GIFT F 
 Prol. E. JVwickson 
 
 B10L03Y 
 
Edward J. '. 
 
 MEE 
 
 BY 
 MAXWELL T. MASTERS, M.D., F.R.S. 
 
 NEW YORK: 
 
 ORANGE JUDD COMPANY, 
 
 751 BROADWAY. 
 
 1885. 
 
Q \< HI 
 
 BIOLOGY 
 
 LIBRARY 
 
 G 
 
 J t 
 
 MAIM UiMtARY.*tft*COi.TUttC 
 
 Entered, according to Act of Congress, in the year 1884, by the 
 ORANGE JUDU COMPANY, 
 
 lu the Office of the Librarian oi Congress, at Washington. 
 
PREFACE 
 
 Rightly to understand what work is done by living 
 plants, and how it is effected, not only requires a student 
 to be a botanist in the ordinary sense of the word, but 
 necessitates that he should also have a comprehensive 
 knowledge of physics and of chemistry. 
 
 In few individuals can such an extensive knowledge 
 now-a-days be expected. The practical cultivator espe- 
 cially, harrassed by the daily cares of his occupation, is 
 not able to master the endless details of these sciences ; 
 and yet experience shows the increasing necessity for 
 furnishing him with new tools and new weapons to 
 enable him to utilize the resources of Nature, and to 
 contend against adverse circumstances. Such tools, such 
 weapons are furnished by the armory of science. It is 
 the object of this Handbook to point out the nature of 
 these resources, and suggest the methods of utilizing 
 them. Something will be gained if only a right appre- 
 ciation of what cannot be done is obtained, as thereby 
 labor on a sterile soil will be avoided, to be applied with 
 more reasonable hope of success elsewhere. 
 
 In the following pages an attempt has, therefore, been 
 made to supply a sketch, necessarily in faintest outline, 
 of the physiology or life-history of plants ; of the way in 
 which they are affected by the circumstances under which 
 they exist, and of the manner in which they in their turn 
 react upon other living beings and upon natural forces* 
 Of necessity, there has been a little overlapping in the 
 case of some of the subjects treated of in the companion 
 volume, " The Chemistry of the Farm," by Mr. Waring- 
 ton ; but as the matters are looked at from a different 
 
 (in) 
 
 "^ ~ * * 
 
 6 
 
IV PKEFAC& 
 
 stand-point, and as no pretence is here made to impart 
 special chemical knowledge, it is hoped that Mr. Waring- 
 ton and the reader also will forgive any slight incursions 
 into a territory which the writer has no claim to enter 
 except upon sufferance. 
 
 Structural botany, whether dealing with the outer con- 
 formation or the internal organization of plants, is only 
 incidentally treated of in these pages ; the classification 
 of plants is also passed over without notice, as not coming 
 within the scope of this Handbook. 
 
 Detailed text-books of Botany, or of Vegetable Phy- 
 siology, expressly adapted to the requirements of agri- 
 culturists do not exist, but there are many works from 
 which a comprehensive general idea of the present state 
 of knowledge of these subjects may be obtained. 
 
 In the compilation of the following pages the writer 
 has availed himself of Van Tieghem's " Traite de Botani- 
 que," the French translation of Sachs' " Physiologie 
 Vegetale" by Micheli, and Deherain's " Cours de Chimie 
 Agricole," etc. The works and memoirs of Darwin have, 
 of course, been laid under contribution, as well as nu- 
 merous scattered papers by various authors. More es- 
 pecially the writer has to acknowledge his obligations to 
 the voluminous records of the noble series of cultural 
 experiments carried out at Eothamsted for so many years 
 by Sir J. B. Lawes and Dr. Gilbert. The " Memorandum 
 Sheet " published by these experimenters supplies annu- 
 ally a condensed summary of the results of their experi- 
 ments, and is a document that should be carefully 
 studied with due reference to its professed object, by all 
 who have the advancement of agricultural knowledge at 
 heart. M. T. M. 
 
CONTENTS. 
 
 CHAP. PAGE, 
 
 I. PLANT NUTRITION : THE WORK AND THE MATE- 
 RIALS 7-21 
 
 II. NUTRITION. THE MACHINERY 22-44 
 
 III. GROWTH 44- 55 
 
 IV. SENSITIVENESS 56- 70 
 
 V. DEVELOPMENT 71- 81 
 
 VI. MULTIPLICATION 81- 89 
 
 VII. THE BATTLE OF LIFE 89-109 
 
 VIII. PRACTICAL INFERENCES 109-124 
 
 IX. DECAY AND DEATH ._ 124-130 
 
 INDEX _ ---._--...- _____ 131-132 
 
PLANT LIFE ON THE FARM, 
 
 CHAPTEE I. 
 PLANT-NUTRITION : THE WORK AND THE MATERIALS. 
 
 Introductory remarks. What plants do and how they do it. Receipts. 
 Expenditure. Accumulation. Transformation. How plants 
 feed. Influence of temperature. Water and the machinery by 
 which it is supplied and distributed. Protoplasm. Cells and their 
 contents. Ingress and movements of water. The first stage of 
 nutrition. Diffusion. Osmosis and the requisite conditions for it. 
 Saturation. Varying degrees of, according to the nature of the 
 liquid. Amount absorbed. Supply and demand. Differences of 
 composition of plants grown in the same soil, how explained. 
 Continuous change. Nutritive value of water. Nitrates ; agency 
 of Bacteria. Potash. Sulphur. Phosphorus. Iron. Lime. 
 Principles of manuring. Power of selection. 
 
 He who can make two blades of grass grow where only 
 one grew before is universally looked on as a benefactor 
 to his kind. No one will dispute his title to our grati- 
 tude ; but at the same time it must not be overlooked 
 that the claims of him who can make one grow where 
 none at all existed before, are even greater, because the 
 difficulties to be overcome are more formidable, for where 
 one exists already it is relatively easy to bring about its 
 increase. 
 
 In any case, it is clear that, before either problem can 
 be satisfactorily solved, as full a knowledge as possible of 
 all the conditions requisite for the process must be in 
 
LIFE OK THE FAKM. 
 
 some way or another obtained. Success in a practical 
 pursuit like agriculture, depends largely on the extent of 
 our knowledge, and still more upon our power of apply- 
 ing it under various circumstances. In the following 
 notes an attempt will be made to supply indications of 
 some among the phenomena of the life of plants of which 
 it seems most desirable that the cultivator should take 
 heed. Some slight knowledge of the general conforma- 
 tion of plants on the part of the reader is assumed, but 
 explanations of the more important points will be given. 
 A living plant feeds, breathes, grows, developes, mul- 
 tiplies, decays, and ultimately dies. In so doing it re- 
 ceives, it spends, it accumulates, it changes. Some of 
 these processes are always in operation, very generally 
 more than one is going on at the same time, and the 
 action of one is modified by and controlled by that of 
 another. Some circumstances and conditions favor these 
 operations, others hinder them. The practical cultiva- 
 tor has his concern in all these matters, so that it is of 
 no slight moment to him to realize what is the work 
 which a plant does, and how it does it. 
 
 How Plants Feed. The nutritive process has to be 
 entered on the creditor side as a receipt. The plant will 
 indeed feed upon itself for a time, or rather it will feed 
 upon what its predecessor left it as an inheritance for this 
 very purpose, or upon the stores accumulated in the plant 
 itself during the preceding season ; thus, when a seed, or 
 rather the young plant within the seed, begins to grow, it 
 is at first unable to forage for itself, but it depends for 
 its sustenance on the materials laid up for its use during 
 the preceding season by the parent plant. So the bud of 
 a tree awakening into life, and beginning its career as a 
 shoot which is to bear leaves and flowers, derives its first 
 meals from the reserves accumulated the autumn previ- 
 ously in the parent branch. Very generally a little water, 
 
PLANT NUTRITIOK. 9 
 
 supplied from without, is required before the plant can 
 avail itself of these stored-up provisions, but this is not 
 always indispensable. Potatoes begin to sprout in their 
 cellars or pits, as growers know to their cost, before they 
 can have obtained a drop of water from without. In 
 this latter case there is water enough already in the tu- 
 ber to allow of food being utilized. 
 
 Effect of Temperature, A certain degree of useful 
 heat is, of course, quite indispensable. Practically, no 
 plant will feed when its temperature is reduced as low as 
 the freezing point, and in most cases the heat requires to 
 be considerably greater. Each kind of plant, each indi- 
 vidual -plant, and indeed each part of a plant, feeds, and 
 performs each item of its life-work, best at a certain tem- 
 perature, and ceases to work at all when the temperature 
 falls below or rises above a certain point. The particu- 
 lar degree, whether most or least favorable, varies accord- 
 ing to the plant, its age, stage of growth and various ex- 
 ternal circumstances, which we need only mention, as 
 their effects will be readily understood without the ne- 
 cessity of explanation. 
 
 It is clear then that a suitable temperature and access 
 of water, either liquid or in the form of vapor, are the 
 first essentials in the feeding process in plants. Practi- 
 cally, and from force of circumstances, the gardener has 
 more control over both temperature and the supply of 
 water than the farmer ; nevertheless by drainage, by 
 choice of aspect, site, by shelter, and other means, even 
 the farmer has some power to regulate the temperature 
 and the amount or influence of water to which his crops 
 are subjected. 
 
 Water, Leaving, however, on one side, the temper- 
 ature, we have to consider the water which is so essential, 
 not only in the feeding processes with which we are now 
 concerned, but with every other action of plant life. 
 
10 PLANT LIFE ON THE FAKM. 
 
 Fortunately there is, in general, no lack of it ; the earth 
 and the air contain their shares of this elementary com- 
 pound in varying proportions and varying modifications 
 as liquid or gaseous. Besides, the plant itself has so 
 much of it that even at the driest condition compatible 
 with life, it still constitutes a very large proportion of the 
 entire weight. Now, it is as a rule when the plant, the 
 seedling, or the bud is at its driest that growth begins, 
 the necessity for food first manifests itself, and the demand 
 for a further supply of water becomes imperative. How 
 is the demand supplied ? We have seen that there is no 
 lack of that fluid. How is it to get into the plant ? 
 The answer to this question brings us at once to the con- 
 sideration of the raw material and of the fabric of plants 
 by whose agency alone it is that the water gains entrance 
 to the plant. 
 
 Ingress and Movements of Water ; Diffusion, Osmo- 
 sis. Our first inquiry, then, must be to ascertain how 
 the water, whose presence in sufficient quantity we have 
 assumed, gets from without through the cell-membrane 
 into the protoplasm how, in fact, the first stage in inde- 
 pendent nutrition is accomplished. When one liquid, 
 say spirit, is poured into another, say water, the two 
 gradually mix. If we suppose these liquids to consist of 
 a number of molecules,* then, mixture may be taken to 
 
 *It may be well, once for all, to explain the sense in which the term 
 "molecule" is here used. It is now generally assumed by physicists 
 that every substance in nature is made up of excessively minute parti- 
 cles called atoms, which are indestructible. An atom cannot exist by 
 itself, but in association with others. Such a group of atoms is called a 
 " molecule." A molecule, therefore, is the smallest group of atoms 
 capable of existing separately and independently. These molecules may 
 be of different sizes in different cases, and they are believed to be so 
 arranged as just not to touch, but to leave spaces between them ; 
 smaller in the case of a hard solid, wider in that of a liquid, still wider 
 in that of a gas. The extent, moreover, of these interspaces may be 
 increased or diminished by varying degrees of heat, 
 
PLANT NUTRITION. 11 
 
 be the result of the displacement say of one molecule of 
 water by one molecule of spirit, and so, throughout the 
 whole quantity of liquid, there is displacement and re- 
 placement until at length equilibrium is restored and a 
 thorough diffusion results. This power of diffusion does 
 not always exist. The molecules of water and of oil will 
 not mix or diffuse freely through each other. "Water 
 containing carbonic acid gas will not mix, in this sense 
 of the term, with water containing acetate of lead ; and 
 when the attempt is made, chemical change is set up, 
 the heretofore clear solutions that containing the gas 
 and that containing the lead -become when combined 
 opaque and milky, owing to a chemical change, resulting 
 in the formation of a white insoluble lead carbonate. 
 
 It may be a truism to say, that for the process of dif- 
 fusion the liquids must be diffusible, but the fact must 
 be carefully borne in mind in all questions relating to the 
 feeding of plants. In the case of plants, the phenomenon 
 of diffusion, or the gradual admixture of two liquids of 
 different natures, is complicated by the presence of a 
 membrane in the shape of the cell-wall. The water from 
 the outside has to pass through the membrane to reach 
 the protoplasm on the other side. Speaking broadly, 
 there are no holes in the membrane through which the 
 water can pass. Ingress is secured by that process of dif- 
 fusion to which reference has just been made, and by 
 virtue of which the molecules of the membrane and the 
 molecules of the water shift and change places ; the 
 space that was occupied by a molecule of membrane is 
 now occupied by a molecule of water, and vice versa. 
 The access, therefore, of water into the interior of a 
 closed cell is the result of the process of diffusion. 
 Where two liquids mix without any intervening mem- 
 brane, the mixture is called diffusion simply ; where 
 there is an intervening membrane, the diffusion process 
 
12 PLANT LIFE OiT THE FAEM. 
 
 Protoplasm Cells, The raw material (the term is not 
 quite accurate, but for illustration sake it may pass) is 
 that very marvellous substance now called " protoplasm." 
 We must leave it to chemists and microscopists to ex- 
 plain its composition and indicate its appearance. Suffice 
 it here to call it, as Huxley did, "the physical basis of 
 life. " Without it, or when it is dead, the plant is dead 
 too ; with it the plant lives, without it it dies. It is a 
 viscid, colorless, jelly-like substance, endowed with all 
 those varied properties which constitute in. the aggregate 
 all that we can tangibly realize of the manifestations of 
 life. 
 
 With few exceptions, which it is not necessary here to 
 particularize, the protoplasm does not exist in one un- 
 broken mass, but is contained in little membranous bags 
 called " cells." These cells are of various shapes and 
 sizes, and may undergo various modifications during the 
 growth of the plant. They are large enough to be seen 
 by the naked eye in the pulp of an orange, but usually 
 they require the aid of the microscope to discern them. 
 They are lengthened into tubes placed end to end to form 
 conduits, or thickened into fibres. The cells, then, vari- 
 ously combined and modified, constitute what we have 
 termed the fabric of the plant. Each living cell consists 
 essentially of a certain proportion of protoplasm contained 
 within a membranous bag or bladder, called technically 
 the "cell-wall." There may be, and generally are, other 
 things besides the protoplasm within the cell-wall, such, 
 for instance, as a small ovoid body known as the " nu- 
 cleus," and green coloring matter or "chlorophyll ;" but 
 these other things, important as they are, we may leave 
 out of consideration for the present. 
 
 Every plant and every part of every plant is made up 
 of cells such as have been mentioned. As a cell a plant 
 begins its independent life ; with and by cells it lives, 
 grows, multiplies ; by their decay it dies. It is, as has 
 
PLANT NUTRITION. 13 
 
 been said, the protoplasm, which is the essential agent 
 in all these processes ; but, subject to a few exceptions, 
 which need not now be specified, this protoplasm is 
 always shut up within a cell-wall. Nor is it absolutely 
 necessary that there should be more than one cell. Most 
 plants with which the cultivator has to do consist of ag- 
 gregations of such, but there are myriads of other plants 
 which consist of but one cell ; in such a case the cell is 
 the plant, the plant is the cell. Now this is important, 
 because it shows us that all the processes of life can be, 
 and often are, carried on in one cell only, that is, by one 
 fragment of protoplasm. Where the fabric becomes 
 more complex, one cell is more or less dependent on 
 another, but still there is always a measure of indepen- 
 dence left to each individual cell. Were it not so, the 
 scythe of the mower or the grazing of the sheep, by de- 
 stroying a portion, would kill the entire plant. 
 
 It follows that the life-history of a plant is, in essence, 
 the life-history of protoplasm and of its covering, the 
 cell-wall ; and hence it is that the microscopist or the 
 chemist in the laboratory studying what goes on in isolat- 
 ed cells, placed as far as possible under uniform condi- 
 tions, is really adopting the best means of investigating 
 what takes place in the entire plant ; a circumstance 
 which the "practical man," so called, compelled to work 
 in the field under such very different, more complex and 
 much less definite conditions, finds it difficult to realize. 
 
 Conditions of Diffusion, Diffusion, it will readily be 
 understood from what has just been said, is not equal or 
 alike in all cases ; it depends upon the extent to which 
 the two liquids are diffusible, upon their different densi- 
 ties, upon temperature, and a variety of other conditions. 
 So, in the case of osmosis, we have not only the nature 
 of the two fluids to consider, but their relation to the 
 membrane that separates them. The membrane may be 
 
14 PLANT LIFE ON THE FARM. 
 
 much more permeable to one of the two fluids than to 
 the other. Thus, in the case of a living cell, the mem- 
 brane or wall is much more permeable to water than it is 
 to protoplasm ; and so it happens that, while water 
 readily penetrates the membrane and diffuses itself in the 
 protoplasm, protoplasm does not nearly so readily per- 
 meate the membrane as the water. Ingress of water is 
 easy and of constant occurrence, egress of protoplasm is 
 rare and exceptional. 
 
 Pure water or weak saline solutions, such as are gener- 
 ated in the soil under certain circumstances, pass readily 
 through membrane that is, the molecules of the one 
 shift and change places with those of 'the other while 
 those of gummy or albuminoid substances like proto- 
 plasm do not. After a time, if there is no outlet for the 
 water absorbed, or if it is not utilized within the plant in 
 some way, absorption and diffusion cease, the cell becomes 
 saturated with water, and until something happens to 
 disarrange the balance, no more is absorbed. But, even 
 in the case where the cell is saturated with water, it may 
 still take up other liquids, because the diffusive power 
 of those other liquids, in relation to the cell-wall and to 
 the protoplasm, is different from that of water, and this 
 absorption must go on in its way till saturation point is 
 reached for each one of them, just as in the case of water. 
 On the other hand, it may happen that the plant may be 
 saturated with other substances, and incapable of taking 
 up more of them, while at the same time pure water may 
 be freely taken up. 
 
 Quantity absorbed. Just so much and no more of 
 each particular substance is absorbed, the exact quantity 
 of each being regulated in all cases by the condition and 
 requirements of the cells, their membranous walls, and 
 their contents. Thus it happens that some particular 
 substances may be found by the chemist to exist in large 
 
PLANT NUTKITIOST. 15 
 
 relative proportions in the plant, while the quantity in 
 any given sample of the soil from which it must be de- 
 rived, is sometimes so small as to elude detection. The 
 plant in this case, or some part of it, is so greedy, if we 
 may so say, for this particular substance, that it absorbs 
 all within its reach, and stores it 'up in its tissues or uses 
 it some way, the demand ensuring supply. On the 
 other hand, the soil may contain a large quantity of 
 some particular ingredient which is incapable of being 
 absorbed, or which the plant does not or cannot make 
 use of, and, in consequence, none is found within the 
 plant. The supply is present, but there is no demand. 
 
 The different physical requirements of the plant sup- 
 ply also the explanation of the fact that different plants, 
 grown in the same soil, supplied with the same food, yet 
 vary so greatly in chemical composition. Thus, when 
 wheat and clover are grown together, and afterwards 
 analyzed, it is found that while lime is abundant in the 
 clover, it is relatively in small quantity in the wheat ; 
 and silica, which is abundant in the wheat, is absent 
 from the clover. Poisonous substances even may be ab- 
 sorbed, if they are of such a nature as to be capable of 
 absorption ; and so the plant may be "killed by its own 
 action by suicide, as it were. 
 
 The entrance of water into the plant and the entrance 
 of those soluble materials which a plant derives from the 
 soil are therefore illustrations of the process of osmosis, 
 and are subjected to all the conditions under which os- 
 mosis becomes possible, or under which it ceases to act. 
 The study of these conditions is a question for the physi- 
 cist, and the full explanation of them must be sought in 
 works relating to physics. So the investigation of the 
 substances which are absorbed with the water, of the 
 food materials, and their transformations within the 
 plant, is the work of the chemist, and their history must 
 be sought in chemical books. 
 
16 PLAKT LIFE OK THE FA11M. 
 
 Continuous Changes in Plants, In this place we must 
 confine ourselves to the few passing references already 
 made, but one thing we must strive to impress forcibly 
 on the reader, because, if the notion is well grasped, it 
 will enable him to understand plant life so much more 
 vividly. We allude to' the continual changes that are 
 going on throughout the whole living fabric of the plant 
 while in its active condition. Cell membrane, the pro- 
 toplasm, the entire mass of liquid and solid constituents 
 of which the plant consists, are, as we have seen, made 
 up of molecules, each, as it were, with a life of its own, 
 undergoing continual changes according to different cir- 
 cumstances, acting and reacting one upon another, so 
 long as any active life remains. Active life, indeed, is 
 ceaseless change ; dormant life is a condition of equi- 
 librium, more often talked about than realized in fact, 
 it is merely relative it implies merely a lessened degree 
 of activity. From this physical point of view the death 
 of a cell is only a change, a rearrangement of particles, 
 never, however, to be recombined into a new growing 
 cell, as happens in the case of a still living cell in the 
 full tide of growth and activity. 
 
 Nutritive Value of the Substances absorbed by Plants, 
 
 The importance of water may be judged from the fact 
 that while succulent vegetables contain more than ninety 
 per cent of water, timber felled in the driest time seldom 
 contains less than forty per cent (Warington). 
 
 As to the nature of the saline substances, reference 
 must, as has been said, be made to the "Chemistry of 
 the Farm " and other works for full details. Suffice it 
 here to say that certain of them, though always in rela- 
 tively small proportions, are essential to the life of the 
 plant ; certain others, generally met with, though useful, 
 are not indispensable. The former comprise salts of 
 potash, magnesia, lime, iron, and in addition phosphorus 
 
PLANT NUTRITION. 17 
 
 and sulphur. The latter comprise saltc of soda, silica, 
 manganese, together with chlorine and occasionally other 
 ingredients. 
 
 Of the salts just mentioned, the nitrates are of extreme 
 importance, inasmuch as nitrogen is an essential con- 
 stituent of protoplasm without nitrogen there can be 
 no protoplasm, without protoplasm there can be no plant. 
 The nitrogen is supplied to the plants from the soil in 
 the form either of nitrates (potassic nitrate, sodic nitrate), 
 or of ammonia salts in which the nitrogen is in combina- 
 tion with hydrogen. The ammonia in the soil is made 
 to combine with oxygen, and thus to form nitric acid, 
 through the agency of minute organisms called " Bac- 
 teria," which, like the yeast fungus, act as ferments ; and 
 by their agency it is, as Mr. Warington has pointed out, 
 in confirmation of the researches of Schloesing and 
 Muntz, that the ammonia salts, which themselves are 
 inert, or it may be harmful, get converted into useful 
 nitrates. Ammonia salts applied to some soils do no 
 good, because the needful germs or ferment bodies are 
 not present in the soil ; but where they do exist, they 
 convert the useless into the useful, as before said. These 
 bacteria occur in all fermenting material, such as farm- 
 yard dung, whose value as manure is in part accounted 
 for by their presence and agency. It is probable in the 
 future that just as the brewer uses his yeast to secure the 
 conversion of starch into sugar, and the chemist "seeds" 
 his solutions to effect the changes he wishes to bring 
 about, and just as the gardener sows the spawn or germs 
 of mushrooms in his mushroom bed, and obtains thereby 
 a crop of succulent fungi, so the farmer may be able to 
 apply to the soil the ferment-producing germs needed to 
 change its quality, and render it available for plan^ food. 
 When we have arrived at that point, manuring will be 
 reduced to a science, and a pinch of the right material 
 will be as efficient as a torn of our present compounds, 
 
18 PLANT LIFE Otf THE FAKM. 
 
 the large? part of which are undoubtedly wasted under 
 existing circumstances. 
 
 Potash salts are also essential, more so in some cases 
 than in others. At Rothamsted, potash, after having 
 been employed for a number of years as a manure-con- 
 stituent on a certain grass plot, was discontinued ; the 
 produce, in consequence, rapidly declined, and the 
 quantity of carbon fixed in the tissues of the plants pro- 
 portionately diminished, although the amount of nitro- 
 gen absorbed was the same in the two cases. The pres- 
 ence, therefore, of an adequate supply of potash, in the 
 soil, seems essential to the full assimilation of the car- 
 bon which is derived, as we shall presently see, from the 
 air, in the form of carbonic acid gas. It is believed from 
 recent experiments that without potash no starch can be 
 formed ; and starch, as we shall see hereafter, is of 
 primary impoctance in the nutrition of the plant. In 
 any case the value of potash manures for increasing the 
 yield of certain crops, particularly potatoes, is a fact be- 
 yond dispute. 
 
 Sulphur and phosphorus are also derived from the 
 soil as sulphates and phosphates. Both occur in asso- 
 ciation with the albuminoid contents of the protoplasm ; 
 and phosphorus seems specially needful in the formation 
 of the pollen the fertilizing powder in the flowers and 
 in the ripening of seeds, while its effect on the growth 
 of turnips is familiar to all practical men. 
 
 Iron is essential to the formation of leaf -green 
 " chlorophyll " and chlorophyll is essential to the pro- 
 duction of starch ; hence iron in some shape is essential 
 to plants, and it also is supplied from the soil in the 
 form of saline solutions. 
 
 What precise function lime plays in the plant's economy 
 is not known ; but indirectly it is of importance as a 
 means of introducing phosphorus and other essential in- 
 gredients. At Bothamsted, in two of the plots upon 
 
PLANT NUTRITION. 19 
 
 which barley has been grown for thirty years in succes- 
 sion, a mineral manure with nitrogen has been applied ; 
 but in the one case lime has been added, in the other 
 (otherwise treated exactly in the same way) no lime 
 has been added. The plants on the plot without the 
 lime are always of a darker green color, but they are rela- 
 tively deficient in carbon. Under equal conditions, it is 
 seen that the amount of carbon assimilated from the at- 
 mosphere in the -manner to be hereafter mentioned is di- 
 rectly dependent on the amount of available nitrogen, 
 which latter is derived from the soil (Lawes and Gil- 
 bert). 
 
 It. must not be forgotten that the substances we have 
 mentioned, as well as others not alluded to, though pos- 
 sibly not directly concerned in the nutrition of the plant, 
 yet are so indirectly by causing changes in the soil, by 
 rendering some matters soluble and capable of osmotic ab- 
 sorption which would not be so without their aid, by 
 storing up and preventing the waste of ingredients useful 
 as plant food, and so forth ; but these matters pertain 
 rather to the physical and chemical history of the soil, on 
 which account they may be passed over here without 
 further mention. 
 
 Principles of Manuring, The few remarks we have 
 thought it right to make as to the nature of the substances 
 absorbed with the water from the soil have an impor- 
 tant bearing on the theory and practice of manuring. 
 The nitrogenous and the saline substances are taken 
 from the soil, used up in the plant, and removed in the 
 crop. The annual produce of hay on un manured land at 
 Rothamsted, has been found to be about two thousand 
 five hundred and seventy-six pounds per acre, over an 
 average of twenty-five years, the range of variation ac- 
 cording to season having been from nine hundred to four 
 thousand three hundred and sixty-eight pounds. On the 
 
20 PLANT LIFE OK THE FARM. 
 
 other hand, the most highly manured plot has yielded 
 for the same period an average of seven thousand one 
 hundred and sixty-eight pounds of hay per acre, varying 
 in separate years from four thousand four hundred and 
 eighty to eight thousand nine hundred and sixty pounds, 
 according to season. These figures will suffice to illus- 
 trate the amount of food derived from the soil and from 
 the atmosphere, and the .beneficial effects of suitable cli- 
 matal conditions. The decline not only of produce, but 
 also in mineral and nitrogenous ingredients in- the soil, 
 in the case of the continuously unmanured plots at Eoth- 
 amsted, is very marked. To insure continued fertility, 
 therefore, and obviate exhaustion, some restitution must 
 be made ; and this is effected by the addition at the right 
 time, in the right condition, and in the right quantities, 
 of an appropriate manure ; or the exhaustion may be 
 compensated by suitable rotation, or the growth in alter- 
 nate periods of plants having different requirements, as 
 wheat after potatoes or clover after wheat. 
 
