SHELTER-BELT DEMONSTRATIONS ON THE GREAT PLAINS. 
25 
the results of this study is given in Table 10, which shows for each 
species the average height attained in all plantings in each State 
and the maximum height attained in any planting in the State. 
The low average heights of willow and poplar as compared to the 
maximum heights are due to the continual freezing back of these 
species in most of the plantings. It will be noted that with the ex- 
ception of green ash, all of the species made the best growth in 
South Dakota. As the figures for green ash in that State are based 
on three plantings only, they can not be considered adequate. Sub- 
sequent plantings have shown the same relatively higher growth for 
green ash. The comparatively better conditions as to rainfall and 
temperature which prevail in South Dakota will probably explain 
this increased growth. The data given in Table 10 are shown dia- 
gramaticallv in Figure 13. 
Fig. 14. — An unpruned shelter belt in the third summer of growth. Planting in Valley 
County, Mont. 
EXPERIMENTAL PLANTINGS. 
In addition to the shelter-belt demonstrations under actual farm 
conditions, a number of special experimental plantings have been 
made at the Xorthern Great Plains Field Station. 
Species testing blocks. — Since 1914 more than 80 different species 
of trees have been planted as pure stands in blocks containing ap- 
proximately 100 trees each. These plantings are intended to serve 
primarily as hardiness tests. Some of the most important results 
from this work have been embodied in the discussion under the head- 
ing " Xotes on tree species," page 6. 
Methods of care for shelter belts. — Ten blocks of identical shelter- 
belt plantings similar to the regular demonstrations were set out in 
