CONE-BEARING SEED PLANTS
There are two major groups of seed plants that differ in their methods of pollination, in the seed bearing structure, and in the leaf form, among other things. "Conifers", which include both true Coniferophyta and also the palm-like Cycadophyta, are primarily wind-pollinated and bear the seeds in an open cone. Flowering plants (Anthophyta) are primarily fertilized by animals visiting their flowers, and their seeds are enclosed in true fruits. A minor group (minor at least in the Recent) that has some characteristics of both are the ginkgoes (Ginkgophyta). Some small conifers existed in the late Paleozoic, and of course there are still many species around today, but these plants dominated the Mesozoic world. Anthophytes are more prevalent in Cenozoic rocks, and did not appear at all until late in the Mesozoic.
Conifers are easily recognized from their needle-like leaves and their cones.
The true conifers are familiar plants. The first picture shows a portion of Pinus echinata (short-leaf pine) near Plains, GA. The needles and cones are obvious. (Photo by B. Carter.)
The next photo shows a fossilized cone, probably of a fir- or spruce-like tree. The pointers indicate the more obvious scales of the cone, the ends of which are broken off. The scale bar is 1cm. (Photo by B. Carter.)
The final photo of a 'conifer' shows the cone of a cycad and parts of some leaves. The cone is about 8 cm across at the base. (Photo by B. Carter.)
Taken on GSW campus, Americus, GA. Cone is about 7 cm in diameter. (Photo by B. Carter.)
Ginkgos have leaves that are veined like conifers (veins continue from the base to the edge without branching) but shaped like flowering plants (flattened). There is one living species, Ginkgo biloba, that is widely used as an ornamental plant but is probably extinct in the wild. The next photograph shows a mid-sized specimen in fall foliage in Americus, GA
Ginkgo biloba near the GSW campus in Americus, GA. (Photo by B. Carter.)
The leaves of ginkgoes are very easy to recognize. They are fan-shaped, usually with a long petiole ('stem'), and the veine run continuously from the base of the leaf blade to the outer edge. The final photograph is of fragments of fossil Ginkgo adiantoides leaves from Paleocene rocks of North Dakota. The scale bar is 1cm. (Photo by B. Carter.)
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