Botany

Botany is that sub-science of biology which has for its special province the phenomena of the vegetable world. Its general origin and rise, its place among the sciences, its progress in morphological and physiological analysis, and its broadest generalisations, have thus been already outlined under BIOLOGY (q.v.); here it remains to give a sketch of the history of the special study of plants, an account of its present state, and an indication of the most direct and profitable way of approaching the subject. From this brief account the reader may therefore pass on the one hand to the major article BIOLOGY, with its subordinate general articles like MORPHOLOGY, PHYSIOLOGY, &c., and on the other to any of the numerous minor articles concerned with the details of the subject.

1. History of Botany.—The special history of the science may be very briefly outlined. Aristotle's treatise On Plants, if indeed it was Aristotle's, is lost, but the writings survive of his pupil Theophrastus, who not only describes about 500 plants, but discusses the vegetable world with something of his master's philosophic spirit. The 1st century produced the Materia Medica of Dioscorides—in which 600 plants are named, 400 with descriptions—as well as the writings of the elder Pliny, which, however, contain no original matter, but are simply a compilation of literary and popular knowledge, chiefly with reference to practical uses. Although some knowledge of botany must have been conserved in the medical traditions of the following centuries, we hear nothing of botany until the time of Charlemagne, who was a hearty patron of gardening as well as agriculture. The early Greek knowledge of the subject found its way through the Herbal of Avicenna into Western Europe, and it is probably to this transmission that we owe the 13th-century work of Albertus Magnus, although this is a mere worthless commentary upon the classical writers already mentioned. The merit of initiating the independent observation of plants themselves is usually ascribed to Otto Brunfels of Strasburg, whose Kräuterbuch was published in 1537, three years after his death. Similar descriptive efforts followed with increasing rapidity during the remainder of this and the following century, to which period belong many botanists of honourable memory. Among these may be especially named, in Germany, Bock, Fuchs, and the brothers Bauhin; in Switzerland, Gesner; in the Netherlands, Dodonæus, Lobel, and Clusius; in France, Ruellius and Delechamps; in England, Turner; and in Italy, Cæsalpinus; while the rate and reality of progress may be judged from the fact that while Brunfels describes only 240 species, Bock has 800, Lobel 2191, and Bauhin (in 1623) 6000 species. Botanical travellers also arose, among whom Clusius in Europe and Albini in the east are especially remembered. Botanic Gardens (q.v.) next were founded, classificatory attempts were made with more and more frequency, and the advent of Linnæus was thus fully prepared for. The later portion of the 17th and beginning of the 18th century is also memorable for the fruitful application of the microscope to the study of plants by Malpighi (q.v.), whose discoveries were continued and extended by his English exponent Grew, as well as by the indefatigable enthusiasm and industry of Leeuwenhoek. The study of cryptogamic plants was thus rendered possible, and its initiation is ascribed to the labours of Micheli and Dillenius during the second quarter of the 18th century. The rise of Vegetable Physiology (q.v.) is also dated from the classic observations (1727) of Stephen Hales upon the movement and pressure of the sap.

The descriptive botanist still necessarily occupied by far the foremost place, especially as the progress of botanical travel was now passing the limits of Europe to bring home an indefinite variety of plant marvels from all the most distant countries. Many stately monographs thus date from the same pre-Linnean period, while the replacement of the crude and empirical classifications due to Cæsalpinus and other writers of the 16th century became increasingly hopeful as well as urgent. The classifications proposed by Morison, Ray, and Tournefort were especially of service, and will be considered at VEGETABLE KINGDOM. Under this head must also be discussed the epoch-making Systema Naturæ of Linnæus, as well as the various phases of that necessary replacement of his artificial method of larger grouping which has been in progress during the past hundred years. Although the foundation of the 'Natural System' is with substantial justice assigned to the two De Jussiens (uncle and nephew), it must also be remembered that its essential principle—that affinities are to be determined not by any single character, but by the sum of all—had been more or less familiar to many of the earlier botanists, particularly to Ray, as certainly also to Linnæus himself. He in fact proposed his artificial system avowedly as provisional; and the blame of its obstinate and bigoted retention for well-nigh two generations after Linnæus and the elder De Jussieu had departed, must thus, as in so many other historic cases, be ascribed, not to the purpose of the master, but to the blind and indiscriminating reverence of his disciples in adhering to the letter of his writings at the expense of their general aim and spirit.

