78 



GENERA OF tTNCERTAIN POSITION 



[CH. 



Permian of the Lower Tunguska on which Schmalhausen founded 

 his species Ginkgo integerrima^ ; the characteristic features are: 

 the transversely elongate form of the entire lamina, the spreading, 

 dichotomously branched, veins and the short and relatively broad 

 stalk-like basal portion of the lamina. As Zeiller^ says, this 

 species is probably identical with Ginkgo martensis^ from Permian 

 beds near Toulon-sur-Arroux (Saone-et-Loire) founded on a single 

 leaf 3 cm. broad and 1-6 cm. deep. Zeiller reproduces Renault's 

 figure in his volume on the flora of Blanzy and Creusot* and states 

 that the specimen could not be found : he retains the name Ginkgo 



Fio. 664. C, Ginlcgopsis Czdcanowskii. A, B, Nephropsis integerrima. (From the 

 originals of Schmalhausen's figures, supplied by Prof. Zalessky; nat. size.) 



but with the addition of a question-mark. The Permian leaves 

 differ from those of Ginkgo in the absence of marginal veins — though 

 this is of secondary importance — in the absence of a true petiole, 

 in the form of the lamina and, from the majority of recent Ginkgo 

 leaves, in the entire margin. The supposed leaves may be leaflets 

 of a compound frond or possibly bracts from some fertile shoot. 



^ Schmalhausen (79) A. p. 85, PI. xvi. figa. 12- 



2 Zeiller (96) A. p. 475. 



" Renault (88) p. 232, fig- 47 c. 



^ Zeiller (06) B. PI. XLvm. fig. 3. 



-15. 



