340 



BOTANICAL GAZETTE 



[NOVEMBER 



formation of the moraines and with the numerous societies of Populus 

 tremtiloideSj it is less open than either of the other pine formations of 

 the mountains. In some places the trees are separated by an average 

 interval of but a few decimeterS; which is usually the case in the 



Fig. 8. — ^Boulder Creek between Nederland and Eldora, approximate altitude 

 2490tn; in the canon bottom A Inns tenuijolia and Salix Nuttallii dominate; the 

 canon sides are clothed with a mixture of the Apinus flexilis, Pinus Murrayana, 

 Pseudotsuga-Picea, Picea-Abies, and Pinus scopulorum formation. 



younger groves. In the older forests there is ordinarily a greater 

 inter\^al between the trees. The normal abundance of the species in 

 a forest formation in a n _ 



F 



extensively as have the mountains of Boulder County is obviously 



determine 



But in comparison of apparently 



