Feb., 1923 ] 
CLAYTON — TEMPERATURE AND FUSARIUM WILT 
83 
Table 2. .A resume of the results of Experiment V, in which tomato plants were grown for 
one month in inoculated soil. In this experiment , as in Experiment IV, both air and soil 
temperatures were controlled. 
Temperature 
Discoloration 
of Vascular 
Bundles 
Wilting 
Incubation 
Period of 
Disease 
Comparison of Green Weight 
of Inoculated Plants with 
that of Check Plants 
Air 
Soil 
0 
O 
17 0 C. 
3 plants none 
3 plants traces 
None 
— 
— 
i 7 ° C. 
27 ° C. 
6 plants marked 
None 
— 
- 19% 
0 
P 
35° C. 
3 plants none 
3 plants traces 
None 
— 
- 6% 
27 0 C. 
17 ° C. 
3 plants none 
3 plants traces 
None 
— 
- 8 % 
27° C. 
27 0 C. 
2 plants marked 
Marked 
13 days 
— 72% (4 plants out 
of 6 killed) 
27 ° C. 
35° C. 
3 plants none 
3 plants traces 
Traces 
20 days 
- 28% 
33° C. 
i 7 ° C. 
4 plants none 
2 plants traces 
None 
— 
+ 12% 
33° C. 
27 0 C. 
3 plants marked 
Marked 
10 days 
— 62 % (3 plants out 
of 6 killed) 
33° C. 
33° C. 
4 plants none 
2 plants traces 
Traces 
25 days 
- 28% 
wilting symptoms observed. For example, when the soil temperatures 
were warm (27 0 C.) and the aerial parts were surrounded by cool air (17 0 
C.), there was heavy discoloration at the base of the stem which neither 
progressed far above the soil line nor resulted in the usual wilting. The 
effect of the disease on the green weight, given in the last column of table 2, 
was calculated by using as 100 percent the green weight of tissue produced 
by a similar number of uninoculated plants grown under like conditions of 
temperature. As may be seen from the table, only two of the nine com¬ 
binations of soil and air temperature so favored the development of the 
disease as to result in the death of plants. When soil temperatures were 
low (17 0 C.), infection was always slight; at the higher soil temperatures, 
when infection was abundant, it did not progress into the aerial parts of 
the plant if those parts were surrounded by cool air. On the other hand, 
when the soil temperatures were high enough (27 0 C.) to favor infection 
and the air was warm enough (27 0 or 33 0 C.) to favor the spread of the 
fungus through the aerial parts, the plants were badly diseased. Contrary 
to results obtained in previous experiments, the plants grown at soil temper¬ 
atures of 35 0 C. and air temperatures of 27 0 C. showed some external 
