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UNIVERSITY OF COLORADO STUDIES 



of plant growth to the topography and its various edaphic factors. 

 Furthermore, such a record of existing conditions can be used for com- 

 parison with other areas and in subsequent study of the same area. 

 The latter will be valuable in studying invasion or succession and in 

 finding out the effects of competition. 



Fig. 2. — Indian Currant. Symphoricarpos occidentalis Hook.— This plant forms 

 one of the prominent societies of the mesa. It reaches its greatest development on the 

 north slopes in moist places, especially in the ravines. Patches are frequent on the 

 expanses back from the streams in both gulches. (See Fig. 2, Plate I.) A few patches 

 occur on the upper part of the mesa top among the older pine trees. 



In discussing the distribution of the trees and shrubs of this area, 

 humidity, temperature, wind, light and pressure need not be taken into 

 consideration as being directly effective factors. Water content of the 

 soil seems to be the important factor determining their distribution. 



