14 BULLETIN 195 ; U. S. DEPARTMENT OF AGRICULTURE. 
Table I, — Record of potato crosses made at Burlington, Vt., in 1909 — Continued, 
Parentage of cross. 
Num- 
ber of 
flowers 
crossed. 
Num- 
ber of 
seed 
balls de- 
veloped. 
Percent- 
age of 
success. 
Number 
of tuber- 
bearing 
seedlings. 
Average 
number 
of seed- 
lings per 
seed ball. 
11 
12 
1 
8 
6 
1 
72.7 
50 
100 
70 
75 
15 
8.8 
Solarium utile Klotzsch X Seedling 962 
12.5 
15 
1,599 
458 
28.6 
18,947 
41.4 
1 Called S. utile by Pierre Berthault, Recher. bot. sur le Solanum tuberosum, 
6th Ann., p. 181, fig. 1, 1911. Mexican species. 
In Ann. de la Sc Agron., 
In the first cross of the third seed parent, Professor Maerker X 
Apollo, both the seed and pollen parents are of German origin, 
the latter being one of the most disease-resistant varieties in 
the collection. Nine seed balls are recorded from 12 flowers 
pollinated and 275 tuber-bearing plants were obtained from 
this lot, or an average of 30.6 plants per berry. Fifteen flowers 
pollinated with pollen from Early Silversldn produced 15 seed 
balls, from which 555 plants were obtained, an average of 37 plants 
per berry. When crossed with Keeper, 12 seed balls were developed 
from 13 flowers and these gave 326 plants, or an average of 27.2 
plants per berry. Pollen from Rand's Peachblow proved ineffective. 
It is interesting to compare the results from the two crosses, 
Sophie X Keeper and Professor Maerker X Keeper. In the first 
instance the percentage of success is 80 and in the latter 92.3. 
Carrying the comparison farther, however, we find that the first 
cross averaged over 140 plants per berry, while, the latter averaged 
only 27.2. These data make it at once apparent that some 
varieties develop fewer ovules than others. 
Two of the most interesting crosses in Table I are those of Sola- 
num utile Klotzsch with seedlings 949 and 962, from which some 90 
tuber-bearing plants were produced. Solanum utile is a wild Mexican 
species producing tubers rather sparingly on long, spreading stolons. 
The tubers rarely exceed or even reach the size of a small hen's egg 
and when well developed are of a purple color. Immature tubers 
do not show color, and owing to this characteristic Heckel 1 was led 
to conclude that he had secured a mutant when white-colored tubers 
were observed to produce colored ones. The seedlings of these two 
crosses, while varying considerably from the seed parent, neverthe- 
less bore a very striking resemblance to it. A number of them made 
a much stronger and larger vine growth and produced larger tubers, 
some of which bore a more or less distmct resemblance to the pollen 
parent. Seed balls were borne rather sparingly on some of the 
seedlings. Up to the present time these seedlings offer little, if any, 
promise except in the possibility of their possessing greater resist- 
ance to disease. 
i Heckel, E. M. Sur les Origines de la Pomme de Terre Cultiv^e, 82 p., illus., 8 pi. Marseille, 1907. 
(Seep. 71.) 
