18 



GINKGOALES 



[CH. 



veins spread from the base of the lamina, the veins in the middle 

 of the leaf being generally about 0-8—1 mm. apart. 



The stomata are practically confined to the lower surface of 

 the lamina. The epidermal cells are polygonal and the walls 

 slightly sinuous as in the recent species, and over the veins the 

 cells are longer and narrower (fig. 636, A). Many of the larger 

 epidermal cells have a cuticular ridge in the middle of the outer 

 wall, represented in the figure by a black line. The stomata agree 

 closely with those of Ginkgo biloba ; the two guard-cells are sur- 

 rounded by a group of subsidiary cells characterised by their 



Fig. 636. Ginkgoites digilata; epidermal cells (A) and stoma (B). 

 C. Stoma of Ginkgo biloba in two planes. (A, B, drawn by Miss N. Bancroft.) 



papillose heavil)' cuticularised walls overarching the stoma (fig. 

 636, B). The features shown in fig. 636 are not brought out in 

 drawings from cuticles of the same specimen reproduced by Dr 

 Stopes^ in her account of fossil plants from Brora : this may be 

 due in part to a difference in the level at which the stomata were 

 drawn. The stoma of Ginkgo biloba represented in fig. 636, C 

 illustrates the considerable difference produced by viewing a stoma 

 in shghtly different planes^. 



No seeds have been found attached to stems bearing leaves of 

 G. digitata, but seeds closely resembUng those of the recent species 



1 Stopes (07) p. 380. - Seward (11) p. 47, PI. v. fig. 62. 



