majority of the fungi grow on the trunks and limbs of
trees, some attack the leaves, some the twigs and others the roots.
Some fungi grow on living wood some on dead wood and some on both.
Those that attack the living trees are the most dangerous from the
standpoint of disease.

The chestnut disease: The disease which is threatening the destruction
of all the chestnut trees in America is a fungus which has, within
recent years, assumed such vast proportions that it deserves special
comment. The fungus is known as _Diaporthe parasitica_ (Murrill),
and was first observed in the vicinity of New York in 1905. At that
time only a few trees were known to have been killed by this
disease, but now the disease has advanced over the whole chestnut
area in the United States, reaching as far south as Virginia and as
far west as Buffalo. Fig. 111 shows the result of the chestnut
disease.

The fungus attacks the cambium tissue underneath the bark. It enters
through a wound in the bark and sends its fungous threads from the
point of infection all around the trunk until the latter is girdled
and killed. This may all happen within one season. It is not until
the tree has practically been destroyed that the disease makes its
appearance on the surface of the bark in the form of brown patches
studded with little pustules that carry the spores. When once
girdled, the tree is killed above the point of infection and
everything above dies, while some of the twigs below may live until
they are attacked individually by the disease or until the trunk
below their origin is infected.

All species of chestnut trees are subject to the disease. The
Japanese and Spanish varieties appear to be highly resistant, but
are not immune. Other species of trees besides chestnuts are not
subject to the disease.

[Illustration: FIG. 111.--Chestnut Trees Killed by the Chestnut
Disease.]

There is no remedy or preventive for this disease. From the nature
of its attack, which is on the inner layer of the tree, it is
evident that all applications of fungicides, which must necessarily
be applied to the outside of the tree, will not reach the disease.
Injections are impossible and other suggested remedies, such as
boring holes in the wood for the purpose of inserting chemicals, are
futile.

The wood of the chestnut tre