82 
The Ohio Naturalist. 
[Vol. VII, No. 4, 
merit of the disease is checked. This explains why the potato 
blight fungus seldom occurs to any extent in sections where the 
mean or normal daily temperature exceeds for any length of 
time 77° F. ” 
I am unable to state at this time the basis upon which the 
above statements rested at the time, but with certain modifica¬ 
tions they will fully cover Ohio conditions. Recalling that the 
years 1883 to 1886 inclusive, and 1903 to 1906 in Ohio, were 
periods of prevalence for Phytophthora infestans in Ohio, we may 
glance at the weather conditions for these periods and compare 
with the means of the past 24 years. It seems only necessary 
to consider the months of June, July and August. Unfortunately 
our data do not extend back further than 1883. 
I have prepared a table showing the mean summer tempera¬ 
tures and mean rainfall in Ohio for 1883 to 1906: 
Mean Summer Temperatures and Rainfall in Ohio 1883-1906 
Year. 
1883 
1884 
1885 
1886 
1887 
1888 
1889 
1890 
1891 
1892 
1893 
1894 
1895 
1896 
1897 
1898 
1899 
1900 
1901 
1902 
1903 
1904 
1905 
1906 
Ohio... 
The summer temperatures for the years 1883 to 1886, taken 
as a whole, were decidedly below the normal. The same is true 
for the summer months for the years 1902 to 1906, excepting the 
month of August 1906. 
Mean Temperatures. 
June. 
July. 
August. 
Season’s 
Mean. 
69 
.0° 
72 
. 1° 
68 
2° 
69 
.8° 
71 
.1 
71 
.5 
70 
. i 
70 
.9 
67 
. 1 
75 
. 2 
68 
.9 
70 
.4 
67 
.5 
72 
.0 
70 
.9 
70 
1 
71 
.0 
77 
.9 
77 
.9 
75 
.6 
70 
.4 
72 
1 
70 
4 
71 
0 
66 
7 
72 
.5 
69 
1 
69 
4 
73 
3 
73 
0 
68 
8 
71 
7 
71 
0 
69 
0 
70 
0 
70 
0 
73 
0 
73 
0 
71 
0 
72 
3 
70 
6 
74 
5 
70 
7 
71 
9 
71 
3 
74 
3 
71 
2 
72 
3 
72 
0 
71 
6 
73 
5 
72 
4 
69 
5 
73 
2 
71 
8 
71 
5 
68 
1 
75 
5 
69 
4 
71 
0 
71 
9 
70 
0 
73 
5 
71 
8 
71 
5 
74 
1 
73 
7 
73 
1 
69 
8 
74 
1 
76 
3 
73 
4 
70 
9 
78 
1 
73. 
1 
74 
0 
66. 
9 
74. 
0 
67. 
4 
69. 
4 
64. 
4 
72. 
9 
70. 
7 
69. 
3 
68. 
4 
71. 
4 
68. 
8 
69. 
5 
69. 
2 
73. 
o ! 
71. 
7 
71 . 
3 
69. 
8 
72. 
i 
74. 
6 
72. 
2 
69. 
7° 
73. 
9° | 
71. 
5° 
71. 
7° i 
Mean Rainfall. 
June. 
July. 
August. 
Season’s 
Total. 
Inches 
Inches 
Inches 
Inches 
4.25 
1.16 
1.88 
10.29 
2.96 
3.83 
1.45 
8.24 
4.34 
3.20 
6.33 
13.87 
3.53 
2.88 
3.62 
10.03 
3.85 
2.16 
2.39 
8.40 
3.41 
2.40 
5.10 
10.91 
4.13 
4.25 
1.50 
9.88 
4.50 
1.99 
4.70 
11.19 
4.82 
3.82 
3.07 
11.71 
5.61 
3.80 
2.99 
12.40 
34 
2.49 
2.17 
8.00 
2.65 
1.56 
1.67 
5.88 
2.47 
2.00 
2.96 
7.43 
4.81 
8.11 
3.38 
16.30 
2.85 
4.65 
2.72 
10.22 
2.86 
3.98 
4.50 
11.34 
2.96 
4. 18 
1.82 
8.96 
2.99 
4.62 
3.68 
1 1 .29 
4.38 
2.73 
3.32 
10.43 
7.48 
4.69 
1.67 
13.84 
3.97 
3.67 
3.20 
10.84 
2.88 
4.13 
2.74 
9.75 
4.72 
3:93 
4.46 
13.11 
3.41 
5.14 i 
4.72 
13.27 
3.94 
3.97 
3.04 
10.95 
