247 



The stomata here also are placed very slightly above the 

 level of the leaf-surface ; they are most numerous outside the 

 veins (in the angles between the lobes), but are not entirely 

 absent from along their length. 



The mesophyll is exactly like that of S. ceniua. What has 

 been said above of the palisade-cells, spongy parenchyma and 

 veins of the latter species will apply without any alteration to the 



Fig. 3. Saxifraga rivularis. 



Л, (-11) Leaf-form. B, Upper epidermis. C, Transverse section of leaf. D, Longitudinal 



section of tip of same with hydathode. (5, C, and D ^'/i). 



present species also. The palisade-cells in this plant also are 

 oblique; Borgesen evidently did not observe this feature, neither 

 does he describe the hydathodes; the latter are exactly like 

 those of S. cernua. It is extremely interesting to note how 

 the modes of life of these two closely-allied species are reflected, 

 with such close correspondence, in the anatomical structure of 

 their leaves. 



The material upon which the description here given is based, 

 comes from the following localities: — Jan Mayen (July 22, 



