6 BULLETIN 45, HAWAII EXPERIMENT STATION. 
ings. Here the best available seed should be planted and plants care- 
fully watched and cared for through the growing period. 
Roguing. — Koguing the seed plat is practiced with the object of 
eliminating undesirable plants before the tubers are harvested in 
order that such plants may not be propagated. The plants are ex- 
amined from time to time and those not true to the variety or those 
diseased or otherwise undesirable are destroyed. Varietal mixtures 
can best be detected at flowering time. In roguing, a knowledge of 
potato diseases is valuable. 
Fig. 2. — Potatoes that may be planted after treatment : A, Black scurf ; B, common scab. 
Such potatoes may be planted after treatment, but it is better still to select perfect 
types of seed tubers, like those illustrated by C and D, for planting. (From U. S. Dept. 
Agr., Bur. Plant Indus., C, T., and F. C. D. Circ. 3.) 
Seed from productive plants. — As many unproductive plants are 
found within a variety, selection should be practiced within the 
variety. Stuart x has recorded the following results with 12 varieties, 
showing the average yields from planting the progeny of strong and 
weak plants : 
Strong tuber units: 3.28 pounds of primes, 1.18 pounds of culls, 
total 4.46 pounds. 
Weak tuber units: 0.20 pound of primes, 0.51 pound of culls, total 
0.71 pound. 
1 Stuart, W. Good seed potatoes and how to produce them. U. S. Dept. Agr., Farmers' 
Bui. 533" (1913), p. 7. 
