Scrophulariaceae. 419 



Stomata occiir on both leaf-surfaces, but they are more 

 numerous on the lower surface; the proportion between the 

 number of stomata on both surfaces proved to be about 1 

 to 2. On the upper surface the lateral walls of the epidermal 

 cells are slightly porose, especially near stomata; the guard- 

 cells are surrounded by 3 — 6 cells, and are on a level with 

 the surface, or project slightly (Fig. 18, A and B). 



The transverse section (Fig. 18, A and B) shows 1 — 3 

 palisade-layers. Both A and B were drawn from sections 

 of leaves taken from specimens from West Greenland, and 

 in both cases the leaves were chosen from the middle of the 

 stem. A is seen to be somewhat thicker than 5, and to have 

 an assimilatory tissue consisting of as many as 3 cell-layers, 

 the elements of this tissue are somewhat irregular and 

 some of them are slightly branched; B probably represents 

 the more common type. The transverse section of the leaves 

 of the Norwegian piants resembles, on the whole, the trans- 

 verse section shown in B, with the exception that the pali- 

 sade-cells are slightly higher. The spongy parenchyma con- 

 sists of rather copiously-branched cells. In the palisade- 

 tissue and spongy parenchyma chlorophyll-grains are pre- 

 sent in abundance. 



The leaves are rather densely covered with hairs; the 

 following types of hair occur: — 



(1) Non-glandular hairs, with one or many cells, thin- 

 walled, glabrous and pointed (Fig. 19, C and E); (2) Glan- 

 dular hairs with longer, two- or many-celled stalk and a 

 2—4 celled head (Fig. 19, A, B and D)- (3) Glandular hairs 

 with short, one-celled stalk and 2 or commonly 4-celled head 

 (Fig. 19, i^j; (4j Glandular hairs of the kind illustrated in 

 Fig. 19, G, H, I and K with a low somewhat sunken stalk- 

 cell, and a cupola-like extremely thin-walled 4-celled head. 



By comparision of the figures in question with Fig. 14' 



