POTATO BREEDING AND SELECTION. 
17 
number of tuber-bearing plants, less than 13 per seed ball. On the 
other hand, Keeper, which gave only 13.9 per cent of successes, 
produced an average of 41.5 tuber-bearing plants per seed ball. 
As both of these pollen parents are known to produce an abundance 
of viable pollen, it would seem as if a greater affinity existed between 
Keeper and Up-to-Date than between Irish Seedling and Up-to-Date. 
In the case of Factor, a total of 74 hand-pollinated flowers, with 
pollen from 9 varieties, 1 of which was Keeper, produced but 1 seed 
ball, and that was devoid of seed. 
It is apparent from these data that the Up-to-Date class of plants 
are, as a rule, poor seed bearers. Frequent examination of the 
flowers of both Factor and Up-to-Date failed to disclose at any 
time the presence of viable pollen. To all intents and purposes, 
varieties of this class may be considered as belonging to the male 
sterility group, and in consequence thereof they can not be suc- 
cessfully employed as pollen parents. 
POTATO CROSSES MADE IN 1910. 
In 1910 a few crosses were made by W. V. Shear and the writer 
between several varieties of potatoes growing on the Potomac Flats, 
Washington, D. C. The success of some of these crosses was so 
striking that it seems desirable to mention them in the present dis- 
cussion. The specific crosses to which attention is called are those 
numbered 8708, 8709, and 8718, the data concerning them being 
presented in Table III. 
Table III. — Results of potato crosses Nos. 8708, 8709, and 8718, made on the Potomac 
Flats, Washington, D. C, in 1910. 
Field notes. 
Laboratory notes. 
Parentage of cross. 
Date 
emascu- 
lated. 
Datepol- 
linated. 
Num- 
ber of 
flowers 
crossed. 
Num- 
ber of 
seed 
balls 
devel- 
oped. 
Seed ball. 
Num- 
ber of 
plants 
potted. 
Per- 
Num- 
ber of 
cross. 
No. 
Num- 
ber of 
seeds. 
centage 
of seeds 
germi- 
nated. 
8708 
Irish. Cobbler X Irish 
Seedling 
July 28 
July 30 
G 
6 
f a 
b 
c 
' d 
e 
I / 
133 
108 
160 
57 
256 
250 
105 
86 
136 
47 
221 
176 
78.9 
79.6 
85.0 
Total 
82.5 
86.3 
70.4 
964 
771 
80 
Irish Cobbler X Irish 
Seedling 
July 28 
July 30 
7 
5 
8709 
f a 
b 
\ c 
d 
{ c 
2S9 
200 
192 
169 
134 
264 
155 
166 
121 
116 
91.3 
77.5 
86.5 
Total 
71.6 
86.6 
9S4 
822 
83.5 
Eureka X Keeper 
Total 
July 28 
July 30 
7 
5 
S71S 
[ a 
b 
\ c 
d 
[ e 
256 
297 
167 
189 
245 
189 
238 
122 
159 
196 
73.8 
80.1 
73.1 
84.1 
80 
1.154 
904 
78.3 

7925; 
-Bull. 195—15- 
