Botany

BOTANY, the science which includes everything relating to the vegetable kingdom, whether in a living or in a fossil state. The name is derived from the Greek gorluni, a plant. It embraces a consideration of the external forms of plants—of their anatomi cal structure, however minute—of the functions which they per form—of their classification—of their distribution over the globe at the present and at former epochs—and of the uses to which they are subservient. It examines the plant in its earliest state of development, and follows it through all its stages of progress until it attains maturity. It takes a comprehensive view of all the plants which cover the earth, from the minutest organism, only visible by aid of the microscope, to the tall forest tree. It marks the relations which subsist between all members of the plant world, including those between existing groups and those known only from their fossilized remains preserved in the rocks. We deal here with the history and evolution of the science.

Descriptive Botany to the Time of Linnaeus.

The plants which adorn the globe more or less in all countries have attracted the attention of mankind from the earliest times. Solomon "spake of trees, from the cedar of Lebanon to the hyssop on the wall." The Chaldaeans, Egyptians and Greeks were the early cultivators of science, and botany was not neglected, although the study of it was mixed up with crude speculations as to plant life, and as to the change of plants into animals. About 30o B.C., Theophras tus wrote a history of plants, and described about Soo species used for the treatment of diseases. Dioscorides, a Greek botanist and a physician in the Roman Army, wrote on Materia Medica; his contemporary, the elder Pliny (A.D. 23-79) described about a thousand plants, many of them famous for their medicinal virtues. Asiatic and Arabian writers also took up this subject. Little, how ever, was done in the science of botany, properly so called, until the 16th century, when the revival of learning dispelled the dark ness which had long hung over Europe. Otto Brunfels, a physician of Bern, has been looked upon as the restorer of the science in Europe. In his Herbarium, printed at Strassburg (153o-36), he gave descriptions of a large number of plants, chiefly those of central Europe, illustrated by beautiful woodcuts. He was fol lowed by other writers—Leonhard Fuchs, whose Historia Stirpium (Basel, 1542) is worthy of special note for its excellent wood cuts; Hieronymus Bock, whose Kreutter Buck appeared in 1539; and William Turner, "The Father of English Botany," the first part of whose New Herbal, printed in English, was issued in 1551. The descriptions in these early works were encumbered with much medicinal detail, including speculations as to the virtues of plants. Plants which were strikingly alike were placed together, but there was at first little attempt at systematic classification. A crude system, based on the external appearance of plants and their uses to man, was gradually evolved, and is well illustrated in the Herbal, issued in 1597 by John Gerard a barber surgeon, who had a garden in Holborn.

One of the earliest attempts at a methodical arrangement of plants was made in Florence by Andreas Caesalpinus (1519 1603), who is called by Linnaeus prinvus verus systematicus. In his work De Plantis (1583), he distributed the 1,520 plants then known into fifteen classes, the distinguishing characters being taken from the fruit.

The Englishman John Ray (1627-1705) did much to advance the science of botany, and was also a good zoologist. He promul gated a system which may be considered as the beginning of a natural system (Methodus Plantarum, 1682). He separated flowering from flowerless plants (ferns, mosses, seaweeds, fungi, etc.) and divided the former into Dicotyledons (with a pair of seed-leaves) and Monocotyledons (with a single seed-leaf ). His orders (or "classes") were founded to some extent on a correct idea of the affinities of plants, and he far outstripped his con temporaries in his enlightened views of arrangement.

In 1669 Robert Morison' (162o-83), the first professor of botany at Oxford, published a systematic arrangement of plants, largely on the lines previously suggested by Caesalpinus. He divided them into eighteen classes, distinguishing plants accord ing as they were woody or herbaceous, and taking into account the nature of the flowers and fruit. In 1690 promulgated a classification founded chiefly on the forms of flowers. J. P. de (1656-1708), who about the same time took up the subject of plant-classification, was long at the head of the French school of botany, and published a systematic arrangement in 1694-1700. He described about 8,000 species of plants, and dis tributed them into 22 classes, chiefly according to the form of the corolla, distinguishing herbs and under-shrubs on the one hand from trees and shrubs on the other. Tournefort's system was for a long time adopted on the Continent, but was ultimately dis placed by that of Carl von Linne, or Linnaeus (1707-78, q.v.).

Linnaean System of Classification.

