. The structure and development of mosses and ferns (Archegoniatae). s described, and that sometimes the apical part ofthe sporogonium w^as occupied by a sort of cap of sterile cells(Fig. 25, C). When ripe, the cells of the capsule-wall in Targionia de-velop upon their walls dark-colored annular and spiral thicken-ings much like those of the elaters. These thickenings arequite w^anting in Fimhriaria. The dehiscence of the capsule is either irregidar. , or by a sort of lid, , Grimaldia, or by a numberof teeth or lobes, , Liinnlaria, Marchantia. In some formsafter fertilisa
. The structure and development of mosses and ferns (Archegoniatae). s described, and that sometimes the apical part ofthe sporogonium w^as occupied by a sort of cap of sterile cells(Fig. 25, C). When ripe, the cells of the capsule-wall in Targionia de-velop upon their walls dark-colored annular and spiral thicken-ings much like those of the elaters. These thickenings arequite w^anting in Fimhriaria. The dehiscence of the capsule is either irregidar. , or by a sort of lid, , Grimaldia, or by a numberof teeth or lobes, , Liinnlaria, Marchantia. In some formsafter fertilisation there grows up about the archegonium a cup-shaped envelope, perianth, pseudoperianth, which in Fini-6 ^ MOSSES AND FERNS CHAP, briaria especially is very much developed, and projects farbeyond the ripe capsule (Fig. 21). The germination of the spores corresponds in the main withthat of Riccia. Except in cases where the exospore is verythin, in which case it is not ruptured regularly, the exosporeeither splits along the line of the three converging ridges upon. Fig. 27.—Targionia hypophylla. Germination of the spores, X about 200. In B twogerm tubes have been formed; C and E are optical sections; x, apical cell; r,primary rhizoid; sp, spore membrane. the ventral surface, and through this split the endospore pro-trudes in the form of a papilla, as in Riccia; or in Targionia(Fig. 27) the exospore is usually ruptured in two places onopposite sides of the spore, and through each of these a filamentprotrudes, one thicker and containing chlorophyll, the othermore slender and nearly colourless. The first is the germ tube,the second the first rhizoid. In Fimhriaria Californica thefirst rhizoid usually does not form until a later period. InTargionia a curious modification of the ordinary process isquite often met with (Fig. 27, B). Here, by a vertical divi-sion in the very young germ tube, it is divided into two similarcells, which both grow out into germ tubes. Whetherboth of the
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
