TAXILA. 65 TAXONOMY. India. It was situated near the modern village of Dheri Shalian, on the little stream Tabranala, in the District of Rawalpindi, in the Punjab. It vas one of the most populous and wealthy of all the cities of India. It was the residence of A^oka (q.v. ) while he was Viceroy of the Pun- jab. During the early part of the second cen- tury B.C. Taxila probably formed part of the dom.inions of the Gra-co-Bactrian King Euera- tidcs. The Sus or Abars became its masters B.C. rjO. only to lose it at the beginning of the ne.xt century to Kanishka, King of the Kushans. Con- sult: JlcCrindle, Invasion of India by Alexander the Great (Westminster, 189(3) ; id., Aneie^lt India as Described in Classical Literature (ib., 1901). TAXONOMY (from Gk. rdfis, taxis, ar- rangement + cA/ios, notnos, law, from v^ixuv, nemcin, to distribute) ix Plants. The classi- fication of plants. Probalily the first scientific .study of plants was the attempt at classification. Artificial classifications, beginning with the most ancient one into herbs, shrubs, and trees, and culminating in the Linnoean system (see BoTAKY) in the middle of the eighteenth century, were at first necessary on account of lack of knowledge of the structure of plants. Such classifications simply catalogued and pigeon- holed the rapidly accumulating material, in preparation for a classification based upon nat- ural relationships. Natural systems have been evolving since the eighteenth century; being modified by every advance in morphological knowledge, none are abreast of current opinion, and no final classification seems to be in sight. Each newly proposed system, however, ap- proaches to it. The present system is a com- posite one, not being referable to any single systematist, but having had a somewhat nat- ural and very slow development. In its larger outlines it is presented below. xll of the groups mentioned are described under their several titles. At present four primary divisions of the plant kingdom are recognized, as follows: IV. Spermntoph.vtes or Seed-plants. III. Pteridoph.Ytea or Fern-plants. II. Brvfipliytes fir Moss-plants. I. Thallophytes or Thallus-plants. These categories are distinct enough, and there is no difficulty in assigning all plants to them, but the question arises, Are they equivalent groups 1 Some think there should be more pri- mary groups, and others fewer. Beginning with the lowest great division, there is an increasing complexity. An easy difTerential way of separat- ing the groups is as follows: TliaUophi/tcs have thallus-bodies but no archegonia (q.v.) ; bri/o- phytcs have archegonia but no fibro-vascular bundles : pteridophi/tes have fibro-vascular bundles but no seeds; spermatophytes have seeds. I. Thallophyte.?, the least n.atural group of the four, comprise what seems to be a heteroge- neous mass of forms. They are divided into two great parallel sei-ies, algpp and fungi, the former containing chlorophyll (green pigment) and be- ing independent plants, the latter containing no chlorophyll and being parasites or saprophytes. The algse are usually subdivided as follows: Rhoiiophycea? or red alffap, . . , Plueophyeeffi or brown alfrje. Algffi <^ Chlorophyeei^ or p:reen alsiJP. Cy.anophyceffi or blue-green algae. It is a serious question whether the Cyano- phyceoe should be included in this way with the other algs, for they appear to be far more nearly related to the bacteria, a group of fungi. The classification of the fungi is in a very unsatis- factory state, but the plants are for the most part being treated under the following heads: Basidiom,vcet^?s or basidiuni fiing-i (toadstools and their allies, including rusts and snuits). Asconiycetes or sac-fungi (mildews, lichen- fungi, etc.). Phycomycetes or alga - like lungl (molds, downy mildews, etc.). Schizomyi-etes or fission-fungi (bacteria). Myxomycetes or slime molds. first three groups are regarded as true tlie last two are problematical as to their relationships, often being regarded as dis- tinct from the fungi. II. Bryophy'tes form a very natural group, the two great series being liverworts (Hepatieae) Fungi The fungi ; and mosses (Musci). visions are as follows: Bryophyta • Their principal subdi- f Bryales. I .Sphagnales. Hepaticffi ("An i .Tui (Ma thocero tales, ngernianniales. archantiales. III. Pteeidopiiytes also form a natural group, though the main divisions are very dissimilar in appearance. They are as follows: ( Lycopodiales or club-mosses. Pteridophyta^ Erjuisptales or horsetails, f Filiejiles or fern.s. IV. SpEBMATOPHYTES should probably be di- vided into two primary groups, although at pres- ent they are treated as one. The two great di- visions, gj'mnosperms and angiosperms. differ more in essential features from one another than does the former group from pteridophytes, but they are held together at present by the common character of seed production. The existing gymnosperms are groujjed as follows: [ Gnetales. ^, ., Coniferales (pines and their allies). Oymnospermaj j f;i„up„aie8 (maiden-hair tree). [ Cycadales (cycads). The angicsperms comprise a vast assemblage of forms that are easily separated into two great series, monocotyledons and dicotyledons, but whose further division is at present in a some- what chaotic state. Most of the subdivisions heretofore suggested are confessedly artificial, and probably as far as one may go safely with natural groups is as follows : Angiosperm.f'-'■^■^^-Hi^o"S^^iSydea,. f Monocotyledones The unit of classification used by taxonomists is the species, a group very difiicult to define, but understood in a general way. The species always bears two names, as Quercus alba, the systema- tist's name for white oak, 'alba' indicating the species, and 'Quercus' the genus to which the species belongs. In some eases forms of a spe- cies may be distinct enough to be characterized, and are called varieties, being designated by adding a third name to the species binomial. The next higher taxonomic group is the <)eniis, which comprises one or more species. For ex- ample, 'Quercus' is the oak genus, containing one or many species. The next higher taxonomic category is the family, which comprises one or more genera, and is indicated except in a few ex- ceptional cases by the common termination
