NO. 3.] DESCRIPTION OF SPECIES. H 



CONIFER. 



GINKGO, Linne. 



The Ginkgo forms found here are among the most interesting remains 

 of the entire flora. Unfortunately, most of the leaves are but fragmentary, 

 so that it is difficult to determine with any certainty how many species really 

 occur. The occurrence of at least two species I consider fairly certain, prob- 

 ably the number is still larger in reality. 



Ginkgo polaris, Nathorst. 

 PL I. figs. 819 and (magnified) 51. 



Ginkgo polaris Nathorst, Nansen's 'Farthest North', London, vol. II. 

 p. 486, fig. 6. Tram over Polhavet', Christiania, vol. II. p. 520, fig. 6. 



This species is represented here with a perfect leaf (fig. 8) which has 

 already been figured and named in the short summary of fossil plants of 

 Franz Josef Land, included in Nansen's description of the Fram expedition 

 1893 96. The leaf has a truncated base, and, in the manner characteristic 

 of this genus, is repeatedly dichotomously divided into eight lobes, the apex 

 of which is rounded, or mostly somewhat truncated with a depression in the 

 middle. The petiole of the leaf is short and slender. The number of veins 

 in the lobes vary from five to ten. 



Of the other specimens included under the same species, those represented 

 in figs. 14, 15, and 17, differ by having a more wedge-shaped base, but it is 

 just possible that the two latter figures only present the one half of the leaf. 

 If the specimen fig. 8 be imagined as divided into two halves, the base of 

 each of the halves would also be wedge-shaped. On the other hand as re- 

 gards the specimen fig. 14, it is probably a young leaf which has not yet 

 undergone any further division. 



Of the species already described, Ginkgo polaris can especially be com- 

 pared with Ginkgo stbirica Heer and Ginkgo fldbellata Heer (Flora fossilis 

 arctica, vols. 4 & 5) from the Jurassic strata of East Siberia, without the 

 existence of any complete agreement with either. The leaves of the former 

 are larger, with a more powerful petiole, the lobes also being more rounded. 

 This is also the case with the lobes of Ginkgo flabellata, which moreover, 

 are narrower; the number of veins in the lobes being also fewer (according 

 to Heer but 35). 



