Mayij. i9i8 Some Bacterial Diseases of Lettuce 379 



LOSS OF VIRULENCE 



No loss of virulence vvas noticed when inoculations were made within 

 eight months to a year after isolation. 



GROUP NUMBER 



According to the descriptive chart of the Society of American Bac- 

 teriologists, the group number is 211.3332523. 



The name ' 'Bactermm vitians, n. sp.," is suggested for this organism. 



BRIEF TECHNICAL DESCRIPTION OF THE ORGANISM 

 Bacterium vitians, n. sp. 



A short motile rod Avith rounded ends, flagella bipolar, but usually one at one pole; 

 capsules, pseudozoogloeae, no spores, involution forms rare and few t3'pes, aerobic; 

 agar colonies, light-cream color, smooth, thin, round, light and dark areas in an hour- 

 glass arrangement when young; when older, shading disappears, and all are cream- 

 yellow. Growth on potato cylinders is abundant, bright yellow; produces alkaline 

 reaction in litmus milk, with a gradual separation of the whey from the curd, curd 

 partly digested; liquefies gelatin slowly; produces ammonia, hydrogen siilphid, 

 indol (slight); does not reduce nitrates; feeble diastasic action on potato starch; grows 

 in Uschinsky's solution; grows feebly or not at all in Cohn's solution; thermal death 

 point 51° to 52° C. Maximum temperature for growth 35° C, minimum below 0° 

 C, optimum 26° to 28° C. Vitality two months to over a year in liquid media, de- 

 pending on temperature and evaporation. Is Gram negative, and is not acid-fast; 

 stains readily with basic anilin dyes. Not killed very readily by drying, not very 

 sensitive to sunlight; slight toleration of acids and alkalies (tolerates tartaric in neu- 

 tral beef bouillon to -5-23 Fuller's scale, malic +25 Fuller's scale, citric -I-17; toler- 

 ates sodium hydroxid in beef bouillon to —25;; retains its virulence over one year. 



ISOLATIONS AND INOCULATIONS WITH ORGANISMS FROM VIRGINIA 



LETTUCE 



Two organisms were isolated from the spots in the diseased plants 

 from the lettuce-growing sections along Hampton Roads, Virginia: 

 one (8) the Louisiana organism, Bacterium viridilividum (PI. 35, D), 

 and the other the South Carolina organism, Bacterium vitians. 

 Isolations were m.ade from plants from three different farms, and what- 

 ever skepticism there might have been at first because of the presence 

 of two distinct pathogenic organisms was dispelled when the tv^^o familiar 

 colonies persisted in appearing on the plates. 



The isolations of Bact. Tiridilividum produced spotting of the leaves 

 when inoculated into greenhouse plants (PI. 37, A). The isolation of 

 Bact. vitians also produced spotting and rotting of leaves when in- 

 oculated into greenhouse plants (PI. 38), and likewise the typical stem 

 disease when inoculated into the stems (PI. 37, B). There was no nat- 

 ural infection of the stems in the diseased lettuce from the Virginia 

 fields, but the inoculations in the stem were made to prove the full 

 pathogenicity of the organism as compared with that isolated from the 



