LUTHER BURBANK 



subordinate race or "pure type." Thus from the 

 same mixed stock sundry races of relative giants 

 and of relative dwarfs, as well as numerous inter- 

 mediate races, are formed. 



Now it would appear that such a case as that 

 of the prune, in w^hich we are able to work out 

 by artificial selection a race characterized by 

 tendencj' to early fruitage, is in keeping with these 

 studies of the so-called "pure lines'* of descent to 

 which Professor Johannsen has given attention. 



But it must be understood that it is exceedingly 

 difficult to carry the experiment in the case of 

 the prune to the stage at which the type becomes 

 absolutely fixed, for the reason that there are so 

 many other qualities to be considered. 



This matter of varying qualities represented in 

 the same seed we have discussed before, and we 

 shall have occasion to refer to it again and again. 

 Here it suffices to note that the case of the prune 

 is akin to others that we have examined, for 

 example the hybrid walnuts and the early cherries, 

 in that the qualities for which we have bred are 

 so numerous and so varied that they can be 

 aggregated only in one seedling among many 

 thousands, and could not be fixed without a long 

 series of generations of additional breeding. 



Fortunately this is of no practical consequence, 

 because the prune, like other orchard fruits, may 



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