20 
BULLETIN 1248, U. S. DEPARTMENT OF AGRICULTURE. 
yields. The 3-ounce halved and 3-ounce whole tubers came next. 
In 1915, with the average yield per acre more than double that of the 
previous season, the highest net yield was obtained from the 3-ounce 
whole tubers; the 2-ounce whole sets gave the second highest yield, 
and the 3-ounce halved sets came third. With greatly reduced 
yields in 1916 the 2-ounce halved sets gave the highest net yield, 
4-ounce quartered second, and 3-ounce quartered third. In 1917, 
with yields quite similar to 1916, 4-ounce quartered sets gave the 
most net bushels of primes per acre, closely followed by 6-ounce 
quartered, 6-ounce halved, and 5-ounce halved sets. The following 
year, 1918, 5-ounce quartered sets gave the highest net yield of 
primes, 6-ounce quartered sets came second, and 4-ounce halved sets 
third. A further study of the data in Table 8, based on the average 
net yields for the four years from 1915 to 1918, inclusive, shows that 
2-ounce halved seed gave the largest net yield of primes, closely fol- 
lowed by the 3-ounce halved tubers. The largest average yield of 
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Fig. 2— Average yields in bushels per acre from Irish Cobbler potato sets of different weights at Presque 
Isle, Me., in 1916, 1917, and 1918. 
primes minus the seed used for the years 1916 to 1918 was obtained 
from the 4-ounce quartered seed. The 2-ounce halved came second, 
closely followed by the 5-ounce and 6-ounce quartered and the 4- 
ounce and 5-ounce halved. (See fig. 2 for total yields.) If, how- 
ever, the average net yield of the 5-year period from 1914 to 1918 be 
taken for the 2-ounce whole and the 3-ounce and 4-ounce whole and 
halved sets, the 3-ounce halved sets show the highest net merchant- 
able yield, closely followed by 4-ounce halved and 3-ounce whole 
sets. The 2-ounce whole seed was fourth and the 4-ounce whole 
seed last. 
The foregoing explanation of the data and the relative value of 
the size of set used has been based entirely upon the net yield of 
merchantable tubers. This comparison has been made because it is 
believed that this is the most important commercial aspect of 
potato production. One should not lose sight, however, of another 
aspect of the subject, viz, the production of seed stock. For ex- 
