RECORDING THE EXPERIMENTS 



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 thornless 

 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 determined, and 

 through which the plant is given the impulse to 

 variation, are also explicitly shown. 



But when, particularly in case of a fruit 

 having 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 variations devel- 

 oped, for two very explicit and sufficient reasons. 



One reason is that the numbers of seedlings 

 involved are so great that it would be physically 

 impossible for any one carrying on hundreds of 

 different series of tests at the same time to make 

 numerical count in accordance with the statistical 

 method adopted by workers who are experi- 

 menting on a limited scale. 



The second reason is that even if such a count, 

 showing the exact number or percentage of seed- 

 lings with different combinations of traits, were 



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