SHELTER-BELT DEMONSTRATIONS OX THE GREAT PLAINS. 7 
the region furnishes what is perhaps the most important source of 
material for shelter-belt planting. 
Figure 2 shows the native growth of western cottonwood. box elder, 
and green ash in the river bottom, with western yellow pine on the 
adjoining hills in the Yellowstone River valley at Pompeys Pillar in 
southern Montana. 
Figure 3 is a view in the Turtle Mountains. Bottineau County. 
X. Dak., showing the native tree growth, consisting of cottonwood. 
balsam poplar, aspen, white elm. bur oak. and green ash. 
The species that make up this native growth are of two general 
classes : Those which have progressed up the Mississippi-Missouri 
River system from the east and those which have advanced down the 
western sources of this same svstem from the Rockv Mountains. 
Fig. 3. — View in the Turtle Mountains. Bottineau County. N. Dak., showing native tree 
growth consisting of cottonwood, balsam, poplar, aspen, white elm, bur oak. and green 
Beside these native trees a number of species have been introduced 
from other parts of the United States and Canada and from certain 
European and Asiatic countries. Some of these introduced species 
are fully as adaptable to shelter-belt use as any of the native species, 
while a number of the native trees can not be successfully trans- 
planted to the open plains. 
The following paragraphs give brief descriptions of practically 
all of the trees which have been used in shelter-belt planting in the 
northern Great Plains region. The list is not exhaustive, however, 
as there are a number of other species that can doubtless be made 
to grow, but about which little data are available at the present 
time. 
DECIDUOUS OR HARDWOOD SPECIES NATIVE TO THE REGION". 
Box elder. — The box elder {Acer negumdo) is found in practically 
all of the river valleys to the foothills of the Rockv Mountains. 
