378 



the (lilTerence, recorded by Simmons (I. c), in the direction of 

 the ri|)e stems in the two species in qnestion apparently can- 

 not lie explained hy the anatomical features. The pith was 

 broken down thronghonl the entire stems. 



The leaf is almost or (juite glabrous. The radial walls 



Fig 26. R. nivalis. 



A, Transverse section of leaf. B, Epidermis of ihe upper surface. C, Epidermis of the 



lower surface. D, Surface section of uppermost palisade-layer. E, Surface section of 



spongy parenchyma. (A, B, C, D, E are from Kaafjord, Norway; '^-Vi). 



of the epidermal cells of the upper surface are somewhat un- 

 dulating but less so than those of the lower surface (Fig. 26, 

 B, C). The stomata are on a level with the surface and occur 

 in greater numbers upon the lower surface. The relations 

 between the numbers upon the upper and lower surface is 

 somewhat uncertain; Borgesen (I.e. p. 229) found 4 and 11 



