A Bacterial Disease of Stone Fruits 409 



being covered with black paper. After six days, on each of six plates 

 there were numerous colonies on the covered parts but none on the 

 exposed parts. A few colonies, however, developed on the uncovered 

 parts of all the plates exposed for fifteen, twentj'. and thirty minutes. 



Effect of germicides. — Poured Hiss-glucose plates were made with the 

 plum organism after it had been exposed to various concentrations of 

 copper sulfate, inercuric chloride, formaldehyde, lime-sulfur solution, 

 the self-boiled lime-sulfur mixtures, and arsenate of lead. 



In a copper sulfate solution (1-10,000), colonies appeared in five days 

 on all plates on which cultures were made of the organism which had been 

 exposed for one-half minute and for five minutes. However, there were 

 only one-fourth as many colonies on the five-minutes exposures as on the 

 one-half-minute exposures. No colonies appeared on any of the plates 

 on which the organism had been exposed for fifteen minutes and for thirty 

 minutes. 



In a mercuric chloride solution (1-150,000), colonies appeared in five 

 days on all plates on which cultures were made of the organism which 

 had been exposed for one-half minute and for five minutes. The colon- 

 ies on the plates exposed for five minutes remained small and failed to 

 develop the yellow color. No colonies appeared on any of the plates on 

 which the organism had been exposed for fifteen minutes and for thirty 

 minutes. 



In a formaldehyde solution (1-300), colonies appeared in five days on all 

 plates on which cultures were made of the organism which had been ex- 

 posed for one-half minute and for five minutes. However, there were three 

 times as many colonies in the one-half-minute exposures as in the five- 

 minutes exposures. No colonies appeared on any of the plates on which 

 the organism had been exposed for fifteen minutes and for thirty minutes. 



In a lime-sulfur solution (15-15-50 formula) in a 1-10,000 dilution, 

 colonies appeared in five days on all plates on which cultures were made 

 of the organism which had been exposed for one-half minute and for five 

 minutes. However, there were only one-half as many colonies on the 

 five-minutes exposures as on the one-half-minute exposures. No colonies 

 appeared on any of the plates on which the organism had been exposed 

 for fifteen minutes and for thirty minutes. 



In a self-boiled hme-sulfur mixture (8-8-50 formula) in a 1-52 dilution, 

 colonies appeared in five days on all plates on which cultures were made 



