Primulaceae. 219 



lower surface of the leaves of many Primulas and which is 

 known to be a resinous substance secreted from the head 

 of the glandular hairs, is not met with, or only in a 

 very limited degree, in the Arctic species closely related to 

 Pr. farinosa (viz. Pr. egaliksensis, Pr. stricta and Pr. sibirica), 

 but Pr. farin. V. groenlandica may have the leaves "mealy" on 

 the lower surface, at least on vigorous specimens (Abromeit). 



The leaves of the Androsaces species are covered with 

 cover hairs, on the margins and the upper surface, those of 

 Androsaces sept, being short and branched, while on Andro- 

 saces chamaej. they are long, hyaline and simple. 



The lateral walls of the epidermal cells of Pr. nivalis 

 and Androsaces sept, are straight or nearly so on the upper 

 surface of the leaf ; on the lower surface, however, they are 

 undulating. The other Primiilae and also Dodecatheon frigi- 

 diim and Androsaces chamaej. have undulating lateral walls 

 on both surfaces of the leaf. Fine cuticular striations were 

 present on the outer walls of the cells of the genus Primula 

 and also in the case of Androsaces sept. 



Primula nivalis and Dodecatheon frigidum have stomates 

 only on the lower surface of the leaves, but the other spe- 

 cies are provided with stomates on both surfaces. Pr. 

 egaliksensis, Pr. sibirica, Pr. stricta, Pr. farin. v. groenl. and 

 Androsaces sept, have always by far the greater number on 

 the lower surface. In Androsaces chamaej. the number of 

 stomates on the upper and lower surfaces is almost the same, 

 but only where the leaves are crowded together in dense 

 rosettes, so that the stomates, on account of this, are mainly 

 situated towards the apex of each leaf; where the leaves are 

 arranged more favourably for development, as on the few- 

 leaved shoots, then the stomates are much more numerous 

 on the lower surface. 



The stomates are level with the surface of the leaf, at 

 times even somewhat raised above this. 



