THE JURASSIC FLORA OF CAPE LISBURNE, ALASKA. 55 



Ginkgo digitata (Broiigiiiart) Heer. 



Plate VI, lii^ure o. part; Plate VII. figures 3-5. 



Ginkgo diffitata (Brongniart) Heer. Flora fossilis arctiea, vol 4, pt. 1, p. 40, PI. X. figs. 1, 5a, b, G, 1876. 

 Ginkgo huttoni (Sternberg) Heer, Fontaine, in Ward, U. S. Geol. Survey Mon. 48, p. 170, 1905, 

 Ginkgo huttoni magnifolia? Fontaine, idem, p, 170. PI. XLIV, figs. 7, 8, 

 Ginkgo multinervis Heer. Lesquereux, U. S, Nat. ilus. Proc, vol. 11, p, 31, PI. XVI, fig. G. 1888. 



Leaves of Ginkgo are abundant in the Cape Lisburne collections, and it was undoubtedly 

 a cou.spicuous element in this flora, as indeed it must have been in all the northern Jurassic 

 and early Cretaceous floras. In the Oregon collections, for instance, the genus is represented 

 literally by hundreds of specimens, and it was equally abundant throughout eastern Siberia. 



This genus has been very much overburdened, for in deahug with such an abundance 

 of specimens and multipHcity of forms one must needs make either many "species" to accom- 

 modate this diversity, or only one or two, and in view of the known variation exhibited by 

 the single livmg species, the latter plan seems preferable. As a consequence, all the Alaska 

 specimens are here considered as referable to the extremely variable Ginl-go digitata. 



The fii-st Ginkgo leaf known from Cape Lisburne — namely, that found in Woolfe's col- 

 lection — was identihed by Lesquereux as G. multinervis Heer, a species described from the 

 Cenomanian beds of Atane, Greenland. The same specunen was later referred by Fontaine 

 to (t. huttoni (Sternberg) Heer, but while the segments are cut nearly to the base, it does not 

 differ essentially from many referred to (r. digitata. 



The two rather fragmentary leaves from the Dumars collection Fontaine referi-ed with 

 a question to his G. huttoni magnifolia .^ named from the Jurassic of Douglas County, Oreg. 

 The validity of this variety will not be discussed at this time, and it is sufficient to say that 

 the two specimens from Cape Lisburne are here referred to G. digitata. 



I Fontaine, V.'. M., I". S. Ceol. Survey Mon. JS, p. 124, PI. XXXI, flgs. 4-8; PI. XXXII, figs. 1, 2, 1905. 



