84 PRACTICAL FORESTRY 
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stand the rigors of desert life. What the coconut is 
to the shores of tropical seas, the date is to the desert. 
The next great barrier to tree-growth is unsuit- 
able soil. Often there is insufficient soil; often the 
soil contains alkali or salt, and very often there is 
hard-pan near the surface which prevents the penetra- 
tion of roots. It is very seldom that tree-growth is 
prevented by a lack of nourishing food material in 
A SCENE ON OUR WESTERN PRAIRIES. 
the soil. Although trees are often in a half-starved 
condition, it is an extremely poor soil which will not 
support tree-growth of some kind. The formation 
of grass- or savanna-land is often due to hard-pan, 
which is hardened or indurated soil. Hard-pan not 
