Oct 8. tgai Comparative Vigor of Fj Wheat Crosses and Their Parents 59 



ility is mentioned by Kezer and Boyack (ii) as occurring in the F^ gen- 

 eration of the cross Fultz Mediterranean by Black Winter Emmer. In 

 crosses between Algerian Macaroni and Algerian bread wheats, Free- 

 man (9) reports that the F^ generation developed normally but in the 

 F2 generation all degrees of sterility appeared from complete sterility to 

 complete fertility. 



Hayes, Parker, and Kurtzweil (10) crossed varieties of Triticum vul- 

 gare with varieties of T. durum and T. dicoccum. The parental varieties 

 showed an average of 4 per cent of barren florets. The F^ crosses of 

 varieties of durum with varieties of vulgare and the reciprocals showed 

 a barrenness of 47 per cent. The Fi crosses of T. dicoccum crossed with 

 varieties of vulgare showed 26 per cent barrenness and the reciprocal 29 

 per cent. The results are not in agreement with the conclusions of 

 Tschermak (13). 



In the present experiment a count was made of the total number of 

 outer florets per plant and the number of these which were barren. 

 From these data the percentage of barren florets was computed. (Table 



Table VI. — Barrenness of outer florets in wheat varieties and Fi crosses 



Variety or cross. 



Number Percentage 



plants of barren 



consid- outer 



ered. florets. 



Marquis 



Velvet ChaJBf 



Penny 



Haynes Bluestem 



Bobs 



Little Club 



Emmer 



Mindum 



Average 



MarquisXPenny 



MarquisXBobs 



Velvet Chaff X Penny 



Velvet Chaff X Bobs 



Haynes Bluestem X Marquis 



PennyXBobs 



Marquis X Little Club 



Velvet Chaff X Little Club. . 



Average 



MarquisX Emmer 



Velvet Chaff X Emmer 



Little Club X Emmer 



Average 



MarquisX Mindum 



Velvet Chaff X Mindum .... 

 Little Club X Mindum 



Average 



15 

 38 

 34 

 47 

 59 

 47 

 49 

 44 



18 

 21 

 IS 



18 

 17 

 25 

 18 



19 



42 



19 



18 



65 



27 



93 

 18 



22 

 57 

 37 



17 

 14 

 15 

 13 

 17 

 15 

 17 

 14 



70 



