Apr. 7,19^3 Influence of Soil Temperature on Fusarium in Cabbage 59 
March when the light was weak and the day short. Other experiments 
were carried out in May and June when the light was stronger and the 
plants were grown for a longer period of time. 
Tabi^E II .—Weights of Wisconsin Hollander seedlings grown 20 days from seed at 
different soil temperatures 
Soil 
temperature. 
Wet weight 
per plant. 
Dry weight 
per plant. 
Ratio of wet 
weight to 
dry weight. 
"C. 
Gm. 
Gm. 
14 - 5 
0. 29 
0. 020 
14-5 
17. 0 
•34 
.023 
14. 7 
20. 0 
•51 
.031 
16. 4 
23.0 
•45 
. 029 
IS -5 
26. 0 
•37 
.023 
16.0 
29. 0 
•36 
. 024 
iS-o 
32. 0 
•32 
. 022 
14 - 5 
35*0 
. 18 
. 014 
12.8 
38.0 
i 
. 06 
. 006 
10 
It will be seen from Table II that 20° C. proved to be the optimum soil 
temperature for the growth of these cabbage plants for the first 20 days. 
At soil temperatures above 20^^ there was a gradual decrease in weight 
up to 35°, where there was a sudden drop; at 38° the plants soon died. 
Accompanying this difference in weight was a marked difference in the 
appearance of the plants grown at low and at high temperatures. At 23° 
and below they were stocky and had a dark green color. There was also 
a slight difference in the height and size of the plants at the different 
temperatures. From 26° to 32®, inclusive, the plants became more strict; 
that is, the petioles were proportionately longer and approached a 
vertical position. The color also graded into a lighter shade of green. 
At 35® the plants were decidedly stunted, and they assumed a distinctly 
pale green color. 
Moreover, if we consider the ratio of wet weight to dry weight, a 
marked difference will be noticed at the different soil temperatures. At 
the intermediate temperatures, where the greatest wet and dry weights 
developed, the ratio of the wet weight to dry weight was greatest. This 
simply means that the plants were most succulent at these tempera¬ 
tures, and it seems possible that for this reason they may have offered 
a more favorable medium for the invasion of the parasite than was 
offered by the plants at the extreme temperatures. This suggestion is 
favored to some extent by the occurrence of a higher precentage of yel¬ 
lows in plants growing in naturally infested soil at these temperatures. 
On the other hand, as will be seen later, the highest percentage of yel¬ 
lows occurs in plants grown in artificially inoculated soil above 26° C., 
where the moisture content of the plant is lower and the plants must be 
in an abnormal condition. These results indicate that some factor other 
than succulence of the host plant must be concerned in determining the 
degree of infection. 
In order to determine whether similar temperature relations obtained 
for longer periods, the seedlings used as controls in the third experiment 
in studying the disease were allowed to grow at the different soil tempera¬ 
tures for 46 days before the weight determinations were made, as com¬ 
pared with 20 days in the former series. The roots were then washed 
