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Spermatozoids of Microcycas calocoma: Ultrastructure
Knut J. Norstog
Vol. 151, No. 3 (Sep., 1990), pp. 275-284
Published by: The University of Chicago Press
Stable URL: http://www.jstor.org/stable/2995398
Page Count: 10
You can always find the topics here!Topics: Pollen tubes, Gyres, Microtubules, Mitochondria, Microsporocytes, Flagella, Lipids, Evolution, Cytoplasm, Ovules
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Microcycas calocoma, a monotypic Cuban endemic cycad, differs from other cycads in possessing multiple spermatozoids (up to 16 per pollen tube, in comparison with the usual two). The spermatozoids are characterized further by exhibiting a developmental gradient in complexity and motility, ranging from well-organized and actively motile first-formed spermatozoids to less well-organized and less motile last-formed spermatozoids. It is thought that this relationship exemplifies evolutionary reduction and represents a primitive stage in male-gamete evolution and that Microcycas, therefore, is the most primitive member of the Zamiaceae.
Botanical Gazette © 1990 The University of Chicago Press