8 



1208. 



and desert gums may be used also in the drier regions. With ample irrigation 

 the evergreens suggested for region 2 should succeed. 



Region 6. 



Region 6 is the intermountain section, extending from the crest of the Cascade 

 and Sierra Nevada Mountains eastward to the eastern base of the Rocky Moun- 

 tains. The region includes great variations in growing conditions, often in very 

 short distances. As a whole it is semiarid, and in most places trees can hardly be 

 expected to thrive without irrigation, although in some of the mountain valleys 

 and on some of the mountain slopes almost ideal conditions for tree growth 

 exist. 



In the drier parts of the region only those deciduous trees that are weeds 

 under more congenial conditions can be grown. Those that can be planted with 



FIG. 4. Outline map of the United States, showing the regions within which essentially 

 similar conditions for tree growth exist. 



the greatest hope of success are the thornless honey locust, black locust, green 

 ash, hackberry, and where the others do not succeed, the poplars and ash- 

 leaved maple. If it can be watered for a few years the American elm usually 

 can be grown, and in the southern half of the region the Mississippi hack- 

 berry will probably succeed. Near the southern border, on lower elevations, 

 the chinaberry and Texas umbrella can also be planted. In the locations most 

 favored naturally or where irrigation is possible, the trees suggested for region 

 9 can be used. 



Evergreens that may be used for the drier portions of the southern part of 

 region 6 are the Parkinsonia and the Texas palmetto. 



Native trees should be sought and tried. 



Region 7. 



Region 7 is the northern and central parts of the Great Plains area from the 

 foot of the Rocky Mountains at about the 5,000-foot contour line east to the 



