. A textbook of botany for colleges and universities ... Botany. PTERIDOPHYTES 179 ferns, and that Salviniaceae have the transverse wall of the older eusporangiate Marattiaceae. Conclusions. — It is evident that the water ferns are a very specialized aquatic group, probably derived from the leptosporangiate ferns. More- over, the features of the sporangium, in development and output, in- dicate an origin from one of the higher leptosporangiate families. The. Figs. 416, 417. — Female gametophyte of Marsilea: 416, the tissue protruding from the heavy megaspore wall developing a single large arch
. A textbook of botany for colleges and universities ... Botany. PTERIDOPHYTES 179 ferns, and that Salviniaceae have the transverse wall of the older eusporangiate Marattiaceae. Conclusions. — It is evident that the water ferns are a very specialized aquatic group, probably derived from the leptosporangiate ferns. More- over, the features of the sporangium, in development and output, in- dicate an origin from one of the higher leptosporangiate families. The. Figs. 416, 417. — Female gametophyte of Marsilea: 416, the tissue protruding from the heavy megaspore wall developing a single large archegonium; the top of the large nutritive cell with its single nucleus seen; 417, the mature archegonium. — After Campbell. annulus characters, which might have determined the point, are lacking. It is interesting if heterospory has developed in these aquatic conditions; and it is noteworthy that the development of the female gametophyte is very different from that of Selaginella and Isoetes, which resemble gymnosperms in this regard. The fern connections of Marsileaceae are clearer than those of Salviniaceae, which in habit are further removed from the terrestrial 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 Coulter, John Merle, 1851-1928; Barnes, Charles Reid, 1858-1910, joint author; Cowles, Henry Chandler, 1869- joint author. New York, Cincinnati [etc] American book company
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