. Morphology of gymnosperms. Gymnosperms; Plant morphology. CYCADALES 127 The earliest stages in the development of the strobilus, sporophylls, and ovules have not been studied in any of the genera, even so late a stage as the row of megaspores hav- ing been noted only in Stangeria, Cera- iozamia, and Zamia. In these genera the megaspore mother cell when first rec- ognized was deep- seated in the nucel- lus and surrounded by a mass of cells doubtless homolo- gous with the "spongy tissue" of conifers. In Stan- geria (29) and Cera- tozamia (11) the mother cell 'gives rise to a row of t
. Morphology of gymnosperms. Gymnosperms; Plant morphology. CYCADALES 127 The earliest stages in the development of the strobilus, sporophylls, and ovules have not been studied in any of the genera, even so late a stage as the row of megaspores hav- ing been noted only in Stangeria, Cera- iozamia, and Zamia. In these genera the megaspore mother cell when first rec- ognized was deep- seated in the nucel- lus and surrounded by a mass of cells doubtless homolo- gous with the "spongy tissue" of conifers. In Stan- geria (29) and Cera- tozamia (11) the mother cell 'gives rise to a row of three cells, and in Zamia (74) to a row of four cells, the innermost of which becomes the func- tioning megaspore (figs. 118-120), the first cell of a new gametophyte. There is a single massive integu- ment, and the nu- cellus is free only for a short distance. At the apex of the nucellus, some time before the shedding of pollen, a vigorous growth results in the formation of the character-. FiGS. 118-120.—Megaspores of cycads: fig. n8, paradoxa, showing the functional megaspore enlarging at the expense of two functionless cells of the megaspore row; X250; fig. 119, Ceratozamia longifoHa, showing row of three cells, the lowest (functional mega- spore) beginning to enlarge; X266; fig. 120, Zamia flori- dana, the row of four megaspores.—Fig. 118, after Lang (29); fig. 119, after Teeub (ii); fig. 120, after F. Grace Smith (74).. 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; Chamberlain, Charles Joseph, b. 1863; Coulter, John Merle, 1851-1928. Morphology of spermatophytes. Part I. Gymnosperms. Chicago, University of Chicago Press
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