>rayi3, igis Some Bacterial Diseases of Lettuce 377 



the tubes where the transfers v.ere made. The paper became well blackened in 

 every case. 



TOLERATION OF ACIDS 



Tests were made with tartaric, malic, and citric acids, and it was 

 found that the organism is most sensitive to the presence of small quan- 

 tities of citric acid. There was a good growth in neutral beef bouillon 

 with 0.1 per cent of tartaric acid, which titrated +23 on Fuller's scale, 

 but no growth at all where 0.2 per cent of tartaric acid was added. 

 There was good growth also in neutral beef bouillon to which o.i per 

 cent of malic acid was added, which titrated +25 on Fuller's scale. 

 There was no growth in the bouillon to which 0.2 per cent of malic acid 

 was added. Three tests were made with neutral beef bouillon to which 

 0.1 per cent of citric acid was added, but growth occurred only once, in 

 which the medium titrated +17. The negative tests titrated a little 

 higher. 



TOLERATION OF SODIUM HYDROXID 



The organism tolerates sodium hydroxid to —25 on Fuller's scale. 

 Tests were made in beef bouillon containing sodium hydroxid titrating 

 — 20, — ^5, — 30, — 35, and —40. In 2 days there w^as a slight clouding 

 in —20 and in —25, but none in —30, —35, or —40. 



TEMPERATURE RELATIONS 



Thermal death point. — ^When transfers are made from a well- 

 clouded bouillon culture of 24 hours and kept at 52° C. in a water bath 

 for 10 minutes, no growth occurs. This test was repeated many times. 

 Sometimes growth occurred at 51°. The thermal death point lies, 

 therefore, between 51° and 52°. 



Maximum temperature. — The maximum temperature for growth is 

 35° C. 



Minimum temperature. — The minimum temperature for growth is 

 below 0° C. 



Optimum temperature. — The optimum temperature is 26° to 28° C. 



Beef agar and bouillon cultures were used for the three preceding 

 temperature tests. 



Gas formation. — The organism is aerobic and does not form gas. It 

 was tested in fermentation tubes in the presence of each of the following 

 carbon compounds: Glycerin, dextrose, lactose, saccharose, maltose, 

 and mannit, i per cent of these being added to a i per cent water solu- 

 tion of Witte's peptone. No gas formed in any of the tubes, and no 

 growth took place in the closed arm of the tubes. However, growth 

 occurred in the open end of each tube. In the test for acid and alkaline 

 reactions with neutral litmus paper all showed alkaline reactions. 

 4J)386°— 18 3 



