Dec. is, 1920 Effect of Temperature and Humidity on Citrus-Canker 45 1 



Growth is inhibited at 5 C. and again at 33 to 35 . At io° some 

 growth occurs. That the organism is not killed at 5 , but is merely 

 inhibited, was shown when plates kept at this temperature for eight days 

 were transferred to the 30 case. Growth immediately took place at 

 the normal rate for that temperature. The same was true when plates 

 held at 33 to 35 for eight days were transferred to 30 ; the organism 

 started growing. However, when plates held at 38 to 40 for 24 hours 



FlG. i. — Graph showingthe rate of enzym action, as expressed in millimeters, at the various temperatures 

 for a period of eight days on soluble starch agar. 



were placed in the 30 case, no growth took place, showing that the 

 organism had been killed by the higher temperatures. Thus, in working 

 out the temperature relations of Pseudomonas citri, the temperature at 

 which growth is inhibited must be clearly distinguished from the tem- 

 perature at which the organism is killed. 



Table II gives the rate of enzym action at the various temperatures. 

 E?ch reading represents an average of 28 measurements. 



