Mar. 25, 1915 Dissemination of Chestnut-Blight Fungus 495 
the ground without being carried any appreciable distance is not men- 
tioned. Since they germinate at once in rain water, the great bulk of 
such spores would be lost for anything but very local infections. The 
really important point would appear to be the length of time shooting 
continues after a rain ceases, for at that time the conditions of the atmos- 
phere would be such as to favor a wider dissemination. This question 
does not seem to have been satisfactorily answered. The data given on 
height and horizontal distance of projection, as well as the rate of expul- 
sion, certainly indicate the importance of wind transport of spores 
following rainy periods. 
The spore content of the air was studied by means of aspirator tests 
and exposure plates. In this work, carried out during dry weather, 
Anderson and his assistants failed to get positive results under natural 
conditions in the field. ‘They report the use of over 100 exposure plates 
and tests of 500 liters of air without finding a single spore of the chestnut- 
blight fungus. Tests made of aspirated air and by exposure plates gave 
positive results, however, when the cankers were artificially drenched 
with water. For the aspirator tests the horizontal distances of the 
aspirator opening from the canker varied from 2 inches to 5 feet (?) and 
the maximum vertical distance was 22 feet. 
The tests made by exposing agar plates under artificial conditions in 
the field again pointed to the probability of wind dissemination, but one 
is forced to admit that they were not conclusive, since the conditions 
were so different from the natural in that the cankers were drenched 
with water artificially instead of waiting for a rain. The results with 
exposure plates may be summed up as follows: No spores of the chestnut- 
blight fungus were obtained under natural conditions in the field during 
dry weather; by the use of artificially drenched cankers spores were 
obtained at distances varying from 1 inch to 51 feet, with very few at 
the maximum distance. 
The final and most conclusive argument in favor of wind dissemination 
in the minds of the authors cited was afforded by inoculations made by 
offering an opportunity for wind-borne spores to be introduced into 
wounds. ‘There is little doubt in the minds of the writers of this paper 
that infection did take place in the way claimed, but it should be pointed 
out that a covering of cotton would not prevent spores from being washed 
into the wounds by rains (6). A fairly compact mass of cotton has been 
shown to retain but few of the pycnospores present in water passing 
through it. It must therefore be admitted that, under the conditions 
of the experiments reported, infection by spores washed down by rains 
was one of the possibilities. 
It is interesting to note in this connection that Kittredge (10), as a 
result of field observations on the spread of the disease around a center 
of infection, arrives at the following conclusion: 
The location of infected trees in partially infected groups of sprouts shows that 
wind ic mat the ncime factor in the distribution of the spores. 
