Feb., 1922] 
ARNDT — ^THE GROWTH OF FIELD CORN 
55 
week. All the plants in solution ''A" were unquestionably chlorotic, 
which fact indicated that they did not secure sufficient iron. The plants 
grown in solution ''H " were of a normal color. Other experiments showed 
that an increase of iron in this solution did not increase the yield. An 
increase in the amount of ferric phosphate in solution "A" did increase the 
yield. The color of the plants, however, indicated that the iron was not 
available in sufficient quantities. Plate IV and also figure i show clearly 
the difference of growth in the various concentrations. 
II. The Effect of Iron Salts in Solution '*A" 
Two preliminary experiments, in which ferrous sulphate was used as a 
source of iron, were made in the fall of 1920. This was a poor period for 
growth because of the great amount of cloudy weather. The results are 
of interest in comparison with those of the experiment performed under 
more favorable conditions during March, 1921. In this experiment, the 
plants were grown for 25 days in 800-cc. jars. The first two experiments 
will be referred to in table 2 as series i and 2 respectively; the latter as 
series 3. The relative transpiration is reported for the last week of growth 
for series 3. During this period the average daily loss from the white and 
the black atmometer was 11.4 cc. and 13.6 cc. respectively. 
Table 2. The Ej^ect of Iron Salts upon the Relative Yields of Tops and Roots and upon 
Transpiration in Solution " H" — Also tlw Initial pH and the pH After Growth 
Yield of 
Trans- 
pH 
Yield of Tops 
Roots 
piration 
After Growth 
Salt 
Ini- 
tial 
Nor- 
mality 
Ser. I 
2 
3 
3 
3 
I 
2 
3 
0.00 
35% 
4-7 
5 
6.7 
FeS04.... 
0.00005 
74% 
88% 
81% 
.0001 
75 
92 
75 
5-6 
6.6 
.0002 
66% 
88 
100 
84 
.0005 
100 
TOO 
100 
100 
100 
5-5 
(2.6 gm.) 
(4.21 gm.) 
(24.7 gm.) 
(0.48 gm.) 
(790 cc.) 
.001 
68 
66 
54 
67 
52 
5 
5-2 
5-2 
.002 
62 
63 
4-3 
4.1 
.004 
47 
4 
.008 
21 
3-5 
6.8 
6.7 
6.6 
Fe(N03y3' 
.00005 
37 
38 
38 
.0005 
68 
73 
70 
3.9 
.001 
71 
74 
71 
3.5 
.002 
51 
63 
53 
3.2 
4.8 
All plants grown in the solutions containing ferric nitrate were chlorotic. 
This fact, and the low yields associated with it, indicated that ferric nitrate 
was much inferior to ferrous sulphate as a source of iron in solution "A." 
In all cases, the best yield was secured with 0.0005 N ferrous sulphate. 
The above-noted results for series 3 are shown graphically in figure 2. A 
comparison of figures i and 2 shows that the lack of iron does not usually 
