters wide and the area of b, 700 sq. CAUSES OP THfl MOTION OF JUICES. 401 mm. When we consider th° vast root-surface exposed to the soil, in case of a vine, and that myriads of root- lets and root-hairs unite their action in the compara- tively narrow stem, we must admit that the apparatus above figured gives us a very satisfactory glance into the causes of bleeding. Motion of Nutritive or Dissolved Matters; Se- lective Power of the Plant. — The motion of the sub- stances that enter the plant from the soil in a state of solution, and of those organized within the plant is, to a great degree, separate from and independent of that which the water itself takes. At the same time that water is passing upwards through the plant to make good the waste by evaporation from the foliage, sugar or other carbhydrate generated in the leaves is diffusing against the water, and rinding its way down to the very root-tips. This diffusion takes place mostly in the cell- tissue, and is undoubtedly greatly aided by osmose, i. e., by the action of the membranes themselves. The very thickening of the cell- walls by the deposition of cellulose would indicate an attraction for the material from which cellulose is organized. The same transfer goes on sim- ultaneously in all directions, not only into roots and stem, but into the new buds, into flowers and fruit. We have considered the tendency to equalization between two masses of liquid separated from each other by pen- etrable membranes. This tendency makes valid for the organism of the plant the law that demand creates sup- ply. In two contiguous cells, one of which contains solution of sugar, and the other solution of potassium nitrate, these substances must diffuse until they are mingled equally, unless, indeed, the membranes or some other substance present exerts an opposing and prepon- derating attraction. In the simplest phases of diffusion each substance is, to a certain degree, independent of every other. Any 26 402 HOW CROPS GROW. salt dissolved in the water of the soil must diffuse into the root-cells of a plant, if it be absent from the sap of this root-cell and the membrane permit its passage. When the root-cell has acquired a certain proportion of the salt, a proportion equal to that in the soil- water, more cannot enter it. So soon as a molecule of the salt has gone on into another cell or been removed from the sap by any chemical transformation, then a molecule may and must enter from without. Silica is much more abundant in grasses and cereals than in leguminous plants. In the former it exists to the extent of about 25 parts in 1,000 of the air-dry foli- age, while the leaves and stems of the latter contain but 3 parts. When these crops grow side by side, their roots are equally bathed by the same soil-water. Silica enters both alike, and, so far as regards itself, brings the cell-contents to the same state of saturation that exists in the soil. The cereals are able to dispose of silica by giving it a place in the cuticular cells ; the leguminous crops, on the other hand, cannot remove it from their juices ; the latter remain saturated, and thus further diffusion of silica from without becomes impos- sible except as room is made by new growth. It is in this way that we have a rational and adequate explana- tion of the selective power of the plant, as manifested in its deportment towards the medium that invests its roots. The same principles govern the transfer of mat- ters from cell to cell, or from organ to organ, within the plant. Wherever there is unlike composition of two miscible juices, diffusion is thereby set up, and proceeds as long as the cause of disturbance lasts, provided im- penetrable membranes do not intervene. The rapid movement of water goes on because there is great loss of this liquid ; the slow motion of silica is a consequence of the little use that arisos for it in the plant. Strong chemical affinities may V overcome by help of CAtJSES OF THE MOTION OF JUICES. 403 osmose. Graham long ago observed the decomposition of alum (sulphate of aluminium and potassium) by mere diffusion ; its potassium sulphate having a higher diffu- sive rate than its aluminium sulphate. In the same manner acid potassium sulphate, put in contact with water, separates into neutral potassium sulphate and free sulphuric acid.