
Vascular Flora of the Southeastern United States
J. W. Hardin, J. R. Massey, A. E. Radford, J. W. Thieret, eds.
Gymnosperms
Copyright - James W. Hardin, Ph. D., 1998, 1999. All Rights Reserved.
The Gymnosperms, with four of the 16 families and 12 of the 86 genera in the southeastern United States, are characterized as having "naked seeds," i.e., naked ovules at the time of pollination. This is in contrast with the Angiosperms which have the ovules enclosed in a carpel. Therefore, in the Gymnosperms, the pollen actually reaches the ovule at pollination whereas in the Angiosperms, the pollen stops at the stigma. Another difference it that in Gymnosperms the storage tissue of the seed is the pre-zygotic megagametophyte tissue whereas in Angiosperms it is the post-zygotic endosperm formed by double fertilization. Pollination is by wind except for the Zamiaceae which is primarily beetle pollinated. Hardin, J. W. 1971. Studies of the Southeastern United States Flora. II. The Gymnosperms. Jour. Elisha Mitchell Sci. Soc. 87:43-50.
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1. Leaves pinnately compound with linear leaflets; seeds borne on megasporophylls in a strobilus; plants dioecious.....
1. Zamiaceae.
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1. Leaves simple, linear, acicular subulate, or scale-like; seeds solitary on a short stem or several on the scales of a strobilus; plants monoecious or dioecious.
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2. Seeds solitary and partially or completely enclosed by a fleshy aril..... 2. Taxaceae.
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2. Seeds several in a woody,leathery or semi-fleshy strobilus, not arillate.
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3. Leaves acicular or linear, alternate; seed cone scales and bracts distinct..... 3. Pinaceae.
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3. Leaves linear, subulate, or scale-like, alternate, opposite or whorled; seed cone scales fused with their subtending bracts..... 4. Cupressaceae.