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 I 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 Vegetationsforhold! 
that Cassiope tetragona and Rhododendron lapponicum are often 
found in places bare of snow, but only the former may be said 
to thrive well there. The other Zricacee 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 Ericace®, and, 
on the whole, the dwarf shrubs of mocrs 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 Warmine 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. 
