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Journal Article

Microcycas Calocoma

Otis W. Caldwell
Botanical Gazette
Vol. 44, No. 2 (Aug., 1907), pp. 118-141
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Page Count: 28

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Topics: Plants, Gametophytes, Mother cells, Plant cells, Spermatozoa, Cell nucleus, Pollen tubes, Embryos, Ovules, Branches
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1. Small and widely separated groups of Microcycas calocoma occur in some of the mountains of western Cuba. 2. The adult plant is a small tree, and reaches the greatest height and circumference yet recorded for any cycad indigenous to the western hemisphere. The stem may be a straight shaft or may branch many times. 3. The ovulate cone is the largest known; and it and its sporophylls bear more resemblance to those of Zamia than to those of other cycads. 4. Unbranched vascular bundles pass up the stalk of the megasporophyll, anastomose in the expanded portion, then give off five to eight branches to each ovule. Immediately after entering the ovule each branch divides, one subdivision passing unbranched through the fleshy layer, and the other passing into the hard layer and branching many times. 5. The staminate cone is long and slender, and two-thirds of the abaxial side of its sporophylls is densely covered by sporangia which do not show any distinct grouping into sori. 6. In the male gametophyte eight body cells are formed and sixteen sperms. Each body cell has two large blepharoplasts which usually lie on opposite sides of the cell, but sometimes may lie side by side. Sometimes nine or ten body cells are produced. 7. The female gametophyte is often prominently lobed, and develops a large number of archegonia (sometimes exceeding 200), which are produced on any part of the surface or even within the endosperm. 8. Many embryos are produced, the suspensor being very long and spirally coiled and pressing the embryo tip against the endosperm; the cotyledons are three to six in number. 9. Microcycas may be regarded as the most primitive cycad yet described.

Notes and References

This item contains 16 references.

Literature Cited
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  • 2
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