Apr. i6,1917 
Absorption of Nutrients 
75 
The form in which the iron was added varied in some experiments, 
although it was used at the rate of 0.8 gm. of iron per 100,000 c. c. in all 
experiments except IX. The iron-free solution was the same as the com¬ 
plete solution, except for the absence of iron. Water used in the nutrient 
solutions was distilled from a cast-iron still with tin condenser and stored 
in a tin-lined copper tank. 
The solutions were generally changed every four days, except that, when 
the plants were first inserted, they were left for six days. Sometimes 
when growth was especially rapid, as with corn, the solutions were re¬ 
newed more frequently. Transpired water was made up with distilled 
water every day. In all the experiments rice was grown for 40 days and 
corn for 21 days. 
In analyzing the plants the usual analytical methods were used, except 
that iron was determined by the colorimetric method with sulphocyanic 
acid (HSCN) (10). 
' ' EXPERIMENTAL RESULTS 
EXPERIMENT I.—RICE WITH HALF THE ROOTS IN A NITROGEN-FREE 
SOLUTION 
In this test the complete neutral and nitrogen-free solutions shown in 
Table I were used, with ferrous sulphate as the source of iron. In one 
lot half the roots were maintained in the complete and half in the 
nitrogen-free solution. In other lots all the roots were kept either in 
the complete solution or in the nitrogen-free solution. The plants without 
nitrogen were grown in 200-c. c, flasks for 40 days; all others in 200-c. c. 
flasks for 22 days, and in 500-c. c. flasks for 18 days. Six double flasks 
were taken as a unit and the units triplicated for each treatment. Solu¬ 
tions were changed seven times in the course of the experiment. 
Experimental data are given in Tables II and III. 
Table II .—Growth of rice in Experiment I 
Nutrient solution. 
Flask 
No. 
Weight of stalks 
and leaves. 
Number of 
roots. 
Average oven- 
dry weight 
of roots. 
Ratio 
of 
roots 
to 
tops. 
A-flasks. 
B-flasks, 
iGreen. 
1 
Oven- 
dry. 
Av¬ 
erage 
oven- 
dry. 
A- 
flasks. 
B- 
flasks- 
A- 
flasks. 
B- 
flasks. 
Gm. 
Gm. 
Gm. 
Gm. 
Gm. 
i-6 
1. 69 
0 .43 
49 
51 
N itrogen-free. 
Nitrogen-free. 
■ 7-12 
1. 62 
. 41 
■ 0.42 
4 44 
47 
■0.119 
ft. T A A 
0.626 
13-18 
i- 71 
.42 
4 i 
58 
V- -L 44 
19-24 
78.46 
II- 73 
195 
195 
Bo. 
Complete. 
■ 25-30 
80. 83 
11. 88 
•11. 29 
231 
188 
•2.271 
2 m 2 7 A 
.31-36 
73 - 54 
10. 25 
187 
190 
37-42 
96 . 77 
13-13 
215 
193 
Complete.. ... 
' 43-48 
99. 44 
13-31 
12 . 93 
• 225 
194 
•2.198 
2.044 
.328 
49-54 
86. 12 
12. 36 
. 196 
204 
