178 



The Plant World. 



cripples. Just how the snow thus acts so unfavorably can per- 

 haps be partially answered as follows: 



(a) During the prolonged melting period, the wet snow 

 may, so to speak, drown the buried branches by preventing 

 aeration and at the same time promoting the attacks of fungi. 

 This hypothesis is rather strongly supported by the universal 

 presence of fungus mycelia on the portion of the branch 



Fig. 3. Scene in a Selkirk forest. June 20, 1907. Altitude about 1,900 meters. 



which has been held under snow. Mention and figure 



of similar damage due to a species of Herpotrichia are 

 given by Schroeter. Griesch* describes very aptly the 

 relation between Herpotrichia and individual trees at timber 

 line. 



(b) Direct mechanical injury. The weight of the snow 

 and its creeping motion on steep slopes at melting time is re- 

 sponsible no doubt for the bent forms of little trees and the bare 

 and abraded hillward sides which so manv trunks show 



*Grieseh. Andr. Beitrage zur Kenntniss der Pflanzengeographische Verhaeltnisse 

 der Berguenerstoecke Beih. Bd XXII, Heft 3, Sept., 1907., p. 300. 



