Apr, 16,1917 
Absorption of Nutrients 
85 
absorbed, with 29 per cent of their roots, 0.61 as much potassium as the 
complete plants is in good agreement with the results for nitrogen and 
phosphorus, where, with 27 per cent and 33 per cent of the roots, the 
absorptions were, respectively, 0.55 and 0.65. 
In this and the preceding experiment the plants partially supplied with 
potassium absorbed considerably more sodium than plants completely 
supplied with potassium. 
EXPERIMENT IX.—RICE WITH ONE-HALF THE ROOTS IN AN IRON-FREE 
SOLUTION (FERROUS SUPLHATE SOURCE OF IRON) 
As nitrogen, phosphorus, and potash are similar in being used by plants 
in relatively large amount, it was important to test the absorption of a 
mineral element used by the plant in small amount. Iron was used in 
this test, as this element is present in most plants in relatively minute 
quantities and as a deficiency markedly affects growth. 
In this test approximately half the roots of the partial-iron plants were 
maintained in the iron-free solution. Both acid and neutral nutrient 
solutions were used. Ferrous sulphate was the source of iron, used so as 
to supply 0.008 gm. of iron per liter during the first 10 days of the test, 
0.004 g m * °f iron P er liter during the next 10 days, and 0.002 gm. of iron 
per liter during the last 20 days. Four flasks were taken as a unit and 
the units triplicated for each treatment. The no-iron plants were grown in 
200-c. c. flasks for 40 days; all others in 200-c. c. flasks for 27 days, and 
500-c. c. flasks for 13 days. Solutions were changed six times during the 
experiment. Experimental data are given in Tables XVIII and XIX. 
Table XVIII .—Growth of rice in Experiment IX 
Nutrient solution. 
Flask 
No. 
Weight of stalks and 
leaves. 
Average oven- 
dry weight of 
roots. 
Ratio 
of roots 
to tops. 
A-flasks. 
B-flasks. 
Green. 
Oven- 
dry. 
Aver¬ 
age 
oven- 
dry. 
A- 
flasks. 
B- 
fiasks. 
Gm. 
Gm. 
Gm. 
Gm. 
Gm. 
[ I- 4 
1. 42 
O. 26 
] 
Iron-free neutral.. 
Iron-free acid.... 
5-8 
i- 39 
. 26 
> 0.26 
O. 057 
0. 041 
0-377 
l 9-12 
1. 32 
. 26 
J 
[13-16 
29. 62 
4. IO 
1 
Complete neutral. 
<17-20 
33- 80 
4. 78 
4.38 
. 632 
• 547 
. 269 
I21-24 
3 1 - r 9 
4.27 
J 
[25-28 
49-25 
6.34 
1 
Do. 
Complete neutral 
j29-32 
53- 67 
7. OO 
\ 6.61 
.989 
■ 772 
. 266 
I33-36 
50-49 
6.48 
J 
37-40 
36. 10 
4. 78 
1 
Iron-free neutral.. 
Complete acid... 
4i-44 
38. 55 
5- 09 
> 4-6° 
• 539 
. 722 
. 274 
.45-48 
28. 85 
3- 93 
J 
49-52 
48. 42 
5- 99 
Complete acid.... 
.do. 
53-56 
48. 70 
6. 22 
} 6. 27 
. 902 
• 984 
.301 
l57-6o 
5 1 - 97 
6. 61 
1 
