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 

 betweeA 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 represeilting different branches which 

 may diverge in opposite directions, and only come 

 together at the trunk. 



[40] 