* We have seen (pp. 170-1) that the plant, when veg- etating in solutions of salts, is able to decompose them. It separates the components of potassium nitrate — appro- priating the acid and leaving the base to accumulate in the liquid. It resolves chloride of ammonium, — taking up ammonia and rejecting the hydrochloric acid. The action in these cases we cannot definitely explain, but our analogies leave no doubt as to the general nature of the agencies that cooperate to such results. The albuminoids in their usual form are colloid bodies, and very slow of diffusion through liquids. They pass a collodion membrane somewhat (Schu- macher), but can scarcely penetrate parchment-paper (Graham). In the plant they are found chiefly in the sieve-cells and adjoining parts of the cambium. Since for their production they must ordinarily require the concourse of a carbhydrate and a nitrate, they are not unlikely generated in the cambium itself, for here the descending carbhydrates from the foliage come in con- tact with the nitrates as they rise from the soil. On the other hand, the albuminoids become more diffusible in some of their combinations. Schumacher asserts that carbonates and phosphates of the alkalies considerably increase the osmose of albumin through collodion mem- branes (Physik der Pflanzen, p. 128). It is probable that those combinations or modifications of the albuminoids *The decomposition of these salts is begun by the water In which they are dissolved, and is carried on by osmose, because the latter secures separation of the rein-tins substances. 404 HOW CROPS GROW. which occur in the soluble crystalloids of aleurone (p. 105) and haemoglobin (p. 97) are highly diffusible, as certainly is the case with the peptones. Gaseous bodies, especially the carbonic acid and oxy- gen of the atmosphere, which have free access to the intercellular cavities of the foliage, and which are for the most part the only contents of the larger ducts, may bo distributed throughout the plant by osmose after having been dissolved in the sap or otherwise absorbed by the cell-contents. Influence of the Membranes. — The sharp separa- tion of unlike juices and soluble matters in the plant indicates the existence of a remarkable variety and range of adhesive attractions. In orange-colored flowers we see upon microscopic examination that this tint is pro- duced by the united effect of yellow and red pigments which are contained in the cells of the petals. One cell is filled with yellow pigment, and the adjoining one with red, but these two colors are never contained in the same cell. In fruits we have coloring matters of great tinctorial power and freely soluble in water, but they never forsake the cells where they appear, never wander into the contiguous parts of the plant. In the stems and leaves of the dandelion, lettuce, and many other plants, a white, milky, and bitter juice is contained, but it is strictly confined to certain special channels and never visibly passes beyond them. The loosely disposed cells of the interior of leaves contain grains of chloro- phyl, but this substance does not appear in the epidermal cells, those of the stomata excepted. Sachs found that solution of indigo quickly entered the roots of a seedling bean, but required a considerable time to penetrate the stem. Hallier, in his experiments on the absorption of colored liquids by plants, noticed, in all cases when leaves or green stems were immersed in solution of indigo, or black-cherry juice, that these dyes readily passed into CAUSES OF THE MOTION OF JUICES. 405 and colored the epidermis, the vascular and cambial tis- sue, and the parenchyma of the leaf-veins, keeping strictly to the cell-walls, but in no instance communi- cated any color to the cells containing chlorophyl. (Phytopathologie, Leipzig, 1868, p. 67.) We must infer that the coloring matters either cannot penetrate the cells that are occupied with chlorophyl, or else are chem- ically transformed into colorless substances on entering them. Sachs has shown in numerous instances that the juices of the sieve-cells and cambial tissue are alkaline, while those of the adjoining cell-tissue are acid when examined by test-paper. (Exp. Phys. der Pflanzen, p. 394.) When young and active cells are moistened with solu- tion of iodine, this substance penetrates the cellulose without producing visible change, but when it acts upon the protoplasm, the latter separates from the outer cell- wall and collapses towards the center of the cavity, as if its contents passed out, without a corresponding endos- mose being possible (p. 224). We may conclude from these facts that the membranes of the cells are capable of effecting and maintaining the separation of substances which have considerable attrac- tions for each other, and obviously accomplish this result by exerting their superior attractive or repulsive force. The influence of the membrane must vary in character with those alterations in its chemical and structural con- stitution which result from growth or any other cause. It is thus, in part, that