68 
Vol. II, No. i 
Journal of Agricultural Research 
in the following pages was to determine the resistance of pycnospores 
washed into the soil in the field to desiccation in this soil under two 
distinct conditions: First, in the undisturbed soil in the field during the 
intervals between rains; and, second, during a more prolonged period of 
desiccation in the laboratory. 
All except three of the soil samples used in these tests were secured in 
the experimental plat near West Chester, Pa., at the bases of diseased 
chestnut trees bearing certain of the “ pycnospore traps ” used in the analy¬ 
sis of rain water washed down the trunks (Heald and Gardner, I9i3a-b). 
The results of these analyses proved that few, if any, ascospores were 
present in the water washed down the trees into the soil, even late in the 
spring after ascospore expulsion was in progress. From these data and 
from the time of appearance of the colonies in our cultures it is certain 
that the spores with which we were dealing were pycnospores and not 
ascospores (Heald, 1913a). 
TESTS OF LONGEVITY UNDER FIELD CONDITIONS 
The first samples of soil in each series used in determining the power 
of resistance of the pycnospores to desiccation in soil under field condi¬ 
tions were taken as soon as possible after the cessation of a rain. The 
litter and immediate surface soil were scraped away from a small area at 
the base of the tree, and with a sterile knife or spoon a sample of the soil 
thus exposed and immediately adjacent to the base of the trunk was 
removed to a sterile tin receptacle for transport to the laboratory. 
The dilution method with poured-plate cultures was used in ascertain¬ 
ing the number of viable pycnospores per gram of soil. Using sterile 
utensils, 1 gram of the soil was weighed out and placed in a flask containing 
99 c. c. of sterile water. By crushing the soil lumps with a flamed glass 
rod and by agitation of the flask a thoroughly uniform suspension was 
obtained. From this suspension 1 c. c. was transferred with a sterile 
pipette to a second flask containing 99 c. c. of sterile water, and of this 
second dilution measured quantities (1 c. c. and fractions thereof) were 
placed in sterile Petri dishes and plated out in standard 3 per cent dex¬ 
trose agar +10. From the number of colonies of the blight fungus 
developing in these cultures an estimate was obtained of the number of 
viable pycnospores present in the gram of soil tested. 
In securing the second or third samples of soil from each location in the 
field the soil was taken from a point as near as possible to the exact 
source of the first sample and from a similar position relative to the tree. 
The method used in testing these subsequent samples was identical with 
that previously outlined, no allowance being made for loss of weight due 
to drying. In making a second or third test it is evident that a different 
individual portion of soil must be used in which the original number of 
spores contained would probably by no means coincide with the spore 
content of the previous sample from that location. Taking this fact into 
consideration, the discrepancies in the figures are only such as might be 
expected. 
The period of desiccation in these field determinations was necessarily 
limited by the recurrence of rain, so that in series A, B, and C only one 
subsequent test was obtained for each location. In series D, however, a 
rather extended period of dry weather permitted tests to be made after 
relatively longer periods of desiccation. The results obtained are pre¬ 
sented in Table I. 
