Part III. ] R. S. Hole : Useful Exotics in Indian Forests. 
species from the attacks of insects, deer, pigs, monkeys and hares. 
The European larch ( Larix europaa), also, is known to suffer to a slight 
extent from the canker disease induced by the fungus Feziza Willkommii 
when growing in its native home in the Alps at an elevation of 3,000 to 
6,000 feet. This dreaded disease, however, only assumed an epidemic 
character when the tree was introduced as an exotic into the valleys 
and lowlands of Europe. * * In Cape Colony, in Africa, under 
the special circumstances of only a few indigenous species being of 
commercial value, their growth being slow and reproduction poor, 
exotic species have been largely introduced. One of these “ Finns 
Finea (stone pine) was introduced by the early settlers, but some thirty 
years ago it was attacked by a fungoid disease which has almost 
exterminated the species;” and Sir William Schlich remarks : “theonly 
disquieting point is that some of the exotic species introduced on a large 
scale may some day share the fate of the stone pine and be destroyed 
by disease; hence somewhat more attention might have been paid to the 
indigenous species.” 1 
One of the most practical preventive measures against the injuries 
of insects and fungi is to adopt mixed crops, but exotics are frequently 
planted pure, partly no doubt because information is not readily available 
as to what mixture is likely to suit them. It may be argued that, with 
the progress of knowledge in modern times, it should be possible to adopt 
measures which shall prevent, or at all events greatly diminish, such in¬ 
juries. In the first place, however, the only effective remedial measures 
are usually very costly and for this reason alone methods which are 
possible for the arboriculturist, planter and agriculturist are not practicable 
in forestry where the areas to be dealt with are large and the margin of 
profit usually small. The practical destruction of the coffee industry in 
Geylon by the fungus Hemileia vastatrix in comparatively recent years, 
moreover, indicates how futile such measures may be in the case of 
a really severe fungal epidemic. In the case of agriculture the produc¬ 
tion of new, disease-resisting varieties by plant-breeding appears to 
be the line of work which is at present regarded as the most likely 
to give the best results in preventing disease, but measures such as these 
are not at present possible in practical forestry except, perhaps, in so far 
as the collection of seed from the most vigorous and healthy individuals 
may lead to the propagation of disease-resisting strains. In forestry, we 
1 Manual of Forestry, Vol. 1, 1906, pp. 139, 140. 
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