6 o 
Journal of Agricultural Research 
Vol. XXIV, No. r 
out of the soil and dry weights were made separately for roots and 
shoots. The results, consisting of the average per plant for the nine 
plants from each temperature, are shown in Table III. This experiment 
was conducted in May and June, 1919, when the air temperature ranged 
from 18° to 20° C., with a rise of 10° to 12° during the middle of the day. 
Table III. —Dry weights of cabbage plants grown 46 days from seed at different soil 
temperatures 
Dry weight per plant. 
Soil temperature. 
Wisconsin Hollander. 
Commercial Hollander. 
Shoot. 
Root. 
Shoot. 
1 Root. 
1 
•c. 
14. 
Gut. 
0. 245 
i Gm. 
0. 029 
Gm. 
0. 185 
Gm. 
0. 027 
17. 
.316 
•033 
.306 
. 048 
. 281 
. 042 
. 262 
. 041 
. 272 
.044 
. 223 
•037 
26. 
•254 
1 . 041 
. 192 
.025 
29. 
.302 
.052 
. 252 
•035 
32. 
.236 
1 -030 
. 260 
.036 
35 . 
.207 
1 -025 
1 
. 204 
.017 
It may be seen from Table III that the weights are not consistent at 
all temperatures with those of plants 20 days old, although the tempera¬ 
ture for optimum growth remains the same. The weight at 26^^ C., is 
less than that at 23° and 29°, thus giving a distinct bimodal curve when 
the weights are plotted against temperature. This condition exists alike 
with roots and shoots of both strains. 
Inasmuch as the moisture content of the soil was not kept constant by 
weight, it was thought that a difference in moisture, provided there were 
such, might have been responsible for the irregular growth of the plants. 
Therefore, another experiment was conducted, during the winter of 1919, 
in which the whole soil mass was kept up to a uniform moisture content 
by weight. The soil was made up of three parts of fairly rich, virgin 
loam and one part of clean sand. The water-holding capacity of this 
soil was 39.2 per cent (in i cm. tube), or 28 per cent calculated on a wet- 
weight basis, and the moisture was kept at about 15 per cent by weighing 
the receptacles at the higher temperatures every day and less frequently 
at the lower temperatures and restoring the lost moisture. In place of 
the cinders used in the other experiments, a 3-inch pot was inverted in the 
bottom of the receptacle, a glass tube inserted in a hole in the bottom of 
the pot, and the soil filled in around this and tamped fairly firmly. All 
of the water was supplied through the tube. The seed was planted as 
previously described. After the plants were about 5 days old, the stand 
was thinned to three in each receptacle, and the soil surface was covered 
with mineral wool. Both the Wisconsin Hollander and the Commercial 
Hollander were used, the receptacles being handled in duplicate at each 
temperature. 
The experiment was begun October 22 and concluded December 15, 
1919, a total of 53 days. The air temperature during this period ranged 
from 14° to 18° C., with a daily rise of about 5° in the middle of the day. 
