92 PRACTICAL FORESTRY 
danger is correspondingly less. It is rare, indeed, 
that an insect will injure more than one species at a 
time. 
In the case of mixed forests it is possible to grow 
shallow- with deep-rooted species with safety from the 
action of the wind. The soil and air space are utilized 
to better advantage. If the underwood is of the 
proper kind, the soil is protected and improved. In 
Germany the tendency is decidedly toward the en- 
couragement of mixed forests, although in Saxony 
immense areas of pure spruce are raised for pulp, and 
in Prussia and southwestern France one may ride 
through vast stretches of pure pine. The mixture of 
two sorts of trees is almost always advisable, espe- 
cially if one is a broad-leafed species and a shade- 
endurer, and the other a conifer and light-demander. 
It is difficult to regenerate a mixed forest without 
planting, and greater skill is required in its manage- 
ment, so that in many instances pure forests are pref- 
erable. This is so with spruce, which is probably 
the first tree that will be extensively grown artificially 
in forests in our northern regions. 
There will be little difficulty in securing mixed 
forests in this country. They are naturally too much 
mixed. The difficulty will be mainly in excluding 
undesirable species, and in maintaining the desirable 
species in the proper proportions and relations, 
