348 



per sq. mm. upon the upper surface and 28 per sq. mm. upon 

 the lower surface; my computations gave 100 and 33; in the 

 Wpine R. glacialis Wagner found the numbers to be 163 and 54. 

 At the apex of each leaf-lobe there is a hydathode with 

 its opening in a small depression almost at the apex of the 

 lobe (Fig. 8, C). The cells of the epithema nearest to the 

 tracheids are somewhat elongated and have undulating walls, 

 towards the apex of the leaf they become shorter, but are un- 

 dulating there also. 



Fig. 8. R. glacialis. 



A, Epidermis of the iipper surface of the leaf (Tromsö). В. Epidermis of the lower sur- 

 face of the leaf (Tromsö). С, Longitudinal section of leaf-apex, the cross-hatched part is 

 the epithema; o, upper surface; u, lower surface; w, stands opposite to the hollow in 

 which the water-pore occurs (Tromsö). D, Stoma from the lower surface of the leaf 

 (Knudshø). {A, B, wo/i; C, «/i; D, 220/1). 



In the epidermis of both the upper and lower surface 

 sphaero-crystals of different forms occur. 



The stalks of the basal leaves are almost round. The 

 epidermis is more thin-walled than that of the stem, and 

 contains chlorophyll. The structure of the cortex and pith is 

 like that of those of the stem, only the lacunae are even larger. 

 There are about four vascular bundles without accompanying 

 stereom. In the middle of the stalk there is a lacuna of 

 larger or smaller size. 



