371 



of the basal leaves and that of the stem-leaves. The outer 

 walls of the epidermal cells are slightly thickened ; the radial 

 walls are somewhat undulating and almost alike in the epidermis 

 of both surfaces (Fig. 22,0, /)); but above the larger bundles 



Fig. 22. R. sulphureus. 



A, Transverse section of leaf (Storesby Sound). B, Stoma from the upper surface of 

 the leaf. C, Epidermis of the upper surface of the leaf. D, Epidermis of the lower sur- 

 face of the leaf. E, Surface section of uppermost palisade-layer. F, Surface section of 

 spongy parenchyma (B, C, D, E, F are from Spitzbergen; A, C, D, E, F, """/i; B, ^^li). 



the epidermal cells are nearly straight-walled and are elongated 

 parallel with the bundles. The epidermis contains chlorophyll, 

 and sphæro-crystals are found in many cells. The stomata are 

 either on a level with the surface or project slightly, and here 



