. A textbook of botany for colleges and universities ... Botany. 134 MORPHOLOGY extensive that usually only one mother cell functions, all the others contributing to its nutrition (fig. 302). This results in a relatively very. Figs. 298-300. — Sporangium of SelagineUa: 298, section through tip of strobilus, showing young sporangium (two shaded cells) on stem, and below it a young sporo- phyll; 299, further development of sporangium; the superficial cell of the sporophyll containing a nucleus is to give rise to the ligule; 300, sporangium in the mother cell stage. — 298 and 299, after Miss LyoN
. A textbook of botany for colleges and universities ... Botany. 134 MORPHOLOGY extensive that usually only one mother cell functions, all the others contributing to its nutrition (fig. 302). This results in a relatively very. Figs. 298-300. — Sporangium of SelagineUa: 298, section through tip of strobilus, showing young sporangium (two shaded cells) on stem, and below it a young sporo- phyll; 299, further development of sporangium; the superficial cell of the sporophyll containing a nucleus is to give rise to the ligule; 300, sporangium in the mother cell stage. — 298 and 299, after Miss LyoN. large mother cell and a tetrad of four very large spores. In some cases, although a tetrad of spores is started, two or three of them may not develop further, resulting in a sporangium containing only one or two spores. It is this condition of dissimilar spores that is called heterospory, in con- trast with the condi- tion of similar spores (as in Lycopodium), which is called homo- spory. SelagineUa, therefore, is hetero- sporous, while Lycopo- dium is homosporous. The terminology applied to the hetero- sporous condition is simple. The small. 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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