Nov. 15. 1919 Bacterial Blight of Soybean 187 



days, with a light, fluocculent pellicle forming, which later became heavy. 

 Fluorescence appeared in about 10 days and persisted throughout the 

 entire test, 7 weeks. At the end of this time the pellicle had disappeared; 

 but there was a heavy, flaky precipitate at the bottom of the cultures. 



Corn's solution. — The organism grew slowly in Cohn's solution. 

 No fluorescence appeared. 



Starch agar. — There was no evidence of diastatic action on potato 

 starch suspended in beef-peptone agar, when tested with potassium 

 iodid-iodin. 



Indol. — Erlich's test for indol was used with +10 beef-peptone 

 bouillon as the medium. There was a weak, positive reaction from the 

 third to the seventh day. After this time the cultures had grown too 

 dark to give the color test. 



Blood serum. — Stroke cultures on solidified blood serum gave a mod- 

 erate, rather flat growth, smooth, shining, and creamy white tinged with 

 brown. The medium was not liquefied. 



Aerobism. — The organism behaved as a weak facultative anaerobe. 

 Clouding occurred in the closed arm of the fermentation tubes with all 

 the sugars tested except dextrose. Definite though not vigorous growth 

 occurred below the surface in stab cultures. Stroke cultures of agar 

 also gave indication of slight growth for some distance below the surface. 



Litmus agar with sugars. — Litmus-lactose and litmus-maltose stroke 

 cultures developed good growth. In six days the medium began to brown 

 under the streak and finally turned a rich reddish brown throughout. 

 This is the same sort of change that takes place in all beef-peptone 

 media. There was no apparent reddening or bluing due to the predom- 

 inating production of acid or alkali, but, judging from the test with 

 carbohydrates in fermentation tubes, it is probable that such changes 

 took place and were masked by the browning of the medium. 



On litmus-dextrose agar there was abundant growth and a distinct 

 acid reaction. In seven days the cultures had become decidedly scarlet. 

 In about six weeks the red color disappeared again, leaving the cultures 

 about the same color as the controls. 



TEMPERATURE relations 



Cultures on potato agar and in -|- 10 beef -peptone bouillon proved the 

 optimum temperature to be between 24° and 26° C. No growth occurred 

 at 35° either in bouillon or on agar. Rather slow but fairly heavy 

 growth occurred both on agar and in bouillon at 2°. The extreme 

 minimum was not determined. 



Several trials have shown the thermal death point of 2-hour cultures 

 made from 2-day-old cultures to be 48° to 49° C. for freshly isolated, 

 vigorous strains. Consistent results have been secured in trials of three 

 different years. Isolations which have been cultured for some time. 



