58 



Knud Jessen. 



123/7 (Nunatsuk in Greenland), 154« (Gaaseland in Spitz- 

 bergen) and 174« (Botanic Garden in Copenhagen), and 

 the proportion between the thickness of the leaf and the 

 thickness of the palisade tissue was 



^2 



i ' 



and ¥ 



respec- 



tively. The palisade parenchyma consists of 2 — 3 layers of cells. 



Fig. 22. Sibbaldia procumbens. 



A, Transverse section of leaf; B, glandular hair from the upper surface of a leaf: C, epi- 

 dermal cell from the upper surface of the leaf with mucilaginous inner wall ; D, air-cavity 

 below a stoma upon the upper surface of the leaf produced in part by the formation of 

 a 'Trichtercelle" (cf. text). E, Epidermis of the upper surface of the leaf; F, epider- 

 mis of the lower surface of the leaf, and G, section of spongy parenchyma. A, B, C, D, E, 

 F and G 275 /i. A, D from Nunatsuk in Greenland, C from Godhavn in Greenland, D, E, 

 F, G Gaaseland in Spitzbergen. 



Below the stomata there is a large air-cavity which is 

 formed either by the surrounding palisade-cells separating from 

 each other at their upper ends, or by the adjacent cells taper- 

 ing in the form of a funnel to the outside (Fig. 22, D). Sibbaldia 

 procumbens may consequently be placed side by side with 

 those specimens which Rywosch 1 mentions in support of his 



1 Beitr. zur Anat. d. Chlorophyllgewebes, Zeitschr. f. Bot., 1912. 



