236 WILLIAM S. COOPER 



Difference in size of soil particles, expressing itself in difference 

 in water retaining capacity, to the advantage of the moraine, 

 seems to be at least a part of the explanation. 



The effect upon the succession, of destruction wrought by 

 drainage changes is well shown in parts of this flat which have 

 not enjoyed the protection of the terminal moraine. Both 

 erosion and deposition take place, and both are destructive. 

 In one place a layer of cobbles a foot deep had been deposited 

 upon the old pre-morainal surface, and a torrent had recently 

 cut through the superficial layer and into the older substratum, 

 resulting in total destruction of the vegetation in the area affected 

 by the torrent. In the cut bank exposed. by the stream it was 

 shown that partial burial of the woody vegetation does not 

 necessarily destroy it. Willow shrubs were traced to their 

 point of origin in the humus filled upper layer of the pre-morainal 

 deposit. The portions of the stems surrounded by the super- 

 ficial coarse deposit had produced abundant adventitious roots, 

 and the shrubs were in flourishing condition. Stretches of 

 willow thicket with scattered spruces were seen, the bases buried 

 under coarse shingle, but growing vigorously. In such places 

 the development of ground co^'er must begin again with the 

 dry shingle pioneers. Owing to a recent drainage change, the 

 main outlet of the glacier is now rapidly destroying a large area 

 of shingle flat forest, leaving in its place an expanse of cobbles. 

 Such a habitat offers the very worst conditions for the establish- 

 ment of vegetation, and the succession upon it will be an ex- 

 ceedingly slow one. 



5. Secondary Successions 



Under this heading I am able merely to state that the region 

 offers excellent opportunities for the study of Burn and Ava- 

 lanche Successions, the latter being specially well shown upon the 

 slopes surrounding Lake Kinney. 



