Apr. 7 . 19*3 Injiuence of Soil Temperature on Fusarium in Cabbage 71 
perature before they are transplanted, there appear to be only two possible 
explanations for the low degree of resistance in the young seedlings, 
namely: (i) the resistant character is not fully expressed in the young 
seedlings and becomes more manifest as the plants grow older, or (2) 
the high temperatures inhibit or modify the expression of the resistant 
character in seedlings. Experiments have furnished some evidence 
favorable to both hypotheses. Data supporting the second have already 
been presented and discussed. 
The initial experiments for testing the first theory were conducted by 
transferring the receptacles to the 26® C. tank after the plants had grown 
20 days in infested soil at 14®. Plants of the commercial strain grown 
under similar conditions were transferred at the same time for controls. 
The air temperature was the same as that recorded for other experiments 
conducted at the same time, 14° to 18^. In Table VIII the results 
obtained at the end of 10 days are compared with the results obtained 
with seedlings which had been growing at 26® continuously for 20 days. 
Because the number of plants used in these tests was small, the infec¬ 
tion of one or two more plants in one test than in another made a consid¬ 
erable difference in the percentage of yellows. Even so, the results 
are consistent enough to indicate that the Wisconsin Hollander plants 
are more resistant after 20 days than when younger. In Table VIII it 
may be seen that there is an average difference of 54 per cent of yellows 
between the older plants of the Wisconsin Hollander and the Commercial 
Hollander strains at 26°C., while with the younger plants there is a 
difference of only about 14 per cent. At the same temperature the differ¬ 
ence in the percentage of plants killed is equally striking. With the 
younger plants there is a difference of only 18 per cent, while with the 
older ones it amounts to 67 per cent. The disease developed very 
slowly in the Wisconsin Hollander seedlings, and at the conclusion of 
the experiment most of the affected plants showed only slight symptoms 
of yellows, while the reverse condition was manifest in plants of the 
commercial strain. 
These investigations were carried further by planting both kinds of 
seed in sterilized soil and later transplanting the seedlings to “sick*’ 
soil. The plants for the first experiment were grown for 30 days in 
sterlized soil in flats. The temperature of both air and soil ranged from 
18° to 22°C. during this period. In the first experiment, which was 
conducted during May and June, 1918, only three different soil tempera¬ 
tures were used in the series, but the complete series of temperatures 
from 14® to 35® was employed for the second. Three plants were set 
in each receptacle, and after transplantation on May 10 the recepta¬ 
cles were exposed to room temperature (18° to 22°) for three days in 
order to give the plants an equal chance to recover from the shock of 
being transplanted. The surface of the soil was covered with mineral 
wool and the receptacles were placed in the tanks at 15°, 17°, and 26°. 
The final results, recorded 30 days later, are given in Table IX. The 
air temperature during this experiment ranged from 18° to 22^^, with a 
sudden rise of 10° to 15° for a few hours during the middle of the day. 
A contrast of the susceptible plants grown in “sick” soil at 15^ and at 
17® is shown in Plate 2, D, E. 
