LUTHER BURBANK 



applied to various races of animals and plants, 

 when a cross has been made and a record kept of 

 the results with reference to a single pair of unit 

 characters, such as blackness versus whiteness in 

 the case of the guinea pigs. In such a case, where 

 the offspring of the second filial generation are 

 interbred, it has been clearly demonstrated, that 

 on the average, one-fourth of the offspring 

 of the second filial generation will resemble the 

 paternal grandparent, and one-fourth the mater- 

 nal grandparent; the remaining half being of 

 mixed heredity. 



Stated otherwise, there is an even chance that 

 in any group of four offspring of the second filial 

 generation, one individual will resemble each 

 grandparent as regards a given unit character. 



Applying this rule to the case of our cherries, 

 and considering for the moment only the matter 

 of early-bearing versus late-bearing, it should 

 result, if these qualities constitute a pair of unit 

 characters, that by crossing an early-fruiting 

 cherry with a late-fruiting one, the descendants of 

 the second generation would show one specimen 

 in four growing early fruit, one in four growing 

 late fruit, and two of intermediate tendencies. 



All that would then be required would be to 

 breed exclusively from the one-fourth that were 

 early-bearers, destroying the three-fourths that 



[220] 



