161 



15 : 1, considering the number of individuals involved in the F 2 

 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 *) 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 triangulär capsule be represented by the 

 Symbols Cc and Dd 7 the gametic composition in F 2 and the 

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



Table II. 



Number of n Gametic Expected 

 F 2 plants in 16. C ?™P£ Results iu F 3 



1 CDCD All bursa-pastoris. 



2 CD Cd All bursa-pastoris. 

 2 CDcJD All bursa-pastoris. 



4 CDcd Bursa-pastoris and Heegeri 7 15 : 1. 



1 CdCd All bursa-pastoris. 



1 cDcD All bursa-pastoris. 



2 Cdcd Bursa-p)astoris and Heegeri 7 3:1. 

 2 cDcd Bursa-pastoris and Heegeri } 3:1. 

 1 cdcd All Heegeri. 



The facts shown in this table may be summarized in the 

 Statement that among fifteen families raised from F 2 plants 

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

 average seven (1 CDCD + 2 CD Cd + 2 CDcD f 1 CdCd + 1 cDcD) 

 which will breed true to that type, four [CDcd) will produce 

 bursa-pastoris and Heegeri in the ratio 15 : 1 as in the F 2; and 

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

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

 F 2 plants having Heegeri capsules should produce no plants with 

 bursa-pastoris capsules in the F 3 . 



l ) Zeitschrift für Induktive Abstammungs- und Vererbungslehre 

 3 : 341—342, Je 1910. 



Verhandlungen des naturf. Vereines in Brünn. XLIX. Band. \~L 



