Mar. 25, 1915 Dissemination of Chestnut-Blight Fungus 497 
present in the air. At the same time the growth of E. parasitica on this 
medium is vigorous and characteristic. 
As supports or stations on which to expose the plates, it was found con- 
venient and satisfactory to make use of the numerous large flat-topped 
stumps scattered throughout the coppice stand of diseased trees. To 
facilitate the recording of data, all of the stumps used were numbered with 
crayon and carefully described and located with regard to surrounding 
trees (fig. 1). Here it may be mentioned, however, that other supports, 
stich as the top rail of a fence or the top of a stake driven into the ground, 
were used in case of emergency attendant upon certain weather conditions. 
wee TT os 
EXPLANATION 
SIGNS 
e Live Chestnut Tree 
0 Deat ° 
© Trees not Chestnut 
B, Beech., MMaple. 
C,Cherry. K,Oak., 
HArckory,.T, Tulip, 
6, Slack Gum. 
Otter, Ascospore Trap 
Chere ae 
[ilwerer Spore Trap 
AlAspirator, Sortle 
‘Sh Anemometer 
women Si /Viculfural 
Soundary 
Fic. 1.—Map of chestnut coppice growth at West Chester, Pa.,in and near which the experiments on wind 
dissemination of the chestnut-blight fungus were carried out. 
The stumps, rails, and stakes used for this purpose were all of such an age 
or nature that they were entirely free from lesions of the chestnut blight. 
Under conditions of ordinary fair weather the routine followed in 
making the exposures was similar throughout the tests. Plates were ex- 
posed at the rate of one about every half hour during the day, and the 
average length of exposure was about 5 minutes for each plate during the 
first 18 days. Then it was found advisable to lengthen the time of = 
sure, and thereafter 10 minutes, more or less, was the usual time allowe : 
Wind direction determined what stations were utilized each day, since an 
