Dec., 1923] ALLISON AND SHIVE-GROWTH OF SOYBEANS 561 
beneficial effects except upon the development of roots. The accelerating 
influence of aeration on root development, however, is quite pronounced 
both in sand and in solution cultures. The superiority of the roots grown 
in the aerated solutions over those in the simple solution cultures is mani¬ 
fested not so much by the higher dry weight of root substance produced 
as by the development of a very efficient absorbing system. The main 
roots in the aerated cultures were long and slender and thickly beset with 
well developed laterals almost to the very tips, thus giving rise to large and 
efficient absorbing surfaces. This response to aeration, however, was much 
more pronounced in the culture solutions which were continuously renewed 
than it was in those which were only intermittently renewed (every 3^2 
days). The superior root growth resulting from aeration in the drip cul¬ 
tures is particularly reflected in accelerated top growth during the later 
stages of development. This is clearly brought out in the photographs of 
Plate XXXIX, which show an aerated and a non-aerated drip culture 
when the plants were 14 days old (above), and the same cultures at the 
age of 37 days (below). The data of table 3 show that the dry weights of 
stems, leaves, and roots from the drip-solution cultures without aeration 
were inferior to those from the simple solution cultures, although the 
average total dry weights of the former were more than 50 percent higher 
than those of the latter, this superiority of total yield being due entirely 
to the remarkable fruit-production by the plants grown in the continuously 
renewed solutions. 
In the solution cultures, as in the sand cultures, constant aeration of the 
medium in connection with continuous solution renewal produced by far 
the highest yields throughout, the average total dry weights of tops and of 
roots being 133.9 percent and 43.3 percent higher, respectively, than the 
corresponding yields from the simple solution cultures. The average dry 
weight of tops from these aerated-drip cultures was greatly augmented by 
the exceptionally high average yield of fruit, which was approximately one 
half the average total dry weight of the plants. 
The ratios of average dry weights of plant parts to the average total 
dry weights are given in table 4, this table corresponding, item for item, with 
table 2 relating to sand cultures. 
Table 4. Ratios of Average Dry Weights of Plant Parts to Average 
Total Dry Weights of Plants Grown in Solution Cultures 
Cultures 
Tops 
Roots 
Total Dry 
Stems 
Leaves 
Fruit 
Total 
Weights 
Simple solution. 
Simple aerated solution. 
Drip solution. 
Aerated-drip solution. 
0.287 
•333 
• 157 
.185 
0-399 
.523 
•257 
•235 
O.209 
.532 
•512 
O.895 
.856 
.946 
•932 
0.105 
.144 
•054 
.068 
22.220 
I8.O47 
32.9OO 
48.869 
