396 



is nol, ill any essential deforce, stronger than that of llie pros- 

 Irate stem, only there is a lar^-^er amount of close-set puren- 

 ohynia, which becomes lii^^nitied aronnil the bundles durinj,' 

 fruit-setting ; also in the peduncle the pith and the cortex are 

 usually broken down; the subepidermal layer is placed close 

 to the epidermis. 



Fig. 40. Ra7i. hyperboreus. 



A, Transverse section of leaf (Thingvellir; ""/i). B, The epidermis of the upper surface 

 (Greenland; ^^li). C, The epidermis of the lower surface (Spitzbergen; ^•''*/i). D, Surface 

 section of palisade-cells (Greenland; '^"k). E, Surface section of spongy parenchyma 



(Greenland; 33'Vi). 



The leaf is glabrous; the thickness varies from 180 to 

 210 n. The cells of the epidermis have undulating anticlinal 

 walls, those of the upper surface often somewhat more so than 

 those of the lower; chlorophyll is present. The stomata are 

 on a level with the surface; they vary greatly in number, but 

 are always most numerous upon the upper side. In specimens 

 from Nidluitsukøen and Gåseøen (Spitzbergen) they were almost 



