117 



project slightly. Besides the guard-cells the epidermis of the 

 lower surface consists partly of small and partly of large cells ; 

 the latter, as it appears, function as a kind of aqueous tissue, 

 such as often occurs in the neighbourhood of vascular bundles. 

 According to LiDFORSs chlorophyll grains occur both in the upper 

 and in the lower epidermis. 



The palisade-cells occur in a single layer only, but are 

 long (about 80 fi], nearly as long as the spongy parenchyma, 

 and seen in longitudinal section to be placed somewhat obliquely, 

 especially in the neighbourhood of the vascular bundles. The 

 cells of the spongy parenchyma, which are but slightly branched, 

 are usually elongated parallel to the surface of the leaf. Large 

 intercellular spaces occur; in connection with the latter it may 

 be mentioned that the epidermis of the lower surface easily 

 separates from the spongy parenchyma, often forming unusually 

 large air-cavities. 



The stem. The epidermis and the cortex of the young 

 stem are similar to those of A. Uva-ursi. When the secondary 

 cortex arises, and the formation of cork begins at the boun- 

 dary between the primary and the secondary cortex, a layer, 

 which has already previously been distinctly differentiated, is 

 developed as a new epidermis which, as far as I can judge, 

 persists for a shorter or longer time (several years) (Fig. 28, 5). 

 But when once this new epidermis falls off it is not renewed, 

 and then the external investment of the stem is formed by 

 the cork-layer itself, which develops early (see Fig. 28,5) and 

 exhibits no points of interest. The annual rings in the woody 

 part resemble those in A. Uva-ursi] usually they are distinct, 

 with a more or less marked difference between the autumn and 

 spring wood, but sometimes these are somewhat indistinguishable. 

 Normally, vessels are formed in the spring wood and tracheids 

 in the autumn wood. 



I have not examined the roots. 



