LUTHER BURBANK 



to determine which ones have in their germ plasm 

 only the factors that we desire to see perpetuated 

 and which others have the mixed factors that we 

 wish to see eliminated. 



The suggested manner of selecting by isolation 

 of individuals merely enables us to go more 

 directly to the goal. It does not differ in principle 

 from the ordinary method of selection. But the 

 isolation of each individual, so that its traits may 

 be separately tested, enables us to reach the result 

 in two years, instead of requiring perhaps from 

 six to ten years. 



It will be recalled that it was through the appli- 

 cation of this method that Prof. Biff en was enabled 

 to isolate and fix his new race of wheat that is 

 immune to rust in the third generation. But it 

 must be recalled that Prof. Biffen was working 

 with only a few hereditary factors or characteris- 

 tics and that he was also working with a plant 

 that is self-fertilized. 



To follow out the principle in the case of a 

 plant like the Shasta daisy, in which a large num- 

 ber of hereditary factors are under consideration, 

 would involve the handling of very much larger 

 numbers of seedlings. And the fact that these 

 must be isolated not merely in location but must 

 also be guarded against cross-fertilization intro- 

 duces a further complication. 



[148] 



