956 
Journal of Agricultural Research voi. xxiii, no. i* 
Table IX .—Variation in form between different lots of Early Ohio potatoes in 1919 
and 1920 
Lot 
No. 
Place grown. 
Year. 
Form index 
\ width j 
|classes. 
Total 
num- 
ber of 
tubers. 1 
Mean index- 
0.90 
1. IO 
1.30 
1.50 
1.70 
1.90 
2 
Grand Rapids. 
1919 
22 
6 7 
39 
12 
1 
141 
I. 36±. 01 
6 
igig 
2 
58 
103 
59 
7 
229 
1. 3i±. or 
7 
.do. 
1919 
15 
67 
30 
11 
1 
124 
1. 36±. or 
8 
.do. 
igig 
I 
28 
69 
37 
4 
1 
140 
1. 33 ±. or 
2 
Duluth. 
1919 
14 
no 
38 
2 
1 
165 
1. i4±. 01 
7 
1919 
12 
83 
83 
9 
1 
188 
I. 20±. 01 
9 
Hopkins. 
igig 
1 
2 
15 
10 
2 
30 
1. 57±.02. 
2 
Grand Rapids 1 . 
1920 
I 
28 
38 
4 
7 1 
1. 23±. 01 
7 
.do 1 . 
1920 
1020 
I 
14 
3 ° 
1 
45 
1. 231b. or 
9 
.do. 
3 
32 
40 
9 
84 
1. 23±. or 
1 From seed stock grown at Duluth in 1919. 
The mean of lots 2, 6, 7, and 8 grown at Grand Rapids in 1919 ranges 
from 1.31 ±0.01 to 1.36 ±0.01. The mean of lots 2 and 7 grown at 
Duluth in 1919 was 1.14±0.01 to 1.20±0.01, respectively. The differ- 
ence between the lots at Grand Rapids is 3.5 times the probable error 
and between the two lots grown at Duluth 4.2 times the probable error. 
This would appear to be significant. That the difference is probably 
due to other causes than hereditary is indicated by the fact that lots 2 
and 7, between which the greatest difference occurred when grown at 
Duluth, gave the same mean index, 1.36±0.01 at Grand Rapids, and 
when the portions of the lots grown at Duluth were tested out in 192a 
at Grand Rapids they gave an identical mean index, 1.23 ±0.01. In 
1920, lot 9 was obtained from a grower who had selected for a somewhat 
more elongated form of Early Ohio. The lot as obtained in the fall of 
I 9 I 9 gave a mean of 1.57 ±0.02. It was grown at Grand Rapids in 1920 
in comparison with lots 2 and 7. The mean index obtained for the 
three lots was 1.23 ±0.01. The results of the four years 1 study on the 
form of tubers show that the six lots gave an identical reaction, as 
regards the form of the tuber, when grown under similar growth con¬ 
ditions. The mass selection practiced by the growers in lots 2 and 9 
for 21 years had no demonstrable effect on the inheritable form of Early 
Ohio tubers. It was further found that the form of tubers was very 
distinctly influenced by the environmental conditions surrounding the 
development of the tubers. This influence was not found to be carried 
over in any detectable amount to the progeny. As has been pointed 
out, the environmental conditions which resulted in good or poor yields 
did not measureably affect the yield of the progeny. It is therefore 
evident that no correlation was found between the form of tubers and 
their yield. 
EFFECT OF ENVIRONMENT ON OTHER CHARACTERS 
The formation of knobs is an undesirable character. This fact has 
been so obvious to potato breeders that the expression of this character 
by seedlings resulted in their rejection, so that our commercial varieties 
do not form knobs when growth conditions are uniformly favorable 
