GINKGO. 253- 



concluding that ancestral forms of the recent plant existed as 

 far back as the Upper Carboniferous period. Since this paper was 

 written many new facts have come to light, which enable us to 

 extend the geographical distribution of the family and strengthen 

 Heer's conclusion as to the importance of these Gymnospermous 

 plants in the Mesozoic or even in the Pahcozoic epoch. 



Such genera as Ginkgop/tyUum, Saportaa, Trichopitys, Dicrano- 

 phyUwn, Rltijndopsis, Whittlescya, and even Ginkgo itself, have 

 been described from Carboniferous and Permian rocks as probable 

 members of the family to which Ginkgo biloha belongs. As 

 regards some of these genera, there is hardly sufficient evidence 

 in favour of their inclusion in the Ginkgoales ; on the other 

 hand, the close resemblance of the Permian leaves referred to 

 Ginkgopliylluin, Ginkgo, Saportaa, and Baiera, to the recent plant, 

 render it probable that closely allied species existed in the 

 I'aheozoic era. Certain fossil seeds from St. Etienne, of Permian 

 age, described by Brongniart ' as species of Cardiocur/nts, are 

 almost identical in structure with Ginkgo seeds. It is, however, 

 from Mesozoic strata that we obtain the most striking proof of 

 the abundance of Ginkgo-likv trees in the vegetation of the past. 



Although as a rule it is, for various reasons, preferable to 

 avoid the application of the name of a recent genus to fossil 

 species, yet the generic names Ginkgo and Salisburia have been 

 so generally used for fossil leaves, and on evidence of a trustworthy 

 nature, that it would be inadvisable to suggest a departure from 

 so well established a custom. The leaves described by Gardner 

 from the Tertiary beds between the basaltic lava-flows of Mull, 

 and referred to linger' s species Ginkgo adiantoides,'- agree so 

 closely with those of the recent species that we may well hesitate 

 to admit even a specific difference. When we come to examine 

 the Jurassic and Cretaceous species, examples are not lacking 

 which also exhibit the closest agreement with the surviving type. 

 It has been pointed out by more than one author that the number 

 of specific names applied to Jurassic Ginkgo leaves is excessive ; 

 palseobotanical writers have frequently overlooked the wide range 

 of variation exhibited by leaves on the same tree of a living 



1 Brongniart (81). 



2 Gardner (83), pi. EXT. 



