144 IP s t e I s i a 



toria is common in certain peculiar situations. 

 These are the trees which can flourish with the 

 lowest summer temperatures provided that the 

 season of growth is sufficiently long. It is not- 

 able that the three principal species of this for- 

 mation all extend far north along the Alaska 

 coast, and the spruce and hemlock are the last 

 trees to disappear in that direction. The final 

 limit of the forest in the vicinity of Kadiak island 

 seems to be due to the lack of a sufficiently long 

 season of growth, rather than to the winter cold 

 which is not severe. 



The Douglas fir, on the other hand, is es- 

 sentially a tree which needs considerable summer 

 heat, though it will withstand more severe win- 

 ters than the spruce. It is not found anywhere 

 in Alaska, and although it is very abundant in 

 the interior of \'ancouver Island and even on the 

 mountains overlooking the west coast, it does not 

 flourish on the lowlands close to the ocean and 

 the occasional specimens which occur there are 

 small, and oft'er a marked contrast to those which 

 have developed in the more favorable climate of 

 the interior. 



