XL] GINKGOITES 29 



polygonal with straight walls; the stomata are surrounded by 

 5 — 6 accessory cells as in Ginkgo biloba and they are confined to 

 the lower surface. Although there is practically no difEerence, 

 as regards form and venation, between this Wealden species and 

 some of the Jurassic leaves referred to G. digitata var. Huttoni the 

 distinctive specific name is retained for the reason already men- 

 tioned. 



Leaves of a very similar form are figured by Heer as Ginkgo 

 tnuUinervis^ (fig. 635, G), from Upper Cretaceous (Cenomanian) 

 beds of West Greenland, and Baiera arctica from the Kome beds 

 (Urgonian) of West Greenland^. 



The specimen from the Atane (Cenomanian) beds of Greenland 

 figured by Heer as Ginkgo primordialis^ appears to be an entire leaf 

 with a long petiole 2-5 mm. broad : the original inipression in the 

 Stockholm Museum, too incomplete to serve as the type of a species, 

 shows a very imperfect lamina and a long axis that has probably 

 no connexion with the leaf. 



Ginkgoites adiantoides (Unger). 



The Tertiary leaves on which this species was founded were in 

 the first instance described as Ginkgo biloba^ and, as several writers 

 have pointed out, so far as regards form and venation there is no 

 good reason for drawing a distinction between the fossils and the 

 leaves of the recent species. In a note published in 1913 Depape^ 

 definitely adopts the name Ginkgo biloba for Tertiary leaves which 

 he regards as specifically identical with Unger's species. In the 

 absence of any satisfactory evidence as to the nature of the repro- 

 ductive organs and in view of the considerable interval that 

 separates the Tertiary and recent plants, it is clearly inadvisable 

 to assume specific identity. In adopting the generic designation 

 Ginkgoites instead of Ginkgo I am foUo^ving the custom generally 

 recognised of distinguishing fossil forms by a special termination, 

 though there is no implication that all species so named are 

 generically distinct from the surviving type. In proposing the 



1 Heer (82) ii. B, p. 46, PI. vin. figs. 2 — 4 ; PI. ix. fig. 3 6. For an account of the 

 stratigraphy and maps of these plant-beds on the coasts of the Noursoak peninsula, 

 see Johnstrup (83) and White and Schuchert (98). 



2 Heer (75) ii. B. p. 37, PI. m. fig. 3. 



3 Heer (75) ii. B. p. 100, PI. xxvii. fig. 1. 



« See Gardner (86) p. 99, ^ Depape (13). 