the assimilation of external food by the plant is directed, now more to one class of proximate ingredients, as the carbhydrates, and now to another, as the albuminoids, although the supplies of food presented are uniform both in total and relative quantity. If a slice of red-beet be washed and put into water, the pigment which gives it color does not readily dissolve 406 HOW CROPS GEW. and diffuse out of the cells, but the water remains coloi. less for several days. The pigment is, however, soluble in water, as is seen at once by crushing the beet, where- by the cells are forcibly broken open and their contents displaced. Tbe cell-membranes of the uninjured root are thus apparently able to withstand the solvent power of water upon the pigment and to restrain the hitter from diffusive motion. Upon subjecting the slice of beet to cold until it is thoroughly frozen, and then plac- ing it in warm water so that it quickly thaws, the latter is immediately and deeply tinged with red. The sudden thawing of the water within the pores of the cell-mem- brane has in fact so altered them, that they can no longer prevent the diffusive tendency of the pigment. (Sachs.) § 4. MECHANICAL EFFECTS OF OSMOSE ON THE PLANT. The osmose of water from without into the cells of the plant, whether occurring on the root-surface, in the buds, or at any intermediate point where chemical changes are going on, cannot fail to exercise a great me- chanical influence on the phenomena of growth. Root- action, for example, being, as we have seen, often suffi- cient to overcome a considerable hydrostatic pressure, might naturally be expected to accelerate the develop- ment of buds and young foliage, especially since, as com- mon observation shows, it operates in perennial plants, as the maple and grape-vine, most energetically at the season when the issue of foliage takes place. Experi- ment demonstrates this to be the fact. If a twig be cut from a tree in winter and be placed in a room having a summer temperature, the buds, before dor- MECHANICAL EFFECT OF OSMOSE ON PLANTS. 407 ZVT mant, shortly exhibit signs of growth , and if the cut end be immersed in wa- ter, the buds will enlarge quite after the normal manner, as long as the nu- trient matters of the twig last, or until the tissues at the cut begin to decay. It is the summer temperature which excites the chemical changes that re- sult in growth. Water is needful to occupy the expanding and new-form- ing cells, and to be the vehicle for the translocation of nutrient matters from the wood to the buds. Water enters the cut stem by imbibition or capillar- ity, not merely enough to replace loss by exhalation, but is also sucked in by osmose acting in the growing cells. Under the same conditions as to tem- perature, the twigs which are connected with active roots expand earlier and more rapidly than cuttings. Artificial pressure on the water which is pre- sented to the latter acts with an effect similar to that which the natural stress caused by the root-power exerts. This fact was demonstrated by Boehm (Sitzungsberichte der Wiener Akad., 1863), in an experiment which may be made as illustrated by the cut, Fig. 70. A twig with buds is secured by means of a perforated cork into one end of a short, wide glass tube, which is closed below by another cork through which passes a narrow syphon-tube, B. The cut end of the twig is immersed In water, W, which is put under pressure by pouring mercury into the upper 408 HOW CROPS GROW. extremity of the syphon-tube. Horse-chestn ut and grape twigs cut in February and March and thus treated — the pressure of mercury being equal to six to eight inches above the level, M — after four to six weeks, unfolded their buds with normal vigor, while twigs similarly cir- cumstanced but without pressure opened four to eight days later and with less appearance of strength. Fr. Schulz (Karsteri's Bat. Unters., Berlin, II, 143) found that cuttings of twigs in the leaf, from the horee- chestnut, locust, willow and rose, subjected to hydro- static pressure in the same way, remained longer turges- cent and advanced much further in development of leaves and flowers than twigs simply immersed in Avater. The amount of water in the soil influences both the absolute and relative quantity of this ingredient in the plant. It is a common observation that rainy spring weather causes a rank growth of grass and straw, while the yield of hay and grain is not correspondingly in- creased. The root-action must operate with greater effect, other things being equal, in a nearly saturated soil than in one which is less moist, and the young cells of a plant situated in the former must be subjected to greater internal