395 



Arctic North America with the Archipelago, Labrador, the Rocky 

 Mountains, Arctic Siberia, the Himalayas, Arctic Russia, Nova 

 Zembla, Spitzbergen, Northern Scandinavia, Iceland (SimmonsI. 



Anatomy. The epidermis of the roots is thin-walled 

 and the walls are collapsed ; the exodermis has undulating 

 radial walls ; both layers are suberized. The cortex is almost 

 entirely broken down even in roots picked during the early 

 part of summer, only a few layers remaining within the exoder- 

 mis and around the suberized, thin-walled endodermis. The 

 central cylinder is 

 diarch. Root-hairs 

 are present but few- 

 in number; 1 have 

 not found mycorrhiza. 



The stem is 

 rounded and smooth, 

 the cuticle is slightly 

 striped, and the outer 

 walls of the epider- 

 mal cells are thin ; 

 the stomata are on a 

 level with the surface 

 or project slightly; 

 the epidermis con- 

 tains chlorophyll. Anatomically the stem may be divided into 

 two parts, viz. the nodes which have the usual structure of 

 the rhizome (see R. lapponicus p. 401) and the internodes. 

 The latter are exceedingly loose in structure with large inter- 

 cellular spaces; the greater part of the cortex and the pith is 

 broken down at an early stage (Fig. 39), but the extent of 

 disorganisation is no doubt somewhat dependent upon the 

 locality. The 2 — 4 bundles are either quite devoid of stereom 

 or else they have fibrous tissue outside the leptome consisting 

 of some weak strands of bast. The structure of the peduncle 



Fig. 39. Ban. hyperhoreus. 



Transverse section of Uie prostrate stem (Uperniviarsuk. 

 ph. Leptome ;^a-, xylem; I, lacuna." 



