Mar., 1923] CLAYTON — SOIL MOISTURE AND FUSARIUM WILT 
139 
Experiment V. In the work up to this point the principal purpose was 
to determine the effect of constant differences in soil moisture, the moisture 
content ranging from very nearly the minimum for life to complete satu¬ 
ration. The problem of sudden shortage of moisture in connection with a 
rise in temperature which favored the disease was not directly attacked. 
However, as has been brought out, the plants growing in soil so dry that the 
foliage was in a semi-wilted condition most of the time were highly resistant 
to the wilt disease, while, on the other hand, the plants growing under the 
conditions of soil moisture most favorable to growth were the first to be 
attacked. 
On January 15, 1920, fourteen one-gallon crocks were filled with ster¬ 
ilized soil which had been inoculated with a spore suspension of Fusarium 
lycopersici. The weights of the crocks, soil, clay cups, etc., were recorded, 
and two plants were set in each crock. These crocks were then kept in 
the cool greenhouse until March 13, at which time the first blossom clusters 
were well developed. At the end of this period the plants were moved into 
a compartment where the temperature (about 28° C.) was favorable to the 
disease, and there subjected to the following moisture conditions: 
Two crocks were saturated first, the remaining twelve being divided 
into four lots of three each. The experiment was continued for a period 
of 5 weeks, as follows: 
Lot A: The soil was kept moist for all 5 weeks. 
Lot B: The soil was kept very dry for the first week and moist for the next 4 weeks. 
Lot C: The soil was kept moist for the first week and dry for the 4 weeks following. 
Lot D: The soil was kept very dry for all 5 weeks. 
The plants of lot A made a very luxuriant vegetative growth; those of 
lot B were noticeably affected by the week of drought, but grew rapidly 
after this. Those of lot C grew very rapidly during the initial moist period, 
and suffered extremely when the soil was suddenly allowed to become dry. 
Many of the tender tips of the. leaves dried up, and the stems became 
hollow. The plants of lot D were dwarfed and woody, and were practically 
the same size at the end of the experiment as they were at the beginning. 
The data with regard to disease are summarized in table 6. 
Table 6 
Treatment 
Length of Incubation Period 
in Days 
No. Plants 
Dead or 
Diseased after 
5 Weeks 
No. Appearing 
Healthy 
Lot 
Weeks 
Dry 
Weeks 
Moist 
A. . .. 
0 
5 
15 
6 
0 
B . . .. 
1 
4 
22 
6 
0 
C.... 
4 
1 
2 4 
1 
5 
D.... 
5 
0 
Experiment discontinued at 
the end of 35 days 
0 
6 
