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Journal Article

Spermatogenesis in Dioon edule

Charles J. Chamberlain
Botanical Gazette
Vol. 47, No. 3 (Mar., 1909), pp. 215-236
Stable URL: http://www.jstor.org/stable/2467560
Page Count: 26
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Abstract

The sporophylls of the staminate cone are rather large, and bear about 250 sporangia, a larger number than in any cycads except Cycas, Encephalartos, and Macrozamia. The output of spores per sporangium is about 30,000, a larger output than in Zamia, Ceratozamia, or Encephalartos, the only genera in which this feature has been noted. There are twelve chromosomes in the pollen mother cell, but they often split so early that the number may appear larger. There is only one prothallial cell and that is persistent. The report of an evanescent prothallial cell in Zamia is probably due to a misinterpretation. The blepharoplasts are very probably of nuclear origin. The radiations are streams of cytoplasm, which, in early stages, have a peculiar appearance on account of the granules and globules which adhere to them. The solid blepharoplast becomes vacuolated and then breaks up into granules from which the spiral band is formed. The ciliated band makes five or six turns from left to right. The sperms are larger than those of Cycas or Microcycas, but not quite so large as those of Zamia. The sperms are formed within sperm mother cells, from which they are discharged. The same is true of Zamia, Ceratozamia, and probably of other cycads. In addition to the movement by cilia, there is a vigorous amoeboid movement of both nucleus and cytoplasm. Discussion of phylogeny will be reserved until investigations now in progress have been completed.

Notes and References

This item contains 14 references.

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