. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. VL THE BRYALES Undoubtedly the Polytrichacese represent the highest stage of development among the Musci. This is true both in regard to the gametophore and the sporogonium. The former reaches in some species, e. g., P. commune, a length of 20 centimetres and sometimes more. The stem is usually angular and the closely-set leaves thick and rigid. The numerous rhizoids are often closely twisted together and form cable-like strands. The structure of the leaves is very characteristic, and differs
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. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. VL THE BRYALES Undoubtedly the Polytrichacese represent the highest stage of development among the Musci. This is true both in regard to the gametophore and the sporogonium. The former reaches in some species, e. g., P. commune, a length of 20 centimetres and sometimes more. The stem is usually angular and the closely-set leaves thick and rigid. The numerous rhizoids are often closely twisted together and form cable-like strands. The structure of the leaves is very characteristic, and differs very much from that of the simpler type found in Funaria. ^^^^ —±. Fig. 120.—Dawsonia superba. A, upper part of female plant bearing a sporogonium, Xi; B, a leaf, slightly enlarged; C, section of leaf, X about 70; D, part of the same more highly magnified; E, two views of the capsule, Xi5^. In the Polytrichacese (Fig. 121) the midrib of the leaf is very broad and only at the extreme margin of the leaf is the lamina developed at all. A cross-section of the leaf shows that the midrib is greatly thickened in the centre, and gradually merges into the rudimentary lamina. In Dawsonia (Fig. 120), the leaf is almost flat, in Polytrichum (Fig. 121), usually more or less incurved at the margin. The outer, or dorsal, surface of the leaf is covered with a well marked epidermis, whose outer cell-walls are strongly. 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 work.. Campbell, Douglas Houghton, 1859-1953. New York, The Macmillan Company;