 Apparent Power of Selection, how Explained, The 
 
 circumstance that certain crops are specially benefited by 
 particular manures, though they contain relatively little 
 of the substance in their composition, would seem to in- 
 dicate the existence of a power of selection, as also would 
 the fact that plants of such very different constitutions 
 grow on the same soil, but these facts are better explained 
 by the varying osmotic conditions of the plants. Cereal 
 crops and grasses generally are, for instance, specially 
 benefited by nitrogenous manures, though they contain 
 relatively little nitrogen as compared with clover and 
 other leguminous crops, but which, although they con- 
 tain so large a proportion of nitrogen in their constitu- 
 tion, are not particularly benefited by nitrogenous ma- 
 nures. Beet roots and potatoes, which contain a con- 
 siderable proportion of potash in their constitution, are, 
 
PLANT NUTRITIOK. 21 
 
 nevertheless, not proportionately benefited by the appli- 
 cation of potash manures, though they are so to some 
 extent. These cases show that, by virtue of the varying 
 osmotic and digestive powers already mentioned, the 
 plants in question take what they want, and when they 
 want it, and are not induced to take more by the addi- 
 tion of larger supplies. They further show the errors 
 that may arise from the farmer acting too implicitly on 
 the results obtained by the chemist in the laboratory. If 
 he followed the indications of the chemist unchecked by 
 other experience, he would apply to his land what was 
 really not required by the crop. Thus Messrs. Lawes and 
 Gilbert tell us that the exact composition of the crops is 
 no direct guide to the description and amount of manurial 
 constituents that will be most effective, thus although 
 wheat removes more phosphoric acid from the soil than 
 does barley, yet the application of the phosphate is more 
 beneficial to the barley than to the wheat. They con- 
 clude, then, that it is not necessary to supply to the land 
 all the constituents that have been removed from it, or 
 that would be contained in the crops it is wished to grow, 
 but that we should supply all or some, more or less, ac- 
 cording to circumstances. 
 
22 PLAtfT LIFE OK THE 
 
 CHAPTER II. 
 NUTRITION (Continued). THE MACHINERY. 
 
 Roots : their nature. Root-cap. Root-hairs. Root action. Absorp- 
 tion. Leaves and leaf action. Chlorophyll. Absorption of fluid 
 and gases. Leaf work by day and by night. Oxidation and De-oxi- 
 dation. Carnivorous plants. Transpiration. Circumstances pro- 
 pitious to it. The stem and its work. Its characteristics and vari- 
 eties. Buds. Branches. Tubers. Bulbs. Uses of the stem. As- 
 cent of liquids. Sap currents. 
 
 Roots : Their Nature, Etc. So far as regards the ab- 
 sorption of those food materials derived from the soil by 
 the means above-mentioned, the root and its sub-divisions 
 are the agents through which the absorption takes place. 
 It is not necessary to allude to the various forms and 
 modifications of roots which form the study of the bot- 
 anist further than to say that their manifold differences 
 of form depend chiefly on the relative proportion that 
 the body of the root bears to its branches. If, as in a 
 " tap-root," like a carrot, the body is large, the branches 
 are small; if, as in the "fibrous root" of a grass, the 
 body is small, the branches are numerous and long. 
 
 In ordinary language a great many things are called 
 roots which are not strictly so. For most people all parts 
 of the plant situate below the surface of the ground are 
 roots or portions of roots. Botanists, having regard 
 alike to the origin, mode of growth, structure, and uses 
 of roots, are enabled to define roots partly by positive, 
 partly by negative characters. Thus roots originate be- 
 neath the surface, that is from within the tissues of the 
 plant (endogenous), and force their way out through the 
 rind, as contrasted with branches and leaves which orig- 
 inate on the surface (exogenous). The extreme tip of 
 the root, and of its sub-divisions, is furnished with a mi- 
 nute " root-cap " of dead tissue pushed off from the tip 
 
PLANT HTTTKITIOH. 23 
 
 as it grows, as the feathers of a bird are removed during 
 the moulting season. No such cap exists at the end of a 
 branch or leaf. Again, while it is the office of a stem or 
 branch to produce leaves or scales, which are the repre- 
 sentatives of leaves, no root proper, as a rule, produces 
 leaves or flowers. 
 
 Botanists make a distinction between "true roots" 
 which are the direct outgrowth from the original " rad- 
 icle " of the germinating seedling, and, in fact constitute 
 its direct continuation and " adventitious " roots, which 
 spring from the stem and branches, and which are only 
 indirectly derived from the primary root. For our pres- 
 ent purpose the distinction is unimportant. 
 
 The root of a plant and its branches have different 
 forms and subserve different purposes. Whatever food is 
 taken up from the soil is taken up by them. They act 
 as stays and holdfasts, they serve as storehouses of nour- 
 ishment. Their form varies according to their use, their 
 needs, the competition with other roots, the conditions 
 under which they have to grow, and other circumstances, 
 not forgetting the heritage bequeathed to them by their 
 predecessors from generation to generation, for, like all 
 parts of the plant like the plant itself the root is the 
 product of what has gone before, adapted and modified 
 by the exigencies of the present. 
 
 In this place we have to consider the roots chiefly in 
 their character as absorbent organs. The one function 
 common to all roots is absorption. They may have other 
 offices to fulfil, and they have very varied forms ; but 
 when we come to consider the main function of the root, 
 then we find simplicity and relative uniformity of struc- 
 ture. The thick, woody limb of an elm root, as we see 
 it exposed in a hedge-bank from which the soil has fallen, 
 is no organ of absorption ; the thick " bulbs " (so-called) 
 of a turnip or a beet, are not organs of absorption ; 
 neither are these latter, any more than the tubers of po- 
 
24 PLAKT LIFE OK THE FAEK. 
 
 tatoes, stri'ctly speaking, roots. Our best and truest con- 
 ception of a root as an organ of absorption is that of a 
 single fibril or of a dense mass of the finest fibrils root- 
 branches no thicker than a hair. These fibrils grow in 
 length close to their tips, the actual tip being covered 
 with a thin extinguisher-like cap of dead tissue the root- 
 cap already mentioned, and which serves as a shield to 
 the softer tissues within. The structure is of the sim- 
 plest, merely layers of cells such as before described, 
 arranged in more or less longitudinal ranks, the cells 
 themselves delicate and thin- walled. The fineness of the 
 root-fibril, its growth near the tip, its wonderful power 
 of motion, are all well adapted to permit of the fibril 
 ma*king its way between the particles of soil, and extract- 
 ing nourishment from the fluid surrounding them. We 
 have only to examine the root of a wheat plant, or still 
 better of a perennial pasture grass, to see how perfectly 
 this is accomplished. Under such circumstances the 
 root-fibrils form a dense wig, as it were, of feeding 
 threads which occupy the soil so thoroughly that the soil 
 is held together by them. It is easy to see that although 
 the absorbent power of each thread is infinitesimal, yet 
 in the aggregate it must be very large. Fine as they 
 often are, these root-fibrils are very frequently, but not 
 always, provided with yet finer " root-hairs." These are 
 extremely minute threads emerging from the superficial 
 cells of the root, in the vicinity of, but not exactly at, 
 their tips. When their growth is stimulated by the 
 presence of moisture or suitable plant food, they often 
 occur in such numbers as to form a dense cobweb-like 
 investment to the roots. 
 
 Root Action What the Roots do. It has been proved 
 by repeated experiments that the absorption of liquid food 
 (no solid matter can in any case be absorbed) takes place 
 towards the lower end of the root-fibrils, and by means 
 
PLANT NTTTKITION. 25 
 
 of these root-hairs when they are present. The upper 
 portions of the fibril do not act as absorbent organs, the 
 root hairs do not exist in this part of the root, the struc- 
 ture of which becomes gradually less and less adapted 
 for absorption, so that the actual space in each fibril de- 
 voted to absorption is relatively small in relation to its 
 length. The remainder of the fibril acts as a conduit for 
 the transmission of the absorbed fluids upward from cell 
 to cell by osmosis and imbibition, and as a holdfast. 
 
 The passage of the insoluble matters in the soil into 
 the root is effected by an acid liquid produced by the 
 root-hair or cell in consequence of its contact with the 
 particle of soil, aided by the water in the soil. This acid 
 fluid saturates the cell walls, corrodes, and effects the 
 solution of the surface of the particle of the soil in con- 
 tact with the fibril or root-hair. No passage of acid fluid 
 out of the cell takes place, root excretions having no ex- 
 istence ; but the corrosive, and as it were digestive, action 
 above mentioned, is due solely to the absolute contact of 
 the cell of the root with the particle of the soil. 
 
 The soil, therefore, is not to be looked on as contain- 
 ing so much liquid food ready for instant use ; that may 
 be so as regards water, but for other substances the di- 
 gestive action of the roots is necessary. 
 
 In addition to the absorption of liquids as just detailed, 
 roots have the power of freely absorbing the oxygen gas 
 contained in the soil, and if a supply of oxygen be cut 
 off, the roots die from suffocation. One use, therefore, 
 of the plowing and harrowing operations is to keep the 
 soil open and permeable, and thus allow the access of oxy- 
 gen to the roots. 
 
 On the other hand, roots do not absorb carbonic acid 
 
 gas nor exhale oxygen as the leaves do in the sunlight 
 
 but they do give off carbonic acid gas, which, with the 
 
 aid of water, converts the insoluble carbonates of the soil 
 
 2 
 
26 PLANT LIFE ON THE FARM. 
 
 into soluble bicarbonates, and exercises a similar power 
 of solution in the case of phosphates. 
 
 Leaves and Leaf Action. The two great factors in 
 the feeding of the plant are the roots and the leaves. 
 The soil supplies to the roots, as we have seen, water in 
 large quantities, gases, earthly and saline substances ; 
 but the air is an equally important source of nourish- 
 ment, or even more so, since there are rootless plants, 
 and plants which receive no part of their food directly 
 from the soil, while no plant can exist without air, and 
 no plant that is of direct importance to the cultivator 
 can live without light. We insert the word " direct " 
 because there is a whole group of plants which can thrive 
 in the absence of light, but these form no part of the 
 ordinary crops of a farm. Indirectly, however, as has 
 been pointed out, in considering the agency of bacteria 
 as ferments in the soil, these organisms to whose career 
 light is not essential may be of the greatest consequence 
 to cultivators ; and it is probable that the future will 
 show us much more fully how great is our indebtedness 
 to them. For our present purpose, we have to deal with 
 plants producing leaves, to point out some of the work 
 which the leaves do, and to give some indication of how 
 they do it. 
 
 Unlike the root, which originates from within the sub- 
 stance of the plant and breaks its way out to the surface, 
 the leaf, as has been stated, is a direct production from 
 the surface of the stem or branch. It is one of the char- 
 acteristics of a root not to produce leaves ; it is one of the 
 attributes of the stem and its subdivisions to clothe 
 themselves with these appendages. 
 
 In form, texture, size., the leaf presents infinite variety. 
 Sometimes it is a mere dry scale, sometimes a thick, 
 fleshy excrescence ; now it offers a broad, banner-like 
 surface, now it is reduced to the form and dimensions of 
 
PLANT NUTRITION. 27 
 
 a needle. Sometimes it is all in one piece, the e< blade " 
 being unbroken at the edge, or variously notched and 
 indented ; at other times the blade is made up of few or 
 of an infinite number of separate segments or leaflets. 
 If the blade is in one piece, it is " simple," as the leaf of 
 wheat ; if in many pieces, as the leaf of clover, sainfoin, 
 or tares, it is "compound." Very often it has a stalk 
 or " petiole," sometimes it has none. Sometimes it has 
 appendages at its base called " stipules," well seen in 
 vetches or clover ; while the leaves of all grasses, includ- 
 ing all the cereals, are provided with a little mem- 
 branous tongue or outgrowth from the junction of the 
 sheathing stalk of the leaf with the blade, whicli is called 
 a "ligule," and which, though often overlooked, is of 
 some moment to the grazing farmer, as affording one 
 means of distinguishing useful from useless grasses. 
 Further than this we need not go at present in speaking 
 of the form and general appearance of leaves. Nor need 
 we enter very deeply into the minutiae of their structure. 
 All ordinary leaves are flat plates of cells of various 
 shapes variously arranged, and traversed by fibrous bun- 
 dles. These bundles consist of long, tapering cells or 
 fibres filled with woody or other matter, and of rows of 
 similar cells placed end to end in rows, the partitions 
 between the cells being removed, so that they form con- 
 tinuous tubes. There are many kinds of "vessels," but 
 all of them originate from cells. The fibro- vascular 
 bundles, with their wood-cells, bast-cells, and vessels, 
 constitute what are commonly termed the veins of the 
 leaf. Covering over this mass of cells and vessels is a 
 skin or epidermis, consisting of flattened cells usually 
 placed in accurate contact on the upper surface of the 
 leaf, but below, so modified in shape and position as to 
 leave a number of pores or openings called "stomata," 
 the number, arrangement, size, and form of which vary 
 very much in different plants ; suffice it here to say that 
 
28 PLANT LIFE otf THE FARM. 
 
 they are in general very numerous. So far, then, there 
 is little difference to be noted between the structural 
 elements of a leaf and those of a root. The root is more 
 or less cylindric, the leaf is more or less flat ; but the es- 
 sential structures, though differently arranged, are pretty 
 much the same, with one or two notable exceptions. 
 The root has no breathing pores or stomata, and the 
 contents of its constituent cells are so far different from 
 those of the leaves that they contain no green coloring 
 matter. 
 
 Chlorophyll. The main and specially important char- 
 acteristic of the leaf (and of all the green parts of plants), 
 so far as their life-work is concerned, is the presence in 
 the cells of the green matter called "chlorophyll." 
 With and by its agency the leaf can do work impossible 
 to be done otherwise ; work, the measure of which de- 
 termines the health and vigor of the plant, the default 
 of which ensures its death. It is true that chemists and 
 physicists have not yet unravelled all the mysteries of 
 chlorophyll, and there remains a doubt whether it is the 
 potent agent it has hitherto been supposed to be, or 
 whether the power does not reside in some other agent 
 mixed with it. Into these questions we cannot here 
 enter. Whatever be the actual truth of the matter, the 
 transcendent importance of chlorophyll, and of all that 
 its presence implies, is universally admitted. It must 
 suffice to say that chlorophyll is a green, waxy substance, 
 occurring in certain of the cells mixed with their proto- 
 plasmic contents. In amount and appearance it varies in 
 different cases and under varying circumstances. It 
 does not occur in all the cells of the leaf, but chiefly or 
 only in those on the upper surface, and which are there- 
 fore the most directly exposed to the action of the rays 
 of the sun. 
 
PLANT NUTRITION. 29 
 
 Feeding by Leaves. We are now in a position to 
 understand the nutritive process as it is carried on by 
 the leaves, and our first enquiry is as to what they feed 
 on what is the nature of the food they take in ? In 
 the first place, it is clear that they can take in no solid 
 matter. The pores or stomata already alluded to are the 
 only openings by which such matter could get into the 
 interior of the leaf ; and we know, from experience, that 
 if these pores get blocked, the leaf suffers rather than 
 ains. Moreover, the cells, bounding the aperture, open 
 and close according to the condition of moisture of the 
 atmosphere, and at any rate, when closed, they could 
 admit no solid matter. 
 
 Absorption of Water. As to fluids, it is proved that 
 leaves, under certain circumstances, and when there is 
 no structural provision to prevent it (as there often is) 
 can and do absorb, not only watery vapor, but the fluid 
 itself. This happens more especially when the plant is 
 flagging from the rapid exhalation of moisture, and from 
 deficient root supply, and it affords an explanation of 
 the benefit plants derive from the deposit of dew after a 
 hot and drying day. Still, the absorption of water by 
 means of the root seems to be generally of more conse- 
 quence than that by the leaf, so that the entrance of 
 water by the leaf may, for our purposes, be passed over 
 without further mention. 
 
 Absorption and Exhalation of Gases. There remains 
 gaseous food. It has been shown that the root absorbs 
 gases, as oxygen ; but in this respect, as also in the ab- 
 sorption of other gases, the root is surpassed by the leaf. 
 The paramount function of the leaf is the absorption and 
 assimilation of carbon. Carbon, as such, does not exist 
 in the atmosphere, unless, indeed, as an impurity in the 
 air of towns ? and a very prejudicial one to plants. It is 
 
30 PLANT LIFE ON THE FARM. 
 
 in the form of carbonic acid gas a combination of car- 
 bon and oxygen that it is found in the atmosphere, but 
 only in small proportion compared with the other con- 
 stituents. In the plant carbon exists in much larger 
 proportion than any other ingredient, with the sole ex- 
 ception of water. It forms, in fact, about fifty per cent 
 of the dry matter of plants left behind after the water 
 and gases have been expelled by heat. This large 
 quantity of carbon has to be taken up in the form of 
 carbonic acid by the leaves. It is a moot point whether 
 any carbon is taken up by the roots, but, if any, it is 
 only a small proportion. In any given volume or quantity 
 of air, the proportion of carbonic acid is very minute, so 
 that the leaves must be very active in securing and util- 
 izing all that comes within their reach. 
 
 What Leaves do in the Light, Direct experiments 
 have shown that this appropriation of carbonic acid is 
 effected by the agency of the green coloring matter or 
 chlorophyll when exposed to the action of light. In the 
 dark no such appropriation takes place. The plant feeds, 
 so far as its carbon is concerned, on the carbonic acid of 
 the air through the agency of sunlight and of chlorophyll. 
 At least two-thirds of the chlorophyll itself consists of 
 carbon in association with a small proportion of oxygen 
 and hydrogen, and a still smaller quantity of nitrogen. 
 The carbonic acid thus introduced into the plant 
 does not remain as such, but its constituent carbon is 
 retained in the plant for its own purposes, while the 
 oxygen gas is eliminated. The bubbles of gas that rise 
 from a water weed in a pond when exposed to the sun 
 consist of oxygen chiefly, and it has been shown that the 
 amount of oxygen gas given off is about equal to that of 
 the carbonic acid gas absorbed. Hydrogen and oxygen, 
 the absorbed water, are, it is said, assimilated by the 
 plant simultaneously with the carbon. 
 
PLANT HUTKITION. 31 
 
 The first icsult of this assimilation, chemists tell us, is 
 the formation of a soluble substance, " glucose," allied 
 both to starch and to sugar, and which, or a portion of 
 which, becomes starch, and is stored up for future use in 
 that form. No starch is formed in an atmosphere pur- 
 posely deprived of carbonic acid by the experimenter, 
 even if the cell be exposed to the light. Moreover, any 
 starch that may have been previously formed disappears 
 under such circumstances, just as it would do in dark- 
 ness, where the plant is dependent on its reserve stores 
 for its nourishment, and not on those which it procures 
 directly for itself when exposed to light in an atmosphere 
 in which carbonic acid gas forms a part. The changes 
 in question are presumed to take place, not in the pro- 
 toplasm itself, but in the chlorophyll grains ; at any rate, 
 it is in them that the starch first makes its appearance. 
 It is certain, also, that only cells which contain chlor- 
 ophyll and then only when exposed to light can 
 directly assimilate carbon. Cells without chlorophyll, 
 such as those of fungi, obtain their carbon by more indi- 
 rect and complex means. The vital importance of the 
 exposure of the leaves to sunlight might be inferred from 
 the bending of the stems and branches to the light, and 
 placing of the mobile leaves at such an angle as to receive 
 the full benefit of the sun's rays matters which will be 
 spoken of further on. 
 
 What the Leaves do in Darkness. Inhalation of 
 Oxygen. In darkness (as well as under the influence of 
 light, in the case of those cells that do not contain chlo- 
 rophyll) changes go on of a different character to those 
 just described. There is, in fact, a constant elimination 
 of carbonic acid gas, and a corresponding absorption and 
 retention of oxygen gas. The interchange of these gases 
 has been compared to the corresponding changes in the 
 case of the respiration of animals ; but doubts have been 
 
32 PLANT LIFE ON THE FAEM. 
 
 thrown on the existence of any direct connection between 
 the absorption of oxygen and the emission of carbonic 
 acid, in plants, because it has been shown that a green 
 leaf placed in darkness and in an atmosphere deprived of 
 oxygen nevertheless exhales carbonic acid, the emission 
 of which under such circumstances cannot of course be 
 connected with any corresponding inhalation of oxygen. 
 
 Though going on constantly, the energy of the oxi- 
 dizing process is much less than that of the opposite de- 
 oxidizing process, carried on when the chlorophyll cells 
 are exposed to the light. Deprived of oxygen, the move- 
 ments of the protoplasm, the movements of. the roots 
 and of the leaves cease, other manifestations of activity 
 are put a stop to, and the plant dies of suffocation. 
 Moreover, it has been shown that each cell consumes its 
 own supply of oxygen, and if that fails it will die, even 
 though adjoining cells be provided with the gas. In this 
 particular then the cells act, not in concert, but indi- 
 vidually (Van Tieghem). It is not essential that the 
 oxygen should be in a free state ; it may be utilized by 
 plants from a compound containing oxygen, and from 
 which it may easily be obtained. An instance of this is 
 afforded in the case of the disease of animals known as 
 " charbon," which is now known to be caused by the 
 existence in the blood of the animal affected of a micro- 
 scopic plant (Bacillus anthracis), which lives in the blood, 
 and which, not finding sufficient oxygen in its serum or 
 liquid portion, decomposes the matter contained in the 
 red corpuscles and utilizes the oxygen they afford. To 
 live itself, it deprives the creature in which it is estab- 
 lished of its oxygen, and thus not only kills it by suffo- 
 cation, but eventually cuts off its own supply of food. 
 
 The effect of depriving a plant which contains glucose 
 of its oxygen is to convert that glucose into alcohol. 
 Thus fermented liquors, such as beer, wine, etc., owe 
 the alcohol they contain to the temporary cutting off of 
 
PLANT NUTRITION. 33 
 
 the supply of oxygen to the ferment, in consequence of 
 which the glucose they contain becomes converted into 
 alcohol. 
 
 Carnivorous Plants, Parasites, The leaves of certain 
 plants are endowed under certain circumstances with a 
 power of digesting and absorbing animal substances 
 placed in contact with them. When a minute fragment 
 of meat, for instance, is placed upon the leaf of a drosera, 
 or sundew, the tentacle-like glandular hairs of the plant 
 bend over to grasp the intruding morsel, a peculiar di- 
 gestive fluid is formed as a result of the contact just as 
 the gastric juice in the human stomach is secreted when 
 food enters that organ and this fluid effects the solution 
 of the meat, the nutritive solution so formed being 
 absorbed and applied to the benefit of the plant. To 
 common observation the actual gain to the plant by this 
 method of feeding may appear slight, or even none ; but 
 the more delicate tests applied by the botanist have 
 sufficed to prove, not only that the processes just 
 mentioned really do go on, but also that they are ben- 
 eficial to the plant, and contribute to the formation of 
 more numerous and more robust seedlings. The ration- 
 ale of this mode of obtaining nutrition seems somewhat 
 analogous to that in the root, where also the acid fluid 
 with which the cell-wall is permeated, when it comes 
 into contact with the particles of soil, determines their 
 solution and renders them fit for absorption into the 
 plant. Practically this admittedly exceptional mode of 
 nutrition by the leaf might seem of little moment, but it 
 is probable that in the future direct nutrition by this 
 means will be shown to be of much greater importance 
 than it appears to be at present. In any case, the fact 
 that ammonia-solutions and ammonia-vapors are absorbed 
 by leaves with increased manifestations of vital activity, 
 renders this mode of feeding a matter of some conse- 
 
34 PLANT LIFE ON THE FAKM. 
 
 quence to the agriculturist ; and the escape of ammoni- 
 acal vapor from the muck-heap may not after all be the 
 wasteful operation it is usually supposed to be that is, 
 if the circumstances are such that plants can avail them- 
 selves of the exhaled vapor. 
 
 It is a very remarkable fact that fluids which do not 
 contain nitrogen do not give rise to the movements of 
 the leaves, the changes in the protoplasm, the formation 
 of a digestive fluid, and other consequences, which Darwin 
 has discussed in his work on "Insectivorous Plants." 
 Mere mechanical irritation of the leaves is not sufficient 
 to ensure the formation of the ferment requisite for 
 digestion. The different effects of salts of soda and of 
 potash, in the case of the leaves of drosera, are also sug- 
 gestive, for while soda-salts give rise to the physiological 
 activity in the leaves, potash salts do not do so, and some 
 of them are even poisonous. Neither the one nor the 
 other is poisonous to the roots, unless applied in very 
 large quantities. Phosphate of ammonia and phosphate 
 of soda act with remarkable vigor on the leaves, while 
 phosphate of potash is quite inert, the activity in the 
 former cases being probably due to the phosphorus. 
 
 It would thus appear that while almost all plants ab- 
 sorb the inorganic elements, including their nitrogen, 
 from the soil, and derive their carbon from the atmos- 
 phere, there are others, such as drosera, which digest and 
 absorb nitrogenous matters by means of their leaves. 
 Such plants can even extract nitrogenous matter from 
 pollen, seeds, and bits of leaves (Darwin). Other plants 
 absorb ammonia by means of the hairs covering their 
 leaves, and this class is probably more numerous than 
 the foregoing. Others, again, have no faculty of digest- 
 ing by their leaves, though they absorb solutions of 
 decaying animal matter by their means. Some, such as 
 the bird's nest orchis, feed on the decay of vegetable 
 matter, and are themselves nearly or quite destitute of 
 
PLANT NUTRITION. 35 
 
 chlorophyll. Lastly, there is the class of true parasites, 
 such as the broom-rapes ( Orobanche) and dodders ( Cus- 
 cuta), which affix themselves to living plants, and being 
 themselves destitute of chlorophyll, are unable to live, 
 except at the expense of the plants upon which they 
 grow. 
 
 Transpiration of Water, There is a large absorption 
 of water, as has been said, by means of the root, and in 
 some cases, at any rate, there is an absorption of the 
 same fluid or vapor by means of the leaves. On the other 
 hand, there is a loss of water or watery vapor from the 
 surface, which is sometimes so profuse as to cause the 
 plant to wither and flag. We have only to place some 
 leaves in a cool tumbler, and expose them to the light, 
 to see the condensed water on the sides of the glass. 
 The quantity of watery vapor emitted in sunlight by the 
 green surfaces of plants is enormous, and it has been 
 shown experimentally that it is the chlorophyll which is 
 largely concerned in this outflow, for where that sub- 
 stance is deficient and wanting, transpiration of fluid is 
 proportionately reduced or stopped. But while bright 
 light, such as that furnished by the red and yellow ray 
 of the solar spectrum, is most efficacious in stimulating 
 the decomposition of carbonic acid, it is the blue ray 
 which specially favors transpiration of the fluid. A high 
 degree of temperature, as might be expected, favors 
 transpiration, as does also a dry state of the atmosphere. 
 The condition of the plant, its age, and other circum- 
 stances are also important agents in regulating the 
 amount of transpiration. 
 
 Some idea of the amount of water given off may be 
 gleaned from some experiments made by Sir JohnLawes, 
 and recorded in the " Journal" of the Horticultural 
 Society for 1850, thus During one hundred and seventy- 
 two days, March 19 to September 7, the total weight of 
 
36 PLANT LIFE ON THE FAKM. 
 
 water given off from small flower pots containing plants, 
 grown without manure, was as follows : 
 
 Grains. 
 
 Wheat 112,527 
 
 Barley 120,025 
 
 Beans , . 112,231 
 
 Peas 109,082 
 
 or, say, an average loss for each pot for the whole period 
 of over one hundred thousand grains. To show the effect 
 of the season, it may be said that the average daily loss in 
 grains in the case of flower pots containing plants of 
 wheat grown in unmanured soil, was : 
 
 Grains. 
 
 March 19 to 28 . . : 14.3 
 
 March 28 to April 28 40.9 
 
 April 28 to May 25 162.4 
 
 May 25 to June 28 1177.4 
 
 June 28 to July 28 1535.3 
 
 July 28 to August 11 1101.4 
 
 August 11 to September 7 230.9 
 
 Barley lost more in April and May than the wheat, 
 and more also in July and August. Beans lost much 
 less than either of the cereals, the amount increasing 
 regularly to June to July, and diminishing in August. 
 Peas evaporated less than beans, especially in June. The 
 results obtained from the plants grown with various ma- 
 nures were less uniform, and need not here be cited, the 
 object being merely to illustrate the large quantity of 
 water evaporated and its gradual increase with the de- 
 velopment and growth of the plant and the advance of 
 the season. While the precise effect of any particular 
 manure in promoting either absorption or transpiration 
 is not fully known, it has been shown that the alternate 
 use of pure water and of manure water has resulted in a 
 large proportionate amount of water being absorbed and 
 transpired by the plant, and a greater development of 
 the plant than is the case where either fluid is applied 
 alone (Vesque). 
 
