124 LUTHER BURBANK 



grandparent as regards a single 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 speci- 

 men 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 

 lacked this quality or had it mixed with the 

 undesirable quality. 



NOT so SIMPLE IN ACTUAL WORK 



But, unfortunately, the simplicity of the 

 formula vanishes as soon as we come to consider 

 a second, and third, and fourth pair of unit 

 characters. 



Here also the formula has been worked out 

 in mathematical terms ; and it appears that when 

 several characters are involved, we at once come 

 to deal with numbers that are no longer easy 

 to keep track of. Moreover, the various pairs 