The System of Lin naeus was founded on characters derived from the stamens and pistils, the so-called sexual organs of the flower, and hence it is often called the sexual system. It is an artificial method, because it takes into account only a few marked characters in plants, and does not propose to unite them by natural affinities. It is an index to a department of the book of nature, and as such is useful to the student. It does not aspire to any other character, and al though it cannot be looked upon as a scientific and natural ar rangement, still it has a certain facility of application which at once commended it. It does not of itself give the student a view of the true relations of plants, but by leading to the discovery of the name of a plant it is a stepping-stone to the natural system. Linnaeus himself regarded it as only a temporary convenience and in his Fragmenta published in his Philosophia Botanica (17 51) endeavoured to arrange the genera he had already established according to their affinities under 67 orders.

The Linnaean system was strongly supported by Sir James Edward Smith (1758-1828), who adopted it in his English Flora, and who also became possessor of the Linnaean collection. The system was for long the only one taught in the schools of Britain, even after it had been discarded by those in Continental countries.

The French School.

A new era dawned on botanical classi fication with the work of Antoine Laurent de Jussieu (1748-1836). His uncle, Bernard de Jussieu, had adopted the principles of Linnaeus's Fragmenta in his arrangement of the plants in the royal garden at the Trianon. At an early age Antoine became botanical demonstrator in the Jardin des Plantes, and was thus led to devote his time to the science of botany. Having to arrange the plants in the garden, he followed the lines already suggested by his uncle, and developed a system founded in a certain degree on that of Ray, in which he adopted the simplicity of the Linnaean definitions, and displayed the natural affinities of plants. His Genera Plantarum, begun in 1778, and published in 1789, was an important advance, and formed the basis of all natural classifica tions. One of the early supporters of this natural method was Augustin Pyramus de Candolle (1778-1841), who in 1813 pub lished his Theorie elementaire de la botanique, in which he showed that the affinities of plants are to be sought by the comparative study of the form and development of organs (morphology), not of their functions (physiology) . His Prodromus Systematis Natu ralis Regni Vegetabilis was intended to be an arrangement and iR. Morison, Praeludia Botanica (1669) ; Plantarum Historiae Uni versalis Oxon. pars secunda (168o).

(Augustus Quirinus) paterno nomine Bachmann, Intro. ductio generalis in Rem Herbarium (Lipsiae, 169o) .

P. de Tournefort, Elemens de botanique (1694) ; Institutiones Rei Herbariae (1700) .

description of all known plants. This work was continued after his death, by his son Alphonse de Candolle, with the aid of other eminent botanists, and embraces descriptions of the genera and species of the families of Dicotyledons. The system followed by de Candolle is a modification of that of Jussieu.

In arranging plants according to a natural method, we require a thorough comparative knowledge of the form and structure of plant-organs and hence the advances made in these departments have materially aided the efforts of systematic botanists.

British and German Schools.

Robert Brown (1773-1858) was the first British botanist to support and advocate the natural system of classification. The publication of his Prodromus Florae Novae Hollandiae (in 181o), according to the natural method, led the way to the adoption of that method in the universities and schools of Britain. In 1827, Brown announced his important dis covery of the distinction between angiosperms and gymnosperms, and the philosophical character of his work led Alexander von Humboldt to refer to him as Botanicorum facile princeps. In 183o, John Lindley published the first edition of his Introduction to the Natural System of Botany embodying a slight modification of de Candolle's system. From the year 1832 up to 1859 great advances were made in systematic botany, both in Britain and on the Continent of Europe. The Enchiridion and Genera Plantarum of S. L. Endlicher (1804-49), the Prodromus of de Candolle, and the Vegetable Kingdom (1846) of J. Lindley became the guides in systematic botany, according to the natural system.

The least satisfactory part of all these systems was that con cerned with the lower plants or cryptogams, i.e., plants without an obvious flower producing a seed, as contrasted with the higher or flowering plants (phanerogams). The development of the com pound microscope rendered possible the accurate study of their life-histories; and the publication, in 1851, of the results of Wil helm Hofmeister's researches on the comparative embryology of the higher Cryptogamia shed a flood of light on their relationships to each other and to the higher plants, and supplied the basis for the distinction of the great groups in ascending order Thallophyta (seaweeds, fungi, lichens) Bryophyta (mosses), Pteridophyta (ferns) and Phanerogamae (seed-bearing plants) the last named including Gymnospermae (seeds not enclosed in a fruit) and Angiospermae (seeds enclosed in a fruit).

Charles Darwin's Origin of Species (1859) and the consequent theory of evolution suggested a new point of view for botanists. It became evident that a natural system of classification should present not only existing relationships of plant-families but also their past relationships ; a perfect system should be a genealogical tree representing the story of plant-life from its remote origin. But plant-families at the present day represent only the end branches of a great tree most of which has disappeared and the reconstruction of which with the aid of the fragments that have been preserved in the rocks must be a matter of conjecture. The study of phylogeny, i.e., the reconstruction of the genealogical tree, has received much attention from botanists in recent years, some account of this will be found in the articles on the various groups GYMNOSPERMS, ANGIOSPERMS, etc.

