LUTHER BURBANK 



they are JJ; for shipping qualities they are SS; 

 for resistance to disease RR; for hardiness HH; 

 and for productivity PP. That is to say, they are 

 pure dominants for each of these qualities. 



Their germ plasm requires only an infusion of 

 the dominant factor for bigness and their progeny 

 will prove that breeding does tell. 



There is a tradition that passes current among 

 dog breeders which I do not vouch for but which 

 suggests a condition so comparable to that of our 

 cherry that I cite it by way of illustration. It is 

 said that the greyhound had been bred so exclu- 

 sively for speed that it developed all the desired 

 speed qualities of a hunting dog, able to overtake 

 any quarry, but lacked the courage to seize the 

 quarry once it had been overhauled. To over- 

 come this defect, so the story goes, some one 

 crossed the greyhound with the bulldog, thus 

 breeding in a strain of courage; and in subsequent 

 generations eliminated all the bulldog traits ex- 

 cept courage by selective breeding; and so gave 

 us a race of greyhounds in which the one missing 

 quality had been supplied. 



This greyhound legend seems much more 

 plausible to-day, now that attention has been so 

 generally called to the segregation of unit charac- 

 ters, than it formerly seemed. But whatever its 

 truth, the case of the hypothetical greyhound 



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