PLANT NUTRITION. 37 
 
 Summary. The main functions of the leaf may, there- 
 fore, be stated to be the reception and emission of gases 
 now this, now that, according as it is exposed to light 
 or darkness and the absorption and emission of watery 
 vapor. The result of all these varied processes now act- 
 ing together and in unison at other times in antagonism 
 as it were is the nutrition of the plant, the building up 
 of its structure, the formation of most of those ingre- 
 dients which render a plant sightly or useful. The im- 
 portance of these processes may be summed up in the 
 words of an eminent physiologist (" Gardeners' Chroni- 
 cle," 1881, Feb. 5, p. 169) : " All the labor of the 
 plant by which out of air, water, and a pinch of divers 
 salts scattered in the soil, it builds up leaf and stem and 
 roots, and puts together material for seed or bud or 
 bulb, is wrought and wrought only by the green cells 
 which give greenness to leaf and branch or stem. . . . 
 We may say of the plant that the green cells of the green 
 leaves are the blood thereof. As the food which an 
 animal takes remains a mere burden until it is transmut- 
 ed into blood, so the material which the roots bring to 
 the plant is mere dead food until the cunning toil of a 
 chlorophyll-holding cell has passed into it the quickening 
 sunbeam. Take away from a plant even so much as a 
 single green leaf, and you rob it of so much of its very 
 life blood." A warning this against the premature re- 
 moval of leaves, as when leaves are taken from the bulbs 
 of our mangels before they have completed their work of 
 formation and accumulation. 
 
 In this, and other matters, however, the cultivator 
 often has to make a compromise, and act as is best for 
 himself under the particular circumstances of the time. 
 It is not the good of the plant that he seeks in the first 
 instance, but only in so far as it contributes to his own 
 profit ; and although in principle every injury needlessly 
 inflicted on a plant must in the long run be injurious, it 
 
38 PLANT LIFE ON THE FARM. 
 
 may well be and often is the case that the injury to the 
 plant is compensated for by other conditions, and that, 
 in case of difficulties on both sides, it is wisest to choose 
 the least of two. 
 
 The Stem and its Work. As the leaves, whatever 
 their form, are nothing but outgrowths from the stem, 
 and as no leaf exists except it be borne upon a stem, so 
 it would have been more in the natural order of things if 
 mention had been made of it before the leaves. As 
 regards the nutrition of the plant, however, the stem 
 plays but a secondary part, as compared either with the 
 root or the leaves, and on this account it may not inap- 
 propriately be considered after them. 
 
 Botanically, any part of the plant that produces leaves, 
 or the representatives of leaves, is considered to be stem. 
 The root, inasmuch as it bears neither scales nor leaves, is 
 not stem; the "root- stock," inasmuch as it does bear 
 scales and leaves, is truly a stem, even though it may be 
 beneath ground. The long, creeping runners of "twitch" 
 (Triticum repens) are stems, so are the similar parts in 
 thistles and bear-bind (Convolvulus arvensis). The 
 bulbs of kohl rabi are clearly stems, for they bear leaves, 
 or the scars where leaves have once been. Beet roots, 
 mangels, radishes, turnips, parsnips, partake of the 
 nature of roots and of stems ; that is to say, their lower ? 
 tapering extremities are unquestionably roots ; their 
 thick upper end, surmounted by a crown of leaves, is as 
 unquestionably stem. There are anatomical differences 
 such as the presence of a root-cap, the absence of sto- 
 mata in a root, and differences in the mode of growth 
 between roots and stems, but they are not material to our 
 present purpose. It will be seen, from what has been 
 above said, that the definition of a stem (or of a branch, 
 which is only a subdivision of a stem), as that part of 
 the plant told off to bear leaves, admits of very wide dif- 
 
PLANT* NUTRITION. 39 
 
 ferences of form. We have already alluded to some of 
 these differences, according as the stem is above or below 
 ground, covered with mere scale-leaves, or bedecked like 
 a timber tree with true leaves. The pasture grasses and 
 cereals have almost all hollow erect, knotted stems ; the 
 sedges, which resemble the grasses so much, have mostly 
 angular unjointed stems. The clovers have a thick stock 
 giving off branches which trail along the ground. The 
 hop coils around the supporting pole by means of its 
 climbing stem. Then there are the differences in dura- 
 tion associated with corresponding differences in texture 
 and internal construction. There are the so-called 
 annual stems, which would lie down, even if they were 
 not cut down after one season's growth ; there are the 
 perennial stems, like those of fruit or timber trees or 
 shrubs, and the duration of whose existence may be 
 counted by years, and often by centuries. Then, again, 
 there is an intermediate class of cases where the root- 
 stock remains below-ground for a period long enough to 
 justify the term perennial, while the branches or shoots 
 die down after the seed is ripe, or are killed to the ground 
 by a touch of frost, as in the common nettles. 
 
 Buds, Branches, Tubers, Etc, The branches or sub- 
 divisions of a stem originate as buds or " eyes," which 
 are placed at the free ends of the stem or of its branches, 
 or which originate from the side of the stem or branch, 
 in what is called the "axil" of a leaf, or of a leaf -scale, 
 the axil being the angle formed by the base of the leaf at 
 the point where it springs from the stem. The traces of 
 their origin are often lost as the plant grows, but the 
 rule is, as it has been stated, subject to a few exceptions 
 of no moment for our present purpose. It is not usual 
 for a bud to be borne in the axil of every leaf, far from 
 it, but this is the place where the side-buds when they do 
 exist are almost sure to be found, The shoots which 
 
40 PLANT LIFE ON THE FA KM. 
 
 "tiller" up from the base of the stems of the wheat 
 originate as buds from the axils of the lower leaves, while 
 the upper ones are destitute of them. When a tree is 
 "pollarded," a large crop of buds makes its appearance ; 
 and the multiplication of some weeds, like thistles and 
 bindweed, after their stocks have been cut through with 
 the hoe at insufficient depths below the surface, is due to 
 a like formation of buds. 
 
 The tuber of the potato may be mentioned under this 
 heading. Though commonly called a root, because it 
 happens to grow below-ground, it is clearly a stem, 
 because it is provided with " eyes," which eyes, as may 
 be seen when the tuber begins to sprout, are nothing but 
 buds. A tuber, then, is a portion of the stem of the 
 plant, in which the tissues become thickened and filled 
 with nutritive matter (in this case starch), which is pro- 
 vided with buds, and which, when once fully formed, is 
 separated from the parent haulm or stem by the gradual 
 decay and death of the latter. A tuber of this kind ful- 
 fils in the economy of the plant much the same purpose 
 as the seed ; and hence the term ( ' seed potato," though 
 far from correct in a technical sense, conveys, neverthe- 
 less, a not wholly incorrect idea. 
 
 A "bulb," such as that of an onion, is a portion of 
 the stem modified for the same purposes as the tuber ; 
 but whereas in a tuber the stem itself is swollen, and the 
 leaves reduced to the merest scales, in a bulb the condi- 
 tions are reversed : the fleshy scales of an onion bulb are 
 really the bases of the leaves, as any one may see who 
 will examine an onion in growth, while the stem itself is 
 reduced to a mere, flat, and not very thick plate, from 
 the sides of which emerge the leaves. The term balb, as 
 applied to such a root as the turnip, is inaccurate. 
 
 These illustrations, taken from plants most familiar to 
 the cultivator, will suffice to show the general character 
 of the stem and its subdivisions, and will indicate the 
 
PLANT NUTRITION. 41 
 
 great extent of variation there is in its outward charac- 
 teristics. The inward conformation of the stem varies 
 according to the nature of the plant its age and the 
 purpose it fulfils. The structure of the stem of a timber 
 tree and that of a potato tuber both, as we have seen, 
 forms of stems are naturally different. In the one case 
 thin- walled cells filled with starch predominate, in the 
 other wood-cells and fibres filled with woody matter are 
 most abundant. Still, great as are the differences in the 
 manner in which the structural elements are arranged in 
 different cases, those elements are precisely the same as 
 those mentioned as existing in the root and in the leaf ; 
 and the structure of a stem, however ultimately compli- 
 cated, is in the first instance quite simple, being merely 
 an aggregation of cells. Another stem, of very different 
 general appearance it may be, began in precisely the 
 same way. It is only necessary here to allude in passing 
 to the variations in internal structure, according to cir- 
 cumstances, as they must necessarily be referred to again 
 when dealing with the office of the stem and its mode of 
 growth. 
 
 Ises of the Stem the Sap. Having gained a general 
 notion of the nature and construction of the stem, it is 
 necessary to enquire as to its office. What does it do for 
 the plant ? The answer to this may in a measure be 
 gleaned from what has been said as to the office of the 
 leaves. The necessity for their exposure to sunlight has 
 been shown, and to ensure this exposure, and to provide 
 that one leaf shall overshadow and interfere with its 
 neighbor as little as possible, the stem lengthens, and 
 the leaves are thrown off, now on this side, now on that, 
 so that each shall do its own work under the most favor- 
 able circumstances, and hinder its neighbor to the least 
 possible degree. One leaf would not be of much use, 
 but the aggregation of many produces a timber tree. 
 
42 PLA2STT LIFE ON THE FARM. 
 
 One leaf's work would probably not suffice to build up a 
 grain of wheat, the aggregation of them serves to form a 
 sheaf of plump ears. The stem, in fact, is the agency 
 by which the work of individual leaves is combined and 
 concentrated for the general benefit of the plant. Each 
 separate leaf, like each separate cell, has a life of its own, 
 and to some extent is independent of every other leaf ; 
 but, if they are to be of any use to the plant as a whole, 
 there must be a co-operation. The stem and its branches 
 supply the means for this co-operation. Moreover, there 
 must also be co-operation between the root and the leaves. 
 Eoot action by itself wOuld not benefit the plant, even if 
 it were practicable. Leaf action, apart from the root, 
 would soon come to an end. The leaves by their copious 
 evaporating surfaces act as suckers to draw up the water 
 from the soil by the agency of the roots. Thus as the 
 stem is the agent between leaf and leaf, so it is the go- 
 between betwixt the roots and the leaves. Apart, then, 
 from its function of bearing leaves and flowers in such 
 numbers and in such manner as shall secure the greatest 
 benefit to the plant under the circumstances in which it 
 is placed apart also from its office of storing up food 
 for future use we have to consider how it is that the 
 stem acts as the go-between betwixt the root and the 
 leaves, and between the leaves themselves. 
 
 Ascent of Liquids. It is certain that liquids, chiefly 
 water, and gases, mount up from the soil to the leaves. 
 How they enter the root has been explained, and their 
 passage up the stem against the direction of gravity may 
 be accounted for on like principles of diffusion. There 
 are, however, various circumstances which aid the up- 
 ward flow of the liquid. The distended condition of 
 the cells and the swollen state of their walls must exer- 
 cise pressure on the contained fluids, the direction of 
 which is mostly from below upwards. This pressure, or 
 
PLANT NUTRITION. 43 
 
 squeezing process, is augmented by the swaying of the 
 branches or the movements of the leaves. Even more 
 powerful must be the effect of the atmospheric pressure 
 urging up the liquid to fill the place of that evaporated 
 from the leaf surface. This upward current is naturally 
 most active at the period of growth, and the channels 
 through which it flows are necessarily those where the 
 conditions for osmosis are most propitious. In propor- 
 tion, therefore, as the cells become filled with woody or 
 earthy material does the current become less. As the 
 straw ripens or the timber hardens by the formation of 
 wood in its cells, so does the flow of liquid diminish, the 
 leaves in their turn and degree become obstructed and 
 fall, and the current, deprived of their stimulus, becomes 
 feeble. 
 
 But while in thus alluding to some of the duties of 
 the stem, we have had to note the existence during the 
 period of growth of a current of liquid whose general 
 direction is upward, it is necessary to point oat that the 
 direction is not exclusively upward, but that it is mani- 
 fested in whatever direction the resistance is least and 
 where growth may be going on most actively at the time. 
 Again, it is necessary to guard against the still prevalent 
 fallacy attaching to the use of the word " sap." That 
 term was first employed when it was imagined that a 
 regular circulation of fluid took place in plants from 
 root to leaf, and from leaf back to root just as in ani- 
 mals the blood courses from the heart through the arteries 
 to the capillaries, and back from the capillaries to the 
 heart by the veins. In the case of the higher animals 
 there is a continuous series of tubes to convey the fluid, 
 and that fluid is uniformily arterial or venous. It is 
 quite otherwise with plants ; there is no continuous tube 
 or set of tubes, and there is no fluid of uniformily the 
 same composition throughout. Near the root the juice 
 of the plant has one composition, near the leaf another. 
 
44 PLANT LIFE OK THE FARM. 
 
 The word " sap," then, though convenient, must not be 
 used or conceived of as indicating the existence of a cur- 
 rent absolutely fixed in its direction or uniform in its 
 composition. In other words, it has but a remote analogy 
 to the blood, with which it is so often compared. There is 
 an upward current of watery fluid, well marked in spring, 
 there are downward and cross currents varying in direc- 
 tion and intensity according to the requirements of the 
 growing tissues and their conformation. These have 
 only indirect connection with the main upward flow just 
 referred to. 
 
 CHAPTER III. 
 GROWTH. 
 
 Growth and extension. Growth of cells. Growing points. Growth of 
 roots, stems, and leaves. Form as dependent on growth. Move- 
 ments dependent on growth. Movements of protoplasm. Turges- 
 cence. Circumnutation of roots, stems, leaves. Seedling plants. 
 
 In considering the growth of plants we have to distin- 
 guish that growth which is mere extension of old material 
 from that which is the result of the formation of new 
 substance. We have an illustration of the first case in 
 the earliest stages of germination of a seed, or in the 
 sprouting of a potato in a cellar. Growth may and does 
 take place in such instances without any real increase of 
 substance, or any augmented weight save what may be 
 derived from water. The plant in this stage lives upon 
 the resources stored up in its tissues, and will continue 
 to do so until they are exhausted. But growth, in the 
 sense of real increase of substance or of increased weight 
 from the addition of new material, depends upon the 
 amount of carbon assimilated, as already referred to 
 under the heading of leaves, A plant with leaf-green or 
 
GROWTH." 45 
 
 chlorophyll in its tissues (and it is with these alone that 
 we are here concerned) gains carbon in the form of car- 
 bonic acid gas when it is exposed to light, and loses it 
 constantly, whether in light or darkness. Nevertheless, 
 as the total gain is greater than the loss, the balance is in 
 favor of the plant. The plant may thus be considered 
 to be the result of the greater amount of work done 
 (under the influence of sunlight) through the medium 
 of the green cells than of that accomplished by the color- 
 less cells, even though their action is continuous, and 
 that of the green cells intermittent. It is for us now to 
 enquire how this increase of substance, how this growth 
 and building up of new materials takes place. The cir- 
 cumstances that are propitious, or which are antagonis- 
 tic to it, have been considered ; it remains to enquire 
 into the way in which the process itself is effected, and, 
 for this purpose, we must revert to the fabric of the 
 plant, and go back to the cell. 
 
 Growth of Cells, The perfect cell, as has been 
 explained, consists of a membranous bag enclosing the 
 protoplasm, some liquid contents, and in the growing 
 state a small, highly refracting oval body known as the 
 " nucleus." The growth of a cell may take place in one 
 of three different ways. There may be simple extension 
 of the cell membrane, which becomes stretched by the 
 influx of fluid into its cavity, producing a state of "tur- 
 gescence " in the cell. But this turgescence, which is of 
 intermittent occurrence, is of itself hardly to be truly 
 considered as growth in the sense of the formation of new 
 material, although so closely associated with it that no 
 true growth can take place without it. 
 
 A second mode of growth, resulting in the real addition 
 of material, and consequent increase of weight, is that 
 called " intercalary," because new material is supposed 
 to be intercalated or squeezed in between the old. Thus, 
 
46 PLANT LIFE ON THE FABM. 
 
 the molecules of cell-membrane are separated by the pres- 
 sure caused by the turgid protoplasm, and into the inter- 
 stices so formed, new molecules of membrane formed by 
 the protoplasm are, as it were, squeezed. The process is 
 as if a number of grains of sand were laid upon a table, 
 each grain just touching its neighbor, and then a new 
 grain were forced in between two others, only in this case 
 the new grain is formed in the cell itself. The requisite 
 pressure is afforded, in the case of the cell, by the grow- 
 ing protoplasm within, and by the influx of fluid into 
 the cell by osmosis, producing a condition of turgescence. 
 The growth of the protoplasm itself takes place precisely 
 in the same way as that of the cell membrane viz., by 
 the formation of new particles, which are squeezed in by 
 intercalary growth between the older ones. New matter 
 is also deposited on the outer surface of the protoplasm 
 or inner surface of the cell wall. 
 
 Lastly, growth is effected, not merely by extension of 
 old cells, or by incorporation of new materials with old, 
 but by actual increase in the number of cells. This 
 increase in number has been brought about by the sub- 
 division of the protoplasm into two or more segments, 
 each of which becomes invested by cell-membrane. 
 
 For full details as to the various ways in which division 
 of the protoplasm and the formation of new cells take 
 place, reference must be made to text books. What has 
 been here said is sufficient to indicate the general nature 
 of growth in the organs with which we are here most 
 concerned the root, the stem, and the leaf. 
 
 Growing Points. As has been stated, all the parts of 
 plants are at first wholly cellular and structurally indis- 
 tinguishable ; but, as growth goes on, not only their 
 outer form alters, but the form and arrangement of their 
 constituent cells also, so that various tissues fibrous, 
 woody, vascular, or epidermal are formed ; and thus it 
 
GROWTH. 47 
 
 comes about that in the fully developed root the internal 
 structure and the arrangement of the tissues are different 
 in the great majority of cases from those of the stem, 
 those of the stem from those of the leaf, and so on dif- 
 ferent, that is to say, in so far as the arrangement of the 
 elementary cells and tissues go, rather than as far as the 
 cells themselves and their modifications are concerned. 
 But while there is this difference in the structure of the 
 adult leaf, stem, and root respectively, all the time these 
 organs retain their active faculty of growth there remains 
 a portion of the cellular tissue in its original unmodified 
 condition the cells ready to divide and multiply and so 
 bring about the growth of the organ. This portion is 
 called the " cambium "or " meristem." So far as growth 
 in length is concerned, there are certain special points 
 where subdivision of cells is most active. These are 
 called the "growing points." At these places the cells 
 divide rapidly, each cell remaining small, and not, as 
 elsewhere, greatly extending its size by interstitial 
 growth. 
 
 Growth of Roots. The growing point of a root, so 
 far as its length is concerned, is comprised within a 
 small area just above the extreme tip, the extreme tip 
 itself being, as previously stated, covered by a little cap 
 shed off from the skin of the root and serving as a shield 
 to it in its progress through the soil. 
 
 That the growth in length takes place over a very 
 small area adjacent to the tip of the root is proved by a 
 very simple observation. If marks be made on the grow- 
 ing root at equal distances apart, say one-eighth inch, 
 and the progress of growth be watched from day to day, 
 then it will be found that while the uppermost marks 
 remain equi-distant, those near the tip become more or 
 less widely separated. This experiment is easily carried 
 out with a hyacinth growing in a glass vase, or by allow- 
 
48 PLAKT LIFE GIST THE FAftM. 
 
 ing a bean to germinate on the surfafce of wet moss. It 
 will thus also be seen that the actual area in which 
 growth in length is going on is very small., and that its 
 greatest activity is not exactly at the extreme point, but 
 a little above it, between it and the point where the root- 
 hairs begin to emerge. There is, then, in the growing 
 root first, at the extreme tip a root-cap or shield, con- 
 stantly renewed from within by the growth of the cells 
 above or within it ; then a region of very limited extent, 
 devoted to the growth in length of the root ; and above 
 that a portion, usually but not always, provided with 
 root-hairs, and which is especially told oif to fulfil the 
 duties of absorption. 
 
 As the upper, thicker part of the root is relatively 
 fixed, it will be seen how the fine root fibrils are, by the 
 situation of their growing point, enabled to push their 
 way, by constant renewal at their growing point, in 
 amongst the particles of -the soil when the conditions are 
 favorable. 
 
 Growth of the Stem, In the case of the stem and 
 branches, the growing points, by whose agency increase 
 in length takes place, are placed at the summit of the 
 stem or of its subdivisions, the branches. The growing 
 points then form the substance of the " buds," which are 
 either invested by leaf -scales as protectors and stores of 
 nourishment, as in the case of bulb-scales, or by perfect 
 leaves. The increase in the thickness of stems takes 
 place also by means of the growing tissue or cambium, 
 the situation of which is different in the two main groups 
 of "Exogens" and " Endogens." 
 
 To the former series belong all our trees and shrubs, 
 the clovers, beet-roots, turnips, and the vast majority of 
 plants which have the veins of their leaves disposed in a 
 network. In these plants the woody bundles of which 
 the stem is principally made up consist of " wood cells " 
 
GROWTH. 49 
 
 and " bast cells/ 7 with vessels of various kinds ; and on 
 the outer side of each bundle is a thin layer of cambium 
 tissue capable of growth, and in virtue of which the 
 woody bundles increase on their outer surface. These 
 woody bundles accumulate in wedge-like masses, and 
 these again are arranged in concentric rings around the 
 central cellular pith, thus forming the rings visible on 
 the cut surface of the trunk of a tree, one such ring 
 generally indicating, in these latitudes, the growth of 
 one season, or at least of one growing period. 
 
 In Endogens, to which all the cereals, and the grasses 
 and almost all plants in which the veins of the leaf run 
 parallel or nearly so, the woody bundles have their cam- 
 bium tissue in the centre of each bundle, so that their 
 growth in diameter is limited by the pressure of the older 
 tissues outside, and there are no concentric rings in the 
 stem. Indeed, in this country, such plants do not pro- 
 duce a woody stem. 
 
 Growth of Leaves, The growing points of leaves oc- 
 cur in various situations, according to the kind of leaf. 
 Sometimes and more generally the direction of principal 
 growth is from within outward that is to say, from the 
 centre outward (centrifugal) ; in other cases, the general 
 tendency is in the opposite direction (centripetal). In 
 addition to these growing points at definite spots, where 
 new cells are always forming during the active period, 
 new growth may occur in isolated spots by the formation 
 of growing cells in the midst of or between others that 
 have lost their faculty of growth, and thus growth in the 
 substance of the plant may take place by intercalation as 
 well as at the extremities. 
 
 To repeat, then, true growth consists in the formation 
 of new protoplasm from the old, and in the division of 
 the protoplasm into new cells. This division takes place 
 especially and primarily, so far as growth in length is 
 
50 PLANT LIFE OK THE FAKM. 
 
 concerned, at certain definite places called growing points. 
 The new tissues thus formed are at first wholly cellular, 
 some of the constituent cells retaining the faculty of sub- 
 division, though sometimes not manifesting it till a later 
 period ; while others become modified in various ways as 
 growth goes on, forming wood-cells, fibres, epidermis, and 
 so on. 
 
 Form as Dependent on Growth, If we could sup- 
 pose the degree or intensity of growth to be equal on all 
 sides, and without impediment or obstacle, the result 
 would be a spherical plant ; and such plants do exist, 
 but, in the great majority of cases, the conditions are 
 such that growth is greater in amount in one direction 
 than in another ; or it may be that while pait remains 
 stationary another part grows, the result being a change 
 of form. In the case of the main root and stem, the 
 principal direction of growth is vertically upwards and 
 downwards ; in the case of leaves, the main direction of 
 growth is horizontal, so that while a stem or a root may 
 be divided from above downwards into two nearly equal 
 halves, one half the reflex of the other, a leaf must be 
 divided horizontally, and the upper surface and the lower 
 surface are commonly different. Variations in form are 
 dependent not only on variations in the direction of 
 growth, but upon the place where growth is taking place, 
 and whether it be limited, as in the case of the growing 
 points and cambium tissue already referred to, or general 
 throughout the mass. 
 
 The form of the plant or of any particular part of it 
 will also of necessity vary according as the growth is con- 
 tinuous or intermittent, equal or unequal. These are all 
 circumstances readily understood, and they are referred 
 to here because they furnish the reasons for the develop- 
 ment of bulb and root, as of turnip and mangel as con- 
 trasted with that of foliage. In them also must be 
 
GEOWTH. 51 
 
 sought the explanation of thin ears of wheat or defective 
 hay crops. 
 
 Phenomena associated with Growth and Activity. 
 
 Under this heading may be mentioned the various move- 
 ments in the liquid (cell-sap), contained within the cells, 
 and in the protoplasm, which are observed in living cells, 
 especially in those in which the vital processes are most 
 active. Here also may be mentioned the movements 
 associated more or less directly with growth, and the 
 influence of various agencies, such as of gravitation, 
 light, temperature, etc., on plants and their several 
 organs. These phenomena and these influences are more 
 manifest during active growth ; and when they occur in 
 living organs which have ceased their actual growth, 
 they do not essentially differ, though they may do so in 
 degree, and may also, to some extent, be modified in 
 character. 
 
 Movements as Dependent on Growth, But a few 
 
 years ago the notion of movement taking place in plants, 
 other than that produced by the wind or other mechani- 
 cal agency, was, if not entirely ignored, so little con- 
 sidered that the immobility of plants was contrasted with 
 the mobility of animals. We know now that even loco- 
 motion is by no means an exclusive attribute of animals, 
 but for our present purposes we need only refer to those 
 movements more immediately connected with the growth. 
 
 Movement of Protoplasm. The protoplasm is a very 
 mobile substance, and the cell-membrane is very elastic, 
 while both, as has been shown, are permeable in various 
 degrees by water, the consequence of which is that under 
 favorable conditions the cells become turgid. As the 
 degree of turgescence varies according to circumstances, 
 tension being followed by flaccidity, and flaccidity over- 
 
52 t>LAKT LIFE OK THE FAKM. 
 
 come by,turgidity, is of course obvious not only that 
 changes of form must ensue from these differences in the 
 degree of tension of the cells, but that movements of the 
 parts concerned must also take place. These movements 
 are, of course, more obvious when growth is irregular 
 and unequal. Turgescence of the cells, as has been said, 
 is an essential condition of growth, and if this turges- 
 cence take place on one side of a stem, or on one surface 
 of a leaf only, a curve will be produced, the convexity of 
 which will be along the line of greatest swelling and 
 growth the concavity on the opposite side where growth 
 is less active, or altogether inoperative. The rapidly 
 growing upper surface will be restrained as by a bridle 
 by that part which is growing more slowly or not at all, 
 and hence the curvature. 
 
 Circumnutation. Now, let us suppose the very fre- 
 quent case where the greatest intensity of growth is now 
 in one place, now in another, then, of course, we should 
 have the curvatures first in one place, and then in 
 another, and this is what happens in the case of growing 
 shoots whose tips gradually revolve, forming circuits or 
 ellipses of greater or less extent with greater or less 
 rapidity, according to circumstances. This movement, 
 which is not usually perceptible except by the use of 
 delicate instruments, may sometimes be watched by the 
 naked eye, even in the case of such apparently stiff parts 
 as the leading shoots of Firs. Among other objects 
 gained by this movement of ' ' revolving nutation," or as 
 Darwin called it, (< circumnutation," is the exposure of 
 each leaf in turn to the conditions of light most favor- 
 able to it. 
 
 Movement of the Tip of the Root, While the elon- 
 gation of the root near the tip takes place in the manner 
 described, the force of growth is not equal throughout 
 
GROWTH. 53 
 
 the whole region at the same time. Supposing the fibril 
 to be made up of cells piled up one upon another in lon- 
 gitudinal rows, then the greatest energy of growth, 
 marked by the turgescence of the cells, occurs at one time 
 in one row, to shift at another time into the next row, 
 and so on in succession all round the root. The effect of 
 this greater turgescence and intensity of growth now in 
 one place, now at another is to move the tip of the root, 
 not" in a circle, because growth is going on behind the 
 tip as it moves, but in an advancing spiral coil, so that 
 the tip is forced to enter the soil and to penetrate 
 between its particles, just as the point of a corkscrew is 
 made by the pressure of the hand to penetrate the cork, 
 the pressure of the hand being replaced, in the case of 
 the root, by the superincumbent weight of soil. 
 
