130 



in localities which are identical when viewed from a physio- 

 logical point of view. 



Lastly the species within each morphological type should 

 be compared with each other. Quite a distinct matter is the 

 mutual comparison of the types, but into this I shall not enter 

 in the present summary. 



In regard to the localities in which occur the species with 

 which we are here dealing, I have not any exhaustive know- 

 ledge of their nature, but [ feel able to state that on the whole 

 it is scarcely possible that any differences of importance can 

 exist. With respect to all the evergreen forms, the winter and 

 early spring is the time which decides the degree of protection 

 needed against excessive transpiration, but during winter and early 

 spring the nature of the localities is hardly of any consequence, 

 the soil in all cases being entirely frozen; but possibly a more 

 or less thick covering of snow may be of importance. 



Hartz writes in Östgrönlands Vegetation sfo rhold ^ 

 that Cassiope tetragona and BJiododendron lapponiciim are often 

 found in places bare of snow, but only the former may be said 

 to thrive well there. The other Ericaceœ he mentions in the 

 paper in question appear mostly to be covered by snow. It is 

 doubtless customary for all of them to be, as a rule, covered 

 by snow. But if it be now customary for the Ericaceœ, and, 

 on the whole, the dwarf shrubs of moors and rocky flats, to 

 be covered by snow during winter, we may ask of what im- 

 portance are the xerophytic structures. In regard to this I 

 shall first refer to what Warming says in Grönlands Vege- 

 tation. He writes (p. 121) that "it now and then may happen, 

 and happens everywhere in the Polar regions, that large areas 

 remain bare of snow all through the winter or are very early 

 laid bare of snow, consequently, it is evident that it is espe- 

 cially those leaves that live more than a year that must be 



1 Meddelelser om Grönland, Vol. 18, p. 182. 



