species and Varieties 



Their Origin by 

 Mutation 



Lectures Delivered at the University of 

 California 



by 



Hugo DeVries 



Professor of Botany in the'^niversity of Amsterdam 



Edited by 

 Daniel Trembly MacDougal 



Director Department of Botanical Research, Carnegie Institution 

 of Wasliington 



Second Edition, 

 Corrected and Revised 



CHICAGO 



The Open Court Publishing Company 



LONDON 



Kegan Paul, Trench, Trubner & Co., Ltd. 



1906 



