ge, and then a brown, till the leaf is the ordinary dark dull
brown of the dead leaves. This coloration which takes place is
conspicuous. There is your guide, your danger signal. If the disease has
worked very long, half a season, in one locality, you are almost sure of
getting some of these danger signals. Where one is present, you can go
and look up the cause of that danger signal. It may be a broken twig,
but the point is to find out if it is this disease which has caused the
danger signal. We start by looking at the danger signal, then at the
base of the dead area. If we find here some of the reddish pustules
which have been shown on this bark we are quite sure that the disease
is present. Then by cutting into the bark a little, instead of the
normal buff or yellowish tint of the fresh clean bark, we get, when the
disease is present, a rather mottled effect, varying from a brownish to
lighter or even darker. There is a peculiar fan-like effect to this
mycelium which penetrates the bark, so that by shaving off the surface
of the bark, you get this mottled appearance, which gives you another
means of identifying the disease. So we look for the danger signals, and
then look for the meaning of the danger signals. If we find those two
things, the pustules and the mottled mycelium, we can very safely say
that this disease is present.

There are a few fungi which closely resemble this chestnut disease in
general appearance, but they are not very common, and are not confused
with the disease, as a rule, when you get the lens on them.

In regard to the experiments for the control of the disease. I want to
say a few words. As far back as 1907, the United States Department of
Agriculture began experiments on certain experimental plots,
particularly in Long Island near the region where the earliest cases of
this disease were known, to see if it could be controlled on individual
trees after they had become infected. Later, experiments were undertaken
along the same line in Lancaster County, Pennsylvania. Spraying was
tried, although there was no idea that it would be of any use, because
the vegetative stage of this fungus is running through the interior of
the bark, where no spray could reach it. Thus spraying was found to be
of no use whatever. Then the operation of cutting out the disease was
tried. Where the diseased spot appeared, it was cut out with a gouge.
Then the exposed area was covered in various ways with antiseptics