108 



in all Ändromeda-forms is more useful in that respect. Sto- 

 mata occur only on the lower surface ; they often project 

 slightly. The inner sides of the guard-cells, as also the neigh- 

 bouring cells of the epidermis are covered by cuticle. According 

 to LiDFORSs chlorophyll grains occur in the upper epidermis. 

 Palisade-cells occur in 2 — 3 layers about 30—40 /u \n height 



Fig. 23. Andromeda jjolifolia. 



The leaf. 6, shews the aqueous tissue and the thick-walled cells beneath the 1 

 vascular bundle in the middle of the leaf. (1—4, Greenland: Tiningnertok, 62" 20'. 

 •5. Denmark : Sjælland.) (H. E. P.) 



at the most, and slanting towards the apex. The spongy 

 parenchyma is of about the same thickness as is the palisade- 

 tissue and consists of non-branching cells which are usually 

 transversely elongated across the leaf, making the latter some- 

 what isolateral, which circumstance harmonizes with the often 

 somewhat erect position of the leaves. All the cells of the 

 mesophyll are somewhat thick-walled. Tannin occurs abundantly 