The story of this long and laborious indexing of the book of nature is an interesting tale. The wanderings of Clusius were repeated and outdone by the immediate scholars of Linnæus, a generation later by Humboldt, and again by the younger Hooker, with whom the roll of great travellers fitly closes; and the story has in it an element of epic breadth, as becomes what is indeed the modern re-search after the golden apples. Nor should the patient complementary systematic toil, of which the colossal Prodromus Systematis Naturalis, the monument of three generations of De Candolles (Geneva, 20 vols. 1818-73), is only the central work, pass without recognition.

But it is a less favourable aspect of the progress of botany which forces itself on the student. From the petrifying predominance of letter over spirit, no science has indeed been wholly exempt. Yet happily, for the past century at least, no department of knowledge save botany has ever fallen into such utter intellectual torpor, lain in it so long, nay, indeed, even now escaped from it so incompletely. It was much certainly to have done with commentaries upon Dioscorides and Pliny, and again begun after an interregnum of fifty generations to gather fresh flowers and look at them in themselves; still, this return to nature was far less thorough than it seemed. For although the old herbalist's reference-book of dried simples gathered from the fields and woods around his town was growing into a vast herbarium of all the world, and although he had been suddenly raised into a position of high academic honour and influence, the unnoticed drawbacks of such apparently complete scientific success were neither few nor small. The best botanist was thus he who had described most plants and had accumulated the richest herbarium; but the art of describing plants, once clearly learned, became a mechanical routine, a mere Latin clerkship. The inventory done, the interest of the consignment of new plants was exhausted, or thereafter oscillated between the petty pride of priority and possession, and the exercise of the surviving commercial passions in incessant barter. In their new-won academic seats, the systematic botanists in fact speedily absorbed all the vices of the old-world pedantry around them. First, the simple descriptive language of Linnæus was elaborated into a barbarous terminology which he would have been the first to denounce; and the concrete teaching of the facts of botany became more and more pushed aside. The whole course of degeneration was in fact a curiously perfect outcome and reflection of the established course of general education, in which the abstractions of grammar, at first admitted as a preliminary aid to the study of literature, had finally come to exclude that study for the majority of learners altogether. Nor did these vices by any means wholly end with the victory of the Natural System; some residue of them is inseparable from all study of the subject on a purely morphological basis. Linnæus and De Jussieu alike committed themselves to this, and that necessarily so far as their immediate problem was concerned (see BIOLOGY, § 3). They failed sufficiently to realise, or at any rate to point out to their successors, what an abstraction from the realities of the living world is involved in looking at the plant from a primarily morphological point of view—in regarding it as a fixed and empirical phenomenon of pure form, which may be analysed and compared, named and classified, but admits of nothing more. Hence, while their followers rightly continued to avail themselves of this abstraction, which they found to yield a wealth of detailed results, they became unconsciously enslaved by it, and henceforth mistook for the sole method of botany what was really no more than the necessary artifice of its morphological department. They even unhappily lost sight of the only real problem of their subject, that of interpreting the plant as a changing manifestation of life. It was much indeed to pass from the counting of the reproductive organs only with the Linnean systematist to that comparison and scrutiny of all which was initiated by De Jussieu, and hence to extend our knowledge to the cryptogamic world; and much also to discern with Goethe and succeeding morphologists the deep unity of principle which underlies the widest apparent varieties of form, and which has enabled us to reduce all organs to the simple categories of root, stem, leaf, and trichome or hair, and even to analyse these into their component tissues—epidermic, fundamental, and fibro-vascular; and finally most of all with the embryologist to describe all these forms as the final phases of a process of continuous development from unicellular to multicellular, general to special, simple to complex. In this way we at length reach a morphological conception of even the evolution of organic beings, as a kind of phantasmagoria in which the empirically known forms undergo a broadly similar individual and racial development, and in which individuals and species alike are constantly replacing or being replaced by others. Yet so long as our original standpoint is unaltered, our botany is one-sided; nay, our knowledge is not yet truly biological at all, for we are forgetting that it is the phenomenon of life which is the differentia of the science.

