Plant Breeding 



Comments on the experiments of 

 BURBANK & NILSSON. By 



Hugo DeVries, Professor of Botany in the University of Amsterdam. 



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Under the influence of the work of Nilsson, Burbank, and others, the principle of 

 selection has, of late, changed its meaning in practice in the same sense in which it is 

 changing its significance in science by the adoption of the theory of an origin of species 

 by means of sudden mutations. The method of slow improvement of agricultural varie- 

 ties by repeated selection is losing its reliability and is being supplanted by the discovery 

 of the high practical value of the elementary species, which may be isolated by a single 

 choice. The appreciation of this principle will, no doubt, soon change the whole aspect 

 of agricultural plant breeding. 



Hybridization is the scientific and arbitrary combination of definite characters. It 

 does not produce new unit-characters; it is only the combination of such that are new. 

 From this point of view the results of Burbank and others wholly agree with the theory 

 of mutation, which is founded on the principle of the unit-characters. 



This far-reaching agreement between science and practice is to become a basis for 

 the further development of practical breeding as" well as of the doctrine of evolution. 

 To give proof of this assertion is the main aim of these Essays. 



The results of Nilsson have been published only in the Swedish language; those of 

 Burbank have not been described by himself. Prof. DeVries's arguments for the theory 

 of mutation have been embodied in a German book, "Die Mutationstheorie" (2 vols. 

 Leipsic, Vat & Co.), and in lectures given at the University of California in the summer 

 of 1904, published under the title of "Species and Varieties; their Origin by Mutation." 

 A short review of them will be found in the first chapter of these Essays. 



Some of them have been made use of in the delivering of lectures at the Universities 

 of California and of Chicago during the summer of 1906 and of addresses before various 

 audiences during my visit to the United States on that occasion. In one of them(II.D.), 

 the main contents have been incorporated of a paper read before the American Philo- 

 sophical Society at their meeting in honor of the bicentennary of the birth of their 

 founder, Benjamin Franklin, April, 1906. 



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