Anatomy of Plants.

The study of the anatomy and physi ology of plants did not keep pace with the advance in classifica tion. Nehemiah Grew and his contemporary, Marcello Malpighi, were the earliest discoverers in the department of plant anatomy. Both authors laid an account of the results of their study of plant structure before the Royal Society of London almost at the same time in 1671. Malpighi's complete work, Anatome Plantarum, appeared in 1675 and Grew's Anatomy of Plants in 1682. Then for more than a hundred years the study of internal structure was neglected. In 1802 appeared the Traite d'anatomie et de pliysiolo gie vegetabes of C. F. B. de Mirbel (1776-1854), which was quickly followed by other publications by Kurt Sprengel, L. C. Treviranus (1779-1864), and others. In 1812, J. J. P. Molden hauer isolated cells by maceration of tissues in water. The work of F. J. F. Meyen and Hugo von Mohl in the middle of the 19th century placed the study of plant anatomy on a more scientific basis. Reference must also be made to M. J. Schleiden (1804 81) and F. Unger (1800-7o), while in Karl von Nageli's investi gations on molecular structure and the growth of the cell mem brane we recognize the origin of modern methods of the study of cell-structure included under cytology (q.v.). The work of Karl Sanio and Theodor Hartig advanced knowledge on the structure and development of tissues, while Anton de Bary's Comparative Anatomy of the Phanerogams and Ferns (1877) supplied an admirable presentation of the facts so far known. This work was made available for English readers in the translation by F. O. Bower and D. H. Scott (1884) and may be regarded as the be ginning of the modern era of the study of the general arrangement of plant-tissues (anatomy) and the detailed structure of the tis sues themselves (histology) which have been pursued by nu merous workers in Great Britain, France, Germany and America, and in which the study of the structure of fossil plants has played an important part. This is treated in full in the article PLANTS : Anatomy of, Modern Progress of the Subject.

Fertilization.

The subject of fertilization was one which early excited attention. The idea of the existence of separate sexes in plants was entertained in early times, long before separate male and female organs had been demonstrated. The production of dates in Egypt, by bringing two kinds of flowers into contact, proves that in very remote periods some notions were entertained on the subject. Female date-palms only were cultivated, and wild ones were brought from the desert in order to fertilize them. Herodotus informs us that the Babylonians knew of old that there were male and female date-trees, and that the female re quired the concurrence of the male to become fertile. This fact was also known to the Egyptians, the Phoenicians and other nations of Asia and Africa. The Babylonians suspended male clusters from wild dates over the females; but they seem to have supposed that the fertility thus produced depended on the pres ence of small flies among the wild flowers, which, by entering the female flowers, caused them to set and ripen. The process was called palmification. Theophrastus, who succeeded Aristotle in his school in 322 B.C., frequently mentions the sexes of plants, but he does not appear to have determined the organs of reproduction. Pliny (A.D. 23-79) speaks particularly of a male and female palm, but his statements were not founded on any real knowledge of the organs. From Theophrastus down to Caesalpinus, who died at Rome in 1603, there does not appear to have been any attention paid to the reproductive organs of plants. Caesalpinus had his attention directed to the subject, and he speaks of a halitus or emanation from the male plants causing fertility in the female.

Nehemiah Grew seems to have been the first to describe, in a paper on the Anatomy of Plants read before the Royal Society in November 1676, the functions of the stamens and pistils. Grew speaks of the attire, or the stamens, as being the male parts, and refers to conversations with Sir Thomas Millington, Sedleian pro fessor at Oxford, to whom the credit of the sexual theory seems really to belong. Grew says that "when the attire or apices break or open, the globules or dust falls down on the seedcase or uterus, and touches it with a prolific virtue." Ray adopted Grew's views, and states various arguments to prove their correctness in the preface to his work on European plants, published in 1694. In the same year R. J. Camerarius, professor of botany and medicine at Tubingen, published a letter on the sexes of plants, in which he refers to the stamens and pistils as the organs of reproduction, and states the difficulties he had encountered in determining the organs of cryptogamic plants. In 1703, Samuel Morland, in a paper read before the Royal Society (Phil. Trans. xxiii., 1474) stated that the farina (pollen) "is a congeries of seminal plants, one of which must be conveyed into every ovum before it can become prolific." In this remarkable statement he seems to antici pate in part the discoveries afterwards made as to pollen tubes. In 1711, E. F. Geoffroy, in a memoir presented to the Royal Academy at Paris, supported the views of Grew and others as to the sexes of plants (Mem. Acad. Roy. Sci., 1711, 207). He states that the germ is never to be seen in the seed till the apices (anthers) shed their dust; and that if the stamina be cut out be fore the apices open, the seed will either not ripen, or be barren if it ripens. He mentions two experiments made by him to prove this—one by cutting off the staminal flowers in maize, and the other by rearing the female plant of mercurialis apart from the male. In these instances most of the flowers were abortive, but a few were fertile, which he attributes to the dust of the apices having been wafted by the wind from other plants.

