. The structure and development of mosses and ferns (Archegoniatae). Fig. 73.—Spore division in A. fusiformis; opticalsections of living cells, X6oo. 142 MOSSES AND FERNS CHAP. in the epidermis of elongated leaves of Monocotyledons. Inthe older parts some of these cells cease to elongate, and be-come more nearly oval (Fig. 75, A). These are the youngstomata, and exactly as in the vascular plants, each divideslongitudinally by a septum which later separates in the middleand forms the pore surrounded by its two guard cells. Thewalls of the other epidermal cells become much thickened anddistinctl
. The structure and development of mosses and ferns (Archegoniatae). Fig. 73.—Spore division in A. fusiformis; opticalsections of living cells, X6oo. 142 MOSSES AND FERNS CHAP. in the epidermis of elongated leaves of Monocotyledons. Inthe older parts some of these cells cease to elongate, and be-come more nearly oval (Fig. 75, A). These are the youngstomata, and exactly as in the vascular plants, each divideslongitudinally by a septum which later separates in the middleand forms the pore surrounded by its two guard cells. Thewalls of the other epidermal cells become much thickened anddistinctly striated. Each epidermal cell contains two largechloroplasts like that in the cells of the gametophyte, and be-tween the cells are well-developed air-chambers communicat-ing with the stomata, so that there is here a typical assimilativesystem of tissues. The doubling of the chloroplast in the cells of the sporophytehas been noted by Schimper (A. F. W. Schimper (2)), and. Fig. 74.—Ripe spores and elaters of A. Pearsoni, X6oo. this was observed by the writer in both A. fusiformis and A,Pearsoni. About the base of the growing sporogonium is a thicktubular sheath representing in part the calyptra of the otherHepaticse, but involving, besides the archegonium venter, alsothe surrounding tissue of the gametophyte. This sheath keepspace with the growth of the sporophyte for a long time, butfinally the sporogonium grows more rapidly and projects farbeyond it, and this remains as a tube surrounding its growth of the sporogonium continues as long as thegametophyte remains alive, and in A. fusiformis is often 6 IV. THE ANTHOCEROTES 143 B
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