stress than those of one growing in the latter — must, as a consequence, attain greater dimen- sions. It is not uncommon to find fleshy roots, espec- ially radishes which have grown in hot-beds, split apart lengthwise, and Hallier mentions the fact of a sound root of petersilia splitting open after immersion in water for two or three days. (Pliytopathologie, p. 87.) This mechanical effect is indeed commonly conjoined with others resulting from abundant nutrition, but increased bulk of a plant without corresponding increase of dry matter is doubtless in great part the consequence of large supplies of water to the roots and its vigorous osmose into the expanding plant. APPENDIX. COMPOSITION OF VARIOUS AGRICULTURAL PRODUCTS giving the Aver- ago quantities of Water, Nitrogen, Ash, and Ash-ingredients in 1,000 parts of fresh or air-dry substances. According to Prof. E. von WOLFF, 1880. Water. Nitrogen. 01 3 Potash. & 01 8 1 3 Magnesia. Phosphor- ic Acid. Sulphuric Acid. Silica. Chlorine. GRASSES. Rich pasture grass Young grass and after- math 7S2 SOO 700 700 700 SCO S20 800 740 S20 SO.", SSO S5II S70 !I20 sir, !>:i:; 7!Ci 707 Slil) SOO 750 8! 10 '.100 !t()4 '.!.-,( i '.140 '.>:;:! !io:: 888 14:: 140 144 140 14:; 14:; I4:i 144 14.1 14-; 7.2 5.6 5.7 5.4 6.0 5.3 4.8 7.2 5.3 5.6 1.8 2.2 2.1 1.8 1.6 1.9 5.4 4.3 2.7 3.2 3.4 2.4 3.0 4.0 1.6 3.2 4.9 4.7 17.1; 20.7, 10.0 20.:, 16.0 20.8 16.0 17.6 21.1 18.1 17.8 20.4 20.5 14.0 14.7 13.7 19.2 8.6 14.3 9.1 8.2 7.5 6.4 7.1 4.9 10.0 19.7 7.4 9.8 9.5 15.6 9.6 8.0 5.8 8.1 5.0 16.0 10.0 26.7 29.6 12.4 lii.n is.;! 22.:! 1S.O 16.8 17.0 17.9 8.1 5.3 5.9 7.1 7.1 5.1 5.5 4.4 4.5 2.4 3.1 4.8 3.0 :!..-> 2.<) 3.8 1.6 5.4 7.7 2.5 4.7 5^8 5.8 4.3 3.6 2.4 3.7 1.2 2.7 :,.! 4.8 3.3 3.7 3.3 5.6 4.7 (i.2 5.2 2.8 i 5.8 0.3 0.7 O.S 0.7 0.4 0.3 0.3 0.3 0.3 0.3 1.0 l.r> 1.7 0.4 O.(i 0.8 1.0 0.2 0.4 0.2 1.0 0.8 1.5 O.S o.r, 0.0 o.s O.'.t 5.7 0.2 0.4 0.4 0.1 0.5 0.3 0.5 0.3 0.3 0.7 0 '\ 2.6 2.5 1.1 1.5 1.7 3.9 4.5 4.8 8.5 2.9 4.3 0.3 0.9 0.9 0.7 0.4 0.7 1.1 2.0 1.6 0.3 0.3 2.8 1.2 0.5 0.4 0.5 0.6 1.9 0.1 1.0 0.2 0.3 0.2 0.5 0.6 0.5 0.1 0.5 1.2 1.2 0.5 0.4 0.7 1.3 1.6 .1.5 0.9 1.1 1.4 0.4 0.4 0.3 0.2 0.6 0.2 0.6 0.4 0.3 0.3 0.5 0.6 0.4 0.3 0.2 0.2 0.2 1.0 0.3 1.9 2.8 1.9 2.4 2.2 2.0 2.2 2.0 2.1 2.0 1.9 1.4 1.3 2.2 2.4 1.7 1.5 1.3 1.6 0.9 1.8 0.8 1.1 1.1 0.8 0.9 0.5 1.9 2.0 1.3 1.4 1.6 1.4 1.1 1.6 1.2 0.7 0.9 1.6 3.4 6.8 6.5 5.7 8.1 9.0 7.8 9.2 7.9 5.6 8.5 0.7 1.0 0.5 0.8 0.6 0.3 0.4 0.4 1.1 0.4 1.1 0.3 0.5 0.7 0.7 0.3 0.3 *).5 4.11 0.4 0.6 0.6 2.4 1.3 1.0 0.4 o.;! 0.3 1.1 0.4 0.5 0.1 0.1 0.2 0.4 O.I 0.5 Of> 4.1 4.6 5.9 6.5 6.6 0.4 0.4 0.4 1.8 0.3 0.6 0.2 0.2 0.1 0.1 0.2 0.2 1.5 0.7 0.2 0.2 0.1 0.1 0.3 0.5 1.3 0.5 0.7 0.1 10.5 15.6 0.3 1.2 0.3 5.8 0.2 0.3 4.9 0.3 2.1 1.1 1.3 2.1 1.1 0.6 0.5 0.5 0.6 0.5 0.6 0.9 0.4 0.5 0.3 0.3 0.5 0.4 0.3 0.2 0.4 0.3 1.3 0.5 0.3 0.4 0.4 0.3 1.0 0.1 0.3 0.1 0.2 0.1 0.2 0.1 0 1 Orchard grass, Timothy, CLOVK1!* AM) LKlir.MKS. Ited clover, young, Red clover in had, Red clover in flower, . . . Lucorn or Alfalfa, in Alsike clover, White clover in llo\ver, ROOTS, TUBERS, BULKS. Meets Carrots, Rutabagas, Turnips, Sugar-beets, Radish Parsnip Horseradish, Onion Artichoke, Helurnth i/s,. Potato, " VK.iiKTABLES." C a b b a g e, loose outer leaves, Cabbage, heart, Cauliflower, heart, Cucumber, fruit, Lettuce, Asparagus, sprouts Spiuago, Mushroom*, edible, SKKDS OF CEREALS. Oals, Millet, Maize, Sorghum, Spring Wheat, Spring I'.arlev, Spring Rye Winter Wheat, Winter Barley Winter Rve.. .' 410 HOW CROPS GROW. COMPOSITION OF VAKIOUS AGRICULTURAL PRODUCTS.— [rv Water. Nitrogen. | Potaoh. 08 - C V § 3 r. 1 1 it -, •T ~ =< V. Silica. Chlorine. SEEDS OF LEGUMES AND CLOVERS. Morse bean. I'it-id, Garden bean, Phaseolus, Soy bean, 15(1 loo 14:; 150 150 77 122 11* S25 s:;s s:;o 150 150 1.17 ic,r, 1(10 15(1 1(15 1(10 1(10 14:; 14:; 150 14:; 14:; 14:; 1(10 1(10 14:; 14:1 14:; 140 ISO ISO 120 HIS 140 112 loo 40.8 39.0 53.4 :;5.s 30.5 36.5 26.1 32.8 0.6 0.6 1.7 18.5 25.5 19.1 16.3 35.5 24.5 19.7 12.5 23.2 24.0 23.0 5.6 6.4 4.8 5.6 4.8 4.0 13.0 10.4 6.4 5.8 7.2 2.3 34.8 24.6 25.0 62.1 47.2 31.0 27.4 2X.3 23.4 38.3 33.8 33.8 3G.5 2.2 3.3 3.9 2.9 8.8 29.7 82.4 76.0 59.4 S2.3 (ls.4 r,7.n 44.7 (il.l 48.0 (12.0 61.6 45.il 45.:; 38.1 4(1.0 3x.2 51.7 71 .2 S2.7 !I2.0 4.5 140.7 .14.7 8L7 72.9 IK1.4 51.3 12.9 12.1 12..; 10.1 13.5 12.3 lo.'.l 9.4 10.0 6.9 0.8 1.8 2.0 1.7 5.0 7.7 31.6 22.3 19.3 20.2 2". (.7 25.3 18.6 10.0 13.1 11.1 14. c, 16.3 10.7 1.1.4 11.0 6.3 24! 2 9.9 4.5 5.2 s.4 2.3 4o.:' 2S.2 9.7 5.5 17.9 15.X 0.3 0.4 o.:! 0.2 ol> 2..", 0.4 0.7 2.0 O.C, o.:; 0.1 0.1 0.4 1.:; 3.0 1.0 2.0 I.!t 1.4 1.1 1.4 4.4 1.2 1.1 2.0 l.C, 0.5 1.0 O.C, 0.7 1.1 l.x 2.!' o.:; 1.7 o.l 4.5 6.6 2.5 o.<; l.'