. Botany; principles and problems. Botany. Tlll<: I'TERIDOPHYTA 335 moss-like appearance which has given the common name to the group. The internal structure of the stem in Lijcopodium is unique, for its fibro-vascular system is a solid, pithless core, made up of alternating Imnds of wood and bast extending across the central cylindcM- (Fig. 208). The anatomy of the other genera is much simpler. Sporangia are few and large as compared with those of the ferns, and are borne on the upper or ventral leaf-surface. In. Fig. 208.—Transverse section (diagrammatic) of the stem of Lrjcopodium. The f
. Botany; principles and problems. Botany. Tlll<: I'TERIDOPHYTA 335 moss-like appearance which has given the common name to the group. The internal structure of the stem in Lijcopodium is unique, for its fibro-vascular system is a solid, pithless core, made up of alternating Imnds of wood and bast extending across the central cylindcM- (Fig. 208). The anatomy of the other genera is much simpler. Sporangia are few and large as compared with those of the ferns, and are borne on the upper or ventral leaf-surface. In. Fig. 208.—Transverse section (diagrammatic) of the stem of Lrjcopodium. The fibro-vascular cylinder consists of alternating bands of wood and bast. From this cylinder a small leaf-trace departs to each leaf. Wood black, bast dotted. the simpler species, a sporangium may arise on an ordinary vege- tative leaf but in most cases these spore-bearing leaves (which here, as elsewhere among the higher plants are known as sporo- phylls) become stout and scale-like, and are grouped in a cone or strohilus at the tip of a branch. The two main orders Lycopodia- les and Selaginellales are distinguished chiefly by their methods of reproduction. 1. Lycopodiales (Fig. 209).—These are homosporous plants, the spores which they produce being all of one sort, as in the Filicales. The gametophytes vary considerably but tend to develop a stout tuberous, subterranean portion, which may be surmounted ])y a green aerial region on which the sexual organs luv borne (Fig. 210). These are larger and bettor developed than. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Sinnott, Edmund Ware, 1888-. New York, McGraw-Hill
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