The Bacterial Diseases of the Bean 7 



in the field more rapidly and do more damage in a cool season than in a 

 warm season. In the greenhouse, however, excellent infection is obtained 

 at 80° F. 



What part humidity plays is still in doubt. When inoculations were 

 made by injuring the plants, no extra care was taken to place them in a 

 moist atmosphere. Such inoculated plants were allowed to remain on the 

 greenhouse benches under the usual conditions, and inoculations were 

 made at any time during the day. When plants were inoculated by 

 spraying with a water suspension of the organism, without injuring them 

 in any manner, it was considered wise to place them in a moist chamber 

 for about twenty-four hours. This procedure, however, was not based 

 on any experimental evidence. 



The technic of inoculation by injuring the plants was as follows: The 

 pathogene was grown on an agar slant at 27° C., and its age when inocula- 

 tions were made was, as a rule, from twenty-four to forty-eight hours. 

 Seedlings were used which had advanced beyond the primary leaf stage 

 but were still tender and succulent. A small part of the bacterial mass 

 was placed on a very sharp pointed scalpel and the plant was stabbed 

 with this contaminated instrument. The injury was made in most cases 

 at the primary leaf node and extended into the pith. When pods were 

 used in the experiments they were inoculated in a similar manner, the 

 injury being made either on the suture or on the side. 



When experiments were conducted without injuring, the inoculations 

 were made by spraying the plants with a water suspension of the pathogene 

 from the agar slants. The bacteria were washed from the agar with tap 

 water and sprayed from an atomizer. The plants were then placed in a 

 moist chamber for approximately twenty-four hours. When pods were 

 used, the water suspension not infrequently was painted on with a camel's- 

 hair brush. 



Some confusion exists in the literature as to the correct scientific name to 

 be applied to certain of the leguminous plants referred to in this bulletin. 

 Bailey's Manual of Cultivated Plants has been followed here in so far as 

 specific names are concerned. Where varieties have been established on 

 the character of determinate or undeterminate growth habit, they have 

 been disregarded. 



PURE-CULTURE STUDIES 



Before the cultural studies were begun, all strains of the various species 

 and varieties of bacteria used were inoculated into bean plants. After 

 infection had taken place and the disease had progressed to a considerable 

 extent, the organism was reisolated from diseased tissue as far removed 

 from the point of inoculation as possible. Dilution plates were then made 

 and a single colony was transferred to a tube. When the pathogenicity 

 of this culture had been proved, the cultural work was begun. It should 

 be stated here that prior to the foregoing procedure an attempt was made 



