TAXONOMY (from Gk. rd,Scs, taxis, ar rangement + vo.Los, 73.0»10S, law, from vl,tatv, nen,ein, to distribute) IN PLANTS. The classi fication of plants. Probably 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 Linmean system (see BOTANY) 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. All of the groups mentioned are described under their several titles.
At present four primary divisions of the plant kingdom are recognized, as follows: Iv. Spermatophytes or Seed-plants.
III. Pteridophytes or Fern-plants.
II. Bryophytes or Moss-plants.
I. Thallophytes or Thallus-plants.
These categories are distinct enough, and there is no difficulty in assigning all plants to them, hut the question arises, Are they equivalent groups? 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 differential way of separat ing the groups is as follows: Thallophytes have thallus-bodies but no archegonia (q.v.) ; bryo phytes have archegonia but no fibro-vascular bundles : pteridophytes have fibro-vascular bundleshut no seeds; spermatophytes have seeds.