Here, then, it is that the real understanding of the subject must begin; our essential problem is to understand the life of the plant, to comprehend the sum of its functions, to answer first of all the questions natural to every healthy mind, whether child's or beginner's, and inquire what is the use to the plant of its root, stem, and leaves, its flower and fruit. To answer these questions rightly involves indeed at once all the preceding morphological inquiries, yet now in a new spirit; for these parts are no longer to be thought of as forms to be discussed by themselves, but as the result of the adaptations in the past and the present of the living being to its surroundings, of organism to environment, inside to outside. Some of these adaptations are active, enabling the plant to utilise its favourable conditions; others passive, to resist its unfavourable ones. Hence, whether we seek rationally to comprehend the history of botany, or its present state, or profitably to undertake its study, the physiological standpoint is the essential one. While recognising the importance and legitimacy of morphological inquiries, of description of general form, or of the study of organs, tissues, cells, and protoplasm (see BIOLOGY, § 3), we have distinctly to correlate and subordinate this sub-science to the physiological interpretation the mind is primarily seeking. Our biological science is a concrete and dynamic, not an abstract and static one; its highest ideal is a synthetic view of functions and forms, and to this the analysis must be subservient.

Yet in the pre-Linnean, Linnean, and even post-Linnean period, the morphologists predominated almost exclusively: the discovery of the sexes of plants had indeed been made, but lay almost unutilised. Kölreuter might indeed experiment on the fertilisation of plants, and Sprengel exultantly publish his Secret of Nature Discovered, but these admirable labours were absolutely ignored until their repetition a century later by Darwin. The physiological investigations of Hales were similarly left uncontinued until comparatively recent times; and the yet more important line of discovery as to the function of leaves and their relation to the atmosphere initiated by Bonnet, Ingenhousz, and Senebier a century ago, seems to have met with similar indifference so far as professed botanists were concerned, although their transcendent physiological, chemical, and agricultural interest secured their continuance after Priestley by chemists like T. de Saussure and Boussingault.

The tendency towards recovery from this dry-as-dust character of the science can of course be traced in the writings of many botanists, especially after the time of Goethe. From faults of this order the 'Naturphilosophie,' of which Oken (q.v.) was the leading representative, certainly escaped. The peculiar extravagances of his speculations can only be explained as the violent reaction of an original but inaccurate mind of strong physiological bias, and his conspicuous failure to make any substantial contribution to science, and the natural repugnance of all the more exact although narrower minds around him to his baseless hypotheses, had a most disastrous effect in discouraging and postponing any trespass beyond the conventional lines of labour, or any progress to a fresher and more vital point of view. The developmental and physiological attitude was, however, much more effectively reasserted by Schleiden, whose Principles of Botany (1846) is full of a trenchant and perfervid criticism, in spirit and expression often curiously suggestive of Carlyle. His views gained great weight from his high histological and physiological position as the founder of the cell theory; and in no small measure through him progress in Germany henceforth became so rapid as soon to place that country in the van instead of the rear. Not only have the labours of cryptogamists like Hofmeister, Cohn, and De Bary been of wide influence, but great schools have arisen of vegetable physiology—e.g. those of Sachs and Schwendener. Since 1859, the commanding influence of Darwin has been steadily saturating botanical thought. It is to him (see BIOLOGY, p. 161) we owe the authoritative accomplishment of the change from the primarily analytic and static, or morphological view of the plant-world, to the dynamic or physiological one. Here, with the science centred no longer upon the herbarium specimen, but once more, as it were, upon the living dryad, this retrospective sketch of the progress of botany may fitly conclude, leaving further details to be sought for in the articles devoted to the lives of different botanists, and to special departments of the subject.

