6i2 STUDIES IN FOSSIL BOTANY 



leaves differing from those of Ginkgo in their short 

 petioles and other characters, appears to be connected 

 with the typical form by the new genus Ginkgodium, 

 from the Lower Oolite of Japan. The genus Baiera of 

 Braun is the most important group, and is distinguished 

 from the recent Ginkgo by possessing a lamina with 

 more numerous and narrower segments. This distinc- 

 tion, however, has no constant value, as some forms of 

 leaf, even in the recent species, are much more deeply 

 dissected than others. " The genus," says Mr. Seward, 

 " was probably most widely spread during the Jurassic 

 period, but there is fairly strong evidence in favour of 

 extending its range to the Palaeozoic epoch." l Many 

 of the Triassic and Jurassic leaves are referred to the 

 genus Ginkgo itself, and some are even indistinguish- 

 able from those of the recent Maidenhair tree, or can 

 only be distinguished by the microscopic characters of 

 the epidermis and stomata, points which have now 

 been investigated with much success in carbonised 

 specimens. 



The evidence from the leaves is supported by the 

 discovery of specimens of flowers and seeds, which 

 appear to be conclusive as to the existence of the 

 Ginkgoaceae, at least in Mesozoic times. As regards 

 the Palaeozoic evidence, Mr. Seward is of the opinion 

 that " the plants which possessed characters nearest 

 akin to those of Ginkgo were probably members of 

 the Cordaitales, an extinct stock with which the 

 Ginkgoaceae are closely connected" {I.e. p. 142). 



In the Jurassic beds of Siberia, male flowers, agree- 



1 Seward and Gowan, "The Maidenhair Tree (Ginkgo biloba, L. )," 

 Annals of Botany, vol. xiv. March 1900. See also A. Sprecher, Le Ginkgo 

 biloba, Geneva, 1907. 



