Baiera, in the older Mesozoic floras. In the later Jurassic rocks of Yorkshire true Ginkgo leaves as well as those of the Baiera type are fairly common; with the leaves have been found pieces of male and female flowers. Ginkgo and Baiera have been described from Jurassic rocks of Germany, France, Russia, Bornholm, and elsewhere in Europe; they occur abundantly in Middle Jurassic rocks in northern Siberia, and are represented in the Jurassic floras of Franz Josef Land, the East Coast of Greenland, and Spitzbergen (Fig. 20). The abundance of Ginkgo and Baiera leaves associated with male flowers and seeds discovered in Jurassic rocks, approximately of the same geological age as those on the Yorkshire coast, in East Siberia and in the Amur district, has led to the suggestion that this region may have been a centre where the Ginkgoales reached their maximum development in the Mesozoic period. [Illustration: Fig. 20. Fossil Ginkgo leaves. (1/2 nat. size.) A. Tertiary, Island of Mull. B. Wealden, North Germany (after Schenk). C. Jurassic, Japan (after Yokoyama). D. Jurassic, Australia (after Stirling). E. Jurassic, Siberia (after Heer). F. Jurassic, Turkestan. G. Lower Cretaceous, Greenland (after Heer). H. Jurassic, California (after Fontaine). I. Jurassic, Yorkshire. J. Jurassic, N.E. Scotland (after Stopes). K. Wealden, Franz Josef Land (after Nathorst). L. Rhaetic, South Africa. M. Jurassic, Spitzbergen (after Heer). ] It should be added that other genera of Jurassic and Rhaetic fossils in addition to Ginkgo and Baiera have been referred to the Ginkgoales, though evidence of such affinity is not convincing. There is, however, good reason to believe that this widespread group was represented by several genera in the older Mesozoic floras. The occurrence of the Ginkgoales in Jurassic rocks in King Charles Land and in the New Siberian Islands (lat. 78° and 75° N.), in Central China, Japan, Turkestan, California, Oregon, South Africa, Australia, and Graham's Land demonstrates the cosmopolitan nature of the group. During the later part of the Jurassic period and in the Wealden floras both Baiera and Ginkgo were abundant; leaves are recorded from Jurassic strata in the north-east of Scotland, from Lower Cretaceous or Wealden rocks in North Germany, Portugal, Vancouver Island, Wyoming, and Greenland.