50 GINKGO ALES [CH. 



with B. gracilis but is distinguished by the smaller dimensions. 

 The imperfect example shown in fig. 641, B from the Kimeridge 

 beds of Sutherland (Scotland) 1 illustrates the unsatisfactory char- 

 acters on which specific distinctions are drawn in the case of 

 Baiera leaves agreeing in habit with B. gracilis. Better examples 

 are figured by Schenk 2 from the Wealden of North Germany. 



Baiera spetsbergensis Nathorst. 



This species, one of the smallest representatives of the genus, 

 is described by Nathorst 3 from Upper Jurassic rocks of Spitz - 

 bergen ; it is characterised by the very narrow but apparently 

 cylindrical segments and, except in its smaller size, resembles 

 B. Lindleyana. 



iii. FLOWERS AND SEEDS. 



Our knowledge of seeds assigned to Mesozoic and Tertiary 

 representatives of Ginkgo or to Baiera is limited to casts and 

 impressions of detached examples: no reproductive organs have 

 been discovered either in a petrified state or in connexion with a 

 foliar shoot. Reference has already been made to some small 

 Ginkgo-like seeds from the Eocene beds of Sheppey described by 

 Gardner as Ginkgo ? eocenica. Many similar seeds are figured by 

 Heer from Jurassic strata in Siberia and elsewhere, in most cases 

 as detached seeds but in a few instances borne singly or in pairs 

 on an axis resembling the peduncle of Ginkgo biloba*. Heer's 

 seeds are correlated with G. digitata, G. sibirica and other species 

 but only on evidence afforded by association with leaves; they 

 are preserved as oval nuts, sometimes enclosed in a carbonaceous 

 envelope possibly representing an outer flesh, and resemble Ginkgo 

 seeds in shape though they differ from them in their smaller 

 size (8 9 mm. long and 6 8 mm. in diameter) : in some of the 

 Jurassic specimens the nuts have an apical beak. All that can 

 be said is that seeds similar except in their smaller size to those 

 of the recent species are not infrequently found in association 

 with different species of Ginkgoites. 



1 Seward (II 2 ) p. 680. 



2 Schenk (71) B. p. 224, PL m. figs. 914. 



3 Nathorst (97) p. 53, PI. m. figs. 612. 



4 Heer (82) ii. A. p. 16, Pis. iv , v; (77) ii. p. 57, PI. xi. 



