Journal of Agricultural Research 
Vol. VII, No. i 2 
516 
Table IX. —Comparative weights of rice plants grown in acid and neutral solutions , with 
dialyzed iron as the source of iron 
Nutrient 
solution. 
Neutral.... 
Do. 
Do...... 
Do. 
Do. 
Acid. 
Quantity 
of iron, 
per liter. 
O. 002 
. 008 
. 002 
. 008 
. 008 
. 008 
Source of iron. 
Dialyzed iron,. 
...do . 
f Ferrous sul- 
\ phate. 
....do . 
Dialyzed iron.. 
_do. 
Flasks 
No. 
Green 
weight 
of stalks 
and 
leaves. 
Oven- 
dry 
weight 
of stalks 
and 
leaves. 
Oven- 
dry 
weight 
of roots. 
Average oven-dry 
weight of— 
Stalks. • 
and 
leaves. 
Whole 
plant. 
Gm. 
Gm. 
Gm. 
Gm. 
Gm. 
1-6 
O. 67 
O. 15 
O.054 
. 7-12 
. 61 
. 16 
•054 
O. 16 
0. 21 
13-18 
•63 
• 17 
• 054 
.19-24 
. 61 
. 16 
• 054 
. 16 
. 22 
25-3° 
62. 19 
8. 27 
i. 86 
.31-36 
65.07 
8.48 
1. 92 
8. 38 
IO. 27 
37-42 
128. 62 
16.31 
3-73 
.43-48 
* 37 - 50 
16. 73 
4. 01 
16. 52 
20. 39 
49-54 
.90 
.16 
. 062 
, 55 - 6 ° 
•99 
. 19 
. 062 
. 18 
. 24 
73-78 
4-38 
.67 
. 182 
.79-84 
4. 26 
.64 
. 176 
.66 
.84 
Experiment io (Effect of applying ferrous sulphate to leaves of plants 
grown in solutions where iron was markedly unavailable).—In experiment 
4 rice failed to grow appreciably in the alkaline solution when 0.008 
gm. of iron per liter from ferrous sulphate was used, although it made 
a fair growth with 0.002 gm. of iron, and in the previous experiment no 
perceptible growth was made in the neutral solution with dialyzed iron. 
In order to be certain that the inability of the plants to grow in these 
solutions was due to a lack of available iron, the following test was made 
of applying iron to the leaves. 
The leaves of plants in these two solutions were brushed with ferrous 
sulphate, and two control lots were not brushed. The specially treated 
plants were brushed once with a 0.1 per cent solution of ferrous sulphate, 
twice with a 0.2 per cent solution, and three times with a 0.4 per cent 
solution. This was done so that no iron could get from the leaves to the 
solution. Two plants were grown in each flask, six flasks were taken as a 
unit, and the units triplicated for each treatment. The plants were 
grown but 25 days, as results were then decisive, the unbrushed plants 
having ceased to grow perceptibly some time before. The data on 
growth are given in Table X. 
The leaves brushed with the ferrous-sulphate solution became green in 
two or three days. New leaves appearing at intervals between the 
brushings were strongly chlorotic, but became green quickly when 
treated with the solution. Plants 1 to 12 and 25 to 36, ones that were not 
brushed at any time, were always strongly chlorotic and made no appre¬ 
ciable growth. The comparative growths of the brushed and unbrushed 
plants show decisively that the inability of plants to grow in these solu¬ 
tions was due to a lack of available iron. 
