Io4 THE I 1DIL4XV EMIPIRE [CHAP.
the Punjab and in Burma. In the former the principal con-
stituents of these forests consist of Acacia arabica and Tamrarix,
interspersed with Dalbergia Sissoo and poplar, which, however,
gradually give way to scrub and grass as the distance from the
water-supply increases. In Burma the forests spring from a
muddy soil, which at certain seasons is deeply inundated.
Species of Anogeisseus and Mangifera are frequent, while
Eugenia and Elaeocarbpus are also found. The forest vegeta-
tion merges gradually into that typical of the area affected by
tidal influences.
The foregoing description presents a very brief general view
of the forests of the Indian Empire. Considered in detail, it
will be found that the forest growth is influenced by climate,
by aspect, by the composition of the soil, by the depth of the
permanent water-supply, and that these influences account for
the unexpected appearance of species (covering, it may be,
large areas) in zones generally deemed unsuitable to their
growth.
Influence The influence of forests on the climate of the country and
of forests the fertility of the soil is of special interest in India. As
on water-
supply and forests are dependent for existence on water supplied by pre-
climate. cipitation, by percolation, or by inundation, so are they locally
responsible, in India even more than in the more temperate
countries of the West, not only for the storage of rainfall water
in the soil, given off subsequently by gentle flow, but also for
the supply, by transpiration from the foliage, of moisture to the
air. In those vast deciduous forests of Upper India where the
leaf flush occurs in the early hot weather, the effect of the
rapid unfolding of the new foliage in reducing the temperature
is so marked as to be at once perceptible; and indeed these
areas continue, so long as the leaves retain their vigour, cooler
than the surrounding country. On the other hand, the harm-
ful effects of heavy rainfall in localities denuded of forest
growth have necessitated costly works of afforestation even in
Europe, while in India, with its heavy tropical downpours, the
disastrous consequences are far more serious. The water flows
off the bare soil without benefiting the surrounding country,
and may cause disastrous floods many miles below; while the
change in climate following on the withdrawal of moisture
from the air may alter the whole character of the vegetation,
and thus annihilate some cultural industry. In short, the
forests form the head-works of Nature's irrigation scheme in
India; and if these are injured or destroyed, the advantages
of a regular water-supply may be replaced by the tempestuous
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