

XLl] CZEKANOWSKIA 63 



Pines. The dichotomous branching of the lamina in some forms 

 is another feature in which Czekanowskia resembles Baiera and 

 Ginkgo, a resemblance which derives a certain significance from 

 the occurrence of stomata of the Ginkgoaceous type. Nathorst 1 

 has described the cuticular membranes of the superficial layers: 

 the epidermal cells have straight walls and the stomata, more 

 numerous on the lower surface, are accompanied by four or five 

 subsidiary cells : these do not form a circular group as in Baiera 

 and Ginkgoites, but, as the result of elongation in the direction of 

 the long axis of the leaf, the group is relatively long and narrow. 

 Cuticular preparations can often be made from the well-preserved 

 leaves that occur in great abundance in the shales of Gristhorpe 

 Bay and elsewhere on the Yorkshire coast 2 , and some particularly 

 good examples were collected by Prof. Obrutschew from Jurassic 

 rocks in the Djair Mountains in Chinese Dzungaria 3 ; these occur 

 with carbonised remains of Ginkgoites leaves in papery masses 

 similar in the manner of preservation to the Palaeozoic paper 

 coal from Russia 4 . The epidermal cells of the Dzungaria Czek- 

 anowskia, possibly idt ntical with C. rigida but too incomplete to be 

 determined with certainty, have straight walls and are relatively 

 long ; the stomata are scattered and appear as dark patches, their 

 darker colour being due to the thick cuticles of the two or three 

 flanking cells on the sides of the stoma ; the epidermal features are 

 similar to those described by Nathorst 5 , but in the Rhaetic specimens 

 from Scania the heavily cuticularised accessory cells are generally 

 more numerous. 



It has been suggested by Jeffrey 6 that Czekanoivskia may be 

 Araucarian in its affinities, but this opinion rests on the slender 

 evidence of association of Czekanowskia-like leaves in Middle 

 Cretaceous rocks with a stem described as Araucariopitys so 

 named because of the association of Araucarian and Abietineous 

 features. Such evidence of affinity as we have would seem to be 

 in favour of relationship with Baiera and Ginkgo though decisive 

 data are not as yet available. The genus is very widely spread in 



1 Nathorst (06) ; see also Seward (00) B. p. 278. 



2 Seward (00) B. p. 278, fig. 48. 3 Seward (11) p. 49, Pis. iv., v.. vi., vn. 

 4 Vol. i. p. 68. 5 Nathorst (06). 



6 Jeffrey (07) ; Hollick and Jeffrey (09) B. p. 63, PI. vi. figs. 13. 