 Darwin, who has done so much to illustrate and make 
 known the movements of roots and of other organs, cal- 
 culates that the terminal growing part of the radicle (or 
 primary root produced from the seedling plant) "in- 
 creases in length with a force equal to ... the pressure 
 of at least a quarter of a pound probably with a much 
 greater force when prevented from bending to any side 
 by the surrounding earth. While thus increasing in 
 length, it increases in thickness, pushing away the damp 
 earth on all sides with a force of above eight pounds in 
 one case, of three pounds in another case. . . . The 
 growing part, therefore, does not act like a nail when 
 hammered into a board, but more like a wedge of wood, 
 which, whilst slowly driven into a crevice, continually 
 expands at the same time by the absorption of water ; 
 and a wedge thus acting will split even a mass of rock." 
 
 Movement of Stems. The circumnutation of stems as 
 a result, or at least as a concomitant of active growth, is 
 most easily seen in the case of climbing plants like the 
 hop, the free ends of whose growing shoots sweep round 
 
54 PLANT LIFE ON THE FARM. 
 
 in wide cttrves till they come in contact with a support 
 round which to twine,* and thus remove their leaves 
 from the surface, where they would be overshadowed, to 
 a point of vantage where they would be exposed to light, 
 and this with the least expenditure of material. Very 
 similar are the movements executed by stolons and run- 
 ners, as of the strawberry, and probably, though the 
 cases have not been studied, of the trailing rhizomes of 
 the twitch (Triticum repens), the scions of the meadow 
 poa (Poa pratensis), of the clovers, of the milfoil, etc. 
 Such a movement would facilitate the introduction of 
 these runners between other plants, and thus secure the 
 extension of their area of growth. The movements in 
 the stem are more especially connected with growth ; 
 they cease, or become much enfeebled after growth is com- 
 pleted or arrested. Under certain circumstances, however, 
 the faculty of growth is retained in certain spots after it 
 has ceased elsewhere, or if actual growth do not take 
 place, yet some of the phenomena connected with it may 
 occur. Thus the stems of grasses, such as of wheat, are 
 provided with thick "nodes" or joints at the places 
 whence the leaves spring from the stem. When the 
 wheat gets beaten down or laid by a storm of rain and 
 wind, the resumption of the erect position is effected by 
 the medium of the nodes, which grow, or at least become 
 turgescent, especially on the under surface, which thus 
 becomes convex, while the upper surface, which does not 
 grow, or at least not to the same extent, becomes con- 
 cave ; the consequence is that the upper end of the stem 
 becomes raised as may be illustrated thus : Let- 
 represent the joint of the laid stem ; then, by the agencies 
 just mentioned, the straight horizontal position is replaced 
 
 by the ascending one , and ultimately by the vertical one 
 
 *See Darwin, The Movements and Habits of Climbing Plants, 
 
GROWTH. 55 
 
 Darwin has shown that the joints of grass stems continue 
 to exhibit movements on a small scale for a long period. 
 Supposing the stem to be "laid," such movements would 
 clearly aid the upward tendency above described, and 
 facilitate the uprising of the stem. (Darwin, Power of 
 Movement, p. 503). 
 
 MoTements of Leaves, The leaves of plants exhibit 
 several kinds of motion ; some periodic, as in the case of 
 the so-called sleep of leaves, some due to the stimulus of 
 light or its removal, some the consequence of contact, as 
 in the case of the sensitive plant; but those to which 
 mention is here made are the result of the same causes as 
 those before alluded to in the case of stems and roots. 
 The growth movements of leaves are observable in the 
 stalk, or in the blade, or in both, and are chiefly exerted 
 in a vertical direction, so that the leaf rises or falls ; but 
 as the ascent is never quite in fche same line as the de- 
 scent, some side to side motion must also take place. It 
 is noticed that the rise occurs generally in the evening, 
 the fall on the following morning. These movements 
 are probably due to the intensity of growth being greater 
 first on one side, then on the other. 
 
 Growth-movements of the kind indicated have now 
 been shown to exist in the roots, in the stems, and in the 
 leaves. The probability is that they occur more or less 
 wherever growth is going on actively. In accordance 
 with this, it maybe mentioned that seedling plants mani- 
 fest these movements to a remarkable degree. Thus- all 
 the parts of seedling cabbages, the radicle, the caulicle 
 above the radicle supporting the seed leaves or cotyle- 
 dons, as well as these latter organs, were observed by 
 Darwin to exhibit growth movements facilitating the 
 downward passage of the root and the upward progress 
 of the caulicles f 
 
56 PLAixT LIFE Otf THE FARM. 
 
 CHAPTER IV. 
 
 SENSITIVENESS. 
 
 Movements dependent on external conditions. Gravitation, light, 
 heat, moisture. Action of gravity on roots. Geotropism. Influ- 
 ence of light, heat, moisture, and contact on roots. Passage of 
 roots through the soil. Action of gravitation on leaves. Helio- 
 tropism. Sleep of leaves. Action of heat and moisture on leaves. 
 Defensive arrangements. Selection of hardy varieties. Influence 
 of contact on leaves. Action of gravity, light, heat, moisture, and 
 contact on stems. After-effects. Climbing plants. Combined 
 effect of external and internal agencies. 
 
 Closely analogous to the growth-movements are a series 
 of alterations of position dependent upon various circum- 
 stances, such as gravity, the influence of heat and light 
 or their absence, the result of contact or irritation, and 
 so on. They are probably essentially of the same nature 
 as the growth movements, but, unlike them, they are 
 not confined to structures still in a growing state more- 
 over, in some cases they exhibit a sort of reflex action, 
 contact or irritation of one part bringing about a move- 
 ment of some other part at a distance. It is often diffi- 
 cult to dissociate the effects of these several movements ; 
 for a living plant and its parts are subjected at the same 
 time to the combined influence of several of these 
 agencies, and the force and direction of growth are neces- 
 sarily essentially modified by them. 
 
 It may be well in this place to indicate very generally 
 in what manner roots, stems, and leaves are sensitive to 
 the effects of gravity, light, moisture, and actual contact 
 or irritation, and then to specify equally briefly what is 
 the general character of the results produced by these 
 several causes acting singly, or in combination. 
 
 The Action of Gravity on Roots. Oeotropism, The 
 
 downward tendency of the main root is one of its most 
 
SENSITIVENESS. 57 
 
 marked characteristics, and this tendency to grow, or 
 move towards the centre of the earth under the influ- 
 ence of gravitation, is known as "geotropism," the op- 
 posite tendency being called f< apogeotropism." Knight 
 was the first to show that downward tendencies of the 
 root were due to gravitation, and this he did by causing 
 seedlings to grow on a wheel kept in motion. The effect 
 of gravity was here overcome by the movement of the 
 wheel, and the rootlets, instead of growing downwards, 
 were now directed away from the centre of the wheel. 
 Darwin shows (1. c., p. 540) that it is the tip of the root 
 alone that is involved in this downward tendency, the 
 destruction of the tip putting a stop to the movement. 
 While the primary root or radicle under favorable cir- 
 cumstances penetrates the soil perpendicularly downwards, 
 the secondary ones bend obliquely, not perpendicularly, 
 downwards, the tertiary ramifications and their subdi- 
 visions being so little affected by geotropism that they 
 grow out freely in all directions. From this manner of 
 growth in the main root and its branches respectively, it 
 is evident how the whole mass of soil within their reach 
 becomes, under favorable conditions, a happy hunting 
 ground for the roots. Moreover, it has been shown that 
 where the primary radicle, the origin of the " tap" root, 
 has been destroyed as it often must be in nature, by 
 insects or other means the secondary roots, instead of 
 retaining their oblique direction, assume that previously 
 taken by the injured root and pass downwards. 
 
 The Action of Lteht and Heat on Roots, The direct 
 action of light upon ordinary roots is, of course, usually 
 of a negative character. The form and direction of 
 growth in the root may, however, be affected by differ- 
 ences of temperature, experienced now on one side, now 
 on another. Darwin has shown that the movements of 
 roots, due to irritation or contact, are checked by too 
 
58 PLANT LIFE ON THE FARM. 
 
 high or too low a temperature. During their passage 
 through the soil, the roots must be constantly subjected 
 to variations of temperature, first on one side and then 
 on another, these variations giving rise to some of the 
 curvatures and bends of the rootlets. The effect of an 
 excessive amount of heat in the soil upon the germination 
 of seedlings has been studied by M. Prillieux, and is of 
 interest as indicating the conditions under which tuberous 
 roots and root stocks may, under certain circumstances, 
 be formed. When seedlings of French beans and vege- 
 table marrows were grown in an overheated soil, the 
 caulicle or portion of the stem above the root and between 
 it and the seed-leaves became preternaturally swollen 
 and tuberous, while growth in hight was arrested. The 
 increased development arising from the heated soil took 
 place, therefore, in the very same organs which constitute 
 the so-called " bulbs "of turnips or " roots " of swedes 
 or mangels. The increased volume is due principally to 
 an excessive development of existing cells rather than to 
 a multiplication of new ones. 
 
 The Action of Moisture on Roots. Much more 
 obvious to the general observer is the action of moisture 
 on roots. The distance to which roots will travel in 
 search as it were of water, and the way in which luxuri- 
 ant growth and intricate ramification are promoted, when 
 access to it is obtained, are familiar facts. Too frequently 
 drain pipes get choked with a mass of roots whose 
 structure has been changed, and whose excessive growth 
 has been stimulated by the presence of copious supplies 
 of moisture. If there is an equal supply of water all 
 round, the growth of the roots will be uniform ; but if, 
 as is more often the case, there is more water on one side 
 than on the other, then the root will curve to the side 
 where there is the fullest supply, and the power thus 
 exerted to get at the water is greater than that of gravity. 
 
SENSITIVENESS. 59 
 
 When the tip of the root is covered with grease, the root 
 does not bend to the wet surface, on which account Mr. 
 Darwin and his sou infer that sensitiveness to moisture 
 resides specially in the tip. The relation these move- 
 ments and this growth bear to the processes of nutrition 
 carried on by the roots is too obvious to need further 
 comment. 
 
 The Influence of Contact on Roots. The effect of 
 pressure such as that caused by the contact of any sub- 
 stance, even if it be very slight, is to produce movements 
 of curvature in the root, the direction of the curvature 
 varying according to the part of the root touched. Thus, 
 if the root be touched in the region where growth is 
 going on most actively, the root becomes concave on the 
 side which is touched, convex on the opposite side, prob- 
 ably because growth is arrested by the pressure on the 
 one side, while it is unrestricted on the other. The con- 
 sequence of this is that the roots in such case turn 
 towards the obstructing substance, and, if it be of small 
 dimensions, coil themselves around it, or, if it be too 
 large for this purpose, creep over its surface. 
 
 On the other hand, if the extreme tip of the root be 
 touched, the root bends away from the obstruction, 
 becoming convex on the side where contact is effected, 
 concave on the opposite side, the root sometimes making 
 complete loops by its continued curved growth. The 
 object of this sensibility to contact appears to be to 
 enable the roots to overcome the obstacles they meet with 
 in the soil. Thus " when a root meets with an obstacle 
 in its way, the pressure on one side of the tip causes the 
 growing part of the root to grow more rapidly on the side 
 of the obstacle, and thus curve away from it " (F. Dar- 
 win). 
 
 It will be seen that the irritation from the various 
 causes above mentioned is not merely local in its effect. 
 
60 PLANT LIFE ON THE FARM. 
 
 but that it induces movement in adjoining parts, on 
 which account the parts so influenced are spoken of as 
 "sensitive." 
 
 Passage of Roots through the Soil Summary. The 
 
 course followed by a root through the soil is, says Dar- 
 win, " brought about and modified by extraordinarily 
 complex and diversified agencies by geotropism, acting, 
 as has just been explained, in a different manner on the 
 primary, secondary, and tertiary radicles ; by sensitive- 
 ness to contact, different in kind in the apex and in the 
 part immediately above the apex ; and apparently by 
 sensitiveness to the varying dampness of different parts 
 of the soil. . . . The direction which the apex takes at 
 each successive period of the growth of a root ultimately 
 determines its whole course ; it is, therefore, highly im- 
 portant that the apex should pursue from the first the 
 most advantageous direction ; and we can thus under- 
 stand why sensitiveness to gravitation, to contact, and to 
 moisture, all reside in the tip, and why the tip determines 
 the upper growing part to bend either to or from the 
 exciting cause. A radicle may be compared with a bur- 
 rowing animal, such as a mole, which wishes to penetrate 
 perpendicularly down into the ground. By continually 
 moving his head from side to side, or circumnutating, he 
 feels any stone or other obstacle, as well as any difference 
 in the hardness of the soil, and he will turn from that 
 side. If the earth is damper on one than on the other 
 side, he will turn thither as to better hunting ground. 
 Nevertheless, after each interruption, guided by the 
 sense of gravity, he will be able to recover his downward 
 course and to burrow to a greater depth." 
 
 Elsewhere Darwin sums up the root movements as fol- 
 lows : " We believe that there is no structure in plants 
 more wonderful, so far as its functions are concerned, 
 than the tip of the radicle. If the tip be lightly pressed, 
 
SENSITIVENESS. 61 
 
 or burnt or cut, it transmits an influence to the upper 
 adjoining part, causing it to bend away from the affected 
 side ; and, what is more surprising, the tip can distin- 
 guish between a slightly harder and softer object by 
 which it is simultaneously pressed on opposite sides. If, 
 however, the radicle is pressed by a similar object above 
 the tip, the pressed part does not transmit any influence 
 to the more distant parts, but bends abruptly towards the 
 object. If the tip perceives the air to be moister on one 
 side than on the other, it likewise transmits an influence 
 to the upper adjoining part, which bends towards the 
 source of moisture. When the tip is excited by light, 
 the adjoining part bends from the light ; but when 
 excited by gravitation, the same part tends towards the 
 centre of gravity. In almost every case we can clearly 
 perceive the final purpose or advantage of the several 
 movements. Two or perhaps more of the exciting causes 
 often act simultaneously on the tip, and one conquers 
 the other, no doubt, in accordance with its importance 
 for the life of the plant. The course pursued by the 
 radicle in penetrating the ground must be determined by 
 the tip ; hence it has acquired such diverse kinds of sen- 
 sitiveness. .It is hardly an exaggeration to say that the 
 tip of the radicle thus endowed, and having the power of 
 directing the movements of the adjoining parts, acts like 
 the brain of one of the lower animals, the brain being 
 seated within the anterior end of the body, receiving im- 
 pressions from the sense-organs, and directing the several 
 movements." 
 
 Practical Inferences. It will be obvious, then, from 
 what has been before said, that for cultural purposes, 
 such as the various operations connected with tillage, the 
 nature, quantity, and time of application of manure, and 
 the like, the character of root-action in general must be 
 studied in connection with the nature and properties of 
 
62 PLANT LIFE ON THE FAIIM. 
 
 the soil. The special form and characteristics of the 
 root in the particular crop it is wished to cultivate tap- 
 rooted, fibrous-rooted, fleshy, surface-rooting, or deep- 
 rooting, etc. must also be taken into consideration in 
 the same relation. 
 
 Action of Gravitation on Leaves. The tendency of 
 leaves during their growing period so to place themselves 
 that their upper surface looks to the heaven, their lower 
 to the earth, is a matter of every-day observation. 
 Scarcely less familiar are the turns and twists which the 
 leaves or their stalks make to right themselves when by 
 any means their normal position is interfered with. At 
 first sight it would seem that these movements must be 
 due rather to the influence of light than of gravitation ; 
 but as they take place in darkness as well as in light, and 
 as they do not take place when plants are so grown as to 
 be exempt from the influence of gravitation, it is clear 
 what the true cause of these movements is (Van Tieghem). 
 
 Action of Light on Leaves Heliotropism, The 
 
 chemical changes which result from the exposure of the 
 leaves to light have already been alluded to under the 
 head of nutrition. It remains here to mention the power 
 that they have of turning to the light, now called ''helio- 
 tropism," and especially of so placing their upper surface 
 as that it shall form a right angle to the direction of the 
 light. It had been surmised that the horizontal position 
 of leaves, and especially the position with regard to the 
 direction of light, was due to the conjoint action of 
 gravitation of geotropism, of heliotropism, and of the 
 greater relative force of growth on one or the other sur- 
 face. The particular direction assumed by the leaves 
 was supposed to be due to the balance between these 
 forces ; but by means of experiments made with a view 
 of annulling or counteracting the effects of gravitation, 
 
SENSITIVENESS. 63 
 
 and of unequal growth, Mr. Francis Darwin has shown 
 that the power which leaves have of placing themselves 
 at right angles to incident light is due to a special sensi- 
 tiveness. This sensitiveness is capable of regulating the 
 action of other forces, whether external to the plant, as 
 that of gravitation, or internal, such as that controlling 
 the direction and amount of growth. The movements 
 of the leaves towards the light are different from others 
 which are of a periodic character, in that they are influ- 
 enced hy the direction rather than by the intensity of 
 the light. 
 
 The growth of leaves, like growth in general, is re- 
 tarded by the action of light. Growth, therefore, is 
 carried on independently of and not contemporaneously 
 with nutrition by the leaf, so far as the latter consists in 
 the decomposition of carbonic acid and the fixation of 
 the carbon. Thus it has been shown hy Dr. Vines that 
 leaves will grow in darkness, or under the influence of 
 blue light ; in air deprived of carbonic acid ; and even in 
 the absence of chlorophyll. But although there is thus 
 shown to be no direct relation between nutrition and 
 growth, yet there is, of course, an indirect relation ; 
 growth under the apparently adverse conditions just 
 mentioned, being only possible in cases where there is 
 available some store of nourishment previously formed by 
 assimilation. 
 
 Sleep of Leaves. Other movements of leaves are de- 
 pendent chiefly on the amount of light to which they are 
 subjected. Of such nature are the movements popularly 
 supposed to be connected with the sleep of plants, but 
 which have no real analogy with the sleep of animals. 
 Clover and sainfoin leaves show these nocturnal move- 
 ments very clearly, the leaflets folding up at the approach 
 of night, and unfolding in the morning as the light in- 
 creases. Plants exposed to the dark end of the solar 
 
G-i PLANT LIFE ON THE FAKM.- 
 
 spectrum manifest similar movements. Some leaves are 
 raised, others depressed, some fold upwards, some down- 
 wards, but the object in all cases is probably the same 
 namely, to shield the leaves from the cooling effect of 
 radiation from the surface during the night, a process 
 which produces the same effects as actual frost would do. 
 The cause of these movements is due to a swelling or 
 turgescence and a consequent growth first on one side 
 and then on another side. 
 
 Action of Heat and Moisture upon Leaves, But 
 little beyond what has already been mentioned need be 
 said upon the relation of heat and moisture to leaves. A 
 few words upon the influence of excessive temperatures 
 may, however, here be appropriately given. 
 
 If the temperature fall below a given point, variable 
 for each species, and also for each individual plant, the 
 functions of the leaf are held in abeyance, chlorophyll is 
 only imperfectly formed (hence the yellow tinge of 
 frosted wheat) ; and if the temperature be still further 
 depressed death results. 
 
 Action of Frost, When a leaf is frozen the fluid con- 
 tents escape from the cells by permeation through their 
 membrane, and freeze on the outside of the cell, so that 
 the spaces between them are full of ice. It rarely hap- 
 pens that the juices of the cells freeze in the interior of 
 the cells if they do, rupture of the cell wall and death 
 are the most probable results. Under ordinary circum- 
 stances the cells lose that turgescence which, as has been 
 stated, is necessary for their activity. All the functions 
 of life are arrested, not necessarily never to be resumed, 
 for, in some cases, when the ice in the tissues of the 
 plant melts, the water is re-absorbed by the membrane, 
 and life action is resumed. Winter wheat must fre- 
 quently become frozen in this manner, but it is com- 
 
SENSITIVENESS. 05 
 
 paratively rarely that the plant is killed outright, farmers 
 wisely choosing those varieties which experience has 
 shown to be the hardiest. If the cold is sufficient to kill 
 the leaves or any portion of them, the leaves become limp 
 and blackened. The limpness is easily accounted for by 
 the causes we have mentioned,, as well as by the stoppage 
 of supplies of water from the root. The discoloration is 
 the effect of some molecular change in the chlorophyll at 
 present not understood. 
 
 Action of Excessive Heat. Too high a temperature 
 also arrests or perverts all the functions of the leaf. 
 Where transpiration is excessive, and the absorption of 
 fresh supplies not in proportion, the leaves speedily 
 wither, as maybe seen in a field of mangels on a hot day, 
 when the evaporation of watery vapor from the surface 
 is greater than the absorption of moisture by the root. 
 On the other hand, during the night, while the roots are 
 still at work, the transpiring power of the leaf is lessened, 
 and drops of water exude from the leaves. Where the 
 temperature is so high as to kill the plant or leaf out- 
 right, it is the protoplasm which dies ; its constitution 
 and molecular construction become changed, its power 
 of absorbing water destroyed, and thus the turgid condi- 
 tion of the cells is lost. 
 
 Defensive Arrangements. Prejudicial effects, either 
 of a too low or a too high temperature, are moderated 
 by the conformation of the leaf, the thickness of its skin, 
 the arrangement of its tissues, the presence of hairs, and 
 other structural endowments. These circumstances ren- 
 der the selection of the particular variety most suitable 
 for any special locality a matter of the greatest moment. 
 In the case of wheat, for instance, some varieties are 
 much more tender than others. Bearded wheats are as 
 a rule hardier than the beardless ones. A variety known 
 
66 PLANT LIFE OX THE FARM. 
 
 as the Blood Bed is very hardy, owing its immunity possi- 
 bly to it's habit of keeping its leaves close to the ground 
 during the winter and spring, and, therefore, less exposed 
 to sudden changes of temperature. In any case, its 
 leaves are more likely to be protected by a coating of 
 snow. The selection, therefore, of the kind of wheat 
 best adapted for Scotland, for the eastern or for the 
 western counties of England respectively, is a matter of 
 great consequence. A variety which succeeds in a warm 
 moist climate would be quite unsuitable for a drier one, 
 even if the temperature sometimes rose higher. 
 
 In moist air it has lately been shown by M. Vesque 
 that the leaves are both thinner and longer than when 
 grown in dry air, that the vascular bundles of the stem 
 are also thinner, and less perfectly developed than in 
 dry air. Thus, the effects of a saturated atmosphere on 
 the growth of leaves seem to be very similar to those 
 mentioned by Rauwenhof as characteristic of plants 
 grown in obscurity. When fully exposed to the light, 
 in a dry, hot, stagnant atmosphere, where transpiration 
 from the surface of leaves is ample, the leaves become 
 thicker, their anatomical structure is altered, and they 
 show a tendency to become more hairy. 
 
 It would not be worth while for the agriculturist to 
 try and make his plants adapt themselves to different 
 conditions as the experimentalists and physiologists do, 
 but the indications and facts brought forward by the lat- 
 ter may very profitably influence the farmer's selection 
 of the particular varieties best suited, by their conforma- 
 tion or structure, to meet the vicissitudes of particular 
 localities. 
 
 The Influence of Contact on Leaves. This may be 
 
 dismissed with a few words only, as it is not, so far as at 
 present known, of much practical importance to agricul- 
 turists. In addition to the movements immediately con- 
 
SENSITIVENESS. 6? 
 
 nected with growth, gravitation, or the action of light, 
 which are manifested only during active growth, there 
 are others which occur in the fully-developed leaf, as the 
 periodical night and day movements, the movements af- 
 fected by light and temperature, and lastly, those which 
 are caused by mechanical contact, as by the impact of 
 certain nitrogenous substances, as in the so-called car- 
 nivorous leaves before referred to, and those caused by a 
 touch or other mechanical eifect, as in the leaves of the 
 sensitive plant. Chloroform and ether arrest these move- 
 ments, while they have no effect upon the movements 
 that are due to light and heat. The cause of the move- 
 ments in question is attributed to the sudden contraction 
 of the protoplasm, the expulsion of the watery contents 
 of the cells forming the lower portion of the swelling 
 which leaves endowed with this property possess at the 
 base of their stalks. The cells so emptied become flaccid, 
 and the leaf in consequence falls. The water expelled 
 from the interior of the cells passes into the spaces 
 between them and into the stem, as in the case of frozen 
 leaves (p. 65), and is re-absorbed when the irritation 
 ceases. The balance being restored, the leaf resumes its 
 horizontal position. 
 
 The Action of Gravity on Stems, The cause of the 
 upward growth of stems, though so familiar, is not 
 understood. It is in general exerted in opposition to the 
 direction of gravitation. If a stem be bent downwards, 
 growth takes place much more rapidly on the lower sur- 
 face, tending to make it convex on the lower surface, and 
 consequently to raise its free end (see p. 54). It is this 
 tendency, which, as has been previously stated, permits 
 the stalks of the wheat when laid to recover their erect 
 position. Some stem or portions of stem are, however, 
 directly influenced by gravitation, as in the case of under- 
 ground stems and branches, which burrow in the ground 
 
68 PLANT LIFE 02ST THE FAKM. 
 
 to produce tubers ; and it is clear, from the position and 
 direction of the branches of a tree, that the influence of 
 gravity, direct or negative, varies greatly in different 
 cases, so that on the whole it is probable that the direc- 
 tions in question are more especially due to varying de- 
 grees of intensity of growth in different situations, accord- 
 ing to local necessities and the action of light, than to 
 gravitation pure and simple. 
 
 Influence of Light on Stems. The remarks made 
 under the corresponding heading in regard to leaves, 
 apply with the necessary modifications to stems. The 
 stems have often a marked tendency to move or grow 
 towards the light, but the opposite tendency is shown in 
 other instances, as in the ivy, the runners of the straw- 
 berry, and other cases, where this peculiarity favors the 
 application of the stem to the surface of the ground, of 
 a wall, or of any means of support, as in many climbing 
 plants. 
 
 The action of light in retarding growth, already referred 
 to, seems opposed to many of the phenomena just recorded 
 such as the bending of the stems towards the light, 
 the fact that stems grow by day as well as by night, the 
 circumstance that the tissues of plants grown in the dark 
 are feeble and ill-developed. These apparent contradic- 
 tions may be explained by the fact that the retarding 
 influence of growth, which is so manifest when the plant 
 is grown under artificial conditions, when the influence 
 of other agencies is prevented or excluded, is compensated 
 for or overcome by other agencies temperature, moisture, 
 etc. when the plant is grown under natural conditions. 
 Again, what is called the "after effect "has to be con- 
 sidered the facilities for growth afforded by the absence 
 of light, by the agency of heat, or other forces, may con- 
 tinue after those influences have ceased to act, and so a 
 plant may grow for a time under adverse influences by 
 
SENSITIVENESS. 69 
 
 reason of the impetus gained when circumstances were 
 more favorable. 
 
 Influence of Heat and Moisture on the Stem, The 
 growth of the stem is directly influenced by heat, there 
 being in this as in other cases a minimum below which 
 growth cannot take place, an optimum at which it takes 
 place most vigorously, and a maximum beyond which 
 heat is injurious. The favorable influence of heat it is 
 which in part overcomes the influence of gravitation, and 
 enables the stem to ascend. The stem will grow fastest 
 and strongest on the side most exposed to the heat, if 
 that heat be not excessive, and this tendency will remove 
 it from the soil. Similarly a moist condition of the at- 
 mosphere favors growth, and the stem will grow the fas- 
 ter on the side most exposed to the moist vapor, and, 
 owing to the convexity so formed, it will in consequence 
 bend its free end and its concavity towards the drier side. 
 
 Influence of Contact on Stems Climbing Plants, 
 
 The most marked instance of this occurs in the case of 
 climbing plants. We have already seen that the young 
 growing parts of plants very generally exhibit gyratory 
 movements, these movements being produced by inequali- 
 ties of growth, now in this direction, now in that, the 
 result being that the free end moves round, and that 
 these movements are only indirectly aifected by tempera- 
 ture or light. In the case of climbing plants, such as 
 the hop, the dodder, the tendrils of the pea or of the 
 vine, which, are peculiarly sensitive to contact, these 
 movements are much more marked, the object being to 
 secure a suitable means of attachment, and so to expose 
 the leaves when present to the influence of light and air 
 with the least expenditure of force and tissue. Such, 
 plants, in fact, depend upon others for their mechanical 
 support. When the free end of such a plant or a tendril 
 
70 PLAHT LIFE OK THE FARM. 
 
 comes - into contact with the straw of a wheat plant, 
 growth is checked on the surface by which contact is 
 made, while it is increased on the opposite side. As a 
 consequence, one side of the climber is flattened against 
 the supporting plant, while the other side, growing more 
 rapidly, becomes convex, and its tip is forced in process 
 of growth round the supporting stem. The increased 
 growth on the convex side of the coil is thus the direct 
 outcome of the impression produced by contact. 
 
