THE NORTH TEMPERATE ZONE 85 



covered with forest, in which deciduous trees predominated. Many 

 of these, like the white and red oaks, elm, walnut, and others are 

 found practically throughout this whole region. 



In the western sections of this area the rainfall is less, and there 

 occur expanses of open grass-land or prairies, more or less inter- 

 mingled with patches of forest. Still further west the true prairie 

 formation prevails. 



In Canada and the northeast and central states, e. g., Michigan, 

 Wisconsin and Minnesota, are regions of extensive glaciation, 

 abounding in lakes and peat bogs. This is a transition region 

 between the sub-arctic and the true temperate zone, and has many 

 sub-arctic species, and the forest is composed to a considerable 

 extent of conifers. 



West of the Mississippi is a region of treeless plains — prairies 

 with close turf in the east, merging by degrees into the drier 

 prairies and steppes of the regions adjoining the Rocky Moun- 

 tains. Trees are for the most part confined to the banks of streams, 

 or the bottoms of gullies worn down by the streams. 



The western third of North America is verv different from the 

 east. It is a region of lofty mountains and elevated plateaus. 

 The main range of the Rocky Mountains, extending from New 

 Mexico into northwest Canada, has elevations of over 14,000 

 feet, and between this and the great Pacific Cordillera are exten- 

 sive elevated plateaus, and secondary mountain systems. Much 

 of this plateau region is arid, and may be a true desert, as in the 

 vicinity of the Great Salt Lake, and portions of Nevada and 

 eastern Washington. 



Extending the whole length of the continent, parallel with the 

 Pacific Coast, is the great Cordillera which with few breaks, 

 stretches from Alaska to Patagonia, and sharply sets off the coastal 

 region of the Pacific from the rest of the continent. 



The whole of the great mountain region from the Rockies to 

 the Pacific, is very different climatically and floristically from 

 Atlantic North America, and here alone are the mountains high 

 enough to have perpetual snow, and to develop a true alpine 

 flora. Especially on the majestic snow-clad cones of the great 

 volcanic peaks, Shasta, Hood, Tacoma, are these conditions 

 especially favorable. 



In southern California, Arizona and New Mexico, there are 



