12 Knud Jessen. 



had unfolded later in the summer. In the neighbourhood of 

 Copenhagen I found in spring numerous glands upon both sides 

 of the leaf (Fig. 2) and upon the leaf-stalk of Potentilla palu- 

 stris, but they were wanting later in the summer, probably 

 they had then fallen off. With the exception of a few speci- 

 mens, leaf-glands were entirely absent from the Greenland 

 plants which have been investigated. 



Fig. 3. Potentilla palustris. 



Transverse section of leaf from Ivigtut in South Greenland (-^"/i). 



The inner wall of the epidermis of the upper surface is highly 



mucilaginous. 



The under side usually presents a greyish blue colour; 

 this is perhaps due to a thin, granular covering of wax, which 

 must, in addition to the hairs, serve to prevent the under 

 side, which is rich in stomata, from getting wetted. 



Stomata may also be found on the upper side; they then 

 occur either singly or in groups (Fig. 4, C). The stomata are 

 sunken (Fig. 3). The upper side is slightly reticulated and 

 the outer wall of the stout epidermis is not specially thick, 

 about 2.5 /i; the inner wall is highly mucilaginous (Fig. 3). The 