2. Present State of the Science.—While more and more influenced by the historic movement above outlined, the present state of botanical research presents many examples of work in all departments and aspects of the subject. Whole battalions of workers are busy upon each successively deepening plane of analysis (see BIOLOGY, § 3). Thus, although the age of great travellers is necessarily ended, the explorer still finds abundant gleanings in many parts of the world, and the minor fungi and algæ will also long furnish an especially fertile field of systematic labour. The essential problems of the morphology of the higher plants may be said to be mainly solved; and though those presented by cryptogamic plants are less understood, the splendid generalisation which unifies the cryptogamic and phanerogamic plants as members of a single series must always remain the backbone of the subject. As respects tissue and cell, the progress of microscopic investigation is still yielding results of the highest importance, while the study of protoplasm is also rewarding an increasing number of workers. Physiology, as we have seen, is steadily acquiring its due predominance; indeed, the abundance of workers and of results demands a separate discussion. Here we may merely note how these workers fall into two main schools, the one, represented by Sachs, studying protoplasm and cell, tissue and organ, by help of all the resources of chemistry and physics; the other, of which Darwin was the head, concerned with the detailed interpretation of the adaptation of the plant to its mode of life, and with the history of its evolution. In this relation the studies of the botanical geographer and the palæontologist are also of special importance; and it is naturally from this evolutionary school that the synthetic impulse chiefly emanates which is now beginning to be felt in all departments.

The voluminous literature embodying the results of all these labours is published sometimes as of old in separate volumes; more frequently in the proceedings of learned societies; but oftenest in special journals too numerous for mention, of which the weekly Botanische Zeitung may be said to occupy the foremost place. Of this copious outflow of new published matter a partial idea can be obtained from such abstracts of selected papers as are published in the Journal of the Royal Microscopical Society; while the entire literature of each year is indexed and summarised in the volume of the Botanisches Jahresbericht. The most ready and convenient method both of obtaining a general idea of the literature of the subject, and of threading one's way into any of its minor mazes, is by help of Jackson's Guide to the Literature of Botany (Index Society, 1880).

3. Method of Botanical Study.—While the professed student of botany cannot avoid embarking upon this sea of literature, he can now happily obtain such more or less adequate section charts as are afforded by the manuals of Vegetable Physiology, of the Vegetable Kingdom, or of such special groups as Fungi and Bacteria, which the rising synthetic spirit of recent years has fairly commenced to supply. The beginner, however, demands a single introductory text-book; and simple as his demand may seem, it is absolutely the most difficult to supply. At best, such manuals can never replace good practical oral teaching, or keep abreast of the most recent developments of knowledge. Many of the existing manuals are even positively mischievous. Survivals of one or other of the earlier phases of the science, they land the student at the very outset at some long-past stage of its progress, where he is only too likely permanently to remain. And when not altogether pre-physiological and pre-evolutionary, they are apt to introduce the student to evolution and physiology at the conclusion of his course of study, instead of training him from the outset to grasp and interpret everything by their aid.

The worst of these many introductory manuals are mere crowded morphological compilations, all more or less antiquated, if not inaccurate. Even when they do not confuse and repel the student from the outset, they are wont to reverse that fundamental principle of progress from the known towards the unknown which underlies all effective research. To the beginner the cell and protoplasm are not the fundamental units that they are to the teacher; they are precisely the things which lie furthest from his experience, and are only intelligible as the ultimate results of a long process of analysis (cf. BIOLOGY, § 3). Most manuals still retain these grammarian's vices more or less completely; even Sachs's serviceable Text-book is no exception. A partial transition is afforded by the mode of teaching, and series of manuals, of which Huxley and Martin's well-known Elementary Biology is the type. Here, although the attractive but illusory simplicity of proceeding from the solitary cell towards the cell-complex presented by the higher plants is retained, the steps are worked out concretely in the laboratory by the student for himself. Yet this utter change of the field of experience, or at least its sudden narrowing and deepening to that of the microscope, is not found in practice to be widely satisfactory or attractive to the student; for it is with the changeful carpet of the woods and fields, and its world-summary in the botanic garden, that most of the problems of the science and of its general interest alike for ever lie. With child and herbalist the student must begin in the fields, must learn on the one hand to observe and delight in the varied life of plants, and on the other to collect and name and analyse its forms. His studies begin with the buttercup, not with the amoeba; hence should be mentioned Oliver's small manual of Elementary Botany (1st ed. 1863), in which we have some record of the village-school teaching of Henslow, the botanist to whom Darwin was wont gratefully to ascribe the first scientific impulse of his life. Even in the best of such books the morphological bias usually remains; and hence it is that the majority of beginners soon instinctively abandon the whole subject as 'dry,' while the minority tend to become, with too many field naturalists, mere unthinking herborisers, and as Schleiden was wont to bewail, become intellectually lost and smothered amid accumulations of mere unused 'hay.' When this tendency is guarded against, however, a flora is invaluable; while even the worst text-book may be helpful as a work of reference. Among relatively good manuals may be mentioned those of Gray, Van Tieghem, Sachs, Luerssen, &c.

