XL] 



ERETMOPHYLLUM 



59 





E. pubescens Thorn.,, the leaf is from 7 to 10 cm. long and 1 -3 cm. 

 broad ; the apex is rounded or retuse (fig. 658, B), the base tapering 

 gradually towards the petiole. Veins 1 1-5 mm. apart, dicho- 

 tomously branched in the proximal part of the lamina and usually 

 parallel and simple except where they converge at the apex. The 

 epidermal cells (preserved in the Yorkshire species) are polygonal, 

 with or without papillae (fig. 658, D) ; the stomata are characterised 

 by an enclosing group of subsidiary cells as in Ginkgo. 



Eretmophyllum pubescens Thomas. 



Secretory tracts occur between the veins of the smooth lamina 

 (fig. 658, C) like those in the leaves 

 of Ginkgo. The polygonal cells with 

 straight or slightly undulate walls 

 are characterised by papillae (fig. 

 658, JD), one on each cell : these 

 are particularly conspicuous on the 

 lower epidermis to which the sto- 

 mata are confined; the slightly 

 depressed stomata are in regular 

 rows and the guard-cells are sur- 

 rounded by 4 7 subsidiary cells. 

 In another species, E. ivhitbiense 

 from Whitby, the surface of the 

 lamina, which maybe 7cm. long and 

 1-2 cm. broad and slightly falcate, 

 rs rough, and between the veins 

 are strands of elongated cells, pos- 

 sibly denoting the presence of hypo- 

 dermal stereome. Stomata occur 

 on both surfaces and the papillae 

 are confined to the subsidiary cells. - 



A leaf figured by Ettingshausen 1 

 from Wealden rocks as Cyclopteris 

 squamata, which Schenk 2 suggests may be a segment of a Gink- 

 goites, should probably be included in Ervtmophyllum. 



FIG. 658. 



A. Eretmophyllum saigha- 

 nense. B D, E. pubescens. D, 

 epidermal cells. (A, after Seward ; 

 B D, after Thomas.) 



1 Ettingshausen (52) PL iv. fig. 1. 



2 Schenk (71) B. p. 213. 



