12 



than polygonal; the walls are wavy and rather heavily cuticu- 

 larised. 



Although Ginkgo has not heretofore been recorded from 

 South America, the allied Mesozoic genus Baiera has on several 

 occasions, as by Kurtz from the Rhaetic of Mendoza and by 

 Halle from the Lower Cretaceous of the Lago San Martin re- 

 gion. As has been frequently pointed out, and as Halle remarks 

 in discussing the latter, the distinction between the leaves of 

 Baiera and those of Ginkgo is very vague and a considerable 

 number of forms have been described which could be referred 



Sketch of three specimens traced from photographs. X 



to either. In general Baiera has a shorter petiole, a narrower 

 base and a more dissected lamina and is unknown in post 

 Mesozoic time. On the other hand the leaves of the existing 

 Ginkgo biloba in what has been called localized situations, such 

 as in proximity to fruits, on shoots from the trunk or old 

 branches, etc., are frequently as dissected as the present Pata- 

 gonian species, or a number of Mesozoic forms that have been 

 referred to Baiera. I know of no consistent features that can be 

 applied to these intermediate forms, but since the present spe- 

 cies comes from the latter half of the Tertiary I feel sure that it 

 should be referred to Ginkgo rather than to Baiera, although it 

 is just to remark that there would be little difficulty in deriving 

 it from the Lower Cretaceous form from South America which 

 Halle calls Baiera cf. australis M'Coy. 1 



