THE TEMPERATURE OF LEAVES OF PINUS IN WINTER 55 
the leaf maintained, under the conditions given, a temperature of 
6.04° C. higher than the air. This is shown by the averages of columns 
4, 5, and 8. The maximum temperature difference for the day was 
7-95° C. 
The following Table V shows a maximum leaf temperature of 
8.83° above that of surrounding air, the air temperature in this series 
of observations being considerably higher than that shown in Table IV, 
Table V 
February 27, 1914 
Clear. Light breeze. Relative humidity 66.5% 
I 
2 
3 
4 
5 
6 
7 
8 
9 
Time of Ob- 
servation 
No. of 
Obser- 
vations 
Aver. 
Bridge 
Reading 
in Cm. 
Calculated 
Temp. 
Diff. 
Shade 
Temp. 
Black Bulb 
in Vacuum 
Diff. 
Columns 
5 and 6 
Actual 
Leaf 
Temp. 
Wind 
Velocity- 
Miles 
per Hr. 
8.002 
9-15 
9-25 
9-33 
10.05 
5 
4 
5 
8 
5 
5-7 
18.6 
16.4 
32.5 
46.9 
.69° 
2.24 
1.97 
3-90 
5.60 
- 2.0° 
0 
0.8 
1.5 
3-0 
7.2° 
18.9 
20.6 
23-9 
24.4 
9.2° 
18.9 
19.8 
22.4 
21.4 
-1.31° 
2.24 
2.77 
5.40 
8.60 
1.2 
1.2 
3.6 
I.O 
1.2 
10.54 
10.55 
10.555 
10.56 
10.565 
10.57 
10.58 
10.59 
50.5 
66.5 
73-0 
74.6 
58.5 
61.2 
63.0 
57-0 
6.02 
7.93 
8.71 
8.83 
6.98 
7-30 
7-52 
6.80 
> 4.0 
29-3 
25-3 
10.02 
11-93 
12.71 
12.83 
10.98 
11.30 
11.52 
10.80 
►1.2 
11.05 
12.34 
5 
6 
28.1 
18.5 
3-35 
2.20 
4.2 
5.1 
31.7 
32.2 
27-5 
27.1 
7-55 
7-30 
2.4 
2.4 
Average 
3.82 
2.66 
6.48 
The conditions under which the results in Table VI were obtained 
differ somewhat from those of the preceding Table IV. The air 
temperature averaged 3.85° C. lower and the average wind velocity 
was .7 miles per hour greater. Also the difference between the shade 
temperature and that recorded by the black-bulb thermometer was 
2.7° C. lower. Under these conditions the average differential 
temperature between leaf and air was 3.56° C. and the maximum 
5-19° C. 
(2) The Effect of One Fourth to One Half Full Sunlight. — That a 
decrease in the intensity of solar radiation, other conditions remaining 
2 Not included in the averages. 
