The Bacterial Diseases of the Bean 67 



blue and is reduced; a green fluorescent growth appears in Uschinsky's 

 and in Fermi's solutions; there is no growth in Cohn's solution; growth is 

 slight on potato; there is no digestion of starch in starch agar; acid is 

 produced in dextrose broth, but not in saccharose, lactose, or maltose broth; 

 no gas is produced in any of these sugar broths; indol is not produced; 

 nitrates are not reduced to nitrites; hydrogen-sulfide production, if any, 

 is slight; the thermal death-point varies from 48° to 50° C. 



The organism is pathogenic on the bean (Phaseolus vulgaris) and on a 

 number of related leguminous plants. 



ANOTHER STRAIN OF PHYTOMONAS VIRIDIFLAVA 



Another strain of Phytomonas viridiflava was obtained from diseased 

 specimens of bean leaves collected in England. This strain varied in a 

 few respects from the one obtained in Switzerland, but the difference 

 consisted primarily in the English strain being a weaker parasite. Since 

 it has been shown that the Swiss organism loses its virulence, and even its 

 pathogenicity, in pure culture, virulence is scarcely a characteristic to be 

 considered seriously in this species, especially taxonomically. Certain 

 interesting points of pathogenicity, however, are considered worthy of 

 reporting. 



The diseased leaves from which the pathogene was isolated were of the 

 scarlet runner type, and the spots observed on them were, in most cases, 

 small. The largest and most conspicuous of these lesions are shown in 

 figure 14. The leaves were collected in a garden near Canterbury, England, 

 in September of 1927, and the isolation of the pathogene was made a 

 month later. The cultural characteristics and the physiological reactions 

 of the English strain were identical with those of the Swiss strain. This 

 was a sufficient reason for considering them of the same species. 



The peculiarities of the English strain of Phyt. viridiflava became notice- 

 able, however, when attempts were made to infect with it the bean and 

 related species. When inoculations were made on the seedlings of bean 

 plants, infection was not obtained even though the stems of the plants 

 were injured. The bacteria were unable to establish themselves in the 

 tender young tissue of the growing stem, and the mechanical injury made 

 on the plant quickly healed. Small lesions, nevertheless, were produced 

 on the leaves of several species of plants, including Phaseolus vulgaris and 

 P. coccineus. In these cases the leaves had been punctured with a needle 

 at the time when the inoculum was applied. The spots always remained 

 small, but on miscropical examination it was found that the bacteria were 

 in abundance in the dead and dying cells. This showed that the organism 

 was pathogenic, but its virulence appeared to be low. 



Inoculation experiments were then made on the pods of the common 

 bean and a number of related species. Here the results were different, 

 since this tissue proved to be more susceptible to the pathogene. The 



