20 
BULLETIN 195, U. S. DEPARTMENT OF AGRICULTURE. 
has been to discard all those which show undesirable traits, such as 
straggly or weak vine growth, susceptibility to fungous diseases of 
either vine or tuber, deep eyes, imperfect shape or color of skin, poor 
yield, lack of uniformity in size or type, and poor quality. Among 
those which now remain there appear to be a number of very promis- 
ing varieties, three of which are shown in Plates XI, XII, and XIII. 
SEEDLING INHERITANCE IN THE F x GENERATION. 
The study of these seedlings both in the laboratory and in the field 
has furnished an excellent opportunity for observing the inheritance 
of parental characters. It has been a source of considerable surprise 
to the writer to find in a class of plants of the cultivated varieties of 
Solatium tuberosum L., which do not normally reproduce true from seeds, 
such a preponderance of the seedlings showing marked resemblances 
to either one or the other of the parents. These resemblances have 
been sufficiently marked in the case of both vines and tubers to per- 
mit those familiar with the parental characters to recognize the par- 
entage of a group of seedlings, either in the field or in the laboratory, 
simply by the preponderance of certain characters peculiar to one or 
the other of the parents. 
Some rather interesting data have been obtained relative to color 
inheritance in the tubers. Comparatively recent studies by Salaman * 
on color inheritance in the potato seem to warrant the deduction 
that a white skin is a recessive character. In this connection the 
statement is made that a white skin denotes the absence of a color 
pigment or of a factor necessary to color expression. Salaman 
found that when certain white-skinned varieties were selfed, their 
seedlings were all white skinned. 
Table IV. — Color inheritance 
in tubers of F 
! seedlings of 
1910 crosses, season of 1911. 
Number of seedlings. 
Tubers. 
Parentage of crosses. 
Total. 
White 
to 
cream 
yellow. 
Russet. 
Mot- 
tled. 
Flesh. 
Red. 
Purple. 
Violet 
to 
black. 
With- 
out 
color.* 
With 
color. 
Irish Cobbler X Mc- 
Cormick 
32 
1.425 
870 
214 
680 
88 
322 
8 
16 
982 
589 
73 
480 
69 
2.57 
3 
18 
17 
1 
2 
36 
23 
72 
91 
11 
28 
4 
11 
229 
141 
38 
67 
6 
32 
1 
3 
104 
98 
8 
37 
1 
5 
Per ct. 
50.0 
70.2 
69.7 
34.1 
70.6 
79.5 
79.8 
37.5 
Per ct. 
50.0 
Irish Cobbler X 
Irish Seedling 
Irish Cobbler X 
55 
2 
12 
5 
1 
11 
29.8 
30.3 
Irish Cobbler X 
Wild Chilean 
Extra Early Eureka 
X Keeper 
65.9 
29.4 
Green Mountain X 
20.5 
20.2 
McCormick X Chil- 
ean Seedling 
62.5 
* This percentage is based on the number of white to cream yellow and russet tubers. 
1 Salaman, R. N. The inheritance of color and other characters in the potato. In Jour. Genetics, v. 1, 
no. 1, p. 7-46, 29 pi., 1910. (See p. 30.) 
