. Plant studies; an elementary botany. Botany. 322 PLANT STUDIES and archegonia appear, so that it is evidently a gameto- phyte. This gametophyte escapes ordinary attention, as it is usually very small, and lies prostrate upon the substra- tum. It has received the name prothallium or prothallus, so that when the term prothallium is used the gametophyte of Pteridophytes is generally referred to ; j list as when the term sporogonium is used the sporophyte of the Bryophytes is referred to. Within an archegonium borne upon this little prothallium an oospore is formed. When the oospore ger-. Fig. 2
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. Plant studies; an elementary botany. Botany. 322 PLANT STUDIES and archegonia appear, so that it is evidently a gameto- phyte. This gametophyte escapes ordinary attention, as it is usually very small, and lies prostrate upon the substra- tum. It has received the name prothallium or prothallus, so that when the term prothallium is used the gametophyte of Pteridophytes is generally referred to ; j list as when the term sporogonium is used the sporophyte of the Bryophytes is referred to. Within an archegonium borne upon this little prothallium an oospore is formed. When the oospore ger-. Fig. 293. Prothallium of a common fern (Aspldium): A, ventral surface, showing rhizoids (rh), antheridia (an), and archegonia iar); B, ventral surface of an older gametophyte, showing rhizoids (rh) and young sporophyte with root (w) and leaf (b).—After Schenck. minates it develops the large leafy plant ordinarily spoken of as " the fern, " with its subterranean stem, from which roots descend, and from which large branching leaves rise above the surface of the ground (Fig. 293, B). It is in this complex body that the vascular system appears. Xo sex organs are developed upon it, but the leaves bear numer- ous sporangia full of asexual spores. This complex vascular plant, therefore, is a sporophyte, and corresponds in this life history to the sporogonium of the Bryophytes. This. 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 work.. Coulter, John Merle, 1851-1928. New York, D. Appleton and Company