4 86 



Journal of Agricultural Research 



Vol. XX, No. 6 



EXPERIMENT 7 



Heretofore, in all the experiments at low temperature no attempt was 

 made to bring either the plants or cultures to the temperature of the case 

 to which they were subsequently exposed. To check this phase of the 

 work one set of plants was inoculated in the usual way. In the second 

 set, the plants and cultures were held at 15 C. for 24 hours before the 

 inoculations were made, to insure that both the plants and the organisms 

 in culture were at the temperature desired. As will be noted in Table 

 XVII, no canker developed on the plants of either set at 15 during the 

 18-day period they remained at this temperature. However, when both 

 sets were transferred to the 30 case, canker appeared on the citrange 

 and grapefruit plants in about the same proportion. The first method of 

 inoculation which was more generally used compared favorably with the 

 second method herein described. A similar experiment was carried out 

 at 20 . The period of incubation, amount of infection, and growth of 

 the plants were the same in the two experiments. 



Table XVII. — Comparison of methods of inoculating plants at low temperatures 



EXPERIMENT 7 



n R= greenhouse temperature. 

 EXPERIMENT 5A 



The results obtained in experiment 5 seemed to indicate clearly that 

 at 35 C. the growth of grapefruit and plants of the same type was 

 practically inhibited, whereas the trifoliate orange and limequat were 

 both able to make a normal growth. It will be noted that four sets of 

 plants were used in this experiment. After the four sets of plants 

 remained at this temperature overnight, they were inoculated with 

 5-day-old cultures of the organism grown at temperatures of io°, 15 , 

 25 , and 35 C, respectively. 



