. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 366 MOSSES AND FERNS CHAP. tissue is formed, in the projecting apex of which a single large cell occupies a central ; As in Botrychium the arche- sporium is derived from a single hypodermal cell, which ap- proaches more or less the tetrahedral form of the true Lepto- sporangiates, but shows a good deal of variation. As in these the wall of the sporangium is only one-layered, and the tapetum ordinarily two, but occasionally three-layered. The fully-de- veloped sporangium is in sha
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 366 MOSSES AND FERNS CHAP. tissue is formed, in the projecting apex of which a single large cell occupies a central ; As in Botrychium the arche- sporium is derived from a single hypodermal cell, which ap- proaches more or less the tetrahedral form of the true Lepto- sporangiates, but shows a good deal of variation. As in these the wall of the sporangium is only one-layered, and the tapetum ordinarily two, but occasionally three-layered. The fully-de- veloped sporangium is in shape much like that of Botrychium Virginianum, and has a very short massive stalk. Like Hel- minthostachys and Angiopteris, it opens by a vertical cleft, and like the latter there is a rudimentary annulus consisting of a group of thick-walled cells ( 207, r). The Gleicheniace^ These comprise about twenty-five species of tropical and sub - tropical Ferns, which may be all placed in two genera (Diels (I) )— Stromatopteris, with a single species S. moniliformis and Gleichenia with about 25 species. The best known is G. dichotoma, an extremely common Fern of the tropics of the whole world. It has very long leaves, which fork repeatedly, and may be proliferous from the growth of buds de- veloped in the axils of the forked Fig. 208.—Gleichenia pectinata. Prothallia, X4; B, 3 large prothallium seen from below, show- ing a dichotomy of the apex; C, the young sporophyte attached to the prothallium. The Gametophyte The development of the prothallium has been studied by Rauwenhofif (i), and shows some interesting points in which it is internjediate between the Osmundacese and the other Lep- tosporangiatse. The spores of Gleichenia are usually tetra-. 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 Campb
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