THE 



AMERICAN NATURALIST 



Vol. XLV April, 1.911 No. 532 



GENETICAL STUDIES ON (ENOTHEBA. II 

 Some Hybrids of (Enothera biennis and 0. grandiflora 



The status of (Enothera Lamarckiana is a matter 

 which must he given serious consideration in any attempt 

 to judge the value of De Vries 's mutation theory, for the 

 reason that the behavior of this form in throwing off 

 marked variants (mutants) from the type has been re- 

 garded by De Vries as direct experimental proof of mu- 

 tation. Indeed, the theory of De Vries may fairly be 

 said to rest chiefly upon the behavior of this interesting 

 plant, the account of which forms so large a part of his 

 work, "Die Mutