Texas A&M University Department of Biology Herbarium
Field Systematic Botany
GYMNOSPERMS
An Overview

Distinctive features (within the context of vascular plants):

As with the dicot subclass, Hamameliidae, a small group - in terms of species numbers (72 genera in fewer than 11 families, ca. 750 species) that forms a dominant element of the flora in many large parts of the planet's surface and is economically important, mostly as a timber resource.

Cycadophyta

Palm or fern-like plants, no vessels, motile sperm, usually dioecious, seeds born on MEGASPOROPHYLLS, also MICROSPOROPHYLLS, both usually born in STROBILI. None native to Texas, but several cultivated. An archaic group (Triassic to present) now represented by 3 families: Cycad images are available from the University of Wisconsin (Madison) Department of Botany.

Ginkgophyta

Trichopityaceae (extinct) and Ginkgoaceae with at least six extinct genera and a single extant species (Ginkgo biloba) which is native to China and cultivated in urban areas (resists pollution) throughout the world. Apparently identical fossils that are 200 million years old (Mabberley, 1993) but now known only from cultivation and probably saved from extinction via cultivation - broad leaves, motile sperm. Ginkgo biloba images are available from the University of Wisconsin (Madison) Department of Botany, and information on the species can be obtained from the Botanical Garden at the University of Delaware.

Pinophyta

This division includes most of our extant gymnosperms in 6 families with 52 genera and ca. 614 species. Have two genera of the Pinaceae in Texas (Pinus (8) and Pseudotsuga (1)). In the North American flora. Conifer images are available from the University of Wisconsin (Madison) Department of Botany; a detailed (species descriptions) overview of conifers of the Pacific Northwest is provided by Oregon State University; and a nice presentation of the ancient Bristle Cone Pine has been created by Leonard Miller.

Gnetophyta

3 orders - each with a single famly that includes a single genus - with ca. 71 species - unusual gymnosperms


REFERENCES

Correll, D. S. and M. C. Johnston. 1979, Manual of the Vascular Plants of Texas The University of Texas at Dallas.

Flora of North America Editorial Committee (FNA). 1993. Flora of North America (North of Mexico), Vol 2., Pteridophytes and Gymnosperms. Oxford University Press.

Hatch, S. L., K. N. Gandhi, and L. Brown. 1990. Checklist of the Vascular Plants of Texas. Texas Agricultural Experiment Station. (The Texas A&M Bioinformatics Working Group has developed a WWW-based Search of this checklist.

Kartesz, J.T. 1994. A Synonymized Checklist of the Vascular Flora of the United States, Canada, and Greenland. (2 vols.)Timber Press. A product of the Biota of North America Program.

Mabberley, D. J. 1993. The plant-book. Cambridge University Press.


Created by HDW on 19 January 1996, last updated on 22 January 1996
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