78 



GENERA OF UNCERTAIN POSITION 



[CH. 



Permian of the Lower Tunguska on which Schmalhausen founded 

 his species Ginkgo integerrima 1 ; 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 2 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 4 and states 

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



FIG. 664. C, Ginkgopsis Czekanowskii. 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. 



1 Schmalhausen (79) A. p. 85 r PL xvi. figs. 1215. 



2 Zeiller (96) A. p. 475. 



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



4 Zeiller (06) B. PI. XLVIH. fig. 3. 



