1. Pollen grain (with microgametophyte within) directly contacts the ovule to fertilize the egg - in Angiosperms the microgametophyte makes direct contact with the ovule, BUT the pollen does not contact the ovule.
2. no double fertilization to produce endosperm (although double fertilization has been documented in Ephedra) - nutritive tissue in gymnosperms is haploid megagametophytic.
3. absence of vessel elements (exception = Gnetophyta)
4. absence of companion cells in the phloem.
5. presence of a many-celled or many-nucleate megagametophyte
6. presence of archegonia (except in genera - Gnetum and Welwitschia)
7. all woody 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.
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.
Strangeriaceae (2 genera, 4 species)
Zamiaceae (8 genera, 164 species - 1 in the FNA)
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.
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.
Pinaceae - 10 genera, ca. 200 species mostly in the northern hemisphere with 6 genera (Pinus - pine, Larix - larch, Picea - spruce, Tsuga - hemlock, Abies - fir, and Pseudotsuga - Douglas-fir) and 66 species in the North American Flora. See Fig. 60.
Cupressaceae (including the Taxodiaceae) - 25-30 genera, ca. 110-130 species with 30 species in the FNA and 3 genera (Taxodium, Cupressus, and Juniperus) with 11 species in Texas. Includes Sequoia sempervirens (coast Redwood) and Sequoiadendron giganteum (Sierra Redwood), the tallest and most massive living organisms. See Figs. 61, 62
Araucariaceae - (Norfolk Island Pine or Araucaria Family) - 2 genera, 39 species - Once (Jurassic and Cretaceous periods) of worldwide distribution, now restricted to the Southern Hemisphere. "Living fossil" (The Wollemi Pine - New South Wales, Australia) discovered in 1994, probably a new genus - only ca. 20 plants known. See Fig. 59.
Podocarpaceae - 13-17 genera with ca. 170 species - elements form major forests in some parts of the family range - Southern Hemisphere.
3 orders - each with a single famly that includes a single genus - with ca. 71 species - unusual gymnosperms
order Ephedrales - shrubs with jointed stems and reduced leaves, vessels, and double fertilization (no endosperm produced) - Ephedra - ca. 60 species of the Northern Hemisphere and South America, 12 species in the FNA and 6 species in Texas and the University of Texas at El Paso campus.
order Welwitschiales - single species (W. mirabilis) of Namibia (s.w. Africa - 0 to 10 cm of rain per year) - vessels, two leaves, dioecious, cone-like strobili. See images from the University of Wisconsin (Madison) Department of Botany
order Gnetales - single pantropical genus with ca. 30 species. Mostly rainforest lianas (woody vines that occupy the forest canopy), with broad, dicot-like,opposite leaves.
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.