SHELTER-BELT DEMONSTRATIONS ON THE GREAT PLAINS. 
9 
northern tree, ranging nearly to the Arctic Circle, it may not adapt 
itself to the hot summer temperatures of the Great Plains. 
Aspen. — The aspen {Populus t re mul aides) is scattered sparsely 
over portions of the Plains region. It is found in the river valleys, 
on the north sides of small mountain groups, on occasional steep 
bluffs, and in the sand-dune area near the Mouse River in North 
Dakota. It is also found on the borders of lakes in the Coteau du 
Missouri and in depressions or coulees in the prairie where under- 
ground springs exist. It has been used in some instances for farm 
plantings, and makes a dense growth, though of no great size. 
Northwest poplar. — The northwest poplar {Populus sp.) was given 
its name by one of the commercial nurseries in North Dakota. It 
was discovered in the northern part of that State, and is supposed 
Fig. 4. 
-Northwest poplar (row at left) in its fourth year of growth in a shelter belt in 
Sheridan County. N. Dak. 
to be a natural hybrid presumably between the balsam poplar and 
the aspen. Whatever its origin, it is the most promising poplar 
for shelter-belt planting in the Great Plains area that has yet 
been tested. It is perfectly hardy, seems to grow on all types of 
soil, and is superior to the cottonwood on the drier locations. Figure 
4 shows the northwest poplar in its fourth year of growth in a 
shelter belt in Sheridan County, X. Dak. 
Acute-leaved cottonwood. — The acute-leaved cottonwood {Populus 
Oycuminata) is native to the foothills of the Rocky Mountains. It is 
found along the banks of streams in Montana as far east as the 
Powder River and in Wyoming to the Black Hills in South Dakota. 
This tree has been used for street planting in cities of the Rocky 
Mountain region, and is superior for that purpose to the common 
3607°— 22 2 
