. Fundamentals of botany. Botany. 222 STRUCTURE AND LIFE HISTORIES OTHER FORMS 203.'Riccia.—About 4,000 species of liverworts have been described, and it is, of course, possible here to refer to only a very few of the forms, chosen because they illustrate some special idea or step in the evolutionary development of plants. In addition to the forms already mentioned, attention should be called to the genus Riccia,. Fig. 168.—A liverwort (i?ic;(;Jo/»'Jc/toc(i>-^o), X about 35. Cross-section of the thallus, showing young sporogonium in the enlarged venter of the archegonium. (After M. A. Howe.
. Fundamentals of botany. Botany. 222 STRUCTURE AND LIFE HISTORIES OTHER FORMS 203.'Riccia.—About 4,000 species of liverworts have been described, and it is, of course, possible here to refer to only a very few of the forms, chosen because they illustrate some special idea or step in the evolutionary development of plants. In addition to the forms already mentioned, attention should be called to the genus Riccia,. Fig. 168.—A liverwort (i?ic;(;Jo/»'Jc/toc(i>-^o), X about 35. Cross-section of the thallus, showing young sporogonium in the enlarged venter of the archegonium. (After M. A. Howe.) which is of interest because of its aquatic mode of life, and also because of its extremely simple sporophyte—the simplest sporophyte, in fact, of all plants that possess archegonia (Archegonates). The fertilized egg of Riccia develops a sporophyte which has only fertile cells (spores), except for a wall, one cell thick, enclosing the spores (Fi§. 168). In fact, the sporophyte has been reduced to only a very simple spore-case, of short duration; it never projects beyond the venter of the archegonium. Spores are formed in the usual way, as described for the forms. 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 Gager, C. Stuart (Charles Stuart), 1872-1943. Philadelphia, P. Blakiston's son & co.
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