OF LOWEK GREENSAND PLANTS. 



327 



are entirely absent, but there are several kinda of cells unrepre- 

 sented in the pith ; among them are thick-walled stone-cells, 

 and groups and isolated cells with very dark contents which 

 look as if they had contained mucilage, though they are not 

 particularly elongated. 



Text-fig. 110. Colymbetes Edwardsi, sp. nov. A series of photographs of 

 the same leaf-traces in their passage outwards through the wood-rings. 

 A, in the periinedullary wood-zone ; B, in the first wood-ring ; 0, in 

 the second vertically running wood-ring ; D, in the fourth wood-zone, 

 i. e. the second horizontally running wood-ring. X 2. No. V. 6132 g-k. 



In some of the tangential sections of the trunk, which show 

 the leaf-traces in transverse section, the xvlem-elemerits can be 



