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. i). Here it may be mentioned, however, that other supports, 

 such 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. 



Fig. 



-Map of chestnut coppice growth at West Chester. Pa., in and near which the experiments on wind 

 dissemination of the chestnut-bhght 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 expo- 

 sure, and thereafter 10 minutes, more or less, was the usual time allowed. 

 Wind direction determined what stations were utilized each day, since an 



