STEWART'S DISEASE OF SWEET-CORN (MAIZE). 137 



This experiment was repeated in 1908, using a beef broth free from peptone and concen- 

 trating it until it titrated +73. Bad. stewarti from three sources was tested. Each tube 

 was inoculated with three 3-mm. loops from bouillon. There was no clouding for the first 

 three days or more, but afterwards a heavy growth. On the thirteenth day the tubes were 

 heavily clouded with a buff-yellow rim (2 to 3 mm. wide), a thin pellicle, scarcely visible, 

 and considerable buff-yellow flocculent precipitate. Tubes 10 days old but inoculated from 

 a solid culture (potato) were heavily clouded with heavy yellow rims (2 to 3 mm.) and a 

 wide buff-yellow precipitate. 



Bact. stewarti grows in milk for a long time without precipitation of the casein, or suffi- 

 cient production of alkali to render the milk translucent. There is no visible change in the 

 milk, even after several months, although the organism forms on the wall of the tube, at the 

 surface, a distinct yellow bacterial rim and an abundant bright yellow precipitate. There 

 is a change, however, in the milk, as shown by the litmus reaction. In litmus milk there is 

 a gradual slight development of acid. The color of the litmus, on the start a deep lavender 

 blue, becomes a lilac color or dull purple (pi. 1 1, figs. 3, 4, 5). Usually this color does not 

 appear until after about two weeks, and sometimes a longer period intervenes. In the end 

 the litmus is more or less reduced, sometimes entirely. This reduction may occur early, but 

 often not until after several to many weeks. Frequently the acid reaction is obscured by 

 reductions. The organism produces no lab ferment, and not enough acid to cause coagula- 

 tion. No crystals were observed in milk-cultures. 



In 8 tubes of litmus milk (stock 697), inoculated in 1902, the litmus was entirely reduced 

 at the end of 16 days; there was then a slight yellow precipitate ; a pale yellow rim was begin- 

 ning to form at the surface ; the milk was entirely fluid. At the end of a month there was no 

 separation of the casein, the litmus was still entirely reduced in two tubes and nearly reduced 

 in the others, there being, however, a slight pinkish hue at the top. The check remained 

 unchanged. At the end of 10 weeks there was a yellow precipitate about 10 mm. broad, a 

 yellow rim 6 to 7 mm. wide, and in some of the tubes a yellow pellicle or partial pellicle. 

 The amount of litmus reduction varied a little ; it was complete in several tubes and nearly 

 so in the others. The milk in the tube showing most color was pinkish vinaceous (Ridgway) 

 in the upper half. 



At the end of 14 weeks the reduction was still quite marked, but not complete. The 

 returning color of the litmus was various shades of lilac, i. e., quite distinct from the 

 unchanged deep lavender of the check tubes. At this date the milk was still fluid ; there had 

 been no separation of the casein; the bacterial rim was about 10 mm. wide and dirty yellow. 

 Two of the cultures were slightly viscid, one decidedly viscid, and 5 not viscid. Streaks on 

 slant agar made at this time from these tubes yielded 8 pure cultures of Bact. stewarti. 

 These milk cultures were also alive at the end of 7 months, as determined by cultures in 

 bouillon and on potato. 



The same results with litmus milk were obtained in 1908. There was good growth, 

 slow change from blue to lilac color, and no separation of the casein. 



In the following medium Bact. stewarti did not grow. Distilled water i ,000, dipotassium 

 phosphate 2, magnesium sulphate o.i, ammonium phosphate o.i, sodium acetate 5. Bact. 

 campestre grew in it feebly. Repeated several years later (1908) with same result. 



In Uschinsky's solution, Bact. stewarti grew for a long time and very copiously. It is a 

 good medium for differential purposes. 



The general appearance of cultures in Uschinsky's solution was as follows : The growth 

 was slightly retarded and sometimes rather feeble at first, then copious and long continued ; 

 rim whitish at first, then distinctly yellow and of variable width ; a yellow pellicle, sometimes 

 bearing yellow colonies; copious chrome-yellow to buff -yellow precipitate, fluid gradually 

 becomes slightly fluorescent, but less distinctly so than in case of Bact. pruni; pseudozoo- 

 gloeae are present. In one set of tube-cultures made in 1902, in stock 702, there was at the 



