20 



BULLETIN 195;, U. S. DEPARTMEISTT OF AGEICULTUEE. 



has been to discard all those which show undesirable traits, such as 

 straggly or weak vme growth, siisceptibiUty 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 quahty. 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^ 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 

 Solanum tuberosum L., which do not normally reproduce true from seeds, 

 such a preponderance of the seedlings showmg 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 seedhngs, either in the field or in the laboratoiy, 

 simply by the preponderance of certain characters pecuhar to one or 

 the other of the parents. 



Some rather interesting data have been obtamed relative to color 

 inheritance in the tubers. Comparatively recent studies by Saiaman ^ 

 on color inheritance in the potato seem to w^arrant 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. Saiaman 

 found that when certain white-skinned varieties were seHed, their 

 seedlings were aU white skinned. 



Table IV. — Color inheritance 



in tubers of F 



1 seedlings of 



1910 crosses, season q 



f 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- 



32 



1,425 



870 



214 



680 



88 

 322 



8 



16 



982 



589 



73 



480 



69 

 257 



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 



Pcrcf.. 

 50.0 



Irish Cobbler X 



Irish Seedling 



Irish Cobbler X 



Keeper 



Irish Cobbler X 



Wild Chilean 



Extra Early Eureka 



X Keeper 



Green Mountain X 



Keeper 



Gold Coin X Keeper. 

 McConnick X Chil- 



ftn.n Sp.p.rllinCT 



55 

 2 

 12 



5 



1 

 11 



29.8 

 30.3 

 65.9 

 29.4 

 20.5 







20.2 







62.5 













*.This percentage is based on the number of white to cream yellow and russet tubers. 

 1 Saiaman, 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.) 



