880 



paratively few species, and these are almost all piants of the moun- 

 tain or swamp. 



c. The snow-covering. In arctic regions, where the winter 

 is severe and enduiing, the presence or absence of snow is of the 

 upmost importance for vegetation. The mild winters of the Færoes 

 render a snow-covering less essential, but even here the plant co- 

 vered by snow possesses advantages over the unprotected one. The 

 snow not only serves to mitigate the alternations of frost and thaw, 



Fig. 165. Snow-clad landscape, Trang'isvaagfjord on Sydero. 

 (From photo. by O. Effersoe.) 



but it also prolects the piants from direct insolation during frost, 

 and from the dessicating effect of severe storms. 



As no information respecting the duration of the snow-covering 

 is to be found amongst the meteorologicai statistics, I prevailed on 

 Dr. Knud Poulsen to make as many observations on snow-cove- 

 ring as possible, during his sojourn of two winters in Thorshavn. 

 His notes are extensive, but I have no hesitation in quoting them 

 at full length, because they are valuable both from the purely me- 

 teorologicai and from the botanical point of view. 



The Winter 1901 — 1902. 



November 12th: the first snow fell, covering the mountains and 

 lowlands with a thin coating. 16th: Iowlands free from snow, the south- 

 sides of the mountains practically in the same condition. 17th: snow 

 again, covering every place witli a thin and equal coating. 20th: snow 

 gone everywhere. December 9th: a thin coat of snow every where. 

 lOlh: a thaw setting in. Uth and 12th: thaw; the lowlands snowless. 

 13th and 14th: a heavy fall of snow, the lowlands covered. 16th: the 

 lowlands almost free from snow. 17th: snow and wind. 18th: fall of 