Is there then no way of escape from this perpetual tendency to the desiccation alike of the matter and of the spirit of the science? Assuredly; it is simply that while we have indeed to collect, and name, and analyse in death, these are not ends in themselves, but simply means towards widening and deepening the continuance of that observant delight in the sum of living things with which our interest surely began. In a word, the highest modern botany neither harvests plants with the herbalist, nor picks them to pieces with the child, but finds alike its rise and climax in watching the blossoms open and the bees come and go. The pedigree of the science is only on one side from the herbals of Dioscorides and Brunfels to the system of Linnæus or Jussieu; the other and nobler line rises in Virgil's song of living nature, runs through the keen yet simple records of naturalists like those of Selborne and Walden, and culminates in the monumental volumes of the greater naturalist of Down. It is in the school, or rather garden, of Darwin, viewed both as the last of the old-world naturalists and as the first of evolutionists and physiologists, that our modern 'introduction to botany' must begin; studies in the herbarium of the systematist and the special laboratories of the physiologist, anatomist, and microscopist may follow thereafter as occasion requires. For the age of mere analysis, guided only by the love of incessant novelty, or even by that of unity amid details, is ending; the student may now approach the science in a new spirit, since he can interpret its literature as but the incipient record of that vast drama of the evolution of life, at which it is his rare good fortune to be an awakening spectator.

Avoiding at the outset all terminology, and even all anatomy as well, the beginner cannot do better than attempt some actual observation of plants in their living relations, as of flowers to insects, and the like, and read some of the abundant and popular literature of such subjects. Or if his curiosity need awakening, it cannot fail to be stimulated by such a tale of living wonders as Darwin's classic Insectivorous Plants. His introduction to the subject through such characteristically animal attributes as digestion, movement, and sensitiveness, has the peculiar advantage of soon leading him to see how these are only the more conspicuous developments of functions widely diffused throughout the whole vegetable world, and inherent in all living matter alike. When these apparent anomalies are once understood as illustrations of the thorough unity of organic nature, he may still follow the course of Darwin's own mind and work in his Climbing Plants and Movement in Plants, and see how the wonderful sensitive-plant shows only a development of the 'sleep movements' of every cabbage-seedling, or how climbing and twining have been generalised with all other plant-movements as mere developments of the gentle circumnutation of every growing point. This is indeed questioned in detail, yet the fundamental lesson will have been learned, and the conventional Linnean and utilitarian conception of the plant, as a mere specimen, useful or otherwise, will have been clearly replaced by the physiological one.

But plants not only move but grow: they have relations to soil and atmosphere; they thirstily absorb and copiously transpire. Here we have to inquire into the chemical composition of plants, to investigate their ash and their organic constituents, and to inquire how these were respectively obtained (see VEGETABLE CHEMISTRY, SOILS, &c.). The germinating plant and the blossom are manifestly breathing, sometimes as warmly as an animal (see ANIMAL HEAT); yet this, again, is no anomaly, for all living matter must oxidise and burn away. The functions of the leaf next engage us. We find that given green colouring matter (see CHLOROPHYLL), it can seize the energy of sunlight, reduce the carbonic anhydride of respiratory waste, and pour back oxygen into the atmosphere. Leaving for the present the problematical details of this process, but noting the perfect 'balance of nature' between vegetable and animal life, which is the general result, we must pass to the structure of leaves, and study this first in the light of these essential functions, thence working back to the structure of stem and root; and next, in so far as modified in relation to special functions and environment—e.g. floating or submerged, storing or protective from climate or enemies, insect-catching or attracting, and so on; while leaf-arrangement and bud-packing may here be appropriately considered.

