15 : 1, considering the number of individuals involved in the F a 

 cultures and the consistent results yielded by three different 

 pedigrees involving reciprocal crosses. After the pedigrees were 

 all arranged in the spring of 1910 for the testing of this hypoth- 

 esis, Baur J ) suggested the same possible explanation in a 

 review of one of my papers. 



The demonstration of two independent genes for the deter- 

 mination of the same external character is to be found in the 

 composition of the F 3 families grown from self-fertilized F 2 individ- 

 uals possessing the dominant character in question, in this 

 instance the bursa-pastoris type of capsule. Letting the two sup- 

 posed genes for the triangular capsule be represented by the 

 symbols Cc and Dd, the gametic composition in F 2 and the 

 jxpectation in the F 3 is indicated in the following table: 



Table II. 





Expected 

 Results in F 3 



CDCD 



CDCd 



CDcD 



CDcd 



CdCd 



cDcD 



Cdcd 



cDcd 



cdcd 



All bursa-pastoris. 

 All bursa-pastoris. 

 All bursa-pastoris. 

 Bursa-pastoris and Hcegeri, 15 : 

 All bursa-pastoris. 

 All bursa-pastoris. 

 Bursa-pastoris and Heegeri y 3:1. 

 Bursa-pastoris and Heegerij 3:1. 

 All Heegeri. 



The facts shown in this table may be summarized in the 

 statement that among fifteen families raised from F 2 plants 

 laving the bursa-pastoris type of capsule, there will be on the 

 tverage seven (I CD CD + 2 CD Cd + 2 CDcD + 1 CdCd + 1 cDcD) 

 will breed true to that type, four (CDcd) will produce 

 irsa-pastoris and Heegeri in the ratio 15 : 1 as in the F 3 , and 

 four (2 Cdcd -f 2 cDcd) will give these two types of capsules in 

 the ratio 3:1. As in all other recessive types, the offspring of 

 plants having Heegeri capsules should produce no plants with 

 mrsa-pastoris capsules in the F 3 . 



A ) Zeitschrift fur Indtikttve Abstainmuiigs- uud Vererbungslehre 

 : 341 342, Je 1910, 



