131 
protected against excessive transpiration.” Korverup Rosexvince 
writes in Det sydlige Grönlands Vegetation’ “The strong 
winds prevailing in the mountains (Föhnen) will be especially 
dangerous to plants during winter when it either melts the 
snow or causes it to evaporate largely.” The fact that the plants 
are thus casually laid bare during winter, as also the melting 
of the snow in early spring, are both doubtless very dangerous, 
and sufficiently account for the formation of organs that tend 
to check transpiration. In accordance with this, Linrorss writes 
in his paper on the evergreen flora (1907) that it is especially 
the frozen soil during spring that is of importance in the 
above-mentioned respect. The spring is doubtless otherwise a 
very damp season in the Arctic regions. Thus the snow- 
covering hardly plays any prominent part in regard to those 
structures of the Æricaceæ which we are here considering. 
With regard to the two above-mentioned species, Rhodod. lapp. 
and Cassiope tetragona, we are probably not justified in con- 
necting the fact of their occurrence in exposed localities with 
their structure except that such occurrence is due to the fact 
of their structure being especially xerophytic. It should be 
remembered that they occur also in less exposed localities, and 
strictly speaking, most frequently there. On the whole, there 
is hardly any particular feature in the nature of the habitats of 
the Éricaceæ with which we are here dealing, which should 
cause the appearance of different degrees in the adaptations for 
withstanding drought. With regard to light they all stand on 
an equality as far as | can see. 
The species belonging to the deciduous group, which may 
come into consideration in this connection (strictly speaking 
only Vaccinium uliginosum and Arctostaphylos, as Vacc. Myr- 
tillus is not quite Arctic) are doubtless similarly situated as 
regards the external conditions. 
1 Meddelelser om Grönland, Vol. 15, p. 108. 
9* 
