288 HEREDITY AND ENVIRONMENT 



riety of oats two hereditarily separable fac- 

 tors are involved in the production of black. 

 In crosses between red-grained and white- 

 grained wheat he usually got in the second 

 generation the monohybrid ratio of 3 red to 1 

 white, but three strains gave the dihybrid ratio 

 of 15 to 1 and two gave the trihybrid ratio of 

 63 to 1. Consequently he concludes that while 

 the red color of wheat grains is usually due 

 to one factor for red, it may in some cases be 

 due to two or even three factors; notable de- 

 partures from expected ratios may thus be 

 explained. 



Blending Inheritance 



But the most serious objections which can 

 be presented against the universality of the 

 Mendelian doctrine are found in phenomena 

 of "blending" inheritance. In some instances 

 contrasting characters of parents appear to 

 blend in offspring and even in the F 2 and in 

 subsequent generations the descendants remain 

 more or less intermediate between the par- 

 ents. One of the best known illustrations of 

 this is found in the skin color of the mulatto 



