. The structure and development of mosses and ferns (Archegoniatae). uxhaumia, or a perforated membrane, as in Fon-tinalis (Fig. 119, B). The base of the capsule, or apophysis, which Haberlandt(4) has shown to be the principal assimilative part of the sporo^:gonium, and which alone is provided with stomata, sometimesbecomes very large, and in the genus Splachnum (Vaizy (i))especially forms a largely-developed expanded body, which,must be looked upon as a specially-developed assimilating ap-:paratus. - ;orL VI. THE BRYALES 221 Undoubtedly the Polytrichacese represent the highest stageof develop
. The structure and development of mosses and ferns (Archegoniatae). uxhaumia, or a perforated membrane, as in Fon-tinalis (Fig. 119, B). The base of the capsule, or apophysis, which Haberlandt(4) has shown to be the principal assimilative part of the sporo^:gonium, and which alone is provided with stomata, sometimesbecomes very large, and in the genus Splachnum (Vaizy (i))especially forms a largely-developed expanded body, which,must be looked upon as a specially-developed assimilating ap-:paratus. - ;orL VI. THE BRYALES 221 Undoubtedly the Polytrichacese represent the highest stageof development among the Musci. This is true both in regardto the gametophore and the sporogonium. The former reachesin some species, e. g., P. commune, a length of 20 centimetresand sometimes more. The stem is usually angular and theclosely-set leaves thick and rigid. The numerous rhizoids areoften closely twisted together and form cable-like strands. Thestructure of the leaves is very characteristic, and differs verymuch from that of the simpler type found in Funaria. G. 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 thesame more highly magnified; E, two views of the capsule, Xi^. In the Polytrichacese (Fig. 121) the midrib of the leaf isvery broad and only at the extreme margin of the leaf is thelamina developed at all. A cross-section of the leaf shows thatthe midrib is greatly thickened in the centre, and graduallymerges into the rudimentary lamina. In Dazvsonia (Fig. 120),the leaf is almost flat, in Polytrichiim (Fig. 121), usuallymore or less incurved at the margin. The outer, or dorsal, surface of the leaf is covered with awell marked epidermis, whose outer cell-walls are strongly 222 MOSSES AND FERNS chap. thickened, and have a conspicuous cuticle. Within this epi-dermis are closely set, small sclerenchymatous elongated cells,among which are found more or less definite
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
