269 



their habitats. The fact of their occurring more commonly upon 

 the sunny side appears to suggest a predominant xerophytic 

 tendency. At any rate, the anatomy shows, although not very 

 decidedly, several xerophytic features (succulency, fairly well- 

 developed epidermis, narrow leaves, etc.). Bonnier (Ann. des 

 sciences nat., VII ser., ï. XX) has grown the species in Alpine 

 regions (1600 metres) and found the specimens grown there to 

 contain several palisade-layers more than are found in the 

 individuals from the lowlands, — probably a natural result of 

 the more intense light upon mountains. The Arctic specimens, 

 in that respect, resemble rather the lowland than the moun- 

 tain specimens. 



Saxifraga flagellaris Willd. (Figs. 19 and 20.) 



Saocifraga flagellaris Willd. There are too few data re- 

 garding the habitats of this species to enable me to form an 

 opinion concerning the extent of its adaptation. 



The lamina is almost oval and passes gradually into the 

 leaf-stalk. Large glandular hairs occur — along the margin, 

 one upon the leaf-apex itself, and a few scattered over the 

 upper surface (Fig. 19). 



The epidermis of the upper surface (Fig. 20) consists of cells 

 which have undulating walls; above the veins the cells are larger 

 and more straight-walled than outside them. The outer walls of 

 the cells are only fairly strongly developed, with distinct cuticle. 

 The stomata are placed slightly above the level of the leaf- 

 surface, are evenly distributed, and have their apertures parallel 

 with the longitudinal axis of the leaf. 



The epidermis of the low er surface (Fig. 1 9 B), along a very broad 

 longitudinal band down the middle, has less undulating walls 

 than upon the upper surface, and consists of longer cells. The 

 outer walls are somewhat thickened (Fig. 20 D). Along the margin 

 the epidermis, like that of the upper surface, has undulating 

 walls, with only few stomata. 



XXX VI. 18 



