BLENDING INHERITANCE 



181 



ter of red color, each of which is able to give red color 

 to the wheat. Taken together, these three red color 

 determiners behave cumulatively, following the law of a 

 trihybrid. 



For example, if a brown-chaffed wheat with the 

 formula BB', in which B and JB' each represent a 

 brown - chaffed 

 factor, is 

 crossed with a 

 white - chaffed 

 wheat of the 

 formula bb' 9 in 

 which b and b' 

 each represent 

 the absence of 

 B and B' re- 

 spectively, then 

 all the progeny 

 of this cross 

 will be brown- 

 chaffed, having 

 the zygotic for- 

 mula BB'W. 

 When upon ma- 

 turation the gametes form out of the germ-cells from 

 such hybrids, the following four combinations are pos- 

 sible, and no others : BB', Bb', bB', bb'. These repre- 

 sent, therefore, the possible gametes present in each sex 

 of the first filial generation, and upon intercrossing 

 they may combine into sixteen possible zygotes to form 

 the second filial generation, as shown in Figure 37. 



FIG. 37. Diagram of the possible combina- 

 tions in the F 2 generation of brown-chaffed 

 wheat according to experiments of Nilsson- 

 Ehle. B and B' are cumulative factors for 

 the brown-chaff character; b and b' denote 

 the absence of B and B' respectively. 