 Combined Effect of the Preceding Causes. The 
 
 effects of light, heat, gravitation, etc., on growing plants 
 are thus seen to be manifold, and when considered sepa- 
 rately seem often conflicting and contrary to common 
 experience. The reason is that under natural conditions 
 the one influence counteracts the other, the growth of 
 the plant being the outcome of the combined effect of all 
 the causes alluded to, and of the operation at one time, 
 and under one set of circumstances, of the influence of 
 one agency (controlled or not by others), at another time 
 of a different agency. This affords an explanation of 
 the fact that the seasons marked by extraordinary pro- 
 ductiveness are not those wherein some one or more of 
 the conditions have been specially favorable at a particu- 
 lar time, even though that time be the growing period, 
 but those in which the conditions have been generally pro- 
 pitious throughout. The physiologist endeavors to isolate 
 the agencies which influence growth in order to ascertain 
 precisely what each does independently of the others ; 
 the practical man has to deal with the combined effect of 
 all, but it is clear that the combination cannot be 
 properly understood unless the separate effect of each 
 component be first clearly comprehended. 
 
CHAPTER V. 
 DEVELOPMENT. 
 
 Progressive changes during growth. Morphological, physical, and phy- 
 siological. Influence of inheritance. Variation. Selection. Re- 
 serve-materials : their formation and transport. Germination. 
 Maturation. Ripening of fruits and seeds. 
 
 Development as here understood includes those pro- 
 gressive changes of form and appearance which accom- 
 pany the growth of a plant from an infantile to an adult 
 state. It forms no part of our present plan to pursue 
 this part of the subject here, as any elementary text-book 
 contains sufficient details as to the progressive organiza- 
 tion of flowering plants. Growth considered separately 
 results in increase of bulk only, but development includes 
 the whole cycle of changes which convert an atom of 
 homogeneous protoplasm into a tree laden with fruit or 
 into a wheat plant heavy with golden ears. A mangel or 
 a turnip which, under favorable circumstances, gets big- 
 ger and bigger, may be said to grow. It increases in size 
 and weight, but neither its outward appearance nor its 
 internal construction is otherwise much affected. The 
 giant mangels exhibited at root shows illustrate growth 
 rather than development. They are very big, but their 
 nutritive power is by no means in proportion to their 
 size, as the quantity of nutritive matter developed is 
 small indeed as compared with the great quantity of 
 water they contain. Growth, in fact, is but the prepara- 
 tory stage, during which material and machinery are 
 acquired, to be turned to subsequent use in the consoli- 
 dation of the stem, the construction of flower and seed, 
 the formation and storage of reserve food-materials, of 
 starch, of oil, of the various secretions, such as the 
 caoutchouc, the alkaloids, as quinine, morphia, and many 
 others. 
 
 (71) 
 
72 PLANT LIFE ON THE FARM. 
 
 Growjth and development may go on together at the 
 same time, as we see in an oak tree, which puts forth its 
 midsummer shoots at the same time that it is ripening 
 its acorns and consolidating the new wood ; but in an 
 herbaceous plant, like the wheat, as development pro- 
 ceeds growth ceases at least, to a great extent. So in 
 the case of such plants as the turnip, the mangel, and 
 the hop, when the plant commences to enter upon the 
 flowering stage, then changes not merely of bnlk, but 
 of outward form, and to some extent of inward construc- 
 tion and chemical composition occur. So, as the soft 
 tissues harden into solid wood by deposit of woody mat- 
 ter in their wood cells, development takes place ; and, as 
 the water and the salts taken up by the roots and the 
 gases inspired by the leaves act and re-act upon one 
 another aided or not, as the case may be, by the agency 
 of light various changes occur which may be included 
 under the head of development. Development, then, is 
 morphological in so far as it relates to the conformation 
 of the plant, chemical or physical in so far as it includes 
 the chemical and physical changes which accompany the 
 passage from the young to the old, from the crude and 
 imperfect to the complete and mature. The conditions 
 which favor development in the sense here understood 
 are thus more or less opposite to those which foster 
 growth. Gardeners recognize this by affording plenty of 
 water and sufficient heat to their plants when growing, 
 and by reducing the amount of water as the plant is about 
 to produce flower, fruit, and seed. They apply liquid 
 manure in the growing stage, but withhold it in the 
 ripening period. They root-prune their fruit trees when 
 growth is too vigorous and fruit production too scanty. 
 They check rampant growth by keeping the roots in 
 small-sized pots. The farmer unfortunately has not the 
 same control over his plants that the gardener has, but 
 he is careful as to the time when he applies manure. He 
 
DEVELOPMENT. 73 
 
 is not particularly distressed at a wet growing season, but 
 he looks forward with hope to a relatively dry, hot period 
 for the corn to ripen. Of great practical importance also 
 is it to note the different effects of manures as particularly 
 observed at Kothamsted ; some, such as nitrogenous ma- 
 nures, stimulating growth more especially ; others, such 
 as the alkalis and superphosphates, being more particu- 
 larly favorable to the ripening of the seed or the consoli- 
 dation of the straw by the formation of woody fibre. 
 
 Growth is the same throughout all plants, but the 
 mode of development is much more specialized. In its 
 initial stages, the atom of protoplasm that is to be the 
 future potato plant, is not appreciably different from 
 that which is destined to grow into a wheat plant or into 
 a fruit tree. While growth is common to all plants and 
 uniform in character, development is special and different, 
 less or more, in the case of each particular species or kind 
 of plant. Outward conditions greatly influence the 
 amount of growth, while they have relatively less influ- 
 ence on the extent, still less on the direction of develop- 
 ment in the individual plant. 
 
 Inheritance. A particular kind of plant, therefore, 
 may retain its characteristics year after year, century 
 after century, age after age, if the conditions are not 
 greatly altered, because the successor follows, in the 
 course of its development, the same lines as its predeces- 
 sor did. It is thus by hereditary transmission that the 
 characters of plants are perpetuated. 
 
 Variation Selection, But the course of development 
 in the offspring is not always and in all cases the same as 
 in the parents. On the contrary, there is a certain range 
 of variation, by virtue of which a seedling plant does not 
 exactly reproduce either of the parental forms ; indeed, 
 as it is of mixed origin, it could not be expected to do so. 
 4 
 
74 PLANT LIFE OK THE FARM. 
 
 The limits of variation no one can tell ; sometimes they 
 seem very narrow ; at other times we know them to be 
 very wide. Within short periods of time the amount of 
 variations may be inappreciable. Within geological 
 periods the variation in the course of development is 
 sometimes so enormous that, were there not evidence of 
 the fact, it would be difficult to connect the plants and 
 animals that have gone before with those which now 
 exist. Living plants, then, are influenced in the course 
 of their development by two somewhat antagonistic prin- 
 ciples the hereditary principle which, on the whole, 
 tends to keep plants as they are, and the tendency to 
 vary, which is the source of that variation in character 
 which enables plants and animals gradually to become 
 adapted to altered circumstances. This is beneficial to 
 the cultivator, by affording him an opportunity of select- 
 ing the varieties best suited for his purpose. It is by 
 exercising selection of this kind that Mr. Hallett suc- 
 ceeded in raising his "Pedigree Wheat." He simply 
 selected for sowing the best grains from the largest and 
 best ears, and repeated the process year after year, just 
 as the gardener has done for countless generations in the 
 case of fruits and .seeds, as the cattle-breeder does with 
 Shorthorns or other pedigree animals. These processes 
 the farmer might with great advantage practice to a 
 much greater extent than he usually does, and thus se- 
 cure hardy productive varieties best suited to his particu- 
 lar conditions and best likely to fulfil his requirements. 
 
 Formation of the Embryo, The two processes of 
 growth and development may also be illustrated by recall- 
 ing what takes place in the germination of a seed. A 
 ripe seed contains within its coat or husk an embryo 
 plant. Very often that embryo plant is invested, as in 
 the case of the grain of wheat, with a whitish, floury 
 substance, known as the "perisperm." All grass seeds 
 
DEVELOPMENT. 75 
 
 have this perisperm surrounding their embryo. A simi- 
 lar substance is found in the seeds of mangel ; the seeds 
 of turnips, peas, beans, and clover, on the other hand, 
 are destitute of it. An embryo plant consists of a radi- 
 cle, or rudimentary root, surmounted by a caulicle, 
 which is often so short as to be imperceptible to the 
 naked eye, but from which spring the seed-leaves, or 
 cotyledons one only in the case of all the cereals and 
 grasses, two in the case of the other crops of the farm. 
 In the case of the wheat grain, where the perisperm is 
 abundant, the cotyledon is small and thin ; but in the 
 pea or bean, where the perisperm is absent, the cotyle- 
 dons are very thick and fleshy. The difference depends 
 upon the presence, in the one case, of large quantities of 
 reserve-materials in the embryo itself, while in the case 
 of the wheat the reserve-materials are stored up in the 
 perisperm. 
 
 The seed, then, in addition to the young plant, con- 
 tains in the tissues of the embryo plant itself, or in the 
 perisperm surrounding it, reserve -materials destined to 
 supply the young plant with food during its growth and 
 development. 
 
 Reserve-materials: their Transport. Under the 
 
 head of nutrition, mention has been made of the sub- 
 stances formed in plants through various agencies. Some 
 of these are used up at once during growth, while others 
 are reserved for future use, having usually undergone 
 some change in constitution to fit them for their purpose. 
 Speaking broadly, these reserves are either starchy, oily, 
 or albuminoid (nitrogenous) in their character. The 
 starchy or oily ingredients are the direct products of the 
 action carried on under the influence of sun light in the 
 cells containing chlorophyll. Starch cannot be formed 
 in cells containing no chlorophyll, nor, for a continuance, 
 in chlorophyll-containing cells, unless they are exposed 
 
76 fLAKT LIFE OK THE FARM. 
 
 to the light. The starch in a wheat grain, for instance, 
 is not actually formed within the seed it is formed in 
 the leaves and conveyed from them to the seed. But 
 starch is insoluble ; therefore, before it can be conveyed 
 from the place where it is formed to the place where it is 
 to be stored, it must be rendered soluble, and this change 
 is effected by a process of fermentation resulting in its 
 conversion into soluble " glucose." Arrived at the seed, 
 the glucose is turned back into insoluble starch to be 
 reserved for use when required. The process is essentially 
 the same in the case of the tuber of the potato, the 
 "bulb" of the turnip, or the root of the mangel. All 
 these organs are severally storehouses wherein food is ac- 
 cumulated for future use. The food is neither made nor 
 elaborated in them, but simply stored, having been 
 formed in the leaves and conveyed to the storehouse. 
 At one time, therefore, the leaves and stem may be full 
 of starch, at another, they may be destitute of it, owing 
 to its having been transferred to the seed or the bulb. 
 
 While the origin of the starch is now well known and 
 the processes connected with its formation and transport 
 fairly understood, it is not so with the nitrogenous mat- 
 ters. The nitrogen, as we have seen, enters the plant by 
 the root, and is, therefore, not directly dependent on 
 light or chlorophyll action. Nitrogenous compounds are 
 not formed in the seed, but conveyed to them just as the 
 starch is. 
 
 The carbonaceous reserve-materials that is, the starch, 
 the sugar, the oil, the coloring matters are all the direct 
 result of the action of the green matter acted on by light; 
 the starch and the sugar are essential requisites for the 
 building up of the cell-membrane, the albuminoid or 
 nitrogen-containing substances being, in their turn, es- 
 sential to the formation of the protoplasm, and of the 
 chlorophyll. 
 
DEVELOPMENT. 77 
 
 Germination* The conditions under which germina- 
 tion takes place need not be alluded to at any length, as 
 they are the same as those requisite for growth, and 
 practically every cultivator knows that air (oxygen), 
 moisture, and heat, varying in amount according to the 
 plant and according to circumstances, are required, and 
 that his success depends in great measure upon the 
 proper tillage of the soil which secures these requisites. 
 When the seed, or rather the embryo plant within it, 
 begins to grow, water is absorbed, the seed swells, the 
 insoluble starch stored up becomes converted into glu- 
 cose, or a form of sugar, by the agency of a nitrogenous 
 substance which acts as a ferment. These chemical pro- 
 cesses are accompanied by an evolution of heat and an 
 outpouring of carbonic acid gas. Thus is it that in malt- 
 ing barley the grain swells, gets hot, and its starch is 
 converted into sugar. As the seedling grows, both starch 
 and sugar gradually disappear, although the stock of 
 starch is continually replenished so long as the leaves 
 continue to act. The nitrogenous constituents of the 
 seed undergo similar changes from the insoluble to the 
 soluble condition, the latter being capable of transport 
 from place to place as may be required. 
 
 The accumulation of insoluble matter in the seeds is 
 accounted for by M. Deherain in this wise. At the period 
 of maturation the juices of the plant contain the various 
 substances held in solution. These juices are directed 
 towards the seed or towards the store organs, wherein, by 
 virtue of some changes not fully understood, the matters 
 previously held in solution become as it were precipitated 
 and rendered for the time insoluble. As a consequence, 
 the water is deprived of these materials, and to restore 
 the balance fresh supplies are drafted from the leaves 
 towards the store-organs, there in like manner to deposit 
 their starch, their inulin, or albuminoid matter. In the 
 case of biennials like turnips, or mangels, during the 
 
78 PLANT LIFE ON THE EABM. 
 
 first season of growth, the leaves collect and form the 
 nutritive matters which are subsequently transferred to 
 the " root," and the store so accumulated is utilized the 
 following season in the formation of flowers and seeds, as 
 before explained. 
 
 Growth, then, in a chemical sense, may be said to con- 
 sist in the absorption of the raw materials for the food of 
 plants development, in a chemical sense, may be taken 
 as including the various transformations which those 
 raw materials undergo to fit them for the nutrition of 
 the plant, or the formation of reserve-materials to be 
 stored up for future use. The history of these develop- 
 mental changes is a matter for the chemist to clear up 
 with the aid of chemical re-agents, used both with and 
 without the help of the microscope. It is in this de- 
 partment of physiology that our knowledge is at present 
 most imperfect. 
 
 Maturation. The foregoing facts and phenomena have 
 been brought to light principally by chemical analysis of 
 the same kind of plant at different times and in different 
 stages of its growth, and particularly by the analysis of 
 different parts of the same plant, some young, some old. 
 In the case of wheat, it was ascertained by Messrs. Lawes 
 and Gilbert that during the five weeks beginning with 
 June 21, there was but little accumulation of nitrogen in 
 the plant, while during the same period more than half 
 the total carbon was accumulated. The building-up 
 process was thus going on more quickly than that of 
 maturation. In this manner it has also been found, not 
 only that the starchy and the albuminous matters under- 
 go changes and disappear from the leaves, but that 
 mineral matters and salts, such as phosphates and salts 
 of potash, which at one stage of growth abound in the 
 leaves, at another time are almost entirely absent from 
 them, but are found in abundance elsewhere. The mi- 
 
DEVELOPMENT. 79 
 
 gration of these elements has been well studied in the 
 case of the wheat by M. Isidore Pierre, who has conclu- 
 sively shown that what the leaves lose in these respects 
 is gained by the ear. One important feature of matura- 
 tion then consists in the gradual cessation of the work 
 done in the leaf, the exhaustion of its supplies carbo- 
 naceous, nitrogenous, and mineral and the transport of 
 these materials to the organs of reserve, to the bark and 
 young wood of the tree, to the seed in the case of wheat 
 and other annuals, to the roots, bulbs, and tubers in 
 other cases. In the case of an annual herbaceous plant 
 like the wheat it appears that both root-action and leaf- 
 action become reduced to a minimum, or are even 
 altogether stopped some two or three weeks before the 
 wheat is ready to cut, so that during that period no in- 
 crease of weight of the plant as a whole takes place ; and 
 if the ears themselves increase in weight, it is because 
 they derive matter from other parts of the plant, which 
 diminish in weight in proportion. A few figures cited 
 by M. Deherain Avill illustrate the truth of these remarks 
 thus in the case of colza, out of a total of one thousand 
 parts (grammes) of phosphoric acid in the entire plant, 
 four hundred and fifty-six were found in the leaves in 
 March, and only twenty-five in the leaves in June, while 
 the flowering stems at the latter period contained eight 
 hundred and sixty. Results of a similar character might 
 be quoted in the case of potash and albuminoid matters. 
 In all cases while the relative proportions gradually de- 
 cline in the leaves they become correspondingly augment- 
 ed in the flowering part of the stem and in the seeds. 
 
 These results are attributed by M. Deherain in great 
 degree to varying degrees of evaporating power possessed 
 by the leaves. According to him, the older leaves at the 
 base of the stem evaporate but little as compared to the 
 younger leaves near the top. These, by their superior 
 evaporating power, cause the lower parts to be emptied 
 
80 PLANT LIFE ON THE FARM. 
 
 of their contents, which are thus forced upwards towards 
 the upper part of the stem. In a yery dry, hot season, 
 when the light is intense, evaporation and life-action 
 generally go on too rapidly, and the harvest is deficient ; 
 on the other hand, if the summer is wet and the light 
 deficient, maturation is imperfect, the transport of nu- 
 tritive matters from leaves upwards to the fruit and 
 seeds is checked, the younger leaves do not draw upon 
 the lower ones, and the season, though favorable to for- 
 age crops, is not so propitious to grain crops, to fruit 
 ripening, or to timber in which a deposit of woody 
 material in the cells is essential. 
 
 Ripening of Fruits. The ripening of fruits, such as 
 those of the apple and pear is attended with a series of 
 chemical changes which can here only be cursorily allud- 
 ed to. While the fruit remains green, it acts precisely 
 as a leaf does. As it ripens its color changes ; it no lon- 
 ger decomposes carbonic acid and gives off oxygen in the 
 daylight, but it utilizes the oxygen of the carbonic acid 
 to oxidize and burn up the vegetable acid and the sugar 
 which the fruit contains. Subsequently the sugar under- 
 goes a species of alcoholic fermentation, characterized by 
 the emission of carbonic acid gas and by the formation 
 of alcohol, which latter, uniting with the acid of the 
 fruit, produces ethers of various kinds, to which the 
 peculiar odor and flavor of the fruit are due. 
 
 The processes of maturation and fruiting therefore are 
 not dependent upon the mere accumulation of food ; 
 otherwise by increasing the quantity of manure and ap- 
 plying it continuously we should increase the crop. As 
 a matter of fact we know we should not do so, and that 
 the effect of over-feeding under such circumstances would 
 be to render the plant unhealthy by preventing it from 
 assimilating and maturing. Similarly we know from ex- 
 perience that heat alone is not sufficient to induce 
 
MULTIPLICATION. 81 
 
 thorough ripening, but that exposure to light is also 
 requisite, a dull, cloudy summer, even if warm, being 
 unpropitious to ripening, whether of fruit or grain. 
 
 CHAPTER VI. 
 MULTIPLICATION. 
 
 Sub-division. Intermarriage. Buds, Branches, Tillering, Tubers. 
 Fertilization, Stamens, Anthers, Pollen, Pistil. Mechanism of Fer- 
 tilization. Cross-Fertilization. Transport of Pollen. Insect 
 agency. Self-Fertilization. Fertilization of cereals. Hybridiza- 
 tion. Germination. 
 
 Multiplication. There are two special ways in which 
 plants multiply. One is a mere process of extension or 
 subdivision a modified form of growth, in fact. The 
 other is the result of the union or commingling of a por- 
 tion of the protoplasm of one plant with a corresponding 
 particle of another plant. In the lower plants, as they 
 are designated, it is not even necessary that union of 
 particles of protoplasm from different plants should be 
 effected. The contents of one cell blend with the con- 
 tents of another cell on the same plant, and the result is 
 the formation of a seed or spore, by means of which the 
 plant is reproduced. The first process of multiplication, 
 by division, is called asexual, the second sexual, because 
 it is a process of intermarriage requiring the co-operation 
 of two distinct particles of protoplasm. In the very 
 lowest plants these two particles present no appreciable 
 differences, but in the higher plants and animals they 
 present such differences as to enable us to distinguish 
 one as male, the other as female. In the lowest plant 
 the two particles are split off from the same mass of pro- 
 toplasm, while in the higher plants the male element is 
 formed from a different source from the female. 
 
82 PLANT LIFE ON THE FAKM. 
 
 Bud Formation* In the higher perennial plants, 
 among which are included many which come under the 
 notice of the farmer, asexual multiplication is effected by 
 means of buds. When a bud is to be formed, growth in 
 length is checked, the stem or the branch ceases length- 
 ening, the outer leaves often become reduced to a scale- 
 like condition, while the inner, central, and younger 
 ones remain in an undeveloped state until the warmth of 
 spring calls them into growth, when they gradually 
 lengthen into shoots, as in fruit and timber trees. While 
 the buds remain fixed to the trees which gave them 
 origin, their growth and development is a process of ex- 
 tention or branching merely. Similarly the process of 
 " tillering " is simply due to the formation and develop- 
 ment of buds and shoots from the nodes or knots at the 
 base of the stem of the wheat, and is to be regarded as a 
 process of branching rather than of actual multiplication. 
 Such branches are formed more readily in proportion as 
 the seed is not buried deeply. The same process of 
 growth which is desirable in a cereal or in clover is 
 highly objectionable in the case of " weeds," such as 
 docks, thistles, and plantains. The imperfect measures 
 often taken to exterminate these often tend to increase 
 the mischief by bringing about the formation of many 
 new buds. When buds become detached naturally, or 
 are severed from the parent artificially and made to grow 
 as when a gardener takes a " slip," " buds" a rose, or 
 "grafts" a fruit tree the process is really one of multi- 
 plication. So, when a farmer plants a " seed potato," 
 which yields him, it may be, forty-fold, he really plants, 
 not a " seed," nor a root, but a peculiar form of bud 
 called a tuber. 
 
 Tubers. A potato, in fact, is an underground branch, 
 or connected series of buds, forming a swollen subter- 
 ranean shoot, In this are stored up the starch and other 
 
MULTIPLICATION. 83 
 
 ingredients necessary for the nutrition of the young 
 potato plants. The " eyes " of the potato are really 
 buds, as any one may see for himself who will examine 
 the "chits" of a sprouting potato. These latter bear 
 the same relation to the parent tuber that the shoots 
 which spring from the old "stools " in a coppice or from 
 a pollard willow do to the trunk. The presence of these 
 tubers indicates that, under natural circumstances, the 
 plant requires a long period of rest. To this end food is 
 stored in the tuber, and active growth ceases for a time, 
 until again excited by heat and moisture. It may be 
 inferred from this that continuous growth, were it possi- 
 ble, would be injurious because the climatal conditions 
 are unsuited for it, as, indeed, may be witnessed in the 
 way in which the haulms of the early potatoes are injured 
 by spring frost. 
 
 Fertilization* In the case of plants grown for their 
 fruit or seed, as in the case of wheat and cereals generally, 
 much attention has naturally to be paid to the conditions 
 which favor sexual multiplication. 
 
 The morphological characters of the plants undergo a 
 change. In general terms, it may be said that the growth 
 of the stem is arrested, and the growth and mode of de- 
 velopment of the leaves not only arrested, but more or 
 less profoundly modified, so as to form the parts of the 
 flower. All parts of the flower are constructed on the 
 same original plan as leaves, but they gradually assume a 
 very different appearance in the course of their develop- 
 ment to fit them for their work of aiding fertilization. 
 It is not necessary in this place to enter into details as to 
 the floral construction, which varies in different plants ; 
 the important points in relation to our present subject 
 are the stamens and the pistils and their contents. 
 
 Within the green scales which constitute the flower of 
 
84: PLANT LIFE OK THE FARM. 
 
 wheat, .within the butterfly-shaped and brightly-colored 
 petals of the pea or the clovers, and the yellow petals of 
 the flowers of the turnip or the colza, the rape or the 
 mustard, are a series of fine thread-like bodies, the 
 " stamens," varying in number, size, and arrangement in 
 different flowers, but each consisting of a fine thread or 
 stalk, called the " filament." Surmounting this is a sort 
 of pocket or case, called the "anther," containing a yel- 
 low or greenish dust, which, when examined with a lens, 
 is seen to be made up of separate cells or grains, called 
 the pollen grains. Some idea of the number of these 
 pollen grains may be gained from the calculations of Mr. 
 A. S. Wilson, who estimates, from the actual counting 
 of a portion, that each anther of rye contains twenty 
 thousand pollen cells, five hundred thousand of which 
 are needed to make up one grain in weight. A floret of 
 spring wheat in like manner was found to contain six 
 thousand eight hundred and sixty-four grains, but, as 
 the pollen grains of the wheat are larger than those of 
 the rye, only three hundred and ninety thousand are 
 required to make up a grain weight. An acre of wheat 
 may, it is further calculated, produce fifty pounds of 
 pollen, and an acre of rye two hundred and twenty-four 
 pounds. 
 
 Within the stamens, in most flowers with which farm- 
 ers have to do, is a " pistil," consisting of a thick portion 
 below, which contains the young "ovule" destined to 
 become the seed, and which is usually overtopped by a 
 little thread, called the "style," whose upper end, again, 
 is dilated into a " stigma." In the case of the wheat and 
 other grasses these stigmas are covered with fine white, 
 silky hairs. The essential constituents of the flower, 
 without which reproduction cannot be effected, are the 
 pollen grains and the ovule. All other parts of the 
 flower are mere accessories, and some of them are very 
 
MULTIPLICATION. 85 
 
 frequently absent without the process of reproduction 
 being impaired by their absence. 
 
 The process of fertilization may be described in general 
 terms as follows : The ovule contains, in a cell just be- 
 neath the skin at its summit, one special piece of pro- 
 toplasm, the " germ," which is destined to develop into 
 the embryo plant. The pollen-cell consists of an outer 
 coat and an inner lining ; the outer coat bursts, and the 
 inner protoplasmic lining is protruded in the form of a 
 tube, which passes down between the cells of the stigma 
 and style, growing in length and feeding as it goes, like 
 a parasitic fungus, on the contents of the cells of the 
 style, until it reaches the ovule and comes into close 
 proximity to, if not actually into contact with the germ. 
 In consequence of this action a cell- wall is formed around 
 the germ, which latter divides and subdivides in various 
 directions, the result of the subdivision being the forma- 
 tion of an embryo plant, as mentioned at p. 74, while 
 the ovule covering the embryo ripens into the seed. The 
 germ is thus fertilized by the pollen or sperm-cell, and 
 unless the two come in contact, the formation of the 
 embryo plant does not take place. 
 
 Cross Fertilization. It has teen mentioned that the 
 flowers with which the farmer is concerned have for the 
 most part their stamens and pistils in the same flower 
 (hops are an exception*), and therefore they may be de- 
 scribed as structurally hermaphrodite. It does not, how- 
 ever, follow that they are functionally hermaphrodite 
 that is, that the pollen-grain of any particular flower 
 fertilizes the germ-cell of the same flower. As a matter 
 of fact, the reverse usually happens, and the pollen of 
 
 *In the hop, the stamens and pistils are in separate flowers upon 
 different plants. The farmer in the United States will find that the 
 stamens and pistils are in different flowers upon the same plant in In- 
 dian corn, pumpkin, squash, and all other plants of that family. 
 
86 PLANT LIFE ON THE FARM. 
 
 one flower exerts its influence, not upon the germ of its 
 own flower, but upon that of another, perhaps situated 
 on some other plant. Cross-fertilization is often neces- 
 sitated by the circumstance that while the pollen of any 
 particular flower may be ripe, the stigma and the germ- 
 cell of the same flower may not be ripe at the same time, 
 or vice versa, and in such case the co-operation of some 
 other flower is needed. 
 
 Transport of Pollen. It becomes, therefore, needful 
 to ascertain in what manner the pollen is carried from 
 one flower to another. This is effected in various ways 
 sometimes the mere splitting of the anther with some 
 degree of force suffices to scatter the pollen, at other 
 times the currents of air suffice to waft it from one flower 
 to another, while at other times insects of various kinds 
 convey the pollen from one flower and deposit it on the 
 stigma of another. 
 
 The adaptations of floral structure to insect-agency in 
 fertilization, as also the contrivances for excluding unde- 
 sirable visitors, are most varied and most remarkable, 
 but they can only be mentioned here. As a rule, it may 
 be stated that flowers endowed with bright colors, irregu- 
 lar construction (like that of the pea or bean), or rich 
 perfume are fertilized by insect agency. The insects are 
 attracted by the bright colors, the perfumes, and the 
 sweet secretions of the flower. On alighting, they are 
 often compelled by the peculiar construction and mech- 
 anism of the flower to enter or leave it in such a way 
 that they must in the one case brush out the pollen, and 
 in the other deposit it on the stigma. It will be noted 
 how this process of cross -fertilization favors that process 
 of variation to which allusion has previously been made. 
 
