Page:The New International Encyclopædia 1st ed. v. 03.djvu/390

BOTANY. 344 BOTANY. the basis sliifts, as Class XIV. (Didynamia), stamens didynamous; Class XV. (Tetradyna- mia), stamens tetradynamous; Class XVI. (Mon- adclphia), filaments united into one bundle; Class X'1I. (Diadelphia) , filaments united into two bundles: Class XVIIl. (Polyadelphia) , fila- ments united into more than two bundles; Class XIX. { Syngenesia ) , anthers united; Class XX. (Gynandria), stamens and pistil united; Class XXI. (Jlonoecia), llowers staminate and pistil- late, the two forms on the same plant ; Class XXII. (DifBcia), flowers staminate and pistil- late, the two forms on different plants ; Class XXIII. (Polygamia) , staminate. pistillate, and perfect flowers on the same plant; Class XXIV. (Cryptogamia) , flowerless plants. It can be seen that by this scheme flowering plants may be referred readily to different cate- gories, but tiiat many of the categories would not at all represent natural alliances, any more than the accident of the first letter groups words together naturally in a dictionari". During the long use of this great artificial system, a far more natural one was being developed slowly, through the work of such bot^anists as A. L. Jus- sieu '(1789). A. P. de CandoUe (1818-21), Stephen Endlicher (1836-40). A. T. Brongniart (1843), John Lindlcv (1846), Alexander Braun (I8G4), Bentham aiid Hooker (1862-1883), A. W. Eichler (1883), and A. Engler (1892—). Classification. The general classification most in use among botanists at present, though doubtless to be modified very soon, is as follows: The plant kingdom is divided into four great fundamental groups: (1) Thallopliytes (Alga> and Fungi) ; (2) Bryophytes (Liverworts and Mosses) ; (3) Pteridophytes (Ferns, Horsetails, and Club-mosses) : and (4) Spermatophytes (Gymnosperms and Angiosperms) . The Thal- lophytes, as at present constituted, doubtless represent several groups coordinate with the other great groups: and probably the gA'mno- sperms and angiosperms are each to be regarded as worthy of first rank. In any event, the general categories have become fairly well es- tablished. The subordinate classification of an- giosperms is of most general interest, as the group comprises the most conspicuous and best- known forms, the true flowering plants. The two great subdivisions are Monocotyledons (grasses, palms, lilies, orchids, etc.) and Dicoty- ledons (the ordinary trees, buttercups, roses, peas, heaths, mints, sunflowers, etc.). The over- whelmingly large assemblage is the Dicotyledons, vhicli are now grouped under two heads: (1) ArchichlaniydciE, wifli calyx or corolla lacking or of distinct parts: and (2) SympetaUe, with corolla present and its petals more or less united. All subordinate classification is constantly shifting, in order that it may keep step with the very rapidly accumulating body of morpho- logical data; for Classification, or Taxonomy, as it is more technically styled, must include the last expression of our knowledge of plants. Morphology. While from the historic stand- point taxonomy (classification) desei-vcs first mention, probably the nmst fundamental sub- division of botany is Morpliology, which treats of the structures of plants and their development, and upon whose data taxonomy must build. There was an older morphology which dealt mere- ly with the forms of mature plants and their organs, and whose concei>tion of organs was that everything about a plant could be referred to a very few categories, the favorite ones being root, stem, and leaf. Under this belief, every structure which was not evidently root, stem, or leaf was disguised, and the business of morphology was to strip off these disguises and reveal the real nature of the structure. This phase of morphology was dominated by Goethe's doctrine of metamorphosis — a doctrine which has been a serious impediment to botanical i)rogress. The present moriiliology. however, concerns it- self more with the development of structures than with the mature forms, a point of view which dates at least from Hofmeistcr's classic re- searches of IS.tI. It is essentially an embryologi- cal subject, therefore, whose purpose is to dis- cover from developing structures every possible suggestion as to the relationships and origin of great groups. In such study the life-history of a plant is traced from the single cell with which it starts to its mature form, and this life- history at more than one point may give sug- gestions of relationshi|(s. To develop a plant through all of its individual history, or to obtain all the stages in the history of some kind of plant, is a long and difficult piece of work. When this is done for the hundreds of thousands of species of plants recorded, morphology will be in a position to supply the data for a real and relatively permanent classification. At the present stage of morphological progress, however, large problens, sueli as the origin of the great groups, still confront us. In a general way, morphologists may be said to agree to the following statement; The algie represent the most primitive known forms from which the higher plants may be said to have been derived. The fungi are largely regarded as degenerate algje, which have made a certain amount of progress, but have developed no liigher groups. The alga", therefore, represent the great ances- tral group, and directly from them the liver- worts seem to have arisen. The liverworts liave certainly given rise to the mosses, and many claim that they have also given rise to the ferns. It certainly seems true that the ferns have come either through the liverworts or directly from the alg.T. Whatever may be the origin of the ferns, they have undoulitedly given rise to the seed-plants (flowering plants). Just what seedphants have come from what fern- jilants is a matter of discussicm at present, hut it is probable that several lines of seed-plants have arisen from as many branches of the fern stock. For ,a fuller statement of the modern development of morphology, see the articles Al- ternation OF Generations and HETEnosroRY. An.atomv. It was early observed that the bodies of the more complex plants consisted of layers of different constitution, but the real nature of the various structures was not deter- mined until the great improvements made in (he microscope in the latter half of the Seven- teenth Centiny. The first observers of the anat- omy of phints (q.v.) with the microscope were Robert llooke, Malpighi, (irew, and Leeiiwen- hoek, and their descriptions of the constitution of plant-bodies remained authoritative for over a hundred years. Although the discovery was made that plant-bodies are made up of cells of various forms, the real study of cells and their development dates from 1840, following