POTATO BREEDING AND SELECTION. 15 
RECIPROCAL CROSSES. 
In the reciprocal crosses presented in Table II, some additional 
light is shed upon the prolificacy of certain seed parents. 
Table II. — Comparative behavior of reciprocal crosses of 1909 grown in 1910. 
Parentage of cross. 
Keeper X Norcross 
Norcross X Keeper 
Keeper X Round Pinkeye 
Round Pinkeye X Keeper. 
Keeper X Venezuela 
Venezuela X Keeper 
Keeper X Keeper 
Number 
of 
flowers 
crossed. 
Number 
of seed 
balls de- 
veloped. 
Percent- 
age of 
success. 
40.0 
23.5 
64.3 
59.5 
11.1 
66.7 
28.6 
Number 
of tuber- 
bearing 
seedlings. 
13 
480 
227 
553 
10 
457 
30 
Average 
number 
of seed- 
lings per 
seed ball. 
6.5 
40 
25.2 
25.1 
10 
57.1 
15 
The reciprocal cross between Norcross and Keeper shows that when 
Keeper was fertilized with pollen from Norcross, 2 seed balls were 
secured from 5 flowers fertilized, and from these 2 seed balls 13 tuber- 
bearing plants were produced. When Norcross was crossed with 
Keeper, 12 seed balls were secured from 51 flowers crossed, and from 
these 12 seed balls 480 tuber-bearing plants were obtained, or an 
average of 40 plants per seed ball, as against 6.5 from the reciprocal 
cross. From these data we may either assume that Keeper is not as 
prolific a seed parent as Norcross or else that Norcross does not pro- 
duce sufficient viable pollen. On the basis of the first assumption, 
we may compare the behavior of both seed parents to other pollen. 
Keeper when pollinated with Irish Seedling gave an average of 17.3 
plants per seed ball (Table I), and when crossed with Round Pinkeye 
it produced 25.2 plants per berry. Norcross when crossed with 
Round Pinkeye gave an average of 30 plants per berry (Table I). 
This evidence would seem to indicate that the Norcross was a more 
prolific seed parent than Keeper; but it also points to the conclusion 
that Keeper is the best pollen parent, at least in so far as pertains to 
the production of viable pollen. 
The reciprocal crosses between Round Pinkeye and Keeper are of 
considerable interest, owing to their apparent similarity. Keeper X 
Round Pinkeye gave 9 seed balls out of 14 blossoms fertilized and 
these averaged 25.2 plants per berry. Round Pinkeye when crossed 
with Keeper produced 22 seed balls from 37 flowers pollinated, and 
from these an average of 25.1 plants were produced. The rather low 
number of plants forming tubers from these reciprocal crosses would 
indicate that neither parent seemed to possess potency. Apparently, 
the mating of these two varieties was not a congenial one in either case. 
In the reciprocal cross between Venezuela and Keeper, with 
Venezuela as the seed parent, 12 pollinated flowers developed 8 seed 
balls, from which an average of 57.1 plants was secured. Nine 
flowers of Keeper crossed with Venezuela resulted in but 1 seed ball, 
