Mar. 17,1923 Influence of Soil Temperature on Seedling-Blight 
851 
and placed in the sterilized soil in the cans. All series except two were 
inoculated with a spore suspension of 65,000 conidia per cubic centi¬ 
meter. Two series were given a heavier inoculation with 325,000 conidia 
per cubic centimeter. General growth data were taken on the inoculated 
and control plants of each series. In addition, daily notes were taken on 
the number of seedlings showing slight blighting and wilting, and finally 
upon the completion of the experiments the soil was carefully washed on 
a screen and each kernel examined for evidence of germination. The 
columns in Tables V to VII headed “average percentage of germination" 
represent the total number of kernels which had germinated. The 
percentage of kernels germinating, the percentage emerging, the per¬ 
centage of disease-free seedlings, and the percentage of blighted kernels 
were recorded for each series. The data presented in Table V represent 
an average of eight different experiments. The results from each were 
uniform enough to warrant taking an average and explaining the few 
variations in the discussion of results. 
Table V .—Influence of soil temperature on the development of seedling-blight in Marquis 
wheat 
[Average of eight experiments.) 
Average 
soil 
temper¬ 
ature. 
Average 
number of 
days to 
emerge. 
Control. 
Inoculated with Gibberella saubinetii. 
Average erf 
percentage 
germina¬ 
tion. 
Average 
percentage 
of healthy 
plants. 
Average 
percentage 
of germi¬ 
nation. 
Average 
percentage 
of healthy 
plants. 
Average 
percentage 
of blighted 
plants. 
•c. 
8 
16 
80 
80 
84 
84 
O 
12 
IO 
80 
80 
78 
61 
17 
16 
7 
79 
77 
70 
48 
22 
20 
7 
8l 
79 
75 
41 
34 
24 
6 
75 
7 i 
68 
49 
19 
28 
4 
74 
68 
65 
43 
22 
32 
4 
77 
7 i 
73 
54 
19 
36 
6 
41 
16 
5 i 
38 
13 
The influence of soil temperature on the parasite and the hosts has 
been discussed in detail earlier in the paper. The general rate of develop¬ 
ment of the seedling, that is, the rate of emergence and rate of tillering 
and maturing, was not greatly altered by the presence of the parasite. 
The number of plants emerging, the general appearance of the plants, 
the length of roots, and the height of plants as well as the weight of both 
roots and tops, however, were greatly modified by the presence of the 
parasite. 
The germination of spring wheat inoculated with conidia of Gibberella 
saubinetii was reduced by soil temperatures between 12 0 and 28° C. 
At a soil temperature of 8°, however, the germination was equal to 
that of the controls in every series grown. At 12 0 the germination 
was reduced, on the average, only 2 per cent (Table V and fig. 5), while 
at soil temperatures of 16 0 to 28° the germination was lowered about 8 
per cent in each case. The growth of the parasite apparently was 
sufficiently rapid to penetrate and kill a number of the embryos before 
they had increased greatly in size, thus reducing germination very 
