. The structure and development of mosses and ferns (Archegoniatae). Fig. III.—A, Longitudinal sections of a nearly ripe capsule of F. hygrometrica, X260;per, peristome; r, annulus; t, thickened cells forming the margin of the theca; B,the sporogenous cells shortly before the final divisions; i, inner; 0, outer spore-sac, X525- periphery of the broadest part of the operculum. The upperrows of cells are very much compressed vertically, but aregreatly extended radially and have their walls thicker than thoseof the neighbouring cells. These thickened annulus cells formthe rim of the loosened oper
. The structure and development of mosses and ferns (Archegoniatae). Fig. III.—A, Longitudinal sections of a nearly ripe capsule of F. hygrometrica, X260;per, peristome; r, annulus; t, thickened cells forming the margin of the theca; B,the sporogenous cells shortly before the final divisions; i, inner; 0, outer spore-sac, X525- periphery of the broadest part of the operculum. The upperrows of cells are very much compressed vertically, but aregreatly extended radially and have their walls thicker than thoseof the neighbouring cells. These thickened annulus cells formthe rim of the loosened operculum. The two lower rows ofannulus cells—the annulus proper—have thin walls and finallybecome extremely turgescent. It is the destruction of these VI. THE BRYALES 211 cells, when the capsule is ripe, that effects the separation be-tween the operculum and theca. The peristome arises from the fifth layer of cells from theoutside of the operculum. If a median longitudinal section ofa nearly ripe capsule is examined, the row of cells belongingto this layer (Fig
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
