THE BEAN BLIGHT: CAUSE 



287 



(recent tests in +15 peptone beef bouillon). 

 The Idaho organism was dead after 5 months 

 on gelatin at 16° — 20°C. It is less sensitive 

 to sunlight than Bacteriuin inalvacearum. 



On a variety of culture media Bacterium 

 phaseoli is closely like Bacterium campestre 

 (See No. II) but the two organisms are not 

 identical, as shown by the failure of repeated 

 cross-inoculations (cabbage bacterium on 

 beans and bean bacterium on cabbages), but 

 our present means of separating the two 

 forms culturally is insufficient. It is also cul- 

 turally much like Bacterium citri, but with a 

 virulent strain I failed to obtain any scabs on 

 Citrus decumana (about 60 young seedlings). 

 The student, therefore, who has opportunity 

 might direct his attention to comparative 

 studies of the yellow organisms of this group 

 in the hope of finding additional cultural differ- 

 ences by the use of new media. But in any 

 event, Bacterium phaseoli belongs with Bac- 

 terium campestre, Bacterium hyacinthi, Bacter- 

 ium vascularum, Bacterium pruni, Bacterium 

 malvacearum (No. X), Bacterium citri, and 

 Bacterium translucens in a closely related 

 kinship. 



Technic, — Isolations are easy, owing to the 

 abundance and viability of the bacteria. 

 Only such ordinary precautions are necessary 

 as have been described in detail for other dis- 

 eases in this book, both earlier and later. 



Bacterium phaseoli is a good organism to 

 work with because it does not lose virulence 

 readily and plants for inoculation are quickly 

 available at all times of the year. As ma- 

 terial for experiment, both lima beans and bush 

 beans may be used. They can be infected 

 from germination almost to maturity, but the 



/" 



"4 4 



Fig. 220.— Bean 

 pod sprayed with 

 Bacterium phaseoli 

 and kept for 26 

 hours in an inocu- 

 lation cage. The 

 organism used was 

 cultivated from the 

 pod shown in Fig. 

 221. Time, 14 

 days. 1914. 