But leaves are not merely vegetative, nor even confined to the purposes of the individual life; they became modified in relation to that of the species, and so we have ultimately flowers. This subordination of vegetative life powerfully affects the mode of branching, and gives us the phenomena of inflorescence, while in the individual flowers we have to note the forms and uses of all the separate parts—(1) accessory (sepals, petals), and (2) essential (stamens, carpels). We study the adaptation of all these (a) to the collective and general function of (cross) fertilisation, and (b) to their respective special functions—(1) protection from climate and enemies, attractive, mechanical; (2) reproductive. The deep modification of floral types in relation to fertilisation by insects or by the wind, as of the lily type towards orchids on one hand, and grasses on the other, next demands notice; and the corresponding utility of floral details—e.g. position and shape of parts, colours, markings, and perfume—may be exquisitely traced.

In the same way, the mature ovary or fruit opens up a new wealth of interest; and its adaptations must be traced for (1) protecting the seed from climate and enemies; (2) dispersion of seed—(a) passive, by aid of wind, water, or animals; (b) active, by scattering or planting the seed. Finally, the mature ovule or seed rewards attention: its contained embryo has special protection from climate and enemies, its external 'albumen' or its internal store is an accumulated capital for its start in the struggle for existence; and this process of germination has again countless points of interest.

Having in this way gone through the general physiology of the plant, we must not only sum these up into a complete notion of our plants, which we are no longer in danger of thinking of as mere names or specimens, but as varied life-histories. Then, remembering that these are but the individuals of the larger drama, we learn to read some of the complex relations of living beings; to see their incessant individual and interspecific struggle for existence, yet also their increasingly important relations of interdependence.

But this wealth of interesting and varied knowledge, this complex lore of life, encourages us towards a wider and wider acquaintance with the flora, which now promises not merely new specimens for our collection, but an unknown wealth of new knowledge, we may almost say a multitude of strange individual biographies. Yet our observation, to be profitable, must be orderly and detailed; descriptions must be given; and these accurate and exhaustive, yet of tersest, as it were telegraphic brevity. As specimens and descriptions multiply, indexing and nomenclature become indispensable; and thus, at this point, we need help from, and are therefore ready to appreciate, the labours of Linnæus and the whole systematic school. The conceptions of species and genus, and the modes of arranging these into larger groups, are thus no longer the arid abstractions they necessarily seemed before the intellectual need had arisen, but are now indispensable aids; while classification is no longer viewed as an arbitrary jargon only to be learned by rote, but as a provisional attempt towards the rational statement of the actual likenesses and differences between kindred forms, and towards the estimation of their relative importance. See BIOLOGY, § 2.

But since our systematic studies have now brought us face to face with the quarter of a million or more species of the modern herbarium, we require a botanic garden to illustrate a selection of these, nay, a smaller 'type botanic garden' as a key to this again. The phanerogamic series, and in some measure also the cryptogamic orders also, thus commence to lie more clearly before us. Finally, some knowledge of the distribution of the vegetable kingdom in space and time is here seen to be reasonable, and therefore interesting.

Our attempts at classification—at discerning the degrees of likeness—compel a detailed comparison of stems and roots, of leaves and flowers, and this often leads to a difficulty which long perplexed the botanist as well as the zoologist. Obvious and superficial resemblances due to similarity of environment and function are seen to overlie irreconcilable differences of internal structure or principle; while conversely, some given structural principle becomes modified in the most widely different ways for function and environment. This at first led to mere confusion, but the patient and critical researches of the past generation have clearly distinguished between physiological and morphological resemblance (see MORPHOLOGY); while, finally, the study of individual development and racial evolution enable us to interpret these apparently fundamental and often functionless morphological characters as the residual traces of what were once themselves physiological adaptations in their turn; thus finally demonstrating that ultimate subordination of morphology to physiology which has already been so frequently pointed out. Within its minor province, however, which we have now fairly reached, the study of pure morphology must be abstracted from physiological considerations, and thus yields a series of generalisations of an intellectual simplicity and beauty analogous to those of the crystallographer's. The utmost varieties of form in stem and root are generalised into the conceptions of ascending and descending axes; similarly, disregarding shapes and uses, we have bulb-scales, bud-scales, foliage-leaves, and bracts all generalised with sepals, petals, stamens and carpels as appendages. Conversely, the plant thus reduced to axis and appendages may be gradually modelled back into the essential types of the various natural orders.

