30 
Journal of Agricultural Research 
Vol. XXVI, No. r 
The maximum temperature difference observed between the turgid 
and wilted leaves of corn exposed to the direct rays of the sun was 4.3 0 C. 
This temperature value is the average of 20 determinations made during 
a 10-minute period from 11.05 to 11.15 a. m., when the average tempera¬ 
ture of the air for the period was 32.3 0 C., and the transpiration rate 
from the turgid plants was approximately five times that from the wilted 
plants. The average temperature of the turgid and wilted leaves for more 
than 600 determinations during the hours of 9 a. m. to 4 p. m. over a period 
of eight days during the months of July and August was 30.65° and 32.5°, 
respectively. Thus the average temperature of the wilted leaves of corn 
was 1.85° C. higher than that of the turgid leaves, under the conditions 
prevailing during the experiments. The average temperature of the air 
during these experimental periods was 30.65° C., while the average tran¬ 
spiration rate for the turgid plants was 105.3 gm 2 h as compared to 43.2 
gm 2 h from the wilted plants. 
The average transpiration rate of the turgid and wilted sorghum plants 
from 9 a. m. to 4 p. m. over a period of eight days was 110.9 gm 2 h and 
45.6 gm 2 h, respectively. The average of 650 temperature determinations 
of turgid and wilted leaves during that period was respectively 30.77° C. 
and 32.32° C., while the temperature of the air averaged 30.75° C. The 
temperature of the wilted leaves under these conditions averaged 1.55° C. 
higher than that of the turgid leaves. 
In the experiments with soybeans, the average rate of transpiration 
from the turgid plants was 70.5 gm 2 h and from the wilted plants 20.5 
gm 2 h, while the average temperature of the air was 34.i°C. Under these 
conditions the average temperature for 200 determinations over a period 
of four days in July, when the plants had reached their full vegetative 
growth, was 37.5° C. for the wilted leaves and 34.7 0 C. for the turgid 
leaves. The average temperature of the wilted leaves was thus 2.8° C- 
higher than that of the turgid leaves. 
The average temperature of the air during the experiments with cow- 
peas was 35.7° C. and the transpiration rate of the turgid plants was 3.5 
times that of the wilted plants. The average temperature of the turgid 
leaves for 200 observations was 36° C., while that of the wilted leaves 
was 40.65° C. The average difference in temperature between the turgid 
and wilted leaves of cowpeas was 4.65° C. This was the greatest average 
difference observed in the experiments with these four species of plants. 
The maximum temperature difference observed between the wilted and 
turgid leaves of cowpeas was 6.7° C. during a 15-minute period from 1.15 
to 1.30 p. m., when the temperature of the air was 37.6° C. and the trans¬ 
piration rate of the wilted plant was approximately only one-sixteenth 
that of the turgid plants. 
The observations upon the plants just mentioned show that the 
temperature of a wilted leaf in direct sunlight is always higher than the 
temperature of a turgid leaf exposed to the same conditions. The 
average temperature of the wilted leaves of corn, sorghum, soybean, 
and cowpeas during the hours of 9 a. m. and 4 p. m. was respectively 
1.85°, 1.55°, 2.8°, and 4.65° C. higher than that of the turgid leaves. 
These differences in temperature are not striking, and it would seem 
doubtful whether the increased temperature of the wilted leaves, with the 
possible exception of the case of cowpeas, could to any marked degree 
injure the protoplasm or even retard its vital activities. We need to 
know more, however, about the effect of temperature upon the proto¬ 
plasm of these plants before any definite statements can be made con- 
