8 5 8 
Journal of Agricultural Research 
Vo!. XXIII, No it 
Table MU.—Influence of soil temperature with varying degrees of soil moisture 
the development of seedling-blight of wheat 
on 
[Average of two experiments] 
Aver¬ 
age 
soil 
tem¬ 
pera¬ 
ture. 
30 per cent moisture-holding 
capacity. 
45 per cent moisture¬ 
holding capacity. 
60 per cent moisture-holding 
capacity. 
Cox 
trol. 
Inoculat< 
3 d. 
Inoculated. 
Control. 
Inoculated. 
Per¬ 
cent¬ 
age 
germ¬ 
ina¬ 
ted. 
Per¬ 
cent¬ 
age 
dis¬ 
ease- 
free. 
Per¬ 
cent¬ 
age 
germ¬ 
ina¬ 
ted. 
Per¬ 
cent¬ 
age 
dis¬ 
ease- 
free. 
Per¬ 
cent¬ 
age 
dis¬ 
eased. 
Per¬ 
cent¬ 
age 
germ¬ 
ina¬ 
ted. 
Per¬ 
cent¬ 
age 
dis¬ 
ease- 
free. 
Per¬ 
cent¬ 
age 
dis¬ 
eased. 
Per¬ 
cent¬ 
age 
germ¬ 
ina¬ 
ted. 
Per¬ 
cent¬ 
age 
dis¬ 
ease- 
free. 
Per¬ 
cent¬ 
age 
germ¬ 
ina¬ 
ted. 
Per¬ 
cent¬ 
age 
dis¬ 
ease- 
free. 
Per¬ 
cent¬ 
age 
dis¬ 
eased. 
# C. 
8 
12 
16 
19 
23 
27 
3 i 
35 
96 
IOO 
IOO 
88 
76 
92 
92 
36 
96 
IOO 
96 
84 
76 
76 
72 
0 
88 
96 
92 
80 
72 
60 
64 
64 
16 
12 
8 
4 
12 
16 
28 
0 
72 
84 
84 
76 
60 
44 
36 
°56 
IOO 
80 
72 
52 
96 
88 
IOO 
48 
56 
24 
20 
20 
8 
24 
32 
12 
44 
56 
52 
32 
84 
64 
68 
a 12 
90 
IOO 
95 
95 
95 
92 
87 
0 
90 
IOO 
95 
89 
90 
86 
87 
0 
96 
96 
86 
88 
84 
84 
96 
44 
96 
48 
22 
l8 
36 
26 
60 
12 
O 
48 
64 
70 
48 
58 
36 
32 
• Balance killed by high soil temperatures. 
In the control series the germination and number of disease-free seed- 
lings at the two different soil-moisture contents, 30 and 60 per cent of 
tiie moisture-holding capacity, were the same at the lower temperatures. 
At tile higher temperatures, however, the low soil moisture slightly 
inhibited germination and plant development. 
In the inoculated series, on the other hand, the germination percentage of 
seedlings emerging and the percentage of blighted seedlings were greatly 
increased in the low soil moistures and even at the low soil temperatures. 
Soil moisture, then, became the limiting environmental factor to such an 
extent that even the resistance in the seedlings at the low temperatures 
was broken down. At the 8° C. soil temperature, for instance, 72 per 
cent of the seedlings grown at 30 per cent moisture were blighted, 48 per 
cent of them before emerging, while 44 per cent of the seedlings grown 
i 5 ^ e f r ent moisture were blighted, and 24 per cent of these were 
blighted before emerging. This was in marked contrast to the results at 
60 per cent moisture, where, as in the previous experiments, no blight 
occurred. The percentage of blighted seedlings was correspondingly 
increased by low soil moisture at all temperatures (PI. 5). * ' 
Soil moisture, then, was another important factor in predisposing 
the seedlings to attack by Gtbberella saubinetii . And when moisture 
was the limiting factor, it was impossible to obtain the true temperature 
influences. 
TEMPERATURE AND MOISTURE EXPERIMENTS IN THE FIELD 
The greenhouse experiments have demonstrated that wheat and 
com seedlings become susceptible to the wheat-scab parasite only when 
under unfavorable environmental conditions, which may be a single 
factor, such as temperature, moisture, soil reaction, and others, or a 
combination of several of these factors. These experiments have shown, 
further, that the two hosts respond conversely to at least one factor,' 
