82 LUTHER BURBANK 



So the stone not only destroys a part of the 

 usefulness of the plum for man directly, by its 

 presence in the fruit, but it is also indirectly 

 harmful in that it hampers the vigor of the tree 

 in the production of foliage and larger quantities 

 of fruit. 



Yet when the plant improver attempts to re- 

 move the stone that has thus come to be an 

 incumbrance to the plant, he is obliged, as it 

 were, to swim upstream against the hereditary 

 current of the ages. Ten, fifteen, twenty years 

 these are but moments of time when working 

 against tendencies that are fixed by thousands 

 of repetitions under conditions that remained 

 unchanged for numberless generations, and until 

 the immediate present. 



Bearing this in mind* we gain a more vivid 

 impression of the difficulties that confront the 

 plant developer who would endeavor to relieve 

 the plum of its burdensome stone. 



AID FROM NATURE 



But here as elsewhere nature will sometimes 

 seem to forget for a moment the very funda- 

 mentals of her plan ; and through such a lapse the 

 hereditary mechanism of a given organism may 

 be changed more radically, perhaps, in a single 

 generation, than it could be changed by almost 



