Jan., 1923] BAKKE AND ERDMAN — CULTURES OF MARQUIS WHEAT 
27 
sand cultures (12.54-6.67) is found in the lower left central portion of 
the triangle. 
The position of the low-yielding root cultures of the water series is 
identical with that of the low-yielding top cultures, but this relation does 
not hold true, at least under the present experiment, for the sand-culture 
series. 
Climatic Conditions 
In order that environmental conditions might be as uniform as possible, 
the cultures were placed upon two revolving tables. The water cultures 
occupied one and the sand cultures the other. 
The following aerial records were secured for the entire growth period: 
(1) temperature; (2) evaporating power of the air; (3) amount of radiant 
energy absorbed; and (4) number of hours of sunshine. 
Temperature records were obtained from a thermograph placed near the 
revolving tables. The evaporating power of the air was measured by means 
of white and black standardized spherical porous-cup atmometers (Living¬ 
ston, 7). The atmometers were weighed after each 3j-day interval and 
cleaned once a week. The amount of radiant energy (Livingston, 7) 
absorbed was determined by the difference in the losses between the cor¬ 
rected readings of the black cup and the readings of the white cup. The 
duration of sunshine data was kindly furnished by Mr. Charles D. Reed of. 
the United States Weather Bureau office at Des Moines, Iowa. The data, 
relating to environmental conditions are given in table 3. 
Table 3. Weekly Averages of Climatic Conditions for the Growth Period 
Date 
Week 
Evaporating Power 
Radiant 
Energy 
Temperature 
of Air 
Sun¬ 
Ending 
Loss 
White 
Sphere 
Loss 
Black 
Sphere 
Ab¬ 
sorbed 
shine 
Average 
Maxi¬ 
mum 
Average 
Mini¬ 
mum 
Mean 
G. 
G. 
G. 
Hours 
°C. 
°C. 
°C. 
Januarv 24. 
82.7 
105.8 
23.1 
38.6 
23.1 
12.9 
18.0 
3 i . 
64.2 
76.8 
12.6 
18.5 
22.0 
12.1 
I 7 -I 
February 7. 
59-8 
76.9 
17.1 
27.1 
23.2 
12.6 
17.9 
14 . 
69.5 
94.6 
25.1 
33-6 
21.7 
13.2 
17-5 
21. 
84-5 
120.4 
35-9 
71.2 
25.0 
10.8 
17.9 
28. 
74.8 
102.3 
27-5 
48.2 
30.0 
16.7 
23-4 
March 7. 
70.4 
80.3 
9.9 
45-5 
27.6 
13-9 
20.8 
14 . 
64.2 
105.8 
41.6 
33-7 
25.8 
14.8 
20.3 
21. 
92.4 
135-0 
42.6 
72.6 
31.7 
12.9 
22.3 
24. 
36.1 
49.0 
12.9 
14.4 
26.8 
18.1 
22.5 
Total. 
Daily average.... 
698.6 
10.1 
946.9 
13 -7 
248.3 
3-6 
403.4 
25.5 
13.6 
19.6 
An examination of the data presented in table 3 shows that the plants 
