LUTHER BURBANK 



ferent species of oak may interbreed; but the 

 hybridizing of apple or blackberry with any 

 species of oak is almost unthinkable. 



Similarly, in my experiments I have been able 

 to hybridize peach with almond, and almond with 

 plum, and plum with apricot; also apple with 

 quince, and quince with pear. Stone fruit with 

 stone fruit, that is to say, and seed fruit with seed 

 fruit but never stone fruit with seed fruit. 



In a word, the possibility of cross-fertilization 

 between species is conditioned on a certain close- 

 ness of relationship, which we speak of as affinity. 



This, as the evolutionist teaches us, is a matter 

 of actual genetic relationship. All members of 

 the rose family, for example, have branched from 

 the primal ancestral stem at a period much more 

 recent than that at which the common ancestor 

 of the present-day apple and rose and blackberry 

 branched from the primal stock of, let us say, 

 the oaks. 



In the broadest view, there is a cousinship 

 between all species of plants; just as there is 

 relationship between all the twigs of an actual 

 tree. But the species of an existing genus may 

 be likened to twigs on a single branch; other 

 genera representing different branches which 

 may diverge in opposite directions, and only come 

 together at the trunk. 



[40] 