.i OS 1.5 1.5 1.7 1.1 2.5 2.5 1.9 10.9 2.6 7.0 0.1 0.3 0.3 0.3 1.0 7.1 10.1 10.4 3.4 4.3 23.5 20.7 20.1 15.8 18.4 13.6 25.2 4.:; 3.3 4.9 2.6 2.7 4.0 3.5 1.7 0.2 50.7 12.4 6.9 16.8 18.7 2.9 4.3 2.2 2.1 2.5 1.9 4.9 3.9 5.r, 2.<; 4.7 3.7 0.2 0.2 0.2 0.2 0.4 2.4 4.6 5.1 1.7 1.3 7.6 7.(1 6.3 6.9 5.8 5.0 3.1 2.3 1.2 2.6 0.9 1.1 1.2 1.9 3.5 1.5 1.1 1.2 0.2 10.4 0.5 2.0 2.1 7.0 10.1 8.1 12.1 9.7 10.4 s.4 14.5 11.6 10.5 n;.!t u'iii 0.3 0.5 O.C, 0.4 1.4 2.7 7.4 5.9 5.6 6.2 10.0 6.9 5.6 4.4 7.8 4.1 5.3 2.8 1.9 3.8 2.0 2.2 2.5 6.1 3.6 1.3 5.6 4.0 0.2 fl.C, '1.2 4.2 2.1 5.s ;o.5 1.1 1.1 O.X O.s 0.9 1.6 0.7 0.1 0.8 1.8 0.1 0.2 0.2 0.1 0.5 1.4 2.7 4.1 1.5 2.3 1.8 1.7 1.9 1.4 4.5 1.6 3.6 2.0 1.8 2.4 1.2 i!<; 2.7 2.7 3.5 0.1 0.1 8.5 2.2 2.0 0.6 2.9 0.8 1,7 0.2 0.2 0.2 0.5 0.8 0.1 5.5 0.4 0.9 0.1 0.1 0.4 0.1 0.3 7.2 15.9 19.4 24.7 is. 5 2.5 1.8 1.6 3.0 2.7 1.6 5.9 28.8 23.4 13.1 18.2 31.0 18.8 2.9 2J 50.4 (1.1.4 74.7 1.3 s.1 l.C, 1.7 i::.:; 5.5 64 0.5 0.3 0.1 0.4 0.5 0.5 0.5 0.2 0.1 0.1 0.7 8.4 4.5 2.3 6.1 3.3 2.4 2.2 1.3 2.6 2.2 1.9 a 0.6 0.8 O.X 0.8 4.1 2.3 0.8 0.4 0.2 9.4 2.4 1.3 0.6 3.7 04 Pea White Clover, OIL .SKI 1'-. Cotton, Flax, FRUITS. Apple, entire fruit, Pear, entire fruit, Cherry, entire fruit, — Grape, entire fruit HAY. Alpine hay, From very young grass. From young grass and From cereals cut in English rye grass, Ited Clover, young, Red Clover in bud, lied clover in flower,.. Red Clover, ripe, White Clover in flower, Alsike Clover, Luoern (Alfalfa) early STRAW. Oat Karlev, Mai/e Winter Wheat, Winter Rye, Pea, CHAFF, KTC. Oat Chaff, live Chaff, Wheat Chaff, MISCELLANEOUS. Tobacco leaves, Tobacco stems, Mops, entire plant, Cottonseed Cake, Linseed Cake.. . INDEX. Absorption by the root, 260, 269, 272 Access of air to Interior of Plant 313 Afcotic Acid 76 Acetamide, 115 Acids, Definition of 81 Acids, Test for 82 Acid elements 127 Acid-proteids 99 Adhesion, 9,388 Agriculture, Art of 1 Agricultural products, Compo- sition in 1,000 parts, . . .409 Agricultural Science, Scope of . 7 Air-passages in plant, .... 313 Air-roots, 273 Akene, 331 Albumin, 89 Albuininates, 99 Albuminoids, Characters and composition, ... 87, 104, 106 Albuminoids in animal nutrit- ion, 108 Albuminoids, Diffusion of . . .403 Albuminoids in oat-plant, . . 234 Albuminoids, Mutual relations of 107 Albuminoids, Proportion of, in vegetable products, . . . 114 Albumose, 101 Alburnum, 305 Alourone, 110 Alkali-earths, 81, 139 Alkali-earths, Metals of . . .139 Alkali-metals, 138 Alkalies, 81, 138 Alkali-proteids 99 Alkaloids, 120 Allylsulphocyanate, 129 Alumina, 143 Aluminium, 143 Aluminium phosphate, .... 28 Amides, 114, 118 Amido-acids, 114, 118 Amidoacetic acid, 115 Amidocaproic acid, 116 Amidovaleric acid, 116 Amidulln, 52 Amines, 119 Ammonium Carbonate, ... 33 Ammonium Salts in plant, 82, 113 Amylan, . . . • 62 411 Amyloid 43 Amylodextrin, 63 Amyloses, 39, 40 Anhydrous phosphoric a'cid, . 132 Anhydrous sulphuric acid, . .130 Anther, 318 Apatite, 148 Arabic acid, 58 Arabin, 58 Arabinose, 65 Arrow root, 48 Arsenic in plants, . . . 137, 210 Ash-ingredients, .... 126, 161 Ash-ingredients, Excess of . . 201 Ash-ingredients, Excess of, how disposed of, 203 Ash-ingredients, Function of in plant, 210 Ash-ingredients, State of, in plant, 207 Ash of plants, 13, 126 Ash of plants, Analyses, Tables of 164 Ash of plants, Composition of, normal, 177 Ash of plants, Composition of, variations in 151 Ash, Proportions of, Tables, . .152 Asparagin, 116 Assimilation, 364 Atmosphere, Offices of . . . .367 Atoms, 30 Atomic weight, 31 Avenin, 120 Bark, 291, 297 Barium in plants, 210 Bases, Definition of 81 Bast-cells, Bast-tissue, 293, 295, 297 Bean, Leaf, Section of ... .308 Bean, Seed, 334 Berry, 331 Betam, 116 Biology, 10 Bleeding of vine, .... 271, 371 Blood-fibrin, 91 Bone-black, 15 Boron, Boric acid, 210 Buds, Structure of 283 Buds, Development under pres- sure, 406 Bulbs, 289 Butyric acid, 76 412 HOW CROPS GROW. Caesium, Action on oat, . . .209 Caffein, 117 Calcium, 139, 214 Calcium, carbonate, 145 Calcium, hydroxide, .... 143 Calcium, oxide, 139 Calcium, phosphate, . . .28,148 Calcium, sulphate, 146 Callous, 382 Calyx, 317 Cambium 294, 295,299 Cane-sugar, 65 Capillary attraction, . . . . sae Carbamide, 115 Carbh ydrates 39 Carbhydrates. Composition . . 72 Carbhydrates, Transformations of 70 Carbon, Properties of .... 14 Carbon in ash, 128 Carbon dioxide, 128 Carbonates 128, 144 Carbonate of lime, 145 Carbonate of potash, 144 Carbonate of soda, 144 Carbonic acid, 19, 128 Carbonic acid as food of plant, 328 Carbonic acid in ash-analyses, 149 Carboxyl, 75, 77 Casein, 84 Caseose, 101 Cassava, 51 Causes of motion of juices, . .385 Cell-contents, 249 Cell-multiplication, 252 Cell, Structure of 245 Cells, Forms of 247 Cellular plants, 243 Cellular tissue, 255 Cellulose, 40 Cellulose, Composition .... 