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



143 



In test-tubes in beef-broth standing over chloroform the organism grew vigorously with only a 

 slight retardation and remained alive for more than 2 months. Under the same conditions Bad. 

 campestre refused to grow. 



In streaks on slant nutrient agar containing phenolphthalein and 0.5 per cent potassium formate, 

 considerable growth appeared at the end of 48 hours and a faint pink tint on the third day, none on 

 the second. At the end of the tenth day this color was still very faint and after 3 weeks transfers 

 from the tubes failed to grow. 



The organism also grew (after a second inoculation) in neutral beef-bouillon containing 1 per cent 

 potassium formate. 



Infected kernels were nearly sterilized by exposure for 15 minutes to 1 : 1000 mercuric chloride 

 water (see p. 125). 



Heat. The thermal death-point of Bad. stewarti in +15 beef-bouillon (10 minutes' exposure) 

 is approximately 53 C. In Uschinsky's solution it is a little higher. 



The maximum temperature for growth is about 39 C. It grows in the thermostat on most 

 media at 36 to 37 C, but not so well as at room-temperatures of 24 to 25 C. It refused to grow 

 in the thermostat at 40 C, in +0 beef-bouillon and in Uschinsky's solution. 



The minimum temperature for growth was determined as follows: In the earlier experiments 

 tubes of Uschinsky's solution and of alkaline beef-broth (382) were inoculated with a 3 mm. loop from 

 a fluid culture 3 days old and then exposed in the ice-box for 18 days at 2. 8 to 4.5 C. The checks 

 clouded the second and third days, but during all this time there was no clouding of the tubes in the 

 ice-box, and probably no growth because, contrary to Bad. hyacinthi, on removal to room-tempera- 

 tures the fluids did not cloud any sooner than the check-tubes. 



Subsequent experiments (summer of 1909) showed the minimum temperature to be about 9 C. 

 The exposure was for 34 days in the ice-thermostat with the results shown in table 20, four tubes 

 (two strains) being placed in each compartment in +15 peptonized beef -bouillon inoculated from 

 young cloudy bouillon-cultures. 



The checks at room-temperature clouded promptly. The tubes in compartments I, II, III 

 clouded on removal to room-temperature and showed a yellow precipitate. They were first exam- 

 ined on the ninth day. The optimum temperature for growth is above 30 C. 



*Some days later the other tubes showed the same phenomenon. 