 The farmer wishing to keep his stock of seed turnips 
 pure, knows how difficult it is to do this, not only be- 
 cause cross-fertilization is the rule in the particular 
 
MULTIPLICATION. 87 
 
 variety he wishes to grow, but also because, if any other 
 variety is grown in the neighborhood, its pollen is sure 
 to impregnate his variety and produce a mongrel off- 
 spring. Cross-fertilization then acts in antagonism to 
 the hereditary tendency, and secures variation and not 
 only variation, but more vigorous and robust constitu- 
 tion, and more numerous and more healthy descendants. 
 Self-fertilization, or "in and in breeding," occurs, no 
 doubt, in some instances, especially in cereal grasses ; 
 and there are indeed many cases where, for various rea- 
 sons which need not be cited here, no other mode of fer- 
 tilization is possible. Relative permanence of character 
 is secured by this means, and if constitutional vigor and 
 the health of the offspring be impaired by the long con- 
 tinuance of the process, these ill-effects are provided 
 against by the circumstance that a comparatively trifling 
 change in the flower, or in the circumstances by which 
 it is surrounded, will suffice to prevent self-fertilization 
 and secure cross-fertilization. 
 
 Fertilization of Cereals, It has very generally been 
 stated that the wind is the special agency by means of 
 which the pollen is carried from flower to flower of these 
 plants, and no doubt this is true to some extent and under 
 certain circumstances. From the careful experiments and 
 observations of Mr. A. S. Wilson, recorded in a paper read 
 before the Botanical Society of Edinburgh, Scotland, 
 and printed in the " Gardener's Chronicle," March 14, 
 1874, it appears that self-fertilization is the rule among 
 cereals, though cross-fertilization does occasionally take 
 place and has been effected artificially by various experi- 
 menters. The flowers of wheat, barley, and oats open to 
 a slight degree and allow the anthers to protrude, often 
 quite suddenly ; but whether the flowers fully or but 
 partially open, says Mr. W. , they are fertilized before the 
 anthers are visible outside. " The Belgian farmers," he 
 
88 PLANT LIFE ON THE FARM. 
 
 continues, " who trailed ropes over their flowering wheat 
 to insure complete fertilization, were doing that which 
 the very appearance of the anthers told them in whispers, 
 not yet heard, had already been accomplished." The 
 pollen of these plants which the winds disperse, is not 
 that which fertilizes, but that which is not required for 
 fertilization. The success of the process depends, as 
 before said, upon the circumstance whether or not the 
 pollen and the feathery stigma are respectively ripe at 
 the same time. If so, then fertilization results ; if not, 
 there is still a chance of cross-fertilization, but if that 
 fail, the flower remains barren. 
 
 Hybridization is a procedure with which the gardener 
 is much more familiar than the farmer. It is only a 
 further development of cross-fertilization. Cross-fertili- 
 zation, as has been said, takes place between flowers of 
 the same individual plant, or between flowers of two dif- 
 ferent individuals of the same species ; but hybridization 
 is effected by crossing the flowers of two separate species, 
 as in the case of the Alsike clover, which is said to be a 
 hybrid between the white or Dutch clover and the red 
 clover. 
 
 Chemical Changes. The chemical changes which oc- 
 cur during the formation of the flower, and especially 
 during the ripening of the seed, have already been alluded 
 to. The contrast between the composition of the leaves 
 and that of the pollen and of the seeds is very striking, 
 and analysis brings out the fact of the accumulation of 
 nitrogenous and phosphatic and mineral matters in the 
 pollen and in the seed. In haymaking it is better, if 
 possible, to mow before the leaves are exhausted of their 
 contents by the seeds, or at any rate, before the latter are 
 shed. If cutting be delayed, a great part of the nutritive 
 matter is withdrawn from the leaves and stem to be 
 
THE BATTLE OF LIFE. 89 
 
 * 
 
 stored up in the seeds, which fall readily when ripe, and 
 thus occasion a loss to the farmer. Again, as it has been 
 shown that the seeds of cereals contain their full propor- 
 tion of nutritive matter some little time before they 
 would be considered thoroughly ripe, early cutting, 
 where practicable, is to be recommended to secure the 
 crop and obviate possible loss from delay. 
 
 CHAPTER VII. 
 THE BATTLE OF LIFE. 
 
 Plants considered in their relation to theif ^struggle for existence. 
 Effect of adverse external conditions. Hostility of rivals, Weeds. 
 Competition of fellows. Gregarious vegetation. Associated or 
 mixed vegetation. Alternate vegetation, rotation. Objects of the 
 cultivator not the same as those of the plant under natural circum- 
 stances. The battle as studied in pasture-land or meadow. The 
 grass-plots at Eothamsted their botanical composition and the way 
 they are affected by manures of different kinds. The Grasses, their 
 nature and differences ; contrasts between nearly allied species. 
 The Leguminosse. The Miscellaneous weeds. The vegetation and 
 characteristics of the continuously unmanured plot. The effects 
 of different manures and of different combinations of manures upon 
 the struggle. Effects of disuse of manure, and of the substitution 
 of one kind for another. General results. 
 
 In former sections mention has been made of the rela- 
 tions which the living plant bears to the heat, light, 
 moisture, and other physical conditions, by which it is 
 surrounded. These conditions are sometimes favorable, 
 sometimes prejudicial. In the latter case, the existence 
 of the plant becomes a prolonged struggle against adverse 
 influences. To a certain extent it is always so, and when 
 the difficulties can no longer be counterbalanced or over- 
 come, plants, like other living beings, succumb and die. 
 The life of each individual then may be described as a 
 battle against circumstances. 
 
90 PLANT LIEE OJS THE FAKM. 
 
 But -apart from this external conflict with the elements, 
 plants are always more or less in a state of internecine 
 war. Plants of different kinds growing wild in a state of 
 nature may contend one with another for root-hold, soil- 
 food, and for space to expose their foliage to the sun. 
 Under such circumstances, if there is enough for all, it 
 may be that the severity of the struggle may be slight, 
 owing to the different requirements of the different 
 plants, but even then the stronger of the two will eventu- 
 ally prevail. A farmer, however, would hardly call the 
 preponderance of weeds an instance of the survival of 
 the fittest. From his point of view it would certainly 
 not be so, however true it might be in wild nature. 
 Plants of the same kind growing gregariously, like heaths 
 on a moor, have the same requirements, and these are 
 supplied in about equal proportions to all the individual 
 plants. The result is that while the weak ones are 
 crowded out, the survivors are all pretty much on an 
 equality ; but once the balance is destroyed, then that 
 which is the stronger, or the one best adapted to the cir- 
 cumstances under which it is placed, will survive. 
 
 In cultivation we have illustrations of mixed and of 
 gregarious vegetation in the sense above employed, as 
 well as of alternate vegetation as in the case of "rotation." 
 In the case of the cereals, of turnips, of potatoes, and 
 others, we have instances of gregarious vegetation 
 induced, indeed, by the will of the cultivator. His 
 object is to secure the most profitable development of 
 one particular kind of plant, wheat, barley, oats, or what 
 not. To compass this end he grows them together, 
 takes means by appropriate tillage, and by the removal 
 of competing weeds, to enhance the conditions most 
 favorable to their growth and to minimize the effects of 
 those that are injurious. The warfare here is external 
 as regards "weeds," it is internecine between individual 
 plants of the same species and having the same require- 
 
THE BATTLE OF LIFE. 91 
 
 ments. As the competition of alien plants may be pre- 
 vented by weeding, so internecine war between plant and 
 plant of the same kind maybe mitigated by the adoption 
 of thin seeding, which allows each individual to attain 
 its complete development, and enables it to avail itself to 
 the full of the resources at its disposal. Unless under 
 exceptional circumstances and for some special purpose, 
 it is more profitable so to grow plants as to diminish the 
 competition between individuals by affording each the best 
 possible chance. Otherwise, the strongest or best adapted 
 prevails, indeed, over those less favorably situate, but 
 there is, so far as the cultivator is concerned, a loss of 
 energy and a waste of resource in the case of the beaten 
 plants. The cultivator requires for his purpose the 
 largest number of plants of good average quality ; nature 
 favors the development of a few of exceptional power of 
 adaptation, which therefore overcome their fellows, but 
 which are not necessarily the best for the farmer. 
 
 The Battle in the Meadow, The battle of life is per- 
 haps best studied in mixed pastures where a great variety 
 of plants of diiferent families, different construction, and 
 different requirements are grown in association. In 
 such pastures some of the constituent plants are valuable 
 to the farmer, as some of the grasses and most of the 
 leguminous plants ; others are relatively useless and may 
 be positively injurious. The behavior of the different 
 classes of plants so growing in association, but under 
 varied conditions of manuring, for a large number of 
 years, has been made the subject of prolonged and elabo- 
 rate study at Rothamsted. A few of the leading results 
 may here be mentioned in merest outline for the purpose 
 of illustrating the subject of this chapter, and of afford- 
 ing matters for consideration by the practical cultivator. 
 
 The total number of different kinds of plants that 
 have been found on the plots is eighty-nine, of which 
 
92 PLANT LIFE ON THE FARM. 
 
 twenty are grasses, ten leguminous, and the remainder, 
 occurring usually in smaller proportions and belonging 
 to many natural orders, are conveniently grouped as 
 "miscellaneous." The numbers and relative proportions 
 of these, as noted in the growing herbage or recognized 
 in the samples taken from it, differ very much in dif- 
 ferent seasons, and more especially according to the 
 nature of the manure employed. 
 
 The plants vary among themselves, the grasses having 
 certain characters in common, the leguminous plants dif- 
 fering from the grasses, and both more or less from the 
 miscellaneous plants, the members of which latter group 
 differ very considerably among themselves. The varia- 
 tions alluded to depends of course on the varying organi- 
 zation, hereditary endowments, internal structure, habit, 
 constitution, and mode of life of the several plants. Some 
 of these points are much more influenced by external 
 conditions of soil and climate than others. 
 
 The Grasses. *-Of the eighteen grasses which commonly 
 occur on the plots all are perennial except Bromus mollis. 
 
 * In the text the Latin names of the plants mentioned are employed 
 as more precise and uniform in their application, not varying in differ- 
 ent localities, and being in universal use in botanical works ; but as 
 these names may not be familiar to some readers, the most commonly 
 adopted English names are here supplied. It should be remembered 
 that only the more important of the pasture plants are here alluded to. 
 [The common names most in use in the United States are added 
 in brackets.] 
 
 GRASSES. 
 
 Anthoxanthum odoratum -= Sweet vernal grass. 
 
 Alopecurus pratensis = Meadow fox tail grass, 
 
 Phleum pratense = Meadow cat's-tail. [Timothy.] 
 
 Agrostis vulgaris = Fiorin grass. [Red-top.] 
 
 Aira caespitosa Tussack or hair grass. 
 
 Holcus lanatus = Woolly soft grass. 
 
 A vena pubescens = Downy oat-grass. 
 
 " elatior = False oat-grass. 
 
THE BATTLE OF LIFE. 
 
 93 
 
 They occur in very varying proportions on the different 
 plots according to the season and according to the nature 
 of the manure employed. They vary somewhat in ro- 
 bustness of constitution and ability to withstand frost or 
 drouth ; and their structural characters are, generally 
 speaking, characteristically different from those of other 
 plants, and variable as between species and species. Some 
 maintain their ground or even increase when growing in 
 competition or association with their fellows ; others 
 such as AntJioxantlmm odoratum, Festuca ovina, and 
 Agrostis vulgaris can only hold their own or assert 
 themselves when the competition exercised by their asso- 
 ciates is relatively weak, and succumb under the opposite 
 circumstances. 
 
 Avena flavescens = Yellow oat-grass. 
 
 Poa pratensis = Meadow grass. [Blue grass.] 
 
 " trivialis Rough stalked meadow grass. 
 
 Briza media = Quake-grass. 
 
 Dactylis glomerata Cock' s-foot grass. [Orchard G.] 
 
 Cynosurus cristatus Crested dog's-tail grass. 
 
 Festuca ovina Sheeps' fescue. 
 
 " pratensis Meadow fescue. 
 
 " elatior Tall fescue. 
 
 Bromus mollis =- Soft brome grass. 
 
 Lolium perenne Rye grass. 
 
 LEGUMINOS^E. 
 
 Trifolium repens = White clover. 
 
 " pratense Meadow clover. [Red clover.] 
 
 Lotus corniculatus = Bird 's-foot trefoil. 
 
 Lathyrus pratensis = Meadow vetchling. 
 
 WEEDS. 
 
 Ranunculus-various species= Buttercups. 
 Cerastium triviale 
 
 Conopodium denudatum = 
 
 Centaurea nigra = 
 
 Carduus arvensis = 
 
 Bellis perennis = 
 
 Achillea Millefolium 
 
 Taraxacum officinale 
 Plantago lauceolata 
 Rumex Acetosa 
 
 Mouse-ear chickweed. 
 
 Earth nut. 
 
 Knap-weed. 
 
 Common thistle. [Canada T.j 
 
 Daisy. 
 
 Milfoil. [Yarrow.] 
 
 Dandelion. 
 
 Plantain or Rib grass. 
 
 Sorrel-dock. 
 
94 PLANT LIFE ON THE FARM. 
 
 Th^ grasses, both in number of species and in relative 
 and actual amount of produce, exceed the plants of all 
 other orders. The lowest produce occurs on the con- 
 tinuously unmanured plots ; the highest on those to 
 which a highly nitrogenous manure, such as ammonia 
 salts or nitrate of soda, is continuously applied in combi- 
 nation with earthy and alkaline salts especially potash. 
 But while the total gramineous produce is thus increased 
 by the description of manure just mentioned, the num- 
 ber of species of grass is reduced. On the unmanured 
 plots, on the average, sixteen different sorts of grasses 
 may be found, each contributing a fair proportion to the 
 total herbage ; thirteen only are found on the highly 
 ammoniated plots, and of these only a very few contribute 
 materially to the crop, the remainder being present in 
 such small quantities as to make but little difference in 
 the totals. 
 
 The principal external characteristics which favor the 
 growth of the grasses in their competition with other 
 plants are their dense root-growth, monopolizing as it 
 were all the soil within reach, an$ affording little power 
 to the roots of other plants to penetrate the mass. To 
 an extent variable in different species, this root-growth 
 is both superficial as well as deep. In addition to this 
 generally ample root development, many of the species 
 are aided in the struggle by their stout tufted habit and 
 specially by their power of producing creeping offshoots 
 above or below ground which insinuate themselves in 
 between other plants and occupy any vacant territory. 
 No doubt internal anatomical differences are even of 
 greater moment than these external characteristics, but 
 these demand minute comparative study by means of the 
 microscope, under various conditions, and at different 
 seasons, and constitute a branch of inquiry at present 
 hardly even entered upon. 
 
 Although grasses as a whole comport themselves in a 
 
THE BATTLE OF LIFE. 95 
 
 particular manner distinct from that of the other tenants 
 of the plot, yet it is found that individual grasses, and 
 even members of the same genus, vary very much 
 among one another. 
 
 It is instructive to compare the different tendencies of 
 the two most generally prevalent grasses, Festuca ovina 
 and Agrostis vulgaris. As to structural endowments 
 they would seem to be not unfairly matched, but the 
 Festuca is conspicuously worsted on the plots highly 
 dressed with nitrogenous manures, while the Agrostis is 
 befriended by them, and its vigor and tufted habit are 
 increased. Poa trivialis and Holcus lanatus afford con- 
 trasts of a similar character, the Poa being largely in- 
 creased by nitrate of soda, while the Holcus is similarly 
 acted on by ammonia salts. Of the same character are 
 the differences observable between Agrostis vulgaris, 
 which is influenced by ammonia salts, and Holcus lana- 
 tus, Avena pubescens, and Avena flavescens, which are 
 especially acted upon by nitrate of soda. Very marked 
 contrasts between species of the same genus also occur, 
 as between such structurally very closely related plants 
 as Poa trivialis, and P. pratensis, and between the 
 three species of Avena. On the contrary, Bromus mollis 
 and Poa trivialis are so far similar that nitrate of soda 
 is very favorable to them both. Poa pratensis and 
 Agrostis vulgaris concur in their liking for ammonia 
 with mineral salts, while they manifest opposite tenden- 
 cies with regard to nitrate of soda ; Poa pratensis not 
 being favored by it, while the Agrostis is so conspic- 
 uously. 
 
 These are only a few of the remarkable contrasts and 
 similarities that an inspection of the Rothamsted records 
 brings out. Perhaps the most striking point in this 
 connection is the opposite tendency manifested by differ- 
 ent grasses in reference to the action of ammonia salts, 
 and of nitrate of soda respectively, with or without 
 
96 PLANT LIFE ON THE FARM. 
 
 mineral manures in addition in each case. Doubtless, 
 these characteristics are to be correlated with differences 
 of organization and structure, but with the exception 
 that the shallower rooted plants are often favored by 
 ammonia salts, and the deeper rooting ones by the more 
 deeply percolating nitrate, little or nothing has been done 
 in definitely associating the different physiological en- 
 dowments above referred to, with corresponding differ- 
 ences of internal structure. 
 
 The LeguminoSft form a group of plants characterized, 
 so far as this country is concerned, by the presence of 
 "papilionaceous" flowers like those of the common pea, 
 by their leaves being compound, i. e., consisting of separ- 
 able segments, and by the production of a seed-pod, 
 which, when ripe, splits into two valves or flaps ; this is 
 technically called a " legume." By these characteristics, 
 not to mention others, this group which comprises peas, 
 beans, clovers, vetches, sainfoin, lucerne, and other agri- 
 cultural plants, may be known. Some, such as peas 
 and beans are annual, others are perennial, and, as a rule, 
 their habit or general appearance is so strikingly dif- 
 ferent from that of the grasses, that no one ever con- 
 founds them. 
 
 Though containing a larger proportion of nitrogen in 
 their composition than the cereals, they are not specially 
 benefited by nitrogenous manures as the grasses are, and 
 this fact, observed when Leguminosas are grown alone, as 
 in the bean or clover field, is no less marked than it is 
 when they are grown in association as in pasture land. 
 At Kothamsted, the largest proportionate quantities of 
 Leguminosae occur on a plot to which mixed mineral 
 manure with potash is applied. Seasonal characteristics, 
 even when favorable to these plants, do not suffice to 
 overcome the injurious effects of some manures, as during 
 many years of varying character as to climate, they have 
 
THE BATTLE OF LIFE. 97 
 
 been practically banished from the ammonia plots. On 
 the whole their requirements are opposite to those of the 
 grasses, the conditions favoring the latter not being any- 
 thing like so propitious to the leguminous plants. Thus 
 the effect of nitrogenous manures as observed on the ex- 
 perimental plots is to banish or reduce more or less com- 
 pletely the Leguminosae, or so to favor the growth of the 
 grasses, or certain of them, that the Leguminosae are 
 overpowered. On the other hand, mineral manures, 
 which are not by themselves very beneficial to grasses, 
 are very propitious to the growth of leguminous plants. 
 Potash is especially favorable to these plants, their pre- 
 dominance and produce is always enhanced when that 
 substance is used in due proportions as a manure, and 
 always diminished when it is omitted. In illustration, it 
 may be added, that on the plot where the manurial con- 
 ditions are most favorable to Leguminosae, the weight 
 per cent of the whole crop was as follows : Sixty-five 
 per cent grasses, twenty per cent leguminous, and fifteen 
 per cent miscellaneous. The per-centage by weight on 
 the unmanured plot was, sixty-eight grasses, nine legu- 
 minous, and twenty-three miscellaneous. Taking the 
 other extreme where a large quantity of nitrogenous 
 manure was employed, the figures are ninety-five per 
 cent grasses, and five per cent miscellaneous, the Legu- 
 minosae being all but absent (one per cent). 
 
 Of the Leguminosae of pasture-land LatJiyrus praten- 
 sis seems to be able to hold its own under adverse condi- 
 tions much better than its fellows, the clovers or the Lo- 
 tus. Its long, straggling root, and scrambling habit 
 added to its hardihood may be the source of these advan- 
 tages. 
 
 Miscellaneous Plants. In spite of the large number 
 and varied habits of growth of the miscellaneous species 
 found on the plots, their importance as factors in the 
 5 
 
98 PLANT LIFE OK THE FARM. 
 
 struggle is less than that of the grasses and of the legu- 
 minous plants. The proportion in which they occur on 
 the several manured plots is always less than that of the 
 grasses, and they never really attain any very great de- 
 gree of prominence, except in cases where from seasonal 
 or manurial causes the grasses are prevented from attain- 
 ing their full development. Those species which, like 
 Rumex Acetosa, have a powerful underground develop- 
 ment, and abundant capacity for collecting and storing 
 water, etc., of course have an advantage especially when 
 it so happens that they can avail themselves of unoc- 
 cupied territory, which they seize and hold with great 
 success against all comers, and also in cases where the 
 density of the soil is such as to offer an obstacle to the 
 penetration of fibrous roots. But, on the whole, the 
 dense fibrous net-work of roots made by the grasses, 
 which enables them to avail themselves of well nigh 
 every particle of soil within their reach, is a more valua- 
 ble possession than is the more robust underground root- 
 stock possessed by several of the miscellaneous plants. 
 Most of the species occur in too insignificant amounts to 
 be considered as anything more than accidental tenants, 
 and while in others their preponderance depends on the 
 relative inferiority of the growth of grasses, there are 
 also indications that some of them are favorably affected 
 by certain manures, and others by fertilizing agents of 
 different character. But on the whole, these indications 
 observed on plants growing in association are by no means 
 so marked as in the cases of the grasses and the Legu- 
 minosse. 
 
 Growth of Pasture Plants when unaffected by manure 
 of any kind. The changes from year to year in the vege- 
 tation of a plot which has been unmanured for many 
 years must obviously be mainly due to seasonal influ- 
 ences, and progressive exhaustion of the soil, while those 
 
THE BATTLE OF LIFE. 99 
 
 which are observed in the manured plots are as obviously 
 brought about, partly by the manures and partly by cli- 
 matal changes. The produce of hay at Rothamsted, 
 without manure, has varied from eight hundred and 
 ninety-six pounds, to four thousand three hundred and 
 sixty-eight pounds, the average for twenty-five years 
 having been, as before stated, two thousand five hundred 
 and seventy-six pounds per acre. This hay is made up 
 on the average of forty-nine different species in different 
 proportions, as determined by rigid comparative scrutiny. 
 Of the forty-nine plants, seventeen are grasses, four legu- 
 minous plants, and the remaining twenty-eight are pas- 
 ture weeds of various orders, and roughly classified as 
 miscellaneous plants. By weight, grasses furnished sixty- 
 nine .per cent, Leguminosae eight, and miscellaneous 
 plants twenty-three per cent of the total produce. 
 
 The general appearance of the unmanured plots is one 
 of even growth, with no special luxuriance of any par- 
 ticular plant. The herbage is very mixed, the crop 
 scanty, the color yellowish-green, in fact a sort of trades- 
 union equality is produced, between the different mem- 
 bers of the community, no one kind being specially 
 favored. Festuca ovina usually predominates among the 
 grasses. Briza media is more abundant on these plots 
 than on most others. Among the leguminous plants, 
 Lotus corniculatus is more prevalent than LatJiyrus pra- 
 tensis, as is usually found to be the case when there is 
 soil exhaustion and a deficiency of potash. The miscel- 
 laneous plants are generally very abundant, such as the 
 buttercups. Plantago lanceolata, Centaurea nigra, Agri- 
 monia Eupatoria, Scakiosa arvensis, Leontodon hispidus, 
 Prunella vulgar is, Achillea Millefolium, Conopodium de- 
 nudatum, Rumex Acetosa, Luzulacampestris, and Galium 
 verum. The contrast in early summer between the 
 scanty yellowish-green herbage, profusion of flowers of 
 the various weeds, and the almost total absence of flowers 
 
100 PLANT LIFE Otf THE FARM; 
 
 and rich, deep blue-green foliage of the plants in the ad- 
 jacent ammonia plot is very striking. 
 
 The effects of manure upon the struggle. When in 
 a long series of years the effects on the vegetation of a 
 particular plot are observed to be uniform in their nature, 
 if not in degree, the effects are obviously attributable to 
 the manure employed, and the fluctuations are as clearly 
 dependent on climatal variations. In endeavoring to 
 give an idea of the effect of different manures in influen- 
 cing the nature and fierceness of the struggle, it will be 
 convenient to allude first to those cases in which no 
 change has been made in the condition of manuring, 
 mentioning first those plots in which comparatively 
 simple manures are employed, and afterwards those in 
 which a more complex manure is employed. 
 
 Mineral manures alone. One of the plots at Both- 
 amsted illustrates the effects of mineral manures consist- 
 ing of admixtures of various earthy and alkaline salts 
 used by themselves, without the admixture of nitroge- 
 nous substances. Speaking generally, it is there observed 
 that, while graminaceous herbage has, with much fluctu- 
 ation, slightly increased, the proportionate amount of 
 leguminous plants, as compared with grasses, has on the 
 whole been largely increased, although latterly it has 
 shown a tendency to decline. The large increase is 
 mainly due to Lathyrus pratensis, which prevails over 
 all its fellows. The grasses which hold their own best 
 are Festuca ovina, Agrostis vulgaris, and Holcus lana- 
 tus. Achillea Millefolium has increased considerably, 
 Conopodium denudatum and Rumex Acetosa, have usually 
 been abundant. This description of manure seems un- 
 favorable to most of the weeds of pasture-land other than 
 the above mentioned. The crop is generally moderate, 
 with an even and early ripening, and a marked tendency 
 
THE BATTLE OF LIFE". 
 
 to stemmy as distinguished from leafy growth, the color 
 of the foliage being of a light, yellowish-green. 
 
 On the wheat plots, it has been shown that purely 
 mineral manures scarcely increase the yield at all, though 
 they are beneficial to the leguminous crops. These ex- 
 periments confirm Boussingault's assertion that alkaline 
 or earthy salts, although indispensable to plants, never- 
 theless, exercise no action unless combined with matters 
 capable of furnishing nitrogen. 
 
 Superphosphate of lime only. The scanty and stemmy 
 produce on the plot, to which this substance is applied, 
 has been but little greater than that on the unmanured 
 plots. The grasses and miscellaneous plants have been 
 slightly increased, the Leguminosae diminished. There 
 has been a great admixture of species, but little luxuri- 
 ance of any. Holcus lanatus, Avena flavescens, Poa 
 trivialis, Lolium perenne, and Festuca ovina have been 
 among the most prominent grasses, while the freer-grow- 
 ing Dactylis does not apparently find so much sub- 
 sistence as it requires. LatJiyrus pratensis among the 
 leguminous plants, and Rumex Acetosa and AcMllea 
 Millefolium among the weeds, have but slightly benefited, 
 others yielding even less than without manure. Bous- 
 singault's observations, already quoted under the head of 
 mineral manures, apply equally here. The great French 
 chemist found, as in the Rothamsted experiments, that 
 superphosphate, uncombined with substances capable of 
 yielding ammonia, produced little or no effect on vege- 
 tation. Boehm's experiments, however, go to show that 
 young plants raised in distilled water, die before the nu- 
 tritious matter stored up in the seed, or in the seed- 
 leaves is exhausted, but if lime be added, especially in 
 the form of ulinate, before this point is reached, the 
 seedlings resume their healthy appearance, the develop- 
 ment of the radicle, according to Deherain, being par- 
 ticularly favored by this substance. (See p. 18), 
 
LIFE O^s" THE FARM. 
 
 Superphosphate has been proved to be of little or no 
 use to other crops grown separately, except in the case of 
 turnips, where about eight tons per acre have been pro- 
 duced by the use of superphosphate ; the produce with- 
 out manure at all, being one to two tons per acre. 
 
 Ammonia Alone* The average produce with ammonia 
 salts alone has not been very much greater than that on 
 the unmanured plots. The principal differences are in 
 the grasses, which have diminished as to number of spe- 
 cies, but largely increased in proportionate amount to 
 the other plants. Agrostis vulgaris, and especially Fes- 
 tuca ovina, both poor grasses, are so greatly favored, 
 that they constitute the bulk of the crop, while other 
 better grasses have diminished, even Dactylis glomerata 
 not being by any means prominent. Ammonia salts are 
 not propitious to any of the Leguminosae, but Lotus cor- 
 niculatus has had slightly the advantage over the others. 
 Among the miscellaneous plants which, like the Legu- 
 minosse, are well-nigh banished, Rumex Acetosa had the 
 advantage ; Conopodium denudatum also seems to have 
 benefited in some seasons. The crop is generally moder- 
 ate, of a rich, green color, and late in ripening, with 
 much foliage, and relatively little tendency to flower. 
 
