74 
Journal of Agricultural Research 
Vol. II, No. i 
CONCLUSIONS 
The results obtained in these two sets of tests lead to several con¬ 
clusions. The field tests show that the pycnospores are to a consider¬ 
able degree resistant to desiccation in soil in the field and that a large 
number may retain their viability during a period of 2 to 13 days of 
dry weather. 
In the indoor tests, where the period of drying could be prolonged at 
will, more conclusive results were secured. In each sample it is seen 
that, with some irregularities, there is a gradual decrease in the number 
of viable spores as the period of desiccation is prolonged. The irregu¬ 
larities in the figures are due partly to the fact that from the stand¬ 
point of spore content it was impossible to secure a perfectly uniform 
mixture in the soil sample. 
It is evident that in every case except one a large number of spores 
survived two months of desiccation and that in 5 out of the 12 samples 
not all of the spores had succumbed after three months of drying. The 
longevity limit varies from 54 to 119 days, the average being 81 days. 
At the end of periods of desiccation ranging from 121 days for some 
samples to 149 days for others no viable spores were found. The con¬ 
clusiveness of these final tests is enhanced by the fact that relatively 
larger quantities of inoculative material were used in the cultures. 
(See summary of Table II.) 
These results suggest that viable pycnospores are constantly present 
in the soil beneath infected trees, since each succeeding rain replenishes 
the supply. Under normal conditions there would hardly be a period 
of drought sufficiently extended to destroy all of the enormous number 
washed into the soil. 
The fact that a large percentage of the pycnospores which are washed 
into the soil withstand two to three months of drying has an interesting 
bearing upon certain phases of the problem of dissemination of the 
chestnut bark disease and affords at least three possibilities for conjecture. 
First, it shows that pycnospores will resist the degree of drying neces¬ 
sary to reduce the soil to a condition in which it might be easily pul¬ 
verized and blown about as dust. This presents the possibility of wind 
dissemination of pycnospores dried on soil particles. Such a possibility 
has been suggested by Metcalf and Collins (1911), and Collins (1912). 
However, this contingency is rather improbable under natural forest 
conditions, since the soil beneath the trees is more or less protected and 
dries much less rapidly than in the open. On the other hand, there 
would be a fair probability of wind transport of pycnospores in blight- 
infected nurseries without ground cover or from more isolated trees, 
especially if the soil is exposed or the ground cover is sparse. 
In the second place, a means is presented whereby pycnospores might 
be transported in mud dried on insects, on the feet of birds, squirrels, 
and other animals, and even on the shoes of man. Such might be the 
explanation of the presence of pycnospores found on one of the two 
juncos tested during the study of birds as carriers of the chestnut blight 
fungus (Heald and Studhalter, 1913), since the junco obtains nearly all of 
its food from the ground. 
Finally, the results of these tests present the possibility of the trans¬ 
portation of pycnospores in the soil adhering to the stems and roots of 
chestnut nursery stock during shipment. Such nursery stock might be 
