. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 142 MOSSES AND FERNS CHAP. in the epidermis of elongated leaves of Monocotyledons. In the older parts some of these cells cease to elongate, and be- come more nearly oval (Fig. 75, A). These are the young stomata, and exactly as in the vascular plants, each divides longitudinally by a septum which later separates in the middle and forms the pore surrounded by its two guard cells. The walls of the other epidermal cells become much thickened and distinctly striated. Each epidermal cell contains
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 142 MOSSES AND FERNS CHAP. in the epidermis of elongated leaves of Monocotyledons. In the older parts some of these cells cease to elongate, and be- come more nearly oval (Fig. 75, A). These are the young stomata, and exactly as in the vascular plants, each divides longitudinally by a septum which later separates in the middle and forms the pore surrounded by its two guard cells. The walls of the other epidermal cells become much thickened and distinctly striated. Each epidermal cell contains two large chloroplasts 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 assimilative system of tissues. The doubling of the chloroplast in the cells of the sporophyte has 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 thick tubular sheath representing in part the calyptra of the other Hepaticae, but involving, besides the archegonium venter, also the surrounding tissue of the gametophyte. This sheath keeps pace with the growth of the sporophyte for a long time, but finally the sporogonium grows more rapidly and projects far beyond it, and this remains as a tube surrounding its base. The growth of the sporogonium continues as long as the gametophyte remains alive, and in A. fusiformis is often 6. 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 Campbell, Douglas Houghton, 1859-1953. New York, The Macmillan Company;
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