I2 4 



Heredity and Eugenics 



susceptible to a fungus disease called rust, and do not make 

 first-class bread on account of the low percentage of gluten. 

 After many importations, wheats resistant to rust and 

 high in gluten content were obtained, but these were not 

 profitable because of their low yields. Biffen then went 



to work to analyze the 

 transmissible characters 

 of the wheats into Men- 

 delian factors by a large 

 series of crosses. This he 

 was able to do. The rest 

 was easy. He has now 

 produced by hybridiza- 

 tion wheats that com- 

 bine the desirable 

 qualities and which lack 

 those disadvantageous 

 to the grower and the 

 baker. 



Sometimes a very sim- 

 ple recombination is of 

 very great commercial 

 value (Fig. 52). The so- 

 called Havana type of 

 wrapper tobacco grown 

 in the Connecticut 

 River valley has large 



FIG. 52. Nicotiana tabacum variety 

 "Havana." A stocky habit of growth with 

 about 20 large leaves. 



leaves and a short stocky habit of growth. It produces 

 1 8-2 1 leaves. There is another type from Sumatra which 

 has tall habit of growth with about 26 comparatively 

 small leaves. These two types were crossed by Shamel. 

 From this cross a new type called the Halladay has been 



