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establish themselves on the previously diseased stems of trees.
But though such Fungi do not attack healthy trees, their
spawn soon spreads, and speedily destroys the surrounding
healthy tissues. The evil can he stopped only by carefully
cutting out the diseased parts, and washing them with a
strong solution of corrosive sublimate, or other substance
which may destroy the spawn without injury to the tree.
Of those which attack timber when converted to the purposes
of marine and domestic building, the most formidable,
perhaps, is Dry-rot (Plate 2, fig. 1), which derives its name
from converting the wood into a dry powdery mass, though
both the Fungus and wood are often sprinkled with large
drops of moisture. This may, however, be prevented by pre-
viouslv impregnating the pores of the wood with gas-tar, sulphate
of copper, or some other poisonous metallic salt ; or,
when established, may be greatly modified by careful, and, if
needful, repeated washing with a saturated solution of corrosive
sublimate. This treatment may not destroy the whole of
the spawn, hut if not, it will at least greatly diminish its vegetative
power.
I t is still a question amongst shipbuilders, whether winter
or summer felled timber is most subject to he affected. I t is
quite certain that, in dry situations, timber felled when the
trunk is most free from sap, is far more durable. There are
many ancient buildings in which the sapwood is still as free
from insects and decay as the firmest heartwood ; but where
there is not a free current of air, and Fungi can establish
themselves, the mischief is so inherent in either case that it is
only a question of time. In domestic buildings, where little
choice is exercised in the selection of timber so long as it be
of the proper size, and it has not to undergo the scrutinizing
eye of a dockyard surveyor, the ivood is often deeply impregnatcd
with spawn before it is used. This, indeed, is almost
always the case where trees are grown from old stools, and
not from seed. The foxy oak, so common in some districts,
is almost entirely due to this cause ; and I have seen such
timber after a few years covered with Fungi to such an extent
as to necessitate extensive repairs.
A large quantity of Fungi prey on the tissues of living
leaves ; the spawn of some of these runs over the surface ; of
some it creeps amongst the loose tissue of the under side of
leaves ; while in others it is more intimately incorporated with
the firmer cells.
I t is not easy to describe the two first apart, as different
species of the same genus have different habits. The same,
indeed, may be said occasionally of different individuals of the
same species, hut iu either case they are capable of inflicting
great injury. The Hop Mould, the Rose Mildew, the
Vine Mildew, and a multitude of other allied Fungi, partly
by feeding on the proper juices of the plant, and partly by
clogging up the breathing pores, exhaust the plant and impede
its circulation and respiration. Most of these will yield
to suhliinated sulphur, if timely and judiciously applied. The
conditions under which these Fungi appear is very different.
Some of them never perfect their true fruit, being propagated
by a secondary fruit analogous to the reproductive buds of
certain Phænogams, as Begonice. In some there are four or
five distinct modes of propagation, and in consequence they
spread with frightful rapidity. The cultivation of the Vine in
Madeira has almost entirely ceased from this cause, and is
very precarious everywhere. I t is curious that this Fungus
has never been found on the American Vines, or their numerous
varieties, even when cultivated iu Europe. The Isabella,
for instance, a grape of American origin, has been always free