Aug. i6, I9I5 Bacterial Disease of Lettuce 477 



the dark at room temperature (20° to 23° C.) will produce growth up to 

 the eleventh day of drying when such covers are placed in tubes of beef 

 bouillon. 



It is not especially sensitive to sunlight. Petri dishes, one half covered 

 with black paper and exposed bottom up to the noon-day sun in April on 

 a sack of ice, developed 15 to 30 colonies on the uncovered parts exposed 

 for 30 minutes, but none at 40 minutes. The covered part of the 30- 

 minute plates developed from 130 to 150 colonies; that of the 40-minute 

 plates developed from 30 to 55 colonies. 



The organism likewise grows in neutral beef bouillon containing 3 and 

 4.5 per cent of sodium chlorid, but does not grow in the same medium 

 with 5 per cent of common salt. It produces indol, but less abundantly 

 than Bacillus colt, and does not reduce nitrates. 



Stained from young agar cultures, the organism is a short rod with 

 rounded ends. It is less than i to i.25/£ in diameter and 1.25 to 3/1 long. 

 It occurs singly, in pairs, and also in chains. Spores have not been 

 observed. The organism stains readily with carbol fuchsin, gentian 

 violet, methyl violet, and methylene blue. It is Gram-positive, and is 

 not acid-fast. The flagella were stained by Loeffler's fiagella stain. 



A bacterial disease of lettuce has been reported from the Vermont, 

 the Massachusetts, the Florida, and the North Carolina experiment 

 stations. Pietro Voglino (1904)^ in Italy has reported a bacterial dis- 

 ease of lettuce and named his organism "Bacillus lactuacae." As the 

 description of the organism reported in his paper does not agree with 

 our own (pink, nonHquefying, spore-bearing, etc.), it is clear that the 

 Louisiana organism is not the same as the Italian, but is possibly the 

 same as some one of the unnamed forms previously isolated in this 

 country and not carefully described. The name "Bacterium viridi- 

 lividum, n. sp.," is suggested for the one under consideration, owing to 

 its peculiar appearance on steamed potato. 



For purposes of orientation, a short account of the literature on bac- 

 terial diseases of lettuce follows: 



h. R. Jones (1893)^ has given an account of a bacterial stem-rot of 

 lettuce. A large bacillus was found in the diseased stems, but was not 

 isolated. He reproduced the disease (i) by planting healthy plants 

 in soil inoculated with fragments of lettuce plants affected by "stem 

 rot," (2) by crushing a diseased lettuce head in a little water and pouring 

 this water about the roots of healthy plants. 



G. E. Stone (1907) mentions a bacterial disease of lettuce leaves 

 which had been investigated by Mr. Percival C. Brooks six years earlier. 

 It is stated that Mr. Brooks isolated an organism and produced positive 

 results from inoculation experiments. As the disease was believed to 



' Bibliographic citatiMis in parentheses refer to "Literature dted," p. 478. 

 96502°— 15 8 



