8 BULLETIN 907, TJ. S. DEPARTMENT OE AGRICULTURE. 



TEMPERATURE. 



The relation of temperature before fumigation to plant injury is 

 brought out in experiments 2, 3, 5, 14, 15, and 18. In experiment 3 

 it is seen that plants at a shade temperature of 90° F. before fumiga- 

 tion were no more severely injured than others at a temperature of 

 56° F. Practically identical results occurred in experiment 5, where 

 the prefumigation conditions were darkness at temperatures of 64°- 

 66° F. and 90°-102° F., and in both cases merely the tenderest growth 

 was slightly injured. Experiments 3" and 5 were performed at cool 

 temperatures, and the postfumigation environment was cool. On 

 the other hand, experiment 15, which was conducted at the high tem- 

 peratures of 86°-91° F., developed no difference in injury between 

 plants at prefumigation temperatures of 62° and 90° F. 



In experiments 14 and 18 most of the plants showed no apparent 

 difference in injury attributable to temperature before exposure. A 

 few plants, however, did show slightly greater injury than others 

 under similar postfumigation conditions and in these cases all the 

 more severely injured plants were under the highest prefumigation 

 temperatures (80° and 76° F., respectively). These two experiments 

 were performed at comparatively high temperatures (85° to 92° F.). 



It would appear from these experiments, therefore, that where 

 plants are in shade or darkness the temperature immediately previous 

 to fumigation has little influence on the resultant plant injury. 

 Sometimes, however, a difference in plant injury apparently due to 

 heat influences develops, and in such cases the greatest injury appears 

 on those plants subject to the highest prefumigation temperatures. 

 In the experiments in this paper the prefumigation temperatures 

 ranged between 56° and 102° F. Within these limits there was little 

 or no difference in injury where the fumigation and postfumigation 

 temperatures were both below 70° F. However, slightly more 

 increased injury did occur at the prefumigation temperatures of 76° 

 and 80° F. than at 56° F. in two experiments in which the actual 

 fumigation temperature was about 85° F. This would indicate the 

 advisability of keeping plants at a cool temperature prior to fumiga- 

 tion in case the fumigation and postfumigation environments are 

 hot. If the fumigation and postfumigation temperatures are cool 

 a comparatively high prefumigation temperature appears to have 

 little more effect on the results than a cool temperature. 



SUNSHENTE. 



The influence of sunshine on plants before fumigation is shown by 

 the results of experiments 1 to 4, 12, 14, 15, and 18. In experiment 

 1 this influence previous to the gas treatment contrasts sharply with 

 that of diffused light or darkness. Sun and shade exposed plants 

 under cool temperature conditions were fumigated at the same time 

 and on removal from the fumigatorium were placed under five dif- 



