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Journal Article

Spermatozoids of Microcycas calocoma: Ultrastructure

Knut J. Norstog
Botanical Gazette
Vol. 151, No. 3 (Sep., 1990), pp. 275-284
Stable URL: http://www.jstor.org/stable/2995398
Page Count: 10

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Topics: Pollen tubes, Gyres, Microtubules, Mitochondria, Microsporocytes, Flagella, Lipids, Evolution, Cytoplasm, Ovules
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Spermatozoids of Microcycas calocoma: Ultrastructure
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Abstract

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.

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