Dec., 1923 ] 
ALLISON AND SHIVE — GROWTH OF SOYBEANS 
559 
siderable increase in root development. The plants in both the simple and 
the aerated cultures were entirely normal in so far as this could be deter¬ 
mined by observation. It will be observed that the relative dry-weight 
values of the plants grown in the drip cultures are in every instance much 
superior to the corresponding values for the simple cultures, the total 
Table i. Relative Dry Weights of Plants Grown in Sand Cultures 
Cultures 
Tops 
Roots 
Total Dry 
Weights 
Stems 
Leaves 
Fruit 
Total 
Simple solution. 
I.OO* 
(5.520) 
1.019 
1.218 
1.718 
1.00 
( 9 - 257 ) 
.950 
I.I 54 
I.667 
1.00 
(21.831) 
•953 
1.260 
1-455 
1.00 
(36.607) 
.963 
I.254 
1.548 
1.00 
(2.253) 
I.078 
I. 33 I 
1.738 
1.00 
(38.861) 
.970 
1.233 
1-559 
Simple aSrated solution. 
Drip solution. 
Aerated-drip solution. 
* The dry-weight values of the simple solution cultures are taken as 1.00 and corres¬ 
ponding values of the other cultures are expressed in terms of these. The actual dry weights 
of the simple solution cultures are given in parenthesis, in grams. 
weight of tops being 25.47 percent and that of roots 33.1 percent higher 
than the corresponding weights of the plants grown in the simple sand cul¬ 
tures. The most pronounced superiority, however, is shown for the aera¬ 
ted-drip cultures, the average relative yields of tops and roots from these cul¬ 
tures being 54.8 percent and 73.8 percent higher, respectively, than the cor¬ 
responding ones of the simple cultures. The aerated-drip cultures are thus 
shown to be as much superior to the non-aerated drip cultures as the latter 
are superior to the simple cultures. 
It is apparent that constant aeration in connection with continuous 
solution renewal exerted a pronounced accelerating influence upon the 
growth rates of both tops and roots, while in connection with the simple 
cultures (in which solutions were renewed only every three and one half 
days) no such influence is observed. The explanation of this discrepancy 
is not at all clear. It might be suggested, however, that the infrequency of 
solution renewal in the case of the simple cultures may introduce a growth- 
retarding factor which aeration alone can not correct, but which is entirely 
eliminated by continuous solution renewal, and in the absence of this 
factor aeration may exert a powerful accelerating influence upon the growth 
rates of the plants. That such a growth-retarding factor is actually intro¬ 
duced by infrequency of solution renewal is clearly brought out by a com¬ 
parison of the yield values from the simple sand cultures with those from 
the constant drip cultures (table 1). 
The general appearance of the plants of this experiment with respect to 
size, health, and vigor, together with the data presented in table 1, shows 
that constant aeration in connection with continuous solution renewal by 