Linnaeus took up the subject in the inauguration of his sexual system. He divided plants into sexual and asexual, the former being phanerogamous or flowering, and the latter cryptogamous or flowerless. In the latter division of plants he could not detect stamens and pistils, and he did not investigate the mode in which their germs were produced. He was no physiologist, and did not promulgate any views as to the embryogenic process. His fol lowers were chiefly engaged in the arrangement and classification of plants, and while descriptive botany made great advances the physiological department of the science was neglected. His views were not, however, adopted at once by all, for we find Charles Alston stating arguments against them in his Dissertation on the Sexes of Plants (1754) ; (See Essays and Observations, Physical and Literary; Medical Society of Edinburgh, i., 205 ) • Als ton's observations were founded on what occurred in certain uni sexual plants, such as mercurialis, spinach, hemp, hop and bryony. The conclusion at which he arrives is that the pollen is not in all flowering plants necessary for impregnation, for fertile seeds can be produced without its influence. He supports parthenogenesis in some plants. Soon after the promulgation of Linnaeus's method of classification, the attention of botanists was directed to the study of cryptogamic plants, and the valuable work of Johann Hedwig (173o-99) on the reproductive organs of mosses made its appearance in 1782. He was one of the first to point out the existence of certain cellular bodies in these plants which appeared to perform the functions of reproductive bodies, and to them the names antheridia and pistillidia were given. This opened up a new field of research, and led the way in the study of cryptogamic reproduction, which has since been much advanced by the labours of numerous workers. The interesting observations of Morland, already quoted, seem to have been neglected, and botanists were for a long time content to know that the scattering of the pollen from the anther, and its application to the stigma, were necessary for the production of perfect seed, but the stages of the process of fertilization remained unexplored, and no one attempted to raise the veil which hung over the subject of embryogeny.

In 1815, L. C. Treviranus, professor of botany in Bonn, roused the attention of botanists to the development of the embryo, but although he made valuable researches, he did not add much in the way of new information. In 1823, G. B. Amici discovered the existence of pollen-tubes, and he was followed by A. T. Brongniart (1801-76) and Robert Brown. The latter traced the tubes as far as the nucleus of the ovule. These important dis coveries mark a new epoch in embryology, and may be said to be the foundation of the views now entertained, which were material ly aided by the subsequent elucidation of the process of cytogene sis, or cell-development, by Schleiden, Schwann, Mohl and others. The whole subject of fertilization and development of the embryo has been more recently investigated with great assiduity and zeal, as regards both cryptogamous and phanerogamous plants, and details must be sought in the various special articles. The obser vations of Darwin as to the fertilization of orchids, Primula, Lythrur, and other flowering plants, and the part which insects take in this function, gave an explanation of the observations of Christian Konrad Sprengel, made at the close of the 18th century, and opened up a new phase in the study of botany, which has been followed by Hermann Muller, Federico Delpino and others. This phase of the subject, the transference of the pollen from the stamens to the stigma of the flower, is now distinguished as pollination, the term fertilization being restricted to the processes directly associated with the union of the male and female cells which occurs in all plant-groups. (An excellent handbook is Paul Knuth's Handbook of Pollination, Eng. trans., 1906–o9.) Physiology of Plants.—One of the earliest workers at plant physiology was Stephen Hales. In his Vegetable Staticks (1727) he gave an account of numerous experiments and observations which he had made on the nutrition of plants and the movement of sap. He showed that the gaseous constituents of the air con tribute largely to the nourishment of plants, and that the leaves are the organs which elaborate the food; the importance of leaves in nutrition had been previously pointed out by Malpighi in a short account of nutrition which forms an appendix to his anatomical work. The birth of modern chemistry in the work of J. Priestley and A. L. Lavoisier, at the close of the 18th century, made possible the scientific study of plant-nutrition, though Jan Ingenhousz in 1779 discovered that plants incessantly give out carbonic acid gas, but the green leaves and shoots only exhale oxygen in sunlight or clear daylight, thereby indicating the dis tinction between assimilation of carbonic acid gas (photosynthe sis) and respiration. N. T. de Saussure (1767-1845) gave pre cision to the science of plant-nutrition by use of quantitative methods. The subjects of plant-nutrition and respiration were further studied by R. J. H. Dutrochet towards the middle of the century, and J. von Liebig's application of chemistry to agricul ture and physiology put beyond question the parts played by the atmosphere and the soil in the nutrition of plants.

