234 
Journal of Agricultural Research 
Vol. VII, No. s 
TablH IX. — Results of tests of potatoes for resistance to powdery-scab in iqi$ 
Variety. 
Tubers. 
Control tubers (Green 
Mountain). 
Infection® 
in terms 
of p. ct. 
var. X100 
p. ct. G. M. 
Num¬ 
ber 
plant¬ 
ed. 
Num¬ 
ber in¬ 
fected. 
Per¬ 
centage 
of in¬ 
fection. 
Num¬ 
ber 
plant¬ 
ed. 
Num¬ 
ber in¬ 
fected. 
Per¬ 
centage 
of in¬ 
fection. 
Eldorado . 
54 
O 
O 
98 
5 
4.8 
O 
Farys. 
67 
O 
O 
54 
12 
18. I 
0 
Prof. Wohltman. 
60 
O 
O 
53 
19 
26. 3 
0 
Senator. 
215 
0 
O 
159 
9 
5 - 3 
0 
Ursus. 
178 
2 
I. I 
46 
* 5 - 
24. 6 
4 . 473 
Pearl.... 
256 
2 
O. 7 
9 
12. 1 
5 - 7 8 5 
Aldona.‘. 
194 
4 
2. O 
44 
21 
3 2 - 3 
6. 192 
Gryf. 
45 2 
21 
4-4 
24 
9 
27. 2 
16. 176 
Bonar. 
93 
9 
8.8 
26 
14 
35 - 0 
2 5 - 143 
Cimbals. 
68 
3 
4. 2 
^3 
9 
12. 5 
33. 600 
Constantia. 
Gracya.. .. 
3 2 3 
46 
12.4 
17 
7 
20. 1 
42. 612 
Gedymin. 
215 
18 
7* 7 
103 
I 7 
14. 1 
54. 610 
Prof. Wohltman... 
56 
39 
41. 0 
54 
39 
41. 8 
98. 086 
Kalif. 
r 93 
188 
49-3 
34 
34 
5°. 0 
98. 600 
Topaz. 
88 
12 
12. 0 
144 
H 
8.8 
■136. 364 
Soliman. 
147 
61 
29. 6 
5 2 ' 
11 
17.4 
170. 115 
a In order to get a direct comparison between the different varieties, the percentage of infection in any 
variety was divided by the percentage of infection of the Green Mountain variety planted in the same row 
and the result multiplied by 100. 
As shown in Table IX, 4 of the varieties tested escaped the disease, 
but none of the checks were entirely free, the percentage of infected tubers 
in the latter varying from 4.8 to 50 per cent. Out of the 16 rows, 3 
showed over 15 per cent infection in the case of the varieties tested and 
10 in the case of the checks, and the latter fact naturally raised the 
question as to why the percentage of infection varied so in the checks, 
all of which were planted to the same variety. 
While it may be that the soil was not generally infected or that condi¬ 
tions in small isolated spots were unfavorable for the development of the 
disease, the fact that there was often a wide difference in the amount of 
infection in alternate hills of the control and the other variety in the same 
row is significant. A striking example of this latter is shown in the row 
planted to Farys and the row of Ursus, the former showing no infection 
and the latter 1.1 per cent of infection, while the Green Mountain, the 
control variety planted in alternate hills in these rows, showed 18.1 and 
26.6 per cent of infection, respectively. Another interesting reaction was 
that in the Soliman variety, which showed 29 per cent, while its check 
showed only 11 per cent of infection. 
Thirty different selections of seedlings were planted in infected soil, 
and the checks in this case also were planted with the Green Mountain 
variety in alternate hills in each row. Table X gives the details of the 
experiment. 