44 Cellulose, Estimation .... 45 Cellulose nitrates, 43 Cullulose sulphates, 43 Cellulose, Test for 44 Cellulose, Quantity of, in plants, 46 Chemical affinity, 29 Chemical affinity overcome by osmose, '.403 Chemical combination, ... 29 Chemical decomposition, . . . 30 Chemistry, 10 Chlorides, 133, 149 Chloride of ammonium, decom- posed by plant 184 Chlorine, . . 132 Chlorine essential to crops '.' . .1!>4 Chlorine, function in plant, . 218 Chlorine in strand plants. . .191 Chlorophyl, 124, 307, 308 Chlorophyl requires iron, . .220 Chlorophyllan, 125 Choline, .* 119 Circulation of sap, 369 Citric acid 80 Citrates 80,149 Classes of plants, 329 Classification botanical, . . .328 Clover, washed by rain, . . . 204 Colloids 392 Con-lutin 95,97 Combustion 18 Composite plants, 330 Concentration of plant-food, .185 Concretions in plant, . . . .205 Coniferous plants, 330 Copper in plants, 210 Cork, 2i»s Corm, -'ss Corolla :M7 Cotyledon 290,333 Coniferous plants, :>'-'>(] Cryptogams, 315, 329 Crystalloid aleurone, . . . .111 Crystalloids :•>;'- Crystals in plant, 2m: Culms 2*4 Cyanides, 127. rj'.i ( 'yanogen, 12:> Definite proportions, Law of . . :;o Density of seeds 339 J»epth of sowing, 355 Dextrin, 53 Dextrose, *'>'•> Diastase, ...... 67, 10::. ::r.o Diffusion of liquids, . . . Dm-cious plants 318 Drains stopped by roots, . . .276 Drupe * 331 Dry weather, Effect of, on "plants, 157 Ducts 255,294 Dulcite, 74 Dundonald's treatise on Agri- cultural Chemistry, ... 4 Elements of Matter, 8 Kmbryo, 333 Endogens, 259,290,334 Endosmose, 3! '4 Endosperm, •'!•';_' En/ymes 103 Epidermis 2x Fat in oat crop 230 Fat in Vegetable Products. . , XT Ferments Hi2 Ferric oxide 142 Ferric hydroxide, 11- Ferric salts 142 Ferrous oxide 141 Ferrous hydroxide, 141 Ferrous salts, 1 12 Fertili/ation, 319 Fibrin, ,. .. .91, :*; INDEX. 413 Fihrinogen 91,96 Flax fiber. Fig 41, 248 Flax seed mucilage, . . . 58,62 Flesh fibrin, 92 Flower 317 Flow of sap, 371 Fluorine in plants, 209 Foliage, Offices of 314 Food of Plant, 366 Formative layer, 245 Formulas. Chemical, . . . 33, 73 Fructification 3l!» Friii-iose, 63 Fruit 33(1 Galaetin, 61 (ialactnse 65 Gases, how distributed through- out the plant, 404 (ielatiuous Siliea, 136 Genus ; Genera, 328 (ierin. 333 Germination, 349 termination, Conditions of . . 351 Germination, Chemical Physi- ology of 357 Girdling, :!s:: dauber's Salt, 14U Gliadin 92 <;iobulin, IN; Glueoses 39, 63 (;iueosi Growth, 252 Growth of roots, i':,i; Gum, Amount of, In plants, . .62 Gum Arabic, 57 Gum Tragacanth, 57 ! iji/onum, convolvulus, Fertil- ization of, Fig., 295 Pome, 331 Porosity of vegetable tissues, ..".-<.-> Potato leaf, Pores of, Fig., . . 309 Potato stem, Section of, Fig., .304 Potato tuber, Structure and Sec- tion of, Fig., 300 Potash, 138, 144 Potash lye, 139 Potassium, 138,211 Potassium carbonate, . . . .144 Potassium Chloride, 149 Potassium hydroxide, . . . .139 Potassium oxide, 138 Potassium phosphate, . . . .147 Potassium silicate, 134 Potassium sulphate, 146 Prosenchyma, 2">5 Protagon, 123 Proteoses, 100 Protoplasm 245 Protein bodies, or Proteids, . . 87 Proximate Principles, . . . .37 Quack grass, 287 Quantitative relations among ingredients of plant, . . . 220 Quartz, 134 Quince seed mucilage, . ... OB Radicle, 333 Rafflnose, 68 Reproductive Organs, . . 243, 315 Rhizome 287 Rind, 297 Rock Crystal, 134 Root-action, imitated, . . . .400 Root-action, Osmose in ... 399 Root cap, 257 Root distinguished from stem, 258 Root excretions, 280 Root hairs, 265 Root, Seat of absorptive force in, 270,399 Root stock, 287 Rootlets, 260 Roots, Growth of 256 Roots contact with soil, . . . 266 Roots going down for water, . .L'T"' Roots, Search of food by . . . 263 Roots. Quantity of 263 Rubidium action on oat, . . . 209 Runners 286 Saccharose, 60 Saccharose, Amount of, in plants, 66 Sago -51 Salicin 69 Salicornia, 191 Sal-soda, 145 Salsola 191 Salts. Definition of 81 Salts, in ash of plants, . . . .143 Saltwort 191 INDEX. 415 Samphire, 191 Sap, 369 Sap, Acid and alkaline . .. . .378 Sap ascending, 379, 384 Sap descending 382 Sap, Composition of 376 Sap of sunflower, 378 Sup, Spring flow of . . . , . 370 Sap wood, 305 Saponification, 85 Saxifraya crustata, 206 Seed, 332 Seed vessel, 330 Seed, Ancestry of 346 Seeds, constancy of composition 145 Seeds, Density of 339 Seeds, Weight of 340 Seeds, Water imbibed by. . .399 Selective power of plant, . . .401 Seminose, 65 Sepals, 317 Sieve-cells, 303 Sieve-cells In pith, .... 343, 345 Silica 134 Silica- entrance into plant, . .402 Silica, Function of, in plant, . 216 Silica in ash, 197 Silica in textile materials, . . 