Taxonomy of Flowering Plants - LECTURE NOTES
Hugh D. Wilson

The Gymnosperms


Distinctive features (within the context of other vascular plants): As with the dicot subclass, Hamameliidae, the gymnosperms are a small, diverse group (72 genera in fewer than 11 families, ca. 750 species) that forms, however, a dominant element of the flora in many large parts of the planet's surface.  These plants are also economically important, mostly as a timber resource, and poorly understood in terms of biological relationship.

These plants are often treated as a single unit (Division or phyllum Pinophyta) with three primary subunits treated as subdivisions.  The treatment offered here, which follows that of the Flora of North America (FNA), elevates these three elements to division rank and moves Ginkgo biloba from subdivision Pinicae to a monotypic division.  The Plants Database provides this treatment for Texas:

Pinophyta
   Pinopsida
    Pinidae
      Pinaceae (2,12,4)
      Cupressaceae (3,11,3)
   Ephedropsida
    Ephedridae
      Ephedraceae (1,6,2)


see gymnosperm glossary
 

Cycadophyta

Palm (Lepidozamia hopei) 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) that was once large and diverse; now represented by 3 families: Cycad images are available from the University of Wisconsin (Madison) Department of Botany, and the Department of Botany at the University of Hawaii.  See also:  The Cycad Pages from the Royal Botanic Gardens Sydney, Australia and the Gymnosperm Database.

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 Gymnosperm database (Department of Botany, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany).
 

Pinophyta

This division includes most of our extant gymnosperms in 6 families with 52 genera and ca. 614 species. We have two genera of the Pinaceae in Texas (Pinus (8) and Pseudotsuga (1)).  The North American flora (at least that portion covered by the FNA) includes 6 genera and 66 species. Conifer images are available from the University of Wisconsin (Madison) Department of Botany; a detailed (species descriptions) overview of trees 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. 90 species - unusual plants that show, relative to other gymnosperm groups, structural similarities to the flowering plants.
Return to Lecture Notes, the Biology 301 homepage, the Flowering Plant Evolution, or the Pteridophytes
1 Dec 2010 - Mistletoe, Phoradendron, Texas Viscaceae