CH. VIII] THE MAIDEN HAIR TREE 131 



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. 



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 Avidespread group 

 was represented by several genera in the older Meso- 

 zoic floras. 



The occurrence of the Ginkgoales in Jurassic rocks 

 in King Charles Land and in the Xew Siberian Islands 

 (lat. 78° and 75° X.), 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. 



During the Tertiary period, or probably in the 

 earlier days of that era. Ginkgo flourished in North 

 America, in Alaska and in the jNIackenzie River district, 

 Greenland, Saghalien Island, and in several European 

 regions. In Chapter III reference was made to the 



9-2 



