131 



protected against excessive transpiration." Koldercp Rosenvinge 

 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, Lidforss 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 Ericacece which we are here considering. 

 With regard to the two above-mentioned species, Bhodod. 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 Ericacece 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 I 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- 

 tilius is not quite Arctic) are doubtless similarly situated as 

 regards the external conditions. 



^ Meddelelser om Grönland, Vol. lô, p. 108. 