 Nitrate of Soda alone. The general results of the ap- 
 plication of this salt have been an increased proportion 
 of grasses, particularly of Festuca ovina, Alopecurus pra- 
 tensis, Holcus lanatus and Poa trivialis, P. pratensis 
 being scarcely represented. There is in general not 
 much tendency to form stem among the grasses. Legu- 
 minosse exist in but scanty proportions, but among them 
 Lotus corniculatus seems to have slightly the advantage. 
 In the case of beans grown separately, nitrate of soda, 
 unlike ammonia, is found to be beneficial. Among mis- 
 cellaneous plants, Rumex Acetosa and Gentaurea nigra, 
 
THE BATTLE OF LIFE. 103 
 
 are specially noteworthy for their abundance ; Ranunculi 
 are also in fair quantity. Plantago has diminished, but 
 the most remarkable feature is the enormous quantity of 
 Cerastium triviale produced under the influence of this 
 manure. 
 
 Nitrate of soda gives a late-ripening dark green crop, 
 more leafy than stemmy in character, but nevertheless 
 showing a greater disposition to form stem than in the 
 case of plants treated with ammonia. 
 
 Superphosphate and Ammonia. The effects produced 
 by this combination, have corresponded to those which 
 are met with in other plots to which ammonia is added, 
 viz., increased produce, chiefly of graminaceous herbage, 
 greatly diminished leguminous herbage, and relative ab- 
 sence of miscellaneous plants. Festuca ovina has enor- 
 mously increased, and, to a less extent, the hardy creep- 
 ing Agrostis vulgar is. On the other hand Antlioxan- 
 tJium odoratum, Holcus lanatus, and Avena pubescens, 
 have decreased. The crop is usually later in ripening 
 than in the case of that to which the superphosphate 
 alone is applied, and with more dark green leaf and less 
 stem, characters which indicate the presence of ammonia. 
 
 Minerals and Ammonia. In all the plots to which 
 ammonia and minerals have been continuously applied, 
 the produce is large, the per-centage and weight of 
 grasses large, those of leguminous plants small or nil, 
 and those of miscellaneous weeds also small. These effects 
 are greater and more observable, the larger the quantity 
 of ammonia, though the effects are by no means doubled 
 in intensity, when the quantity of ammonia is doubled. 
 The average produce has been larger than that of the 
 other plots. The number of species has diminished, 
 especially in the case of miscellaneous plants. Where the 
 ammonia was in relatively slight proportions, Festuca 
 
104 PLAXT LIFE ON THE FARM. 
 
 ovina> Agrostis vulgaris, Avena elatior, Holcus lanatus 
 and Poa pratensis, are noted to have been predominant, 
 Poa trivialis, on the contrary, being practically banished. 
 The two first-named plants owe their predominance not 
 exclusively to the manure, for they thrive luxuriantly 
 under many other conditions. A similar remark applies 
 to Rumex Acetosa. On those plots where the quantity 
 of ammonia salts was doubled, Dactylis glomerata for 
 some years was in enormous preponderance, Agrostis vul- 
 garis, Holcus lanatus, Alopecurus pratensis and Avena 
 elatior have been also in large quantities. Briza media. 
 Cynosurus cristatus, Lolium perenne, Bromus mollis, all 
 poor grasses, except Lolium, have been discouraged by 
 the ammonia. Poa trivialis also has greatly diminished 
 in proportion to the quantity of P. pratensis. 
 
 Among the miscellaneous plants, Ranunculacese, like 
 the Leguminosse, have been practically banished. Um- 
 belliferae have been almost expelled, Composite largely 
 diminished, Labiates greatly reduced ; Plantago lanceo- 
 lata is unrepresented, and even Rumex Acetosa consider- 
 ably diminished. As these or corresponding effects are 
 generally observed where ammonia forms part of the ma- 
 nure employed, and as they are enhanced when the 
 quantity is increased (though not in direct proportion), 
 it would seem that ammonia must be actually prejudicial 
 to some plants. It is probable, however, that the dimin- 
 ished proportion of these plants is more often due to the 
 increased luxuriance of the stronger-growing grasses than 
 to the directly prejudicial effects of the manures on the 
 other plants. 
 
 It is generally observed, that on the ammonia plots 
 the plants show a great tendency to form leaves, and 
 when mineral manures are added, the period of ripening 
 is hastened, and its degree enhanced. A combination of 
 mineral and ammonia salts, where the latter are not in 
 excessive proportion, is beneficial to almost all crops, as 
 
THE BATTLE OF LIFE. 105 
 
 to Cereals, Crucifers (turnips), Chenopods (beet, man- 
 gels), Solanums (potatoes), etc. 
 
 Minerals and Nitrate, The produce in those cases 
 where this combination is used is generally large, ripens 
 early, is of a dark green color, with abundant foliage 
 and relatively little stem. The per-centage of grasses 
 has been large, that of Leguminosae very small, and that 
 of miscellaneous plants on the whole greatly reduced, 
 effects which, in general terms, are very similar to those 
 observed on the mineral and ammonia plots. 
 
 The mineral and nitrate appears to have encouraged 
 the growth of Poa trivialis, Bromus mollis, and latterly 
 of Alopecurus pratensis, while leguminous and miscel- 
 laneous plants have been discouraged. The following 
 grasses are discouraged by nitrate : Briza media, Cyno- 
 surus cristatus, Poa pratensis. Leguminosae in general 
 and Umbelliferae and some Composites are also discour- 
 aged. 
 
 Cerastium triviale, Plantago lanceolata, Galium verum, 
 Centaur ea nigra, and Ranunculus, are slightly favored 
 by the nitrate. 
 
 The combination of minerals and ammonia favors the 
 growth of Poa pratensis, Agrostis vulgarls, Festuca 
 ovina, etc., more than does the admixture of mineral 
 and nitrate. On the other hand, the following species, 
 among others, are more benefited by mineral and nitrate 
 than by mineral and ammonia : Poa trivialis, Dactylis 
 glomerata, Bromus mollis, and Lolium perenne, etc. 
 
 In some seasons, especially in years of drouth, (1870), 
 Bromus mollis was extremely prevalent, its deep roots 
 giving it an advantage over others. 
 
 Effects of change of Manure, The object sought at 
 Rothamsted in changing the conditions of manuring has 
 been to ascertain definitely to what particular ingredient 
 
106 PLANT LIFE OK THE FARM. 
 
 in a mixed manure a particular effect is due, and to ob- 
 tain confirmation of the results obtained by other 
 methods. By adding or by withholding a particular salt, 
 as the case may be, an answer to the question proposed 
 may be obtained. In the following paragraphs the effects 
 of the disuse of certain manures, and then of the substi- 
 tution of one kind for another, will be very briefly allud- 
 ed to. 
 
 Disuse of Manure of any Kind. On a plot to which 
 farm-yard manure was applied it was observed that while 
 the produce was largely increased, more so indeed than 
 under almost any other circumstances, the per-centage 
 of grasses and of some of the miscellaneous weeds was 
 increased, while the leguminous herbage was diminished. 
 On discontinuing the dung the vegetation of the plot 
 was observed gradually but uniformily to approximate 
 to that of the unmanured plot, the number of species 
 increasing without any marked preponderance of any, 
 and good grasses like Poa trivialis giving place to poorer 
 ones, such as Festuca ovina. 
 
 Disuse of Farm-yard Manure. Another plot which 
 originally received a combination of dung and ammonia, 
 has been treated since 1864 with a small dose of ammonia 
 salts only. Here the grasses and the Leguminosse are 
 diminishing as to numbers, but the luxuriance of those 
 species that remain is increased. The miscellaneous 
 weeds, especially Rumex Acetosa, and the Composites, 
 are decreasing, Ranunculacece decline, and even more 
 markedly so the Umbelliferce and Plantago lanceolata, 
 the latter plant being very sensitive to ammonia. 
 
 Disuse of Potash, The first effect noticeable after 
 the disuse of potash was a diminished produce of grasses. 
 Leguminosae have also continuously and strikingly deT 
 
THE BATTLE OF LIFE. 10? 
 
 creased, while miscellaneous plants, especially Achillea 
 Millefolium and Rumex Acetosa, have increased. 
 
 The increase of Festuca ovina is probably not so much 
 due to any favoring effect of the manure as to the en- 
 feeblement of its competitors. AnthoxantJium odoratum 
 has increased, but almost all the other grasses have 
 diminished. Ranunculacece, Composite, especially Achil- 
 lea, have increased since the disuse of potash. Umbel- 
 lifers, Plant ago lanceolata, and Rumex Acetosa have 
 decreased. 
 
 On the plot where ammonia is added to mineral ma- 
 nures, but where potash is omitted, the grasses show a 
 large per-centage from the effect of the ammonia ; the 
 leguminous plants are almost banished, owing to the 
 combination of unfavorable circumstances, i. e. y the 
 presence of ammonia and the absence of potash. Kanun- 
 culaceae are diminishing, as are also Umbelliferae, Com- 
 posites, Plantago lanceolata, and Rumex Acetosa. 
 
 As a general rule, it is recognized that the growth of 
 plants is checked if the quantity of potash be reduced 
 bevond a certain limit. Deherain has recently shown 
 that in the case of the buckwheat, starch is not gener- 
 ated from chlorophyll unless potash be present. If potash 
 be added, then starch begins to be formed. Neither 
 sodium nor lithium can usefully replace potash, though 
 extremely little is known as to the functions of the lat- 
 ter. Salts of potash and magnesia have also a general 
 tendency to augment the weight of leaves, while chloride 
 of sodium favors the development of stem. 
 
 Substitution of Mixed Mineral Manures for Ammo- 
 nia. The consequences of the disuse of ammonia, and 
 the employment in its stead of mineral manures, are 
 shown in diminished produce, the grasses having been 
 diminished, the leguminous and the miscellaneous plants 
 increasing in number and proportion. Festuca ovina. 
 
108 PLANT LIFE OH THE FARM. 
 
 has been the most prominent grass, while Laihyrus pra- 
 tensis has manifested considerable increase, and Rumex 
 Acetosa has been the most prominent among the miscel- 
 laneous plants. 
 
 The greatest change after some years was, however, 
 not in the distribution of the species, but rather in the 
 character of their development and their increased 
 tendency to form stem and seed. 
 
 Summary. From the foregoing details it is manifest 
 that the plants found on the several plots vary very 
 greatly in number, in character, and in degree of de- 
 velopment, according to the nature of the manurial 
 agent employed, the ever varying character of the sea- 
 sons, and the association or hostile competition of their 
 neighbors. These several conditions rarely, if indeed 
 ever, act singly, but almost always in combination. Cir- 
 cumstances are never exactly twice alike ; a condition of 
 absolute equilibrium is never attained. The nearest ap- 
 proach to it has been reached in the case of the unma- 
 nured plot on the one hand, and of the very highly ma- 
 nured plots on the other, but these, like the others, are 
 influenced by climatal changes occurring now at one 
 stage of growth, now at another. And even when a 
 comparative state of equilibrium is attained, very slight 
 causes, even such as may be roughly called accidental, as 
 the injuries inflicted by insects, or parasitic fungi, suffice 
 to disturb the balance and bring about a different arrange- 
 ment and proportion of species, and a corresponding 
 change in the development of individual plants. 
 
 As to the action of manures on the plants, it is com- 
 paratively rarely that they are employed in such quanti- 
 ties as to be absolutely destructive or poisonous. In most 
 cases even when a particular manure is proved to be 
 more or less directly injurious to particular plants the 
 indirect harm accruing from the beneficial action of the 
 
PBACTICAL IKFEEE^CES. 109 
 
 substance on some other plant or plants, growing in as- 
 sociation with them, is greater than the direct mischief. 
 The manures act very differently on different plants, and 
 vary in their action, even in the same species, according 
 to the time and stage of growth at which they are em- 
 ployed. Some encourage the growth and development 
 of their cellular tissues, at the expense of the woody and 
 fibrous constituents, others favor the consolidation of 
 the tissues, hasten the flowering period, and bring about 
 an increased production of seed. But any change that 
 may be induced is of a physiological kind, affecting the 
 development of the individual, not the character of the 
 species. By no combination of manurial elements is it 
 possible to bring about that kind of change which a 
 naturalist would consider specific. 
 
 CHAPTER VIII. 
 PRACTICAL INFERENCES. 
 
 Objects for which plants are cultivated, and the means of promoting 
 them. Plants cultivated for their roots for their foliage for their 
 fibre for their seeds. Farming operations as aids to propitious cli- 
 matal influences and as counteracting the evil effects of injurious 
 ones. Drainage. Tillage. Manures. Change and variety of crop- 
 ping. Rotation. Improvement of cultivated plants. Selection, 
 Change of seed. Cross breeding. 
 
 Having in the preceding chapters given an outline of 
 the life-history of the plant, the machinery by which it 
 is carried on, the manner in which that machinery fulfils 
 its purpose, and the contest and competition in which 
 living plants are always engaged, it may be well to indi- 
 cate some of the points in which the history so outlined 
 affects the practice of agriculture. Of course, were 
 
110 PLANT LIFE ON THE FARM. 
 
 science perfect, which it is very far from being, and were 
 practice uniformly intelligent and uninfluenced by mere 
 routine or accidental circumstances, it would be found 
 that no single detail of the plant's history was unimpor- 
 tant to the cultivator. As it is, owing to deficient 
 knowledge on both sides, much of what the student 
 learns in the laboratory has no application in the field, 
 and much of what the farmer does on the land is without 
 significance to the student. 
 
 It is the object of the series of Handbooks, of which 
 this is one, to remedy this state of things, and to bring 
 the two classes of workers more into accord, so as to en- 
 sure a greater amount of co-operation beneficial to both 
 parties. The special value to the cultivator of scientific 
 knowledge will probably be found in the power it gives 
 him of availing himself of new resources and of adapting 
 himself to altered conditions no light matter in the 
 present state of agriculture. 
 
 In endeavoring to turn to account some of the lessons 
 which vegetable physiology is able to teach, we have in 
 the first instance to consider what is the special object 
 with which any particular crop is cultivated, because, as 
 has been shown, the conditions suitable, say for the 
 growth of wheat, are not those most fitting for the pro- 
 duction of forage or of root-crops. Then it must be 
 repeated that we grow plants for our own benefit, and 
 only indirectly for the advantage of the plant itself. It 
 may be that the objects for which we cultivate a particu- 
 lar plant are of such a nature as to be best compassed by 
 means most favorable to the general health and welfare 
 of the plant, as in the case of cereals, or it may be that 
 we grow the plant for one particular product, to secure 
 which we endeavor to promote disproportionate leaf- 
 growth or root- growth, as the case may be, at the ex- 
 pense of the other organs of the plant, and so bring 
 about what is really an unnatural and morbid condition. 
 
PRACTICAL INFERENCES. Ill 
 
 In offering a few general considerations on these sub- 
 jects, in addition to the numerous incidental references 
 in other pages, it may here be convenient to arrange 
 plants according as they are cultivated for their roots, 
 inclusive of root-like organs, for their stems, and for 
 their leaves, fruits, or seeds ; omitting all those special 
 details . pertaining to what we may term the individual 
 constitution of plants. 
 
 Plants Cnltivated for their Roots, etc, Under this 
 head are included such crops as turnips, kohl rabi, 
 potatoes, beet-root, mangels, and onions. In all of these 
 the cellular tissue largely preponderates over the fibrous. 
 The cells are filled With water and with various substances, 
 such as starch and other secretions. In the economy 
 of the plant these secretions are manufactured in one 
 season, stored in the cells, and used up in the next season 
 for the production of leaves, flowers, and seeds. The 
 work of the leaves then of these plants differs to some 
 extent according to season ; those of the first year work 
 to build up the plant and to store up the secretions in 
 the " roots" or tubers, while the office of those produced 
 in the succeeding year is more particularly to form and 
 nourish the flower, fruit, and seed, and to secure the ac- 
 cumulation of nutritive matter in the seed. Unless the 
 farmer requires the plants to seed, he uses up the roots 
 for his own purposes before any demand is made upon 
 the plant for flower and fruit building. 
 
 Speaking generally, the indications furnished by the 
 nature of the plants, point to the necessity or desirability 
 of a light, rich, friable soil for their culture, one which 
 will permit of ready root range, and which, while sup- 
 plying ample food, shall not harbor stagnant water. 
 Rapid growth and vigorous leaf-action are also indicated, 
 as, when these are secured, the cellular portions required 
 grow in proportion faster and more freely than the 
 
112 PLANT LIFE ON THE FARM. 
 
 fibrous portions, and the requisite secretions are stored 
 the more readily in the roots. To ensure this rapid 
 growth, more essential in an annual crop like potatoes 
 than in those whose growth occupies part of two seasons, 
 a warm aspect and a well drained soil are essential, while 
 to ensure the formation of the secretions which render 
 the plant valuable, free exposure to light is also requisite. 
 Thus, hoeing and weeding owe their good effects not 
 only to the removal of useless plants occupying space 
 that might more profitably be employed, but they secure 
 to the crop freedom from the shade of the weeds, and 
 promote the access of light to the foliage and of air to 
 the roots. The excessive action of the vegetative organs 
 checks, to a varying extent, the development of the 
 fruiting organs ; indeed, the object of culture is to keep 
 the plant growing and to prevent its flowering. If the 
 seed of such plants is sown too early, growth is apt to be 
 slow, and woody fibre is produced where succulent cells 
 would be preferable, and, moreover, the tendency to 
 produce flowers is enhanced by the high summer tem- 
 perature which follows. If sown late, the growth of the 
 vegetative organs is, for a time, rapid, because the soil is 
 warmer and the sky lighter, while the tendency to form 
 fibre and flower is checked. 
 
 The formation of subterranean tubers may be taken as 
 an indication that the plant prefers a period of rest. 
 The rest is, indeed, not absolute, but relative ; and while 
 little external change may be visible, it is probable, and 
 in some cases certain, that considerable chemical changes 
 go on during the period of apparent inaction. Under 
 natural circumstances the rest is secured, either by the 
 occurrence of heat and drouth, or of a very low tempera- 
 ture, the action of light being, in either case, excluded. 
 These facts supply hints as to the proper mode of storing 
 and pitting potatoes and roots. Moisture, light, and air 
 should be excluded, the temperature kept as low as pos- 
 
PRACTICAL INFERENCES. 113 
 
 sible, short of frost, and what is of even more impor- 
 tance, kept as uniform as possible. By such means the 
 roots may be kept dormant, and the waste to the farmer, 
 which would occur from the unseasonable growth of the 
 plant using up the food intended for his cattle or sheep, 
 obviated. 
 
 Plants Cultivated for their Foliage, Among these 
 are the various green crops and forage plants, cabbages, 
 mustard, clovers, sainfoin, lucerne, vetches and pasture 
 grasses. Apart from the special requirements of each 
 particular 'plant, such as the special influence of nitro- 
 genous manures in promoting leaf -growth among grasses, 
 and of mineral manures in fostering the leafy develop- 
 ment of leguminous plants, and the special demands 
 made by particular circumstances, the object, in all cases, 
 is to ensure a rapid, abundant and nutritious leaf -growth. 
 In some cases where otherwise too great acridity might 
 be produced, it is desirable to secure shade to the leaves, 
 and thus prevent the formation of the objectionable 
 matters. Thus, in the case of cabbages the grower pre- 
 fers those which "heart" well, i. e., those in which the 
 leaves are tightly packed one over the other, and do not 
 readily separate ; and this tendency is increased by con- 
 stantly selecting for seed those varieties in which this 
 peculiarity is seen to be most marked. At other times 
 the production of objectionable secretions is obviated by 
 the process of " earthing up," as in* the case of celery, or 
 by tying up the leaves as in lettuces. 
 
 The development of leaves is of course largely depen- 
 dent on the well-being of the roots, so that, in a general 
 way, all those conditions of soil which are propitious 
 to the development of roots are so also to that of leaves. 
 
 The requirements of particular plants are so varied, 
 according to their affinity and the very diverse modifica- 
 tions of form and structure presented by their roots., that 
 
114 PLANT LIFE OK THE PARM. 
 
 only generalities can here be alluded to. The cultivator 
 must observe for himself whether the plants he wishes to 
 grow are naturally shallow or deep-rooted ; whether the 
 roots break up into a dense leash of fine fibres encom- 
 passing and traversing in all directions the soil within a 
 certain limited area; or whether, as in the case of 
 lucerne, the "root" consists of a long, thick under- 
 ground stem, capable of extending itself for many feet, 
 and giving off, within a small extent, only a compara- 
 tively small number of fibres. The different forms of 
 roots previously alluded to may be looked on as adapta- 
 tions to different . conditions of the soil, especially in 
 relation to water, and the choice of site and mode of 
 tillage must be governed by circumstances. Leaf-de- 
 velopment is thus consequent on root-growth but, in 
 addition, an adequate supply of moisture and heat and 
 full exposure to light are demanded. The adjustment 
 of these agencies is rarely under the control of the far- 
 mer to anything like the same extent that it is in the 
 case of the gardener. The gradener can often contrive, 
 for instance, by appropriate modifications of treatment, 
 to keep his plants in a growing condition, and to prevent 
 them from " bolting " into flower, whereas the agricul- 
 turist is much more the slave of circumstances. Drouth 
 and heat check his crops before their growth is complete, 
 and induce premature development of fibre, of flower, or 
 of seed. Excessive moisture and superfluity of rich food 
 will cause the crops to become too rank in their growth, 
 to develop immature succulent tissue, comparatively 
 devoid of the nutritious secretions in which their value 
 consists, and will check the development of flowers. 
 
 The observant eye of the farmer soon detects the un- 
 healthy state of the crops by the color of the leaves. If, 
 from any cause, root-action is deficient, or sun-heat and 
 sunlight are lacking, the chlorophyll is not formed in 
 sufficient amount, or is imperfectly developed, and the 
 
PRACTICAL INFERENCES. 115 
 
 consequence is a yellow languid look about the leaves, 
 betokening starvation. On the other hand, excessive 
 size and succulence and too deep a green hue indicate an 
 excess of stimulant nitrogenous food and a deficiency 
 both of mineral food and carbon assimilation, in con- 
 sequence of which growth is arrested. In such cases the 
 amount of root-food taken up is out of proportion to the 
 .amount of leaf -food. If the season could be prolonged 
 so as to ensure a longer duration of leaf -action, the 
 balance might be adjusted, but this is rarely the case. 
 Appearances in such cases are apt to be misleading to 
 the inexperienced. There is an appearance of luxuriant 
 vegetation with which the intrinsic nutritive value of the 
 crop is not in accordance. 
 
 Plants grown for Fibre, Apart from timber trees, 
 hemp and flax are the only two crops generally grown 
 on any large scale for their fibre, although the develop- 
 ment of the straw of cereals is dependent on the same 
 conditions. By hereditary transmission these plants 
 manifest a tendency to produce fibre in greater propor- 
 tionate amount than cellular tissue. Heat and light are 
 specially requisite to ensure the formation and proper 
 development of the fibre. Both are naturally plants of 
 hotter, drier, more luminous climates than ours ; never- 
 theless, if they can be grown rapidily they yield fibre, 
 although the secretions of oil, in the seed of the flax 
 (linseed), and of narcotic resin in the case of the hemp, 
 are not produced in a relatively sunless atmosphere. 
 
 The formation of timber is, in general terms, the for- 
 mation of fibre on a large scale. Eoot development, 
 according to the special nature of the tree, of course 
 conduces to the formation and proper development of 
 leaves. Trees, from their root-range being wider than 
 that possessed by herbaceous plants, can collect food over 
 a larger area, and thus can extract nourishment from a 
 
116 PLANT LIFE 0$ THE FARM. 
 
 comparatively poor soil which, would starve other plants 
 with less capacity for food collection and less duration of 
 working life. The larger the leaf -surf ace, and the more 
 fully and thoroughly it can be exposed to light, the 
 greater quantity of timber and the sounder its quality. 
 It may be requisite for certain purposes to have straight 
 unbranched spars, and, in such cases, leaf-action is im- 
 peded and side-growth is arrested by thick plantations 
 and neglect of thinning ; but the actual amount of tim- 
 ber is necessarily less in such trees than in others of the 
 same age allowed to develope freely on all sides. Coppice 
 wood is also grown for a special purpose, which practically 
 justifies that mutilation which, like most pruning opera- 
 tions, is of course at variance with natural growth. In 
 the annual growth of timber it may readily be seen that 
 the greatest activity of growth, i.e., formation of new 
 tissues, takes place in the first few weeks after vegetation 
 commences. After that, the period of maturation or 
 consolidation commences. A moist, warm, growing 
 period is, therefore, most propitious. The process of 
 maturation requires for its fulfilment greater heat, less 
 moisture, and more intense light, and in proportion to 
 the degree in which these requirements are satisfied, are 
 the amount and quality of the timber. Should a wet, 
 sunless autumn be succeeded by an early frost, when 
 maturation is imperfect or incomplete, the results to the 
 young growth, that is, to the crop of timber for the year, 
 are correspondingly disastrous. The effect of mineral 
 manures, especially potash, in promoting the develop- 
 ment of the fibrous tissue in grasses, has been already 
 alluded to ; the largest absolute amount of straw being 
 yielded by a mixed mineral manure with a large supply 
 of ammonia. 
 
 Plants grown for their seed. The remarks just made 
 as to the development of timber as a consequence of 
 
PRACTICAL ItfFEREtfCES. 117 
 
 maturation, apply mutatis mutandis to the development 
 of the fruits and seeds. The farmer, however, especially 
 requires for the culture of seed-plants which are grown 
 as annuals, a rapid, uniform, vigorous growth, followed 
 by a steady progress towards maturity, a condition 
 favored by the gradual cessation or modification of leaf- 
 work, and as simultaneous a ripening of all the fruits or 
 seeds on the plant as possible. The mode of develop- 
 ment of the inflorescence generally considered of mere 
 technical or botanical interest, is here obviously a matter 
 of practical importance, for plants in which the flowers 
 and fruits ripen in succession are obviously less suited 
 for the farmer's purposes than those in which the flowers 
 of a particular inflorescence open approximately at the 
 same time as they do in the cereals. To ensure the 
 production and good condition of the crop, as in the case 
 of cereals, of beans, peas, buckwheat, etc., the first 
 requisites to success are, of course, those which promote 
 the proper germination of the seed, and then those which 
 favor the due development of the root according to the 
 nature of the plant. To a considerable extent the farmer 
 is here master of the situation, and by drainage and 
 tillage appropriate to the varied nature of the soil and 
 the character of the season, he can promote and favor 
 both germination and root-growth. Over leaf-actioa, 
 independent of that which is the direct outcome of root- 
 growth, he has less control, as he is at the mercy of the 
 seasons. If cold, wet, growing periods are followed by 
 dull, cloudy, maturing seasons, the crop must be deficient 
 in quantity or quality, or both. The reasons for this 
 deficiency have been repeatedly given. The farmer is 
 not so able as the gardener to overcome these defects, but 
 he is at least able in a measure to evade them by cultivat- 
 ing not only a variety of different crops, but numerous 
 varieties of the same crop, some of which are sure to 
 prove better adapted to sustain themselves under hostile 
 
118 PLANT LIFE ON TflE FARM. 
 
 conditions than others. Thus spring wheat, barley, of 
 oats, may be made in a degree to supply the deficiencies 
 of the autumn sown wheat, and tares, beans, peas, 
 carrots, etc., etc., employed to compensate for the failure 
 of other crops. 
 
 Manures. By the judicious use of suitable manures 
 at the right time, the farmer is also enabled in some de- 
 gree to provide for and counteract the effects of unpro- 
 pitious seasons. Farm-yard manure, for instance, not 
 only increases the quantity of grain and of straw, but 
 greatly improves the quality of the grain, as measured in 
 pounds per bushel ; and the same holds good of a mixed 
 mineral and nitrogenous manure. 
 
 The time when nitrogenous manures can be most 
 beneficially applied is a matter of great consequence, 
 Messrs. Lawes and Gilbert having proved that the 
 nitrogen carried off the land in the drainage water, is 
 much greater when the manure is applied in the autumn 
 than when used in spring. Another illustration of the 
 use of manures of an opposite character to that just 
 cited, is afforded by the use of common salt (sodium 
 chloride) to check rank growth with its tendency to pro- 
 duce straw rather than grain. 
 
