38 LUTHER BURBANK 



thing of interest has appeared, any point as to 

 which a plant shows differences from its fellows, 

 this has become a matter for recording. 



Moreover, it has been my universal custom to 

 make record of the first hybridizing or crossing 

 through which any particular series of experi- 

 ments is inaugurated. The parentage of the 

 Shasta daisy, the white blackberry, the stoneless 

 plum, the sugar prune, the plumcot, the thorn- 

 less blackberry, the spineless cactus these are 

 matters of clearest and most unequivocal record. 

 The results of the first crossing, through which 

 matters of prepotency and of latency are deter- 

 mined, and through which the plant is given the 

 impulse to variation, are also explicitly shown. 



But when, particularly in case of a fruit hav- 

 ing complex characters, the experiment passes 

 to stages of the third and fourth generations, 

 involving tens of thousands or hundreds of thou- 

 sands of seedlings, it is no longer possible to 

 make detailed and explicit record, with exact 

 count of the different combinations and vari- 

 ations developed, for two very explicit and suffi- 

 cient reasons. 



One reason is that the numbers of seedlings 

 involved are so great that it would be physically 

 impossible for anyone carrying on hundreds of 

 different series of experiments at the same time 



