LUTHER BURBANK 



difficulties the experiments through which I have 

 hybridized the apple with the pear, and with the 

 quince; the cherry with the plum; and the peach 

 with the almond, with the Japanese plum, and 

 with the apricot, without in any of these cases 

 producing a product of value. These crosses, 

 like the ones just detailed, bring together racial 

 tendencies that are too widely divergent to be 

 harmonized. 



It would appear that it is essential to the differ- 

 entiation and perpetuation of species that bounds 

 should be set on the possibility of producing a 

 disturbing influence through hybridization. When 

 plants, even though sprung from the same origin, 

 have diverged so widely and for such periods of 

 time as to produce forms differing from one 

 another so greatly as, for example, the mountain- 

 ash, the apple, and the rose differ from the dew- 

 berry; or the strawberry from the raspberry it 

 would seemingly not be advantageous in the 

 scheme of evolution to permit the hybridizing of 

 these forms. 



The mutations that would be produced, were 

 such hybridization to result in virile offspring, 

 would be too divergent, in all probability, to fit 

 into their environment successfully. At all events 

 the possibility of such crosses would constitute a 

 disturbing influence that would rob the scheme 



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