Dec. i 5 . 1920 Effect of Temperature and Humidity on Citrus-Canker 49 1 



out that there is a distinct relation between temperature and humidity 

 on the viability of the citrus-canker organism, so far as this experiment is 

 concerned. It is interesting to note that at the low temperatures humid- 

 ity apparently has little influence on the viability of the organism on the 

 threads, while at the higher temperatures it is the limiting factor, espe- 

 cially at the higher humidities. At the humidities generally encountered 

 in the field in Alabama the organisms are viable at all temperatures on 

 the threads for eight days. Another puzzling fact is that in ordinary 

 distilled water the organism remained viable at temperatures between 

 io° and 35 C. for a period of eight days, while at the higher tempera- 

 tures (30 ) the organisms are dead at the end of 24 hours in a saturated 

 atmosphere. 



Table XVII. — Viability of Pseudomonas citri on silk threads at varying humidities over 



sulphuric acid 



