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Journal Article

Embryo and Seedling of Dioon spinulosum

Helen Angela Dorety
Botanical Gazette
Vol. 67, No. 3 (Mar., 1919), pp. 251-257
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Page Count: 9

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Topics: Embryos, Cotyledons, Leaves, Hypocotyls, Cylinders, Seedlings, Plants, Plumule, Petioles, Germination
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1. The cotyledons of Dioon spinulosum vary in number from 2 to 4, and they are often lobed and divided so as to appear greater in number. In rare cases the cotyledonary sheath is undivided except near the tip. 2. They are multifascicular, like those of Ceratozamia and Microcycas, rather than like those of Zamia and Cycas, which have but few strands. 3. The arrangement and orientation of the vascular strands of cotyledons, hypocotyl, stem, leaves, and root do not differ in any marked degree from the general cycad arrangement. 4. The stem is large enough to demonstrate the cause of the girdling habit and to bring it into alignment with certain angiosperms of the same habit. 5. There is no extrafascicular cambium or any other vestige of polystyle.