d, even should it be
necessary, in so doing, to make large wounds. Cases of this nature
require the treatment recommended for the last class.

CAVITIES IN THE TRUNK.--Very often, when a tree has been long neglected,
the trunk is seriously injured by cavities caused by the decay of dead
or broken branches. It is not claimed that pruning can remove defects of
this nature; it can with proper application, however, arrest the
progress of the evil. The edge of the cavity should be cut smooth and
even; and all decomposed matter, or growth of new bark formed in the
interior, should be carefully removed. A coating of coal-tar should be
applied to the surface of the cavity, and the mouth plugged with a piece
of well-seasoned oak securely driven into the place. The end of the plug
should then be carefully pared smooth and covered with coal-tar,
precisely as if the stump of a branch were under treatment. If the
cavity is too large to be closed in this manner, a piece of thoroughly
seasoned oak board, carefully fitted to it, may be securely nailed into
the opening, and then covered with coal-tar. It is often advisable to
guard against the attacks of insects by nailing a piece of zinc or other
metal over the board in such a way that the growth of the new wood will
in time completely cover it.

Coal-tar, a waste product of gas-works, can be applied with an ordinary
painter's brush, and may be used cold, except in very cold weather, when
it should be slightly warmed before application. Coal-tar has remarkable
preservative properties, and may be used with equal advantage on living
and dead wood. A single application, without penetrating deeper than
ordinary paint, forms an impervious coating to the wood-cells, which
would, without such covering, under external influences, soon become
channels of decay. This simple application then produces a sort of
instantaneous cauterization, and preserves from decay wounds caused
either in pruning or by accident. The odor of coal-tar drives away
insects, or prevents them, by complete adherence to the wood, from
injuring it. After long and expensive experiments, the director of the
parks of the city of Paris finally, in 1863, adopted coal-tar, in
preference to other preparations used, for covering tree wounds. In the
case of stone fruit trees it should, however, be used with considerable
caution, especially on plum trees. It should not be allowed to
needlessly run down the trunk; and it is well to re