THE BURBAXK CHERRY 131 



to breed traits into a hybrid strain, and then 

 breed them out again. 



In point of fact, no progress in the production 

 of new varieties could have been made in my 

 experiments, were it not for this possibility. 



The Shasta daisy, for example, is not inter- 

 mediate in size between the species from which 

 it sprang, but larger than any of them, the 

 white blackberry is not intermediate in color 

 between the parental strains, but is of a far 

 purer white than its light-colored ancestor. The 

 stoneless plum is more stoneless than the race 

 from which it sprang, although that race has 

 been crossed again and again with strains of 

 plums that invariably produce a stony seed 

 covering. Some of my hybrid walnuts are far 

 larger than either parent stock, and some are far 

 smaller than either. 



And so on throughout the list of the 

 hybridizing experiments through which the 

 new races of plants have been developed at 

 Santa Rosa. Everywhere we find evidence of 

 segregation of unit characters and recommin- 

 gling and reassortment in later generations. 



Nowhere else, probably, can there be found 

 such an aggregate mass of testimony to the 

 operation of this principle as will be supplied 

 in the pages that tell of my various experiments. 



