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1907] 



YOUNG— FOREST FORMATIONS OF COLORADO 



327 



and the summit of the range being 25 '^^ in 1904. The rainfall at 

 the base of the mountains occurs mainly in April and May, but in 

 the higher mountains it is distributed through spring and summer. 



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Fig. 3.— a mountain "park" on Boulder Creek, 35*="^ west of Boulder; in the 

 foreground are a few Pinus Murrayana and Pinus scopuloriim; in the middle fore- 

 ground 13 the upper extension of the Populus angustifoIia-Salix NuttaUii formation 

 intermingled with Populus tremuloides and Piceas; to the right is an aspen grove; 

 on the mountain in the background is a burned area in Pseudotsuga and Pinus Mur- 

 rayana timber, in the lower part of which are a few aspen groves. 



The heavy snows of winter, packed in the ravines by the high winds, 

 do not melt until late in summer and are the principal source of water 

 for irrigation. 



