THE ALMOND 329 



It would appear, then, that the Japanese plum 

 and the almond, as represented by the particular 

 specimens that were used in these hybridizing 

 experiments, were just at the limits of affinity 

 that permitted cross-fertilization, but imposed 

 sterility on the offspring. The parents were a 

 shade more widely removed from each other 

 genetically than were, for example, the plum and 

 the apricot or the Persian and California 

 walnuts. This fact, and not the mixed ancestry 

 of either parent, may have accounted for the 

 diversity of form of the progeny. 



As the plum-almond hybrids were sterile, it is 

 obvious that the experiments through which I 

 had hoped to develop new varieties and perhaps 

 new species of fruits could go no further in this 

 direction. It is of course possible that individual 

 plums and almonds or different varieties of the 

 two races might be found that would combine to 

 produce fertile offspring. This supposition finds 

 support in the fact that my earliest crosses be- 

 tween the plum and the apricot were also sterile ; 

 whereas later ones produced the fertile plumcot, 

 as the reader is aware. 



So it is obviously worth while to continue the 

 experiments of hybridizing the plum and the 

 almond, and there is reason to hope that interest- 

 ing and valuable results may be attained. 



