20 APPLICATION OF PEINCIPLES OF HEREDITY TO BREEDINa. 



The nine different combinations and their relative frequency follow: 



1 HHWW. 2 {H)hWW. 1 hhWW. 



2 HHWw. 4 {H) hWw. 2 hhWw. 

 1 HHww. 2 (77) hww. 1 hhww. 



The sixteen formulae in the squares in the middle of Table I show 

 the results of these sixteen unions. It will be seen that some of 

 these matings are alike; for instance, 2, 5, 12, and 15; 3 and 9; 4 

 and 13. There are only nine different kinds, as shown in the lower 

 part of Table I. These nine different combinations occur in the 

 relative frequencies shown in the numbers preceding each of the 

 nine in the lower part of Table I. Thus, one-sixteenth of the progeny 

 will represent the combination HHWW, four-sixteenths the combi- 

 nation (H)'h Ww, and so on. 



Table II shows the results of a more complex cross which the 

 writer made while connected with the Washington Agricultural 

 Experiment Station, Pullman, Wash. It is a cross between two 

 varieties of wheat, one of which was a winter wheat that lodged 

 easily (that is, had weak straw) and had open chaff, and thus when 

 ripe shattered its grain easily. The other was a variety of spring 

 wheat that did not lodge and had tightly closed chaff when ripe. 

 The first generation ° of the hybrid inherited a very complex lot of 

 characters. Thus, it inherited both winter and spring character; 

 both the lodging and the nonlodging tendency; both the open and 

 the closed chaff tendency. In this cross the winter character, the 

 nonlodging tendency, and the closed-chaff tendency were dominant. 



Letting — 



TF stand for the winter character, 



w for absence of winter character (i. e., spring character), 



iVfor nonlodging (i. e., for stiff straw), 



n for absence of N (i. e., for weak straw), 



C for closed chaff, and 



c for absence of C (i. e., for open chaff), 



the formula of the hybrid was WwNnCc. Now this hybrid can 

 produce, and does produce, in about equal numbers eight different 

 types of ovules and eight similar types of pollen, namely, WNC, WNc, 

 WnC, Wnc, wNC, wNc, wnC, wnc. The union of these eight types of 

 ovules and pollen grains gives sixty-four possible, and equally prob- 

 able, matings. But, as before, some of these matings give identical 



o Professor Bateson uses the symbol for first-generation hybrids. The F is the 

 initial letter of the word "filial." Hence this symbol means "first filial generation." 

 Bateson denotes the second and later generations of a hybrid by F2, Fg, etc. Likewise, 

 he denotes parental generations as follows: 



Pi=parent8 of the hybrid. 



P2=grandparents of the hybrid. 



P3=great-grandparents, etc. 



165 



