FUMIGATION OF CITRUS PLANTS. 17 
in experiments 14, 15, and 18, which were fumigated at temperatures 
ranging from 86° to 92° F. This would appear to indicate that the 
temperature 6f fumigation within the limits of those experiments, 60° 
and 92° F., has little if any modifying influence on the resulting 
degree of injury to plants subjected to the sunshine after treatment. 
It happens, however, that the prefumigation or postfumigation 
conditions in experiments 14, 15, and 18 were exactly comparable to 
those in none of the other experiments mentioned. Although section 
1 of experiment 15 approximates experiment 10 as to prefumigation 
and postfumigation conditions, it is seen that the maximum sun tem- 
perature for the day in experiment 15 was 77° F., whereas in experi- 
ment 10 it was 102° F. Therefore, definite conclusions regarding the 
influence of the temperature of fumigation on plants subsequently 
placed in sunshine can not be drawn until there is further experi- 
mental evidence bearing on this subject. 
The effect of postfumigation sunshine on plant injury appears to be 
modified to a certain degree by the prefumigation light condition. 
This is well shown by experiments 2 and 14, in which the damage to 
the plants under postfumigation sunshine is greater in the case of 
plants exposed to prefumigation sunshine than to plants in prefumi- 
gation shade at a comparable temperature. It is probable that the 
prefumigation temperature modifies to some degree the effect of 
postfumigation sunshine, but this point is not conclusively proved 
in this paper. : 
TEMPERATURE. 
The importance of the temperature to which plants are subjected 
after fumigation as a factor bearing on plant injury is brought out by 
the experimental data presented in experiments 1, and 10 to 19. It 
is shown in experiment 12 that fumigated plants placed immediate'y 
after treatment under a shade temperature of 88° F’. or a darkness tem- 
perature of 90° F. are slightly more injured than those placed at a 
temperature of 60° F. A like condition is presented in experiment 
15 between postfumigation temperatures of 63° F. and 89° or 91° F. 
Experiments 1, 14, and 18 also show slightly increased injury due to 
higher postfumigation temperatures in the shade or darkness. On 
the other hand, each experiment of numbers 2, 10, 13, 16, and 17 
shows the same degree of injury for plants subjected to different 
temperatures of shade and darkness following fumigation. An 
examination of the details of these experiments, however, brings out 
a significant difference between the two groups. In the set of experi- 
_ ments (2, 10, 13, 16, and 17) in which there was no apparent difference 
in injury due to the different postfumigation temperatures it 1s seen 
that the difference between the high and low temperatures in any one 
experiment varies from 9° in experiment 16 to a maximum of 16° in 
experiment 17; furthermore, that the maximum postfumigation 
4533°—Bull. 907—20——_3 
