The Bacterial Diseases of the Bean 23 



lence at times appeared to wane and reisolations were deemed necessary. 

 During the progress of the work a few infected plants were continuously 

 on hand in the greenhouse so that reisolations could readily be made. 

 Inoculations on seedlings made by pricking the stem at the cotyledon node 

 usually caused a wilting of the plant. The incubation period varied; as a 

 rule it was about a week, but in some cases the time was longer. There 

 were no peculiarities of this wilt of seedlings to distinguish it from such a 

 symptom produced by any of the other xylem-infecting organisms. The 

 seedling simply wilted, although, as a rule, rather slowly. 



When young plants past the seedling stage were inoculated, certain 

 characteristic symptoms did occur. Few of the plants died, though many 

 do which are infected with Phytomonas phaseoli, Phyt. flaccumfaciens, or 

 Phyt. medicaginis var. phaseolicola. A leaf or perhaps a tip of a branch 

 or a young pod of the inoculated plant would wilt and die, but the plant 

 as a whole would struggle on. At the point of inoculation, where the tissue 

 of the stem was injured, a necrotic lesion would develop. This lesion 

 extended slowly up the stem, and to a less degree downward. The lesions 

 were reddish brown in color, and were dry; and cracks longitudinal with 

 the stem would sometimes appear. In some cases there was a slight 

 hypertrophy of the tissue about the injury. This symptom rather distin- 

 guishes this disease from others of its type. 



Infection may be obtained on pods of the Red Kidney bean if a water 

 suspension of the pathogene is sprayed or painted on them. If the pods 

 are injured, infection takes place more readily and with greater certainty, 

 although injury is not necessary. The first symptom of the lesion on the 

 pod is a small water-soaked pustule, which, however, soon breaks down 

 and a green water-soaked spot is formed. This condition persists for some 

 time, but later the lesions dry out and become brick red and slightly 

 sunken. When artificially inoculated pods are gathered in the greenhouse 

 and stored in envelopes in the laboratory, the lesions remain green in 

 appearance and rather gummy. In this respect it does not vary greatly 

 from the spots produced by Phyt. phaseoli. The early formation of a 

 pustule is the only difference. Inoculation of the pod at the peduncle has 

 resulted in water-soaked lesions along the suture (Plate IV, C). These 

 are indistinguishable from such lesions produced by Phyt. flaccumfaciens. 

 It was thought that some of the lesions on the stem and the pods had a 

 brownish coloration, which was lacking in symptoms due to the other 

 bacteria. In other instances, however, this color symptom was entirely 

 absent. Lesions produced on the leaves of Red Kidney plants in the 

 greenhouse could not be distinguished from those produced by Phyt. 

 phaseoli. They were in appearance similar to those found in Switzerland. 



In a few cases, young plants inoculated with this pathogene and left in 

 a greenhouse at a temperature of 65° F. did not develop the disease. 

 Other plants, however, of the same lots showed unmistakable symptoms 

 when placed in a temperature of 80° F. A high temperature seems neces- 

 sary for the development of the disease. 



