v] 



HEREDITY 



65 



into one race of wheat the characters previously found 

 in different varieties. 



The chief reason that breeders of plants and 

 animals believe that the race is permanently con- 

 taminated by crossing different breeds is that 

 commonly two breeds differ in several or many 

 pairs of characters. If two pairs of allelomorphic 



b« .....ii 





Fig. 8. A cob of Maize borne by an F x plant from the cross smooth 

 (starchy) seed x wrinkled (sugary) seed, fertilised with its own 

 pollen, showing about three smooth (dominant) to one wrinkled 

 (recessive) seeds on the same cob. (From Bateson.) 



characters are combined in the heterozygote, we 

 have seen that only one in sixteen of its offspring is 

 homozygous for any particular combination ; if three 

 characters, one in 64, if four characters, one in 256, 

 so that it is clear that Mendel's method of considering 

 distinct characters separately must be followed, if 



D. 5 



