Transpiration as a Factor in Crop Production. 89 
Table 24. — Summary of transpiration, free-water-surface evapo- 
ration, and weather factors during successive hours of the day 
and night. (Only the total water losses were obtained for the 
night. Average for 30 days during July 1^ to August 22, 191 U.) 
Hour ending 
Water 
transpired 
from one 
plant (av. 
30 days) 
Water 
evaporated 
from 36 sq. 
in. free 
water surface 
(av. 30 days) 
Mean 
tempera- 
ture (av. 
30 days) 
Mean 
relative 
humidity 
(av. 30 
days) 
Mean 
wind ve- 
locity (av. 
30 days) 
(1) 
Night 
9 p. m 
10 " 
11 " 
12 " 
1 a. m. 
2 " 
3 " 
4 " 
5 " 
6 " 
7 " 
(2) 
Grams 
(3) 
Grams 
(4) 
Degrees F. 
79.1 
77.0 
75.6 
74.5 
73.1 
72.3 
71.2 
70.5 
69.7 
68.6 
69.4 
(5) 
Per cent 
70 2 
75il 
76.8 
79.4 
80.6 
82.2 
84.0 
86.1 
86.8 
88.5 
87.2 
(6) 
Miles 
6 2 
6^8 
7.3 
7.1 
6.5 
6.0 
6.2 
5.8 
5.9 
5.4 
5.2 
Av. for night . . . 
15.8 
2.32 
72.8 
81.5 
6.2 
DAY 
8 a. m. 
84 
4.8 
73.6 
80.2 
6.0 
9 " 
111 
7.7 
77.9 
72.8 
6.9 
10 " 
167 
11.6 
81.7 
67.1 
8.0 
11 " 
215 
15.0 
84.8 
62.7 
8.2 
12 " 
279 
19.2 
87.5 
58.5 
8.7 
1 p. m. 
329 
23.7 
89.5 
55.3 
8.9 
2 " 
356 
24.5 
90.8 
52.7 
9.4 
3 " 
354 
23.8 
91.2 
51.6 
9.2 
4 " 
343 
22.2 
91.0 
50.4 
9.0 
5 " 
294 
18.5 
89.9 
51.1 
8.5 
6 " 
217 
14.1 
88.2 
52.6 
8.3 
7 99 
132 
10.2 
85.1 
58.1 
7.2 
8 " 
64 
6.4 
81.7 
64.5 
6.7 
Av. for day .... 
226.5 
15.5 
85.6 
59.8 
8.1 
tion rates occurred at the same hour — 2 p. m. There is a rather 
long interval, approximately 1:00 p. m. to 4:00 p. m., during 
which the rate of loss is rather constant. As a whole, the water 
losses follow fairly regularly the natural sequence of the climatic 
changes. Transpiration or evaporation from the plant and the 
evaporation from a free water surface respond as nearly alike to 
changes in the climatic conditions during the day as one could 
expect from evaporating surfaces so dissimilar. 