200 Silica unessential to plants, . .197 Silicates, 134 Silicate of potassium, . . . .134 Silicic acids, 135 Silicon, 134 Silicon, Dioxide 134 Silk of maize, ...... .319 Silver-grain 299 Sinapin, 120 Soaps, 93 Sodium, 139 Sodium carbonate 144 Sodium essential to ag. plants? 186 Sodium hydroxide, 139 Sodium in strand and marine plants, • .191 Sodium oxide, 139 Sodium sulphate, 146 Sodium, Variations of, in field- crops, 188 Sodium Chloride, 149 Soil. Offices of 368 Solanin, 121 Solution of starch in Germina- tion, 358, 361 Soluble silica, 135 Soluble starch 52 Species 326 Spirits of salt, 133 Spongioles, 257 Spores 316 Sports, 327 Stamens, 318 Starch, amount in plants, . . 51 Starch-cellulose, ...... 50 Starch estimation, 52 Starch in wood, 373, 376 Starch, Properties of .... 47 Starch, Test for 49 Stearic acid, 86 Stearin, 85 Stem, Endogenous 290 Stem, Exogenous 296 Stem, Structure of 289 Stems 282 Stigma, 318 Stomata, 309 Stool, 287 Suckers 287 Sucroses, 39, 65 Sugar, Estimation of 65 Sugar, in cereals, 69 Sugar in Sap, 377 Sugar of milk, 68 Sulphate of lime, 146 Sulphate of potash, 146 Sulphate of soda, 146 Sulphates, 26,131,146 Sulphates, Function of ... .210 Sulphates reduced by plant, . 208 Sulphides, 26, 130 Sulphide of potassium, . . . .130 Sulphites 129 Sulphur, 25, 129 Sulphur in oat, 208 Sulphur dioxide, . .... 25,130 Sulphureted hydrogen, . .26, 115 Sulphurets, 26 Sulphuric acid, 26, 130 Sulphuric acid in oat, . . . .208 Sulphuric oxide (SOS), .... 209 Sulphur trioxide (SO3), . . .25, 130 Sulphurous acid, 25, 129 Symbols, Chemical 31 Tao-foo, 96 Tapioca, 51 Tap-roots, 259 Tartaric acid, 80 Tartrates, 80 Tassels of maize, 319 Theobromin 118 Tillering 287 Titanic acid, 137 Titanium, 137, 209 Translocation of substances in plant, 237 Trvpsin, 104 Tubers, 273,288 Tuscan hat-wheat, 158 Tyrosin, 116 Ultimate Composition of Vege- table Matters 13, 29 Umbelliferous plants, .... 330 Unripe seed, Plants from . . .338 Urea, 115 Valence, 35 Varieties, 158,326,327 Vascxilar bundle of maize stalk, 291,293 Vascular-tissue, 255 Vegetable acids, 75 Vegetable albumin, 90 Vegetable casein, 94 Vegetable cell, 243 Vegetable fibrin, 92 Vegetable globulins, 97 Vegetable mucilage, 57 Vegetable inyosins, 98 416 HOW CROPS GROW. Vegetable parchment, .... 44 Vegetable tissue, 246 Vi'nvtative organs, 243 Vcrniu, 118 Vicin, 120 Vitality of roots, 282 Vitality of seeds, 335 Vltellin, 96 \\'at(>r. Composition of . ... 37 Water, Estimation of . . . . 39 Water. Formation of .... 24 Water in air-dry plants .... 39 Water In fresh plants, . ... 38 Water in vegetation, Free ... 39 Water in vegetation, Hygro- scopic, . . • 39 Watrr-ovoii, 38 Water-culture, 181 Water-glass, 135 Water Hoots, 273 Wax, 83 Wood, 41, 305 Wood cells, 293 Wood cells of conifers, . . . .301 Woody stems, 305 Woody tissue 255 Xylin, 61 Xylose, 62 Feast 103 Zanthophyl, 125 Zein,' 93 Zinc 21fl STANDARD BOOKS. Commended hy the Greatest Educators of Germany, England and the Unite* States. Endorsed by Officials, and adopted in many Schools Hew methods in Education Art. Real Manual Training, Nature Study. Explaining Processes whereby Hand, Eye and Mind are Educated by Means that Conserve Vital- ity and Develop a Union of Thought and Action By 1. 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Chanters are devoted to the economic erection and use of barns, grain barns, house barns, cattle barns, sheep barns, corn houses, smoke houses, ice houses, pig pens, granaries, etc. There are likewise chapters on bird houses, dog houses, tool sheds, ventila- tors, roofs and roofing, doors and fastenings, workshops, poultry houses, manure sheds, barnyards, root pits, etc. Cloth, 12mo $1.0G Cranberry Culture. By Joseph J. White. Contents: Natural history, history of cultivation, choice of location, preparing the ground, planting the vines, management of meadows, flooding, enemies and difficulties overcome, picking, keeping, pro- fit and loss. Cloth, 12mo $1.00 Ornamental Gardening for Americans. By Elias A. Long, landscape architect. A treatise on beautifying homes, rural districts and cemeteries. A plain and practical work with numerous illustrations an\± instructions so plain that they may be readily followed. Illustrated. Cloth, 12mo $1.50 Grape Culturist. By A. S. Fuller. This is one of the very best of works on the culture of the hardy grapes, with full directions for all departments of propagation, culture, etc., with 150 excellent engravings, illustrating planting, training, grafting, etc. Cloth, 12mo $1.50 STANDARD BOOKS. Turkeys and How to Grow Them. Edited by Herbert Myrick. A treatise on the natural his- tory aad origin of the name of turkeys; the various breeds, the best methods to insure success in the business of