164 PRACTICAL FORESTRY 
ous to tree-growth. It is indeed wonderful, however, 
the amount of heat and drought which some species 
are able to endure. The best way to meet these diffi- 
culties is to encourage the formation of a thick mulch 
of humus on the forest-floor, and to keep the canopy 
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A SHIFTING SAND-DUNE ON THE CoAstT OF NEW JERSEY. 
as dense and even as possible. The bark of some spe- 
cies is scorched by the sun, and several species, such as 
the hemlock, which usually live in the shade of other 
trees, sicken and die when suddenly exposed to the 
bright sunlight. 
Great damage is done to forests by the winds. 
Limbs are broken and often large areas are uprooted. 
The more the forest is opened up, the greater this 
