Mar. 25, 1915 



Dissemination of Chestnut-Blight Fungus 



499 



An anemometer was erected in the experimental plot, and from the 

 successive readings of this instrument the wind velocities were computed. 

 Continuous records of temperature were secured by means of a thermo- 

 graph located in a standard instrument shelter near the plot, and by use 

 of a rain gauge the exact rainfall in inches was determined. As com- 

 plete data as possible were also secured relative to the exact duration of 

 all rains. 



In describing and locating the stations used for exposure plates, meas- 

 urements were made to the nearest diseased trees and to the nearest 

 lesions, the horizontal distance being recorded. To supplement the de- 

 scription, detailed topographic maps were made, showing the location of 

 each station (figs, i and 2). 



The exposed plates were incubated at room temperature, and two rec- 

 ords were usually taken. First, at the end of three days after exposure 

 all fungous and bacterial colonies visible were marked and counted, and 

 those suspected of being Endolhia parasitica were especially noted. After 

 six or seven days of incubation the final record on each plate was taken. 

 This included the total number of fungi, the number of bacterial and yeast 

 colonies, and the number of colonies of E. parasitica, if any were present. 

 In case of doubt as to the identity of the latter, owing to crowding by 

 other colonies, transfers were made to 3 per cent dextrose agar, on which 

 medium the growth of this fungus is even more characteristic than on 

 chestnut-bark agar. 



The results obtained in the exposure-plate tests are presented in a 

 somewhat summarized form in Tables I and II. 



Table I. — Summary of exposure-plate tests at West Chester, Pa., in IQI3, giving number 



0} fungous colonies caught 



78745°— 15 5 