Next, tissues and cells need consideration from the same strictly morphological standpoint, apart from use. Axis and appendages are thus reduced to their constituent systems of tissues—epidermic, fundamental, and fibro-vascular—and these may be either modelled in thought into the many varieties of tissue, of which these furnish the common materials, or traced back to the primeval embryonic tissue from which they are themselves differentiated. This, again, is found to have arisen from the multiplication and differentiation of a single embryonic cell, the (fertilised) plant-egg. And in this way the full magnitude and beauty of Schleiden's deep generalisation of ultimate unity of vegetable composition, which we call the cell theory, becomes manifest when we have similarly worked towards it, and, as it were, rediscovered it for ourselves (see CELL). From this to protoplasm, and thence to the attempt to return along that return wave of progress from simple cell to cell-aggregate and cell-complex, with which, as we have seen, so many manuals attempt to start, is an easy step. Such treatises may now profitably be employed; and we may, as it were, proceed to build up the living world afresh. We thus return once more to the actual living plant with which we started, yet rich in the results of our prolonged analysis. We know the process of development, the facts of structure, and their relation to function; hence the plant, as it were, is transparent to the intellectual eye, and our final mental image of it is something wholly different from the shrivelled index-mummy of an earlier but aberrant botanical school; it is a working thought-model which not only develops under the mental eye from unicellular simplicity to ultimate individual form and complexity, but in which all that is known of the details of structure and processes of life can be summoned up and watched at will, and of which the very incompleteness furnishes a perpetual suggestion and impulse to new research.

Although the processes of physiology and development have thus been kept in prominence from the outset, the cognate question of the origin of plants still remains for discussion. The history of the conception of organic evolution, and the evidences of its actual occurrence, have yet to be set forth; while, if evolution has actually taken place, its rationale still demands explanation. The various hypotheses dealing with this, more especially the current one of natural selection, have thus to be considered; but the problem of variation demands a deeper treatment, of which the essential results have been already indicated under BIOLOGY (§ 6). In any case, so much is clear that our studies culminate in the perception of the vegetable kingdom as a genealogical tree. Our ultimate thought-model is thus 'the great tree of life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications.' The problem of accounting for this incessant branching, of determining the law of this beautiful ramification, may therefore be postponed to EVOLUTION.

4. Botany in Education.—The place of botany in medical education is historically due to its fundamental relation to materia medica, and hence, since pharmacy is becoming completely distinguished from medicine, the teaching of botany is being abandoned in many medical schools. Yet its claims reappear in a far stronger way when it is considered as a preparation in elementary biology. For although the student of medicine may not unjustifiably care little for the collection or dissection of plants, viewed as an end in themselves, he can never dispense with that training in reading the processes of organic life which is afforded by these their simplest manifestations.

As a subject of general education, too, the importance of botany has long been recognised, and now that the dryasdust teaching of the subject is being superseded by a more living and interesting method, its re-adoption into the curriculum both of schools and colleges is in progress, and the botanic garden is becoming a familiar adjunct of the school. At any rate so far as observing goes, the study of botany may more effectively be commenced in childhood than in later life, while initial discipline in drawing, in manipulation, and in the accurate use of language, may all be profitably associated with it. And if it be admitted that for the study of the social sciences preliminary biological studies are requisite, it is in obtaining some concrete acquaintance with the facts of botany that such preparation most conveniently begins.

See, besides BIOLOGY, and the articles on the several plants, groups of plants, and botanical authors, the following: