ut that slide under the microscope
and try to blow those spores off, you can do it just about as easily as
you can blow the shellac off a door. You can brush that film under the
microscope, and you can't see that a single spore has been disturbed.
The explanation, I think, lies in the fact that these spores are of a
mucilaginous nature, and when they dry, they stick to whatever they come
in contact with. That does not mean that these spores cannot be blown,
because they may lie on fragments of leaves and be blown about by the
wind. Again, some of the spores may be detached in a mechanical way and
thus blown by the wind. But I am quite convinced that the spores are not
blown broadcast, simply because they are of a sticky nature.

Now, those spore threads are forced out under certain conditions,
moisture conditions, as a rule. It has been shown after repeated
observation that these spore threads are pushed out a day or two after a
rain. Of course, in the springtime, the atmosphere is much more moist
than later in the season. Consequently, we find more of these spore
threads in the spring than at any other time. You will recall that the
last week of August this year was a week of almost continuous rain. Two
days after that ceased, I saw as many of these spore threads as I had
seen at any one time all summer. So that, although conditions are best
in the spring for greater abundance of these spores, they may occur at
any time. If a bird alights on these spore masses, there is no reason
that I see why they should not be carried. We know the rain water
running down the trunk dissolves these spore masses, and they are
carried down, there to reinfect the tree when insects crawl around.

President Morris: My brother has some Japanese chestnuts twenty-five or
thirty years of age. By cutting off one branch at a time as fast as they
blighted, he has saved those trees.

Professor Collins: You spoke, Doctor Morris, of grafting Japanese on to
American stock. I have seen repeated cases where the Japanese has been
grafted on to American stock. The whole Japanese tree has been killed,
and we find the disease has killed the tree by girdling the American
stock below the graft.

President Morris: Yes, I find this over and over again. In one case
where I had a very choice variety of Burley's chestnut, the _Diaporthe_
attacked the American stock underneath this, and had practically girdled
it when I saw it. There remained a fraction of an i