232 



WILLIAM S. COOPER 



importance. The flat above Lake Kinney is an excellent ex- 

 ample. The lower portion, overflowed, or so near the water 

 level as to be very wet, bears the wet-flat pioneers. The main 

 body of the flat, especially the western portion which has long 

 been free from overflow and which is decidedly above the level 

 of the flowing water, is covered by an almost continuous mat of 

 Dry as Drummondii, with very little else. This species forms 

 roughly circular patches which continually grow larger. In 

 many places these have grown into contiguity, while in others 



Fig. 7. Dry shingle flat at head of Lake Kinney. Dryas Drummondii commu- 

 nity invaded by Picea Engelmanni. 



areas of bare shingle separate them. Occasional specimens of 

 Arctostaphylos Uva-ursi and Juniperus sibirica grow with the 

 Dryas. Here the willow thicket stage is eliminated, and its 

 place is taken by a relatively xerophytic forest stage. This 

 subclimax community is characterized by the addition of Pinus 

 Murrayana and Betula papyrifera to the climax species (here 

 principally Picea Engelmanni and Pseudotsuga mucronata). All 

 these except Pseudotsuga are found as scattered invaders far 

 out in the area dominated by Dryas. Along the edge of the 



