24 Rorer: Bacterial Disease of the Peach 



cut out, thoroughly washed, and then mashed up in sterile water, 

 from which, by the poured-plate method, a yellow motile organ- 

 ism was isolated. Many of the plates proved to be pure cultures 

 containing sometimes 100 or 200 colonies. 



During the summer of 1907, a series of successful inoculations 

 with this bacterium was made at Bentonville, Arkansas. Sterile 

 water was added to pure cultures on slant agar five days old and 

 with a sterile needle the bacterial growth was loosened from the 

 surface of the medium and thoroughly mixed with the water. 

 This liquid, containing bacteria in great numbers, was diluted a 

 little and then sprayed with an atomizer on young Elberta 

 peach leaves. This variety was chosen because it is naturally 

 quite susceptible to the disease. Three sets of inoculations were 

 made on different days and on different trees. From thirty to 

 forty leaves were involved in each spraying. About an equal 

 number of leaves on adjacent trees were sprayed with sterile 

 water alone to serve as a check. The inoculations were made on 

 June 25, 26 and 28. The trees inoculated on the two earlier 

 dates were examined on July 15. From four to six spots of the 

 characteristic appearance were found on most of the leaves 

 which had been sprayed with the bacteria-bearing fluid, while the 

 leaves sprayed with sterile water showed no spots at all. The 

 leaves inoculated on June 28 were examined on July 20, and, as 

 in the previous cases, the leaves which had been sprayed with 

 the bacteria showed spots, three or four to a leaf, while the 

 checks remained free. Sections of these spots on the inoculated 

 leaves, when examined under the microscope, showed the char- 

 acteristic cavities filled with bacteria and plates poured from 

 the smallest spots were practically pure cultures of one organism, 

 the motile yellow bacterium with which the inoculations had been 

 made. Although in no case were the spots on the leaves as 

 numerous as one might expect considering the large number of 

 bacteria in the fluid used, the fewness of the spots may be 

 accounted for by the fact that the weather conditions at the 

 time were very unfavorable, there being scarcely any rainfall and 

 but little dew, and no attempt whatever was made to keep the 

 leaves moist after the inoculations were made. From these ex- 



