an order of gymnospermous plants comprising more than ten genera. Some of these genera belong to the family Ginkgoaceae; the systematic position of the remaining genera is unclear. In contemporary flora Ginkgoales is represented by only one species, the ginkgo, or “living fossil.” As fossils, Ginkgoales begin in the Permian period and reach their height in the Jurassic period and the first half of the Cretaceous; by the beginning of the late Cretaceous period, Ginkgoales were dying out. They grew chiefly in the northern hemisphere, primarily in Asia, in regions with a moderate climate. Some of the genera that were included in this group until recently— Czekanowskia and Phoenicopsis —have now been found to be a separate order of gymnosperms— Czekanowskia. Ginkgoales were probably deciduous trees. Dichotomous venation and the absence of central veins were characteristic of the leaves.
V. A. SAMYLINA