. Nature and development of plants. Botany. 350 GAMETOPHYTE OF SELAGINELLA sitic upon the sporophyte (see page 281). After the spores are shed they complete the growth of the gametophyte by forming the archegonia and filling the space within the spores with a solid mass of cells. This growth ruptures the spore walls at the apical regions, thus exposing the archegonia to the male gametes (Fig. 243, 3). The archegonia are rudimentary structures consisting. Fig. 243. Gametophyte and young sporophyte of Selaginella: I, section of a microspore that has nearly completed its germination—p, a single c
. Nature and development of plants. Botany. 350 GAMETOPHYTE OF SELAGINELLA sitic upon the sporophyte (see page 281). After the spores are shed they complete the growth of the gametophyte by forming the archegonia and filling the space within the spores with a solid mass of cells. This growth ruptures the spore walls at the apical regions, thus exposing the archegonia to the male gametes (Fig. 243, 3). The archegonia are rudimentary structures consisting. Fig. 243. Gametophyte and young sporophyte of Selaginella: I, section of a microspore that has nearly completed its germination—p, a single cell that is possibly a remnant of the large gametophyte or prothallium of pre- vious groups of ferns; an, antheridium consisting of a layer of wall cells which enclose the gamete mother cells. lA, a male gamete. 2, section of a megaspore, showing the stage of germination that is usually attained in the sporangium. 3, mature female gametophyte that has ruptured the wall of the megaspore, thus exposing the archegonia, ar, one of which has developed a young sporophyte or embryo with root, r; stem bearing two leaves, st, foot, /, and the suspensor, ^. 4, young sporophyte with root, stem and leaves emerging from the gametophyte. of but two neck cells, and a single canal cell leads to the female gamete. It is evident that these variations are of great advantage in ensuring the perpetuation of the species. Especially is the nourishment of the young gametophyte by the highly organized sporophyte a distinct gain. In previous types the formation of the gametophyte was dependent upon favorable conditions, such as moisture, light, temperature, etc., and it should be said that. 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 Curtis, Carlton Clarence, 1864-1945. New York, H. Holt
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