POTATO DISEASES IN HAWAII. 7 
The strong plants gave more than 10 times as large a yield of 
primes or merchantable tubers and only a little more than twice as 
many culls as did the weak plants. 
Uniformity. — Selection has shown that within a variety there are 
strains which, when isolated, behave in a more or less uniform manner 
with respect to size and shape of tubers. Selection should be prac- 
ticed from the hills at the time of digging the seed plat, keeping as 
specially desirable seed, tubers from hills yielding a maximum num- 
ber of healthy tubers of fair size and uniform shape. 
Hill selection. — This method of selecting seed consists in marking, 
by stake or otherwise, the most desirable plants during the growing 
season. At digging time those marked plants having a maximum 
number of desirable tubers are specially set aside for seed. In this 
way desirable varietal characters of the plants and high-yielding 
qualities are selected together. 
Immature seed. — European growers have come to believe that, other 
things being equal, larger crops are produced by immature seed than 
by mature seed. This refers to maturing of the seed in the ground. 
Most of the locally grown seed at present is immature, since the fields 
are regularly visited by blight or the tops dry up with the Fusarium 
wilt disease, etc., at about the time of flowering. 
Large v. small seed tubers. — The use of small seed tubers can be 
countenanced only when these are known to be the progeny of 
productive plants. From the quotation from Stuart (p. 6) regarding 
the yield of strong and weak plants it will be seen that the strong 
plants produced more than 16 times as great a weight of large tubers 
as the weak plants, but only a little more than twice as great a weight 
of small tubers. In selecting small tubers from the lot it is evident 
that a large proportion of tubers from unproductive plants would 
be chosen. 
Ballou x writes as follows regarding the use of large and small 
tubers for seed : 
[The use of large tubers gives] : (a) A very heavy, perhaps almost total, 
percentage of the high-yielding strains; (b) a heavy percentage of the average 
or moderate-yielding strains; (c) a very small percentage of the inferior or 
low-yielding strains. 
[The use of small tubers gives] : (a) A very insignificant percentage of 
the superior or high-yielding strains; (b) a small percentage of the moderate- 
yielding strains; (c) a very heavy, almost total, percentage of the low-yielding 
or inferior strains. 
The significance of the above data with respect to the common local 
practice of marketing all fair-sized tubers and keeping only the culls 
for seed needs no comment. 
1 Ballou, F. II. The status of the potato-growing industry in Ohio. Ohio Sta. Bui. 218 
(1910), p. 587. 