The phenomena of movements of the organs of plants attracted the attention of John Ray (1693), who ascribed the movements of the leaf of mimosa and others to alteration in temperature. Linnaeus also studied the periodical movements of flowers and leaves, and referred to the assumption of the night-position as the sleep-movement. Early in the 19th century, Andrew Knight showed by experiment that the vertical growth of stems and roots is due to the influence of gravitation, and made other observa tions on the relation between the position assumed by plant organs and external directive forces, and later Dutrochet, H. von Mohl and others contributed to the advance of this phase of plant physiology. Darwin's experiments in reference to the movements of climbing and twining plants, and of leaves in insectivorous plants, opened up a wide field of enquiry as to the relation be tween plants and the various external factors, which has attracted numerous workers. By the work of Julius Sachs and his pupils plant physiology was established on a scientific basis, and became an important part of the study of plants, for the development of which reference may be made to the article PLANTS : Physiology. The study of form and development has advanced under the name morphology, with the progress of which are associated the names of K. Goebel, Eduard Strasburger, A. de Bary, F. O. Bower and others (see PLANTS : Morphology), while more recently, as cy tology (q.v.), the intimate study of the cell and its contents has attracted considerable attention.

Geographical Botany.

The department of geographical botany made rapid advance by means of the various scientific expeditions which have been sent to all quarters of the globe, as well as by individual effort, since the time of A. von Humboldt (see PLANTS: Distribution and Ecology). The question of the mode in which the floras of islands and of continents have been formed gave rise to important speculations by such eminent botan ical travellers as Charles Darwin, Sir J. D. Hooker, A. R. Wallace, H. B. Guppy and others. The connection between climate and vegetation has also been studied. Quite recently, under the name of ecology, the study of plants in relation to each other and to their environment has become the subject of systematic investigation.

Study of Fossil Plants.

The subject of palaeontological botany (see PALANOBOTANY) has been advanced by the researches of both botanists and geologists. The nature of the climate at different epochs of the earth's history has also been determined from the character of the flora. The works of A. T. Brongniart, H. R. Goeppert and W. P. Schimper advanced this department of science. Among others who contributed valuable papers on the subject may be noticed Oswald Heer, who made observations on the Miocene flora, especially in Arctic regions; Gaston de Saporta, who examined the Tertiary flora ; William Carruthers who studied the fossil Gymnosperms; Sir J. W. Dawson and Leo Lesquereux, and others who reported on the Canadian and American fossil plants. In Great Britain also W. C. Williamson, by his study of the structure of the plants of the coal-measures, opened up a new line of research which has been followed by Robert Kidston, Bertrand Renault, D. H. Scott, A. C. Seward, G. R. Wieland, C. R. Zeiller and others, and has led to important discoveries on the nature of extinct groups of plants and also on the phylogeny of existing groups.

Study of Diseases of Plants.

Plant-pathology or the study of the diseases to which plants are subject, more especially under the frequently unnatural conditions attending cultivation, origi nated as a science mainly in the work of Anton de Bary on the life-history of those fungi which live parasitically on other plants (Comparative Morphology of the Fungi, Mycetozoa and Bacteria, Eng. trans., 1887). The science was developed by A. B. Frank and P. C. M. Sorauer in Germany, Marshall Ward in England'and others, and the subject is becoming increasingly important from an economic point of view (see PLANTS : Pathology). A recent development has been the establishment of bureaux and institutes of Mycology for the study of diseases caused by fungi and the diffusion of information on the subject.

Study of Heredity.

The work of the Abbe Mendel in Mo ravia on the laws governing the transmission of characters in plant-breeding has during the last thirty years given rise to a new department of study, genetics (q.v.), in the development of which William Bateson took a leading part. This new development is of importance not only from a scientific aspect as throwing light on the problems of heredity (q.v.) but also economically from its relation to plant-breeding (q.v.).

Subdivisions.—Botany may be divided into the following departments : I. Structural, having reference to the form and structure of the various parts, including (a) Morphology, the study of the general form of the organs and their development—to be found treated in detail in a series of articles dealing with the great subdivisions of plants (see ANGIOSPERMS, GYMNOSPERMS, PTERI