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Journal Article

Vascular Anatomy of the Seedling of Microcycas calocoma

Helen Angela Dorety
Botanical Gazette
Vol. 47, No. 2 (Feb., 1909), pp. 139-147
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Page Count: 11

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Topics: Cotyledons, Embryos, Petioles, Xylem, Seedlings, Plumule, Hypocotyls, Phloem, Endosperm, Leaves
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1. There is no resting stage in the development of the embryo of Microcycas calocoma. 2. The germination is hypogean. 3. The root is a delayed organ, as in Dioon and Ceratozamia. 4. There are two cotyledons as in all cycads (except, perhaps, Encephalartos). 5. The cotyledons are often fused to form one organic whole, the plumule escaping by bursting the sheath. 6. Mucilage ducts alternate with the 8-10 cotyledonary strands. 7. The cotyledonary node is similar to that of Dioon edule and Ceratozamia, but the vascular cylinder of the hypocotyl is a siphonostele. 8. The hypocotyl contains no cortical vascular tissue, although there are remnants of a broken-up cambial zone. 9. The vascular strands of cotyledons and leaves are endarch at base and exarch in the upper portions. The exarch condition obtains throughout most of the length of the petiole. 10. Girdling of the marginal leaf traces takes place while the tissue is procambial. 11. The root is tetrarch, but may reduce to triarch toward the tip.

Notes and References

This item contains 13 references.

Literature Cited
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