208 



BOTANICAL GAZETTE 



[SEPTEMBER 



Here is a most interesting tension line between the flora of the arid 

 southwest and the more humid north. 



The association descends in some places to 7000 ft., and extends 

 to the top of the range at 10,000 ft., and coincides very closely with 

 the region of deep winter snow. On the western slope its aspect 

 is somewhat different from that of the eastern slope. On the 



Fig. 4. — View toward the south in the Sandia Mountains (about 8500 ft.) m 

 the yellow pine association: in the foreground the oak chaparral (Quercus sp. and 

 Robinia neo-mexicana) and yellow pine, and to left of center a Douglas spruce; in the 

 distance, covering a north-facing slope, is the Douglas spruce association. 



former it reaches its best development in amphitheater-like 

 U-shaped valleys, which collect the winter snow and practically 

 protect the trees from the drying winds and sun of summer. These 

 areas I have called "pine parks." On the east slope, with its 

 greater precipitation, the forests are more extensive and possess a 

 flora which reminds one very forcibly of that of the pine forests of 

 Kentucky, especially where there has been a fire. The dominant 



