PLANT COMMUNITIES OF SANDY SOIL 



317 



lar'oi inermis, Sambucus microbotrys, Acer glabrum, Amelanohier 

 polycarpa, Rosa bourgeauiana. 



Symphoricarpos vaccinoides (fig. 2) may be taken as the most 

 characteristic of the shrubs. It is not confined to the sand but 

 occurs sparingly and as small individuals up and down the canyon, 

 growing in loose disintegrated granite. In sand it is much more 

 luxuriant, forming large clumps commonly 1 to 3 meters across. 

 If two or more of these clumps fuse a single elliptical or otherwise 

 elongated growth results, sometimes 5 or 6 meters long. The 

 plant is able to exist in highly unstable soil. If covered, not too 



Fig. 2. Symphoricarpos vaccinoides growing in loose sand north of Georgetown, 

 Colorado, in Clear Creek Canyon. The absence of other vegetation is apparent. 



rapidly, it grows up through the sand. It also holds its place 

 when the sand around it has been blown or washed away. In this 

 manner mounds may develop 1 or 2 meters high which persist 

 for a long time. The stems of this species are weak and soon 

 bend over, making the plant well suited to sandy soil. The 

 leaves, as in the case of many members of the genus, are subject 

 to great variation in form. Blooming takes place the first or 

 second week of July. 



Rhus trilobata, the well-known "skunk bush" of the mountain- 

 front area reaches here its upper altitudinal limit. In appear- 



"A 

 TO 



ox* 



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