turkey growing. With essays from practical turkey growers in different parts of the United States and Can- ada. Copiously illustrated. Cloth, 12mo. . . $1,00 Profits I' Poultry. Usetti/ and ornamental breeds and their profitable man- agement. This excellent work contains the combined experience of a number of practical men in all depart- ments of poultry raising. It is profusely illustrated and forms a unique and important addition to our poultry literature. Cloth, 12mo $1.00 How Crops Grow. By Prof. Samuel W. Johnson of Yale College. New and revised edition. A treatise on the chemical composition, structure and life of the plant. This book is a guide to the knowledge of agricultural plants, their composition, their structure and modes of development and growrth; of the complex organization of plants, and the use of the parts; the germination of seeds, and the food of plants obtained both from the air and the soil. The book is indispensable to all real students of agriculture. With numerous illustrations and tables of analysis. Cloth, 12mo. $1.50 Coburn's Swine Husbandry. By F. D. Coburn. New, revised and enlarged edition. The breeding, rearing, and management of swine, and the prevention and treatment of their diseases. It is the full- est and freshest compendium relating to swine breeding yet offered. Cloth, 12mo $1.50 Stewart's Shepherd's Manual. By Henry Stewart. A valuable practical treatise on the sheep for American farmers and sheep growers. It is so plain that a farmer or a farmer's son who has never kept a sheep, may learn from its pages how to manage a flock successfully, and yet so complete that even the experienced shepherd may gather many suggestions from it. The results of personal experience of some years with the characters of the various modern breeds of sheep, and the sheep raising capabilities of many por- tions of our extensive territory and that of Canada — and the careful study of the diseases to which our sheep are chiefly subject, with those by which they may even- tually be afflicted through unforeseen accidents — as well as the methods of management called for under our circumstances, are carefully described. Illustrated. Cloth, 12mo, . . $1.00 STANDARD BOOKS. Feeds and Feeding. By W. A. Henry. This handbook for students and stock men constitutes a compendium of practical and useful knowledge on plant growth and animal nutrition, feed- ing stuffs, feeding animals and every detail pertaining to this important subject. It is thorough, accurate and reliable, and is the most valuable contribution to live stock literature in many years. All the latest and best information is cleai ly and systematically presented, mak- ing the work indispensable to every owner of live stock. 658 pages, 8vo. Cloth. . . . . . . . $2.00 Hunter and Trapper. By Halsey Thrasher, an old and experienced sportsman. The best modes of hunting and trapping are fully ex- plained, and foxes, deer, bears, etc., fall into his traps readily by following his directions. Cloth, 12mo. $ .50 The Ice Crop. By Theron L. Hiles. How to harvest, ship and use ice. A complete, practical treatise for farmers, dairymen, ice dealers, produce' shippers, meat packers, cold storers, and all interested in ice houses, cold storage, and the handling or use of ice in any way. Including many recipes for iced dishes and beverages. The book is illustrated by cuts of the tools and machinery used in cutting and storing ice, and the different forms of ice houses and cold storage buildings. 122 pp., ill., 16mo. Cloth. $1.0« Practical Forestry. By Andrew S. Fuller. A treatise on the propagation, planting and cultivation, with descriptions and the botan- ical and popular names of all the indigenous trees of the United States, and notes on a large number of the most valuable exotic species $1.50 Irrigation for the Farm, Garden and Orchard. By Henry Stewart. This work is offered to those Amer- ican farmers and other cultivators of the soil who, from painful experience, can readily appreciate the losses which result from the scarcity of water at critical periods. Fully illustrated. Cloth, 12mo $1.00 Market Gardening and Farm Notes. By Burnett I^andreth. Experiences and observation for both North and South, of interest to the amateur gar- dener, trucker and farmer. A novel feature of the book is the calendar of farm and garden operations for each month of the year; the chapters on fertilizers, trans- planting, succession and rotation of crops, the packing, shipping and marketing of vegetables will be especially useful to market gardeners. Cloth, 12mo. . . $1.00 5 Jfcz. l°}00 THE LIBRARY UNIVERSITY OF CALIFORNIA Santa Barbara THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW.