104 NORTH AMERICA 



The forests on the Pacific side of the Rocky Moun- 

 tains afford but a ragged mantle : in the Alaskan region 

 the thin groves of spruce are limited to the secluded 

 southern valleys : in British Columbia the stunted form 

 of the Murray pine predominates in thin woodlands ; but 

 on the upper reaches of the Columbia River the moist 

 winds penetrate farther inland, and with them, some of 

 the western types, the Douglas and the yellow pine 

 among them, extend to the Pacific slopes of the Rockies. 



Further south the mountains assume a decidedly park- 

 like appearance, with forests in patches, or large copses 

 on the naked slopes. They are clear and open, without 

 undergrowth, and confine themselves more and more to 

 the canons and the higher altitudes. Towards the head- 

 waters of the Colorado River, and south of them, sufficient 

 moisture from clouds, rains and snow is restricted to 

 a belt of 2,000 or 3,000 feet at an elevation of 9,000 to 

 10,000 feet, giving thin forests on the upper slopes which, 

 with the pastures of the lofty plateaus, form here 

 a veritable park region of some luxuriance, far above the 

 adjacent arid lands. 



Probably because it remains too low, the Wasatch 

 branch of the eastern mountain system is still more 

 barren, and displays only a stunted and loose type of 

 woodland on its rocky slopes. The close forests of the 

 north, favoured not so much by rainfall as by the layers 

 of snow which soak the ground in winter, do not recur 

 until the edge of the Colorado plateau, the higher mesas 

 such as the Mogollon, or the higher peaks such as the 

 San Francisco, are reached. Here, above a belt of dwarf- 

 pine and juniper or pifion rises, from 8,500 to 12,000 feet, 

 the high forest which is arranged, in order of increasing 

 altitudes and precipitations, into the three zones of pine, 

 fir, and spruce. 



