230 
Journal of Agricultural Research 
Vol. VII, No. 5 
Tabl 3 VI.— Results of experiments in controlling powdery-scab by seed treatment in IQI4 — 
Continued 
Plot 
No. 
Sound tubers. 
Infected tubers. 
Treatment. 
Num¬ 
ber. 
Weight. 
Num¬ 
ber. 
Weight. 
Per 
cent. 
1 
Check, infected seed.. 
1,790 
Pounds. 
222 
53 i 
Pounds. 
56-5 
22.87 
2 
Seed wet and rolled in sulphur. 
1,613 
200 
221 
26.0 
12.00 
3 
Formaldehyde (1:30), 1 X /Z hours. 
1,613 
200 
56 
9.0 
3-30 
4 
Atomic sulphur (5 per cent), 1 l A hours. 
i ,750 
217 
118 
16.5 
6.30 
S 
Formaldehyde (2:30), hours. 
1,097 
136 
42 
6-5 
3-68 
6 
Mercuric clilorid (2:15), hours. 
1,600 
198-5 
6 
• 75 
*37 
7 
Check, infected seed. 
1,260 
i 55 
170 
2.4 
11. 80 
8 
Copper sulphate (5 per cent), 1% hours. 
1,068 
556 
132-5 
9 
1.0 
•83 
9 
Mercuric chlorid (4:15), 53°-S4° C., 5 minutes. 
69 
7 
•75 
1.24 
iol 
Formaldehyde (2:30), 46°-'>o' s C., 5 minutes. 
Mercuric chlorid (4:15), 44*“45° C., 5 minutes. 
397 
49-25 
2 
•5 
•50 
11 
681 
84-5 
12 
i- 5 
i- 73 
12 
Check, healthy seed. 
1,640 
204 
4 
•5 
. 20 
After treatment the seed was spread out to dry on a laboratory floor 
which had been previously covered with paper. When dry, the potatoes 
were cut and placed at once in i-peck sacks that had been previously 
soaked for three hours in a 1 per cent solution of copper sulphate or in 
sacks that had never contained potatoes. In this way they were kept 
apart from other potatoes and other sources of infection until planted, 
June 13. The seed used in the clean checks was carefully selected from 
several barrels believed to be free from powdery-scab, treated with the 
usual strength of mercuric chlorid, dried, cut, and bagged in the man¬ 
ner just described. Except in the case of clean check tubers, which 
were wholly free, each seed piece bore a considerable number of powdery- 
scab pustules. 
The plot selected for the experiment was an old orchard which sloped 
gently toward the east and which had been in sod the preceding 10 years. 
The soil had been ridged up toward the apple trees; and consequently 
the ground was somewhat uneven. The soil was a black gravelly loam, 
but too wet and heavy for ideal potato land. A complete commercial 
fertilizer was used at the rate of 1,200 pounds per acre. Because of the 
irregularity of the ground and shading from the orchard trees, no 
attempt was made to record the germination of the seed or the develop¬ 
ment of the potato vines during the season. The relative position of the 
plots with reference to each other was the same as in the table, and the 
crop was harvested on October 15. 
As shown by Table VI, the progeny in the plots adjoining plot 11, with 
the exception of one tuber in each of two hills, was free from infection 
by Spongospora subterranean which showed that the land was not infected 
previous to the planting in 1914. Notwithstanding this nominal infec¬ 
tion in the healthy check tubers, the amount of powdery-scab that devel¬ 
oped on the various plots would represent the relative efficiency of the 
various treatments if other conditions were equal, which was not the case, 
