8 LUTHER BURBANK 



generation after generation, for untold centuries. 

 They represent an old, fixed, conservative stock. 

 No one knows how to make them change, except 

 within the narrowest of limits. 



There is a very essential time element, then, 

 that is instrumental in determining the fixity or 

 variability of a race of plants. A plant that has 

 been bred true to a given type for long periods 

 of time, as is the case with the generality of wild 

 plants, will breed substantially true from seed, 

 and as a rule will maintain its racial type even if 

 transplanted to new surroundings. 



But, on the other hand, most of our cultivated 

 plants are of mixed ancestry. Man has, within 

 recent generations, changed them and adapted 

 them to his needs. He has constantly been 

 crossing them, or placing them under condi- 

 tions that resulted in their combination through 

 the visits of bees; and he has selected and cul- 

 tivated the individual specimens that tended 

 to vary, and thus fostered the habit of 

 variability rather than that of fixity of 

 character. 



In the case of most orchard fruits, as we have 

 had occasion to observe more than once, so many 

 strains are blended that propagation from seeds 

 is quite out of the question; unless, indeed, it be 

 desired to secure seedlings of varying qualities in 



