Plant Breeding S— burbInH 



NILSSON. By Hugo DeVries, Professor of Botany in the 

 University of Amsterdam. Pages, XIII by 351. 114 Illustra- 

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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 discov- 

 ery 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 tsecome 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. 



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