 The varying effects of season, according to the nature 
 of the manure employed, suggest also that a variety of 
 manures should be used. In the Rothamsted experi- 
 ments, it has been shown that the seasons which proved 
 most propitious to the unmanured crops, and to those to 
 which only mineral manures were applied, were not 
 equally so for the crops to which nitrogenous manures 
 were applied; hence, says Sir J. B. Lawes/' the best season 
 for land in low condition is not the best for land in high 
 condition." 
 
 The varying effects of manure may be illustrated by a 
 few figures taken from- the Rothamsted "memoranda" : 
 
PKACTICAL USTFEKEtfCES. 119 
 
 thus, in the case of wheat, the average produce per acre 
 over thirty years, was about thirteen bushels on the 
 unmanured plots, as against thirty-six on highly manured 
 plots (mineral and ammonia salts, and mineral and 
 nitrate respectively), some plots also producing the largest 
 quantities of straw, the nitrate producing rather more 
 than the ammonia. The quality of the produce of wheat 
 as measured in pounds per bushel is not so different, 
 that on the unmanured plots being usually nearly equal 
 to that of the highly manured plots. From this point of 
 view, farm-yard manure proved more beneficial than the 
 artificial nitrogenous and mineral manure yielding the 
 largest quantity of grain. The corresponding figures in 
 the case of barley, are seventeen and forty-nine ; the 
 highest produce was with nitrate and. minerals, but the 
 largest amount of straw was yielded with a manure con- 
 taming a large proportion of nitrate of soda with 
 minerals. Of hay, the average produce under like cir- 
 cumstances over twenty years, was two thousand three 
 hundred and fifty two pounds on the unmanured, and 
 six thousand nine hundred and forty-four pounds on 
 highly manured plots (mineral and ammonia.) 
 
 In like manner, turnips varied from one or two tons per 
 acre without manure to eight tons with superphosphate, 
 and nine to twelve tons with superphosphate combined 
 with nitrogenous manure, such as ammonia or rape-cake. 
 Sugar beet produced, when unmanured, from seven to 
 eight tons per acre in the earlier, to five tons in the later 
 years, but eighteen tons with farm-yard manure ; nitro- 
 genous manures increased the yield largely, but super- 
 phosphate was of no use to the beet and mangel. With 
 mangel, the produce on the unmanured plot was from 
 one to six tons per acre (average 4.6 tons), as compared 
 with nineteen tons with farm-yard manure (or on the 
 average fourteen tons). Potatoes varied from about half 
 a ton on the unmanured, or about two tons on the 
 
120 PLAHT LIFE OK TSE FARM. 
 
 average, to four to five tons with farm-yard manure, 
 and to six to seven tons with mixed mineral and am- 
 monia. The tendency to disease, however, increases with 
 the higher manuring, in larger proportion than does the 
 produce. 
 
 The data of science on the effect of manures must, 
 however, only be taken as indications by the practical 
 farmer, who must be guided by financial considerations 
 and local conditions, in determining what it is best for 
 him to do under particular circumstances at any given 
 time. 
 
 An interesting circumstance may here be mentioned, 
 viz : that many of our cultivated plants, such as cab- 
 bages and mangold wurzel, have sprung from wild plants 
 growing by the sea, and are hence especially benefited by 
 the use of salt as a manure. Onions, the growth of 
 which is also favored by salt, probably originated from a 
 wild stock growing in salt desert regions. 
 
 Fallow, The good effects of this may be judged from 
 the results of some Eothamsted experiments, in which 
 the produce of wheat is recorded, after bare fallow, com- 
 pared with that of wheat grown continuously on the 
 same soil, without the intervention of fallow, and equally 
 without manure. Under such circumstances, the aver- 
 age produce for twenty -five years after fallow has been 
 eighteen bushels per acre, as contrasted with an average 
 of twelve bushels where the wheat has been grown con- 
 tinuously. The weight per bushel was the same in both 
 cases. The average quantity of straw after fallow was 
 one thousand seven hundred and eighty-six pounds, as 
 contrasted with one thousand two hundred and twenty- 
 one pounds, where the crop was grown continuously. 
 
 Rotation. The practice of rotation of crops is amply 
 borne out by what occurs in nature and by chemical ex- 
 
PRACTICAL ItfFEREKCES. 121 
 
 periments, although not in the manner that might at 
 first have been supposed. Leguminous plants, such as 
 clover, beans, vetches, though containing so much nitro- 
 gen in their composition, are not only not specially bene- 
 fited by nitrogenous manures, but they absolutely leave 
 the land richer in nitrogen than it was before (Lawes 
 and Gilbert), and thus prepare it for the growth of grain 
 crops, which, though chiefly starch -producing, 'are yet 
 specially benefited by nitrogenous manures. 
 
 In growing beans and wheat alternately at Kotham- 
 sted, it was found that eight crops of wheat grown al- 
 ternately with beans supplied nearly as much produce 
 (grain), and nearly as much nitrogen in that produce as 
 were furnished by sixteen crops of wheat grown without 
 manure. Here, then, the manure supplied to the beans 
 not only favored those plants, but left a residue in an 
 available form for the wheat. 
 
 Botanically, the good effects of rotation are dependent 
 on the variations in the mode of growth and in the in- 
 ternal structure of roots, which allow of different layers 
 of soil being utilized for plant-food, while the specially 
 different requirements of different classes of plants obvi- 
 ate the exhaustion of any one ingredient, and give time 
 for the accumulation of fresh supplies. 
 
 Improvement of Cultivated Plants. This has already 
 been alluded to, but its importance justifies repetition, 
 the more so as to a considerable extent it is a matter that 
 the farmer can do for himself. A series of small experi- 
 mental plots might well be instituted on every farm. 
 The first and perhaps most general use to which such 
 trial grounds should be put, would be to test the quality 
 of purchased seed, and ascertain what proportion might 
 be expected to grow under different conditions. Other 
 experiments should be devoted to the purpose of ascer- 
 taining what particular varieties are likely to do best in 
 6 
 
PLANT LIFE OK THE FAKM. 
 
 particular places. The investigator who sets to work to 
 produce really improved varieties, has a more difficult 
 task before him, owing to the number of excellent varie- 
 ties already in existence. The consequence of this is 
 that much labor and patience must be expended before 
 any real improvement on what is already in existence can 
 be expected, although there is the chance that a real ad- 
 vance may be made almost at once. The large capital 
 employed by the seed-houses in raising and introducing 
 improved varieties real or so-called is, at least, a testi- 
 mony that the practice is pecuniarily profitable to the 
 trader, and forms therefore a resource which the agricul- 
 turist might develop for himself to a larger extent than 
 he does. He would reap the advantage on his own farm, 
 even if he lacked the capital and enterprise requisite to 
 conduct a commercial speculation away from it. 
 
 Selection. The improvement of the races of cultivated 
 plants, as previously alluded to, is indicated by Nature 
 herself. In a wheat field or bean crop no two plants are 
 exactly alike : one is more robust than another, one 
 tillers more than the rest, the ears of one are plumper 
 and fuller, this one grows earlier or later in spring, is 
 therefore hardier or more tender, as the case may be. 
 The careful observer notes these points, and instead of 
 passing them over, endeavors to turn them to account by 
 selecting the plant which shows a tendency to vary, 
 taking seed from it and growing that seed another season. 
 A certain proportion of the offspring is pretty sure to 
 reproduce the desired qualities, probably even to mani- 
 fest them in an enhanced degree. This leads to further 
 and repeated selection, till, at length, a new race or 
 variety is established. When it is remembered whab 
 vast results have accrued from the improvement of wheat 
 and turnips by selection of this kind, it seems remarka- 
 ble that further efforts are not made in this direction, 
 
PRACTICAL INFERENCES. 
 
 and especially by selecting forms which observation 
 would show are specially suited to a particular locality. 
 Thus Rivett's red wheat produced at Rothamsted, on an 
 average of eight years, fifty-three bushels of grain per 
 acre, while Hallett's original red, grown under the same 
 conditions, yielded only thirty-six bushels. 
 
 Change of Seed. This is a practice followed with ad- 
 vantage by both gardener and farmer, for it is found that 
 the crop is improved when seed even of the same variety 
 is obtained from a distance where it has been grown 
 under different conditions of soil and climate. In such 
 cases it is better, where possible, to select seed grown on 
 a poorer soil and under more unfavorable conditions than 
 obtain where it is proposed to sow. The increased vigor 
 and degree of fertility resulting from this process have 
 been commented on by Darwin. 
 
 Cross Breeding by means of artificial fertilization 
 is an operation not so much within the power of an 
 ordinary agriculturist, owing to the delicacy of manipu- 
 lation and length of time required to ensure results worth 
 having. Such experiments would be better accomplished 
 in the laboratory or experimental garden of the professed 
 physiologist. The experiments carried out by Andrew 
 Knight, Maund, and Sheriff, in the case of wheat and 
 oats are, however, encouraging. "When undertaken for 
 practical purposes, it is specially desirable that mere hap- 
 hazard crosses should not be encouraged, much less made 
 purposely, but that a definite object should be pursued 
 in a definite manner. The experimenter should set him- 
 self to work to endeavor to produce an earlier, a hardier, 
 a more prolific variety, as the case may be, selecting for 
 his purpose such varieties to breed from as he has ascer- 
 tained by experience to be of such a nature as likely to 
 yield promising results. It is not possible to give detailed 
 
PLANT LIFE ON THE FAEM. 
 
 instructions here as to the way in which cross-breeding 
 may be carried out ; it is difficult with cereals, less so 
 with leguminous plants, easiest with the cabbage tribe. 
 Indeed, as growers know to their cost, it is difficult to 
 keep the races or strains of the cabbage-tribe pure and 
 uncontaminated, owing to the facility with which the 
 flowers are fertilized by insects which bring the pollen 
 from the flower of some other variety. Too high breed- 
 ing, however, often entails a delicacy of constitution or 
 a defective productiveness which may be overcome by a 
 fresh cross with a stronger strain. 
 
 CHAPTER IX. 
 DECAY AND DEATH. 
 
 Change, waste and repair. Disturbance of the balance. Death of the 
 protoplasm. Causes of death. Natural death. How plants die: 
 impaired nutrition, starvation, suffocation, structural injury and 
 paralysis. Death beginning at the root. Death beginning at the 
 leaf. 
 
 Decay and Death* Life is one continual series of 
 changes 
 
 "By ceaseless action all that is subsists." 
 
 The result of these changes is gain or loss, waste or 
 repair, now one, now the other ; or occasionally (and 
 indeed generally) both simultaneously. While a proper 
 balance and equitable adjustment between gain and loss 
 exists, the plant lives and is healthy. Directly the bal- 
 ance is disturbed the plant may live indeed, but it be- 
 comes unhealthy; and if the disturbance continue if 
 waste overtake repair if nutrition be persistently im- 
 paired, still more if it be arrested, the plant inevitably 
 
DECAY A^D DEATH. 125 
 
 dies. This is that gradual and slow but sure inarch of 
 destiny which comes sooner or later to all living things 
 at their appointed time. That time comes when the 
 tissues are from that degeneration of their substance 
 which may be a morbid process resulting from injury, 
 or which may be merely the necessary result of the 
 growth and maturation of the plant, or from the failure 
 of supplies no longer able to carry on their life-work. 
 The period in question varies as to its occurrence. A 
 wheat plant uses up its life within a few months, an oak 
 tree within a few centuries, and there is every inter- 
 mediate period. 
 
 But, in addition to changes which are the result of an 
 inevitable march of events, death in plants sometimes 
 comes suddenly from violence, life action is arrested in 
 its full flow and tide, and by much the same essential 
 causes as those which extinguish the life of animals. 
 The death of plants is the death of the protoplasm. Pre- 
 vent the access of oxygen to the living cell, and the 
 movements of the protoplasm will be arrested and ulti- 
 mately cease altogether. The properties and functions 
 of protoplasm have already been explained. It is their 
 destruction and their cessation which constitute death. 
 But the death of a part is not necessarily the death of 
 the whole, and the individual cells of plants are, as a 
 rule, much more independent one of the other than are 
 the individual cells of an animal. A root or a leaf, or a 
 mass of roots, and a number of leaves may be injured, or 
 even killed, and the plant will still live on, because there 
 are more left behind uninjured ; and these, relatively 
 speaking, do not suffer from the damage done to their 
 fellows. A tree may be stripped of its leaves and may 
 still live, because there are cells which are uninjured, and 
 which will do their parts towards compensating the 
 injury. A felled tree by the roadside will often be seen 
 pushing up new shoots in a manner that would be im- 
 
126 PLANT LIFE ON THE FARM. 
 
 possible in the case of an analogous injury done to one 
 of the higher animals. The lower the organism, the less 
 special in its conformation and construction, the more 
 independent are its constituent cells. The higher the 
 organism, and the more specialized its structure, the 
 more dependent one upon another are the structural ele- 
 ments of which it is compounded. 
 
 Natural death may be described as an exhaustidn of 
 the protoplasm its water evaporates or is drafted else- 
 where ; and so with its soluble or liquid contents the 
 insoluble and the useless remain behind. We see this in 
 the case of the leaves every autumn ; their protoplasm 
 dries up, their chlorophyll degenerates and disappears ; 
 they are emptied of starch and other matters, which are 
 conveyed to some other part of the tree to be stored up 
 for future use by the new growths in the following sea- 
 son, until at length nothing is left but a framework of 
 dry cellulose, a quantity of mineral or earthy matter, and 
 such material as could not be dissolved or transported. 
 In other organs the continuous maturing process at 
 length results in the blocking up of the cells and tubes 
 by continued deposit in the interior. Osmosis can no 
 longer go on between them, for their altered structure 
 prevents it, and in consequence the protoplasm disap- 
 pears. Just as in human beings, the minute blood-ves- 
 sels get " bony " or otherwise deteriorated in structure, 
 so do the cells and fibres of plants become unfit to carry 
 on the processes of life. 
 
 For the purposes of the cultivator, it is very desirable 
 that he give an eye to the way in which plants die and to 
 the causes in which induce death. The subject may be 
 looked at from various points of view. From the struc- 
 tural point of view, death may begin in the cells of the 
 root, in those of the stem, in those of the intermediate 
 "collar," or in those of the leaves, and the appearances 
 presented will be found to differ correspondingly. 
 
, DECAY AKD DEATH. 127 
 
 From a physiological point of view death may result 
 from starvation or from suffocation ; the process in each 
 case may be partial and gradual or immediate and com- 
 plete. Sudden death, or death by violence, results from 
 the injuries inflicted by too high or too low a tempera- 
 ture, electric shocks, sunstroke, strong corrosives, and 
 the like. These destroy life by disorganizing the pro- 
 toplasm, breaking up the tissues, and arresting the 
 natural movements, and cause death by destroying the 
 machinery or paralyzing its action. The gradual effects 
 produced by such injurious agencies as noxious vapors 
 from kilns or factories, or as insects, or parasitic fungi 
 are the same as those produced by starvation or suffoca- 
 tion. In the neighborhood of towns it may happen that 
 the relative absence of oxygen, or, what comes to the 
 same thing, the inability to use what there is, may con- 
 duce to the death of plants quite as much as the direct 
 injury caused by noxious vapors. A perusal of the fore- 
 going -chapters as to the food and growth of plants will 
 suffice to show why plants die ; and a consideration of 
 their life-history as here set forth will show how the 
 cause that may kill at one stage of active growth may be 
 all but harmless at another stage of growth (see p. 64). 
 
 Death beginning at the Root. When death begins at 
 the root, the supply of water and of the air and food de- 
 rived from the soil is cut off, and the plant ultimately 
 perishes of starvation. Death at the root may result 
 from injury inflicted by small parasitic worms, insects, 
 rats, or other creatures from unsuitable conditions of 
 soil, too much or too little water, deficient drainage, 
 deficient aeration, or from the presence of really poison- 
 ous ingredients. If the cause is widespread, so as to in- 
 volve a majority or the whole of the roots, the conse- 
 quences are proportionately serious ; if only a few are af- 
 fected; the plant may not be visibly or materially injured, 
 
PLAKT LIFE ON THE FAKM. 
 
 The effects will be first and most especially olrvious at 
 the point of injury, and at the growing points, where the 
 life-functions happen to be going on most vigorously at 
 the time. Thus, if the young shoots and young leaves 
 are in full activity at the time when root-mischief occurs, 
 they will the soonest show the effect of cutting off sup- 
 plies they will wither and droop. If the process is slow 
 and gradual, the leaves will become emptied of their 
 contents, their chlorophyll will change color, the plant 
 will assume a sickly yellow look very characteristic to 
 the practiced eye. The older portions of the plant, with 
 their reserve stores of water and food, may not immedi- 
 ately suffer ; and it is from them that the materials 
 requisite for any effort at repair and reorganization must, 
 if it be possible, be made. Thus a plant may grow for 
 some time after injury, and then suddenly flag because 
 its reserve supplies are at length exhausted. It follows 
 from this that death from starvation as a consequence 
 of root-mischief is not generally a sudden, but more often 
 a gradual process, the length of time of course varying 
 according to the nature of the mischief, and specially 
 according to the nature and condition of the plant. 
 
 Death beginning at the Leaf, This may be appre- 
 ciated from what has been before said as to the functions 
 of the leaf. The leaf is an organ of nutrition, of respira- 
 tion, and transpiration; if its functions are sufficiently in- 
 terfered with, death will result, either from inanition or 
 from suffocation, or from both combined. The power of 
 resistance that a leaf has may be inferred from its 
 structure. A thick, fleshy leaf, with layer after layer of 
 chlorophyll-containing cells, with abundance of pores 
 and a thick skin, is obviously better able to resist in- 
 jurious agencies than a thin leaf whose delicate texture 
 speedily withers and falls a prey to adverse circum- 
 stances. 
 
DECAY AND DEATH. 129 
 
 The fall of the leaf in the case of deciduous trees has 
 heen already alluded to. It is only requisite here to say 
 that, under the circumstances, <tbafc it is a natural 
 process ; and it is one that is provided for from the 
 beginning. From a very early stage in the development 
 of the leaf, a special layer of cells has been gradually 
 forming at the base of the leaf -stalk at right angles to 
 the others, which ultimately cuts off the dying and dead 
 leaf -cells from the living tissues of the bark, much as 
 the " drop scene" of a theatre separates the body of the 
 house from the stage at the close of the performance. 
 The leaf is emptied of its contents, and further supplies 
 from below are eventually stopped off by the intervention 
 of the layer of cells above described. A similar process 
 takes place in the disarticulation of branches and of ripe 
 fruits. 
 
 When disease or injury affects the leaves while still 
 growing as in the case of noxious vapors from chemical 
 works or kilns, or in the case of insect injury its effects 
 are naturally most obvious and most severe at the grow- 
 ing points the tips and margins of the leaf ; and when 
 the margins become thus arrested in their growth, while 
 the disc remains in full activity, the result is a cup- 
 shaped appearance or a crumpled surface resulting from 
 the dead or dying portions having lost their elasticity 
 and acting as a curb on the growing portions. Sun-burns 
 and especially the attacks of insects and parasitic fungi 
 are not so much confined to the margins, at least when 
 the leaf is not in a growing state ; they produce their 
 effects in the shape of circular or irregular spots of brown 
 decayed protoplasm. The effects of frost and the reason 
 it kills have been explained in a former page. Nothing, 
 however, can be advanced in explanation of the reasons 
 why some plants of the same species, like the different 
 varieties of wheat, are so much more tender than others. 
 Death by the leaf is rarely immediately fatal, because 
 
130 PLANT LIFE OK THE FAKM. 
 
 there are many leaves, and they are not often all 
 affected in the same way at the same time ; and, more- 
 over, in the case of plants other than (t annuals," the 
 fall and death of the leaves does not involve the death of 
 the plant, as before explained. Even in the case of 
 annuals, the life, like the nutritive matter, goes out of 
 the leaves only to enter the seed. 
 
 Successor thus follows predecessor in one invariable 
 rhythm, and although the limits of the individual exis- 
 tence can be but too readily recognized, the real ' end of 
 life, so far as the whole race of living creatures whether 
 plant or animal is concerned, is as incapable of being 
 appreciated by the physiologist as is its beginning. 
 
INDEX. 
 
 ABSORPTION 10 
 
 Amount of 14 
 
 by leaves 29,31 
 
 by roots... 23, 24 
 
 of gases.. 29,31 
 
 of water 29 
 
 Alcohol 32 
 
 Ammonia Salts 17 
 
 Action of 102 
 
 and mineral salts 103 
 
 Annuals : 39 
 
 Anthers...., 84 
 
 BACILLUS 32 
 
 Bacteria 17,26 
 
 Barley 19. 119 
 
 Bast-cells 27,49 
 
 Beet 20, 105, 119 
 
 Branches 39 
 
 Buds 39 
 
 Bud-formation 82 
 
 Bulb* ' 39 
 
 Bundles, woody 48 
 
 CABBAGE : 113 
 
 Cambium 47, 48 
 
 Carbon 29 
 
 Carbonic acid 29 
 
 Carnivorous plants 33 
 
 Caulicle 75 
 
 Cells, bast 49 
 
 growth of ... 45 
 
 their nature 12 
 
 wood .49 
 
 Cereals 20, 87,89, 105 
 
 Changes, chemical 88 
 
 in plants 16, 130 
 
 Chlorophyll 12,28,30 
 
 degeneration of 114, 126 
 
 Circumnutation 52 
 
 Climbing plants 69 
 
 Clover 15 
 
 Alsike 88 
 
 Color 115 
 
 Colza 79 
 
 Contact, Action on leaves 66 
 
 roots 59 
 
 stems 69 
 
 Cotyledons 74 
 
 Crossbreeding 85, 123 
 
 DEATH, at leaf 128 
 
 at root 127 
 
 from frost 64 
 
 heat 65 
 
 starvation 127 
 
 Decay 124 
 
 Deoxidation 32 
 
 Diffusion 11 
 
 condition of 13 
 
 Drainage water 118 
 
 EMBRYO, formation of. 74, 85 
 
 Endogeus , . . 48 
 
 Epidermis 27 
 
 Exogens 48 
 
 Eyes 40 
 
 FALLOW 120 
 
 Farm-yard manure.- 106, 118 
 
 Feeding of plants 9 
 
 Ferments 17, 76 
 
 Fertilization 83 
 
 cross 85, 123 
 
 Fertilization of cereals 87 
 
 Fibre crops 115 
 
 Flowers, structure of 83- 
 
 Foliage crops 113 
 
 Form of leaves 26 
 
 as dependent on growth 50 
 
 of roots 22 
 
 of stems 38 
 
 Frost, action of 64 
 
 Fruits, ripening of 80 
 
 GASES, absorption of 29 
 
 emission of 29, 31 
 
 Geotropism 56 
 
 Germination 44,48, 77 
 
 Germs... 17 
 
 Glucose 32,76,77 
 
 Grasses 20,39,91,92 
 
 cereal 20, 87, 105, 123 
 
 pasture - 94 
 
 Gravitation, effects on roots 56 
 
 effects on stems 67 
 
 Growing points 46 
 
 Growth 44,72 
 
 of cells 45 
 
 of leaves 49 
 
 of roots 47 
 
 of stems 48 
 
 HAT 19,88 
 
 Heat, action on leaves 64 
 
 onroots 67 
 
 on stems 69 
 
 (See also Temperature). 
 
 Heliotropism 62 
 
 Hops 69, 85 
 
 Hybridization 88 
 
 IMPROVEMENT of plants ,121 
 
 Inheritance 73 
 
 Iron 18 
 
 LEAVES 26 
 
 absorption by 29 
 
 action in darkness 31 
 
 of contact on 66 
 
 of gravity on 62 
 
 of heat on 64 
 
 of, in light 30 
 
 of light on 67 
 
 of moisture on 64 
 
 fall of 129 
 
 feedingby 29 
 
 forms of 26 
 
 functions of 37 
 
 growth of 44 
 
 movements of 55 
 
 parts of 27 
 
 sleep of 63 
 
 Leguminosae 93,96 
 
 Light, action on leaves 62 
 
 roots 57 
 
 stems 68 
 
 Ligule . 27 
 
 Lime, action of 18,101 
 
 Liquids, ascent of 42 
 
 pressure 43 
 
 MALTING 77 
 
 Mangel 105, 119 
 
 I Manures 19, 118 
 
 ammonia 102 
 
 I changeof. 105, 107 
 
 1 disuse of... ....106 
 
 (131) 
 
132 
 
 IKDEX. 
 
 Manures, effects of... 20, 73,100, 107, 108 
 
 fann-yafd 106, 118 
 
 mineral 100 
 
 with ammonia 103 
 
 nitrate 105 
 
 nitrate of soda 102 
 
 potash 18 
 
 disuse of 106 
 
 substitution of 107 
 
 superphosphate . . 101 
 
 with ammonia .... 103 
 
 Manuring, principles of 19 
 
 Maturation 78, 80 
 
 Meristem 47 
 
 Molecules 10 
 
 Movements 51, 56 
 
 of leaves 55 
 
 of protoplasm . . 51 
 
 of seedlings 55 
 
 of stems 53 
 
 of the roots 52 
 
 NITRATES 17 
 
 of soda 102 
 
 Ni trogen 17 
 
 loss of 118 
 
 Nucleus 12 
 
 OBJECTS of cultivation 119 
 
 Onions 39, ISO 
 
 Osmosis 10 
 
 Oxygen in soil 25 
 
 Inhalation of 31 
 
 Ovule 84 
 
 PARASITES 33 
 
 Pasture plants 91 
 
 grown without manure. 98 
 
 Perennials 39 
 
 Perisperm 75 
 
 Petals 83 
 
 Petiole 27 
 
 Phosphorus 18 
 
 Pistil 84 
 
 Pith 49 
 
 Plants, carnivorous 33 
 
 climbing 66 
 
 Plant food. 16 
 
 Pollen, action of 84 
 
 transport of 84 
 
 Potash salts 18,10,106 
 
 Potatoes 20, 39, 82, 121, 112, 119 
 
 Protoplasm, decay of 125 
 
 its nature 12 
 
 movement of 51 
 
 RADICLE . . 53, 60, 75 
 
 Reserve materials, transport of... .75, 77 
 
 Ripening. See Maturation 
 
 Root 22,24 
 
 action of contact on 59 
 
 gravity on 56 
 
 light and heat on 57 
 
 moisture on 58 
 
 cap 22 
 
 crops Ill 
 
 fibrils 24 
 
 functions of 24 
 
 growth of 47 
 
 hairs 24 
 
 movements of 52 
 
 nature and origin of 23 
 
 passage through soil 60 
 
 Root stock 38 
 
 Rothamsted, pasture at 91 
 
 experiments 18, 19, 21, 35, 78, 109, 121 
 
 Rotation 90, 120 
 
 Runners 38 
 
 SALT 118 
 
 Salts 16 
 
 Sap 41 
 
 Seeds 116 
 
 change of 123 
 
 Seed crops 116 
 
 Selection 73 
 
 power of, by roots 20 
 
 Sensitiveness, 56 
 
 Silica 15 
 
 Sodium, chloride 107, 118 
 
 Stamens 84 
 
 Starch 18, 31, 75, 77 
 
 Starvation 127 
 
 Stem 38 
 
 action of contact on . . 69 
 
 gravity on 67 
 
 heat on 69 
 
 light on 68 
 
 moisture on 61 
 
 growth of. 48 
 
 nature of 38 
 
 uses of 41 
 
 work of 38 
 
 Stigma 84 
 
 Stipules 27 
 
 Stomata 27 
 
 Straw 116, 118 
 
 Struggle for life 100 
 
 Style.' 84 
 
 Suffocation 27 
 
 Sugar 1 76 
 
 Sulphur ,18 
 
 TEMPERATURE, effects of (See Heat).. 
 
 Tillering 40,82 
 
 Timber 115 
 
 Transpiration 35 
 
 Transport 75 
 
 Tubers 39,82,112 
 
 Turgescence 45, 51 
 
 Turnips 102, 119 
 
 Twitch 38 
 
 VARIATION 73 
 
 Vegetation, alternate 121 
 
 gregarious 90 
 
 Vessels 27 
 
 WATER 10 
 
 absorption of 29 
 
 diffusion of 11 
 
 importance of 16 
 
 ingress of. 11 
 
 supply of 10 
 
 transpiration 35 
 
 Weeds 93.97 
 
 list of pasture 93 
 
 Wheat, composition of 15 
 
 embryo 74 
 
 laid 54 
 
 pedigree 74 
 
 produce of 119 
 
 ripening , 28 
 
 Wood...? 48 
 
 cells 48 
 
 Btructureof 48 
 
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