The infection nowhere runs less than 3 per cent., and it was impossible
to find an acre with less than this amount of blight on it. On most of
the ridge the percentage of diseased chestnut runs from 17 to 30 per
cent., although there are spots where it is much higher. The centers of
infection are not confined to any characteristic slope or environment.
Generally, the blight has spread over larger areas on the summit and
south slope than on the north slope. The centers along the south
slope and summit show more trees killed by the blight than those of
any other part of the mountain. This is doubtless due to a more rapid
spread of the blight in these situations. Scattered dead trees are less
common along the north slope than elsewhere; however, several centers
containing a dozen or more large trees entirely killed are found on the
north slope.
The blight is so uniformly distributed between the centers that it
was difficult to determine the facts relative to the dissemination of
the disease by wind. However, most of the infected areas show a wider
zone of distribution east and north of the infection center, giving
the areas of thick infection an egg-shaped outline, with the oldest
infections nearest to the western boundary. No definite information
was obtained on this tract concerning the part played by birds as
disseminators of the disease.
The south slope of the ridge is more dry and barren than the north
slope. The only springs found there are near the eastern end of the
ridge, and a few small springs are scattered along the lower portions
of the south slope, but these are below the zone of chestnut growth.
The north slope is a more gradual incline, and there are numerous
shallow dips resembling miniature gullies. Some of these are moist
enough to support alder bushes and several species of moisture loving
ferns; also trees of the lowland types, such as tulip and maple,
are quite common in these depressions. Most of these dips contain
springs, but not all of them; however, there are numerous small springs
scattered all along the north slope of the ridge. Most of these are
well down toward the base, but several are well up toward the summit.
So far as could be ascertained, no relation exists between the thickly
infected areas and moisture conditions.
The data collected lead to the belief that the infection is distributed
without any regard to elevation. For instance, along the base of the
north slope high percentages of infection are found. Similarly, an
increase in the percentage of blight is found half-way toward the
summit. While the summit seems to support more infection than any other
portion of the mountain, there is no reason to suppose that this is due
to elevation. The stand here is almost pure young chestnut coppice, and
the conditions appear to be more favorable to the rapid spread of the
disease in such stands. The base of the south slope supports coppice
growth similar to that found at the summit, and here the per cent. of
infection compares very closely with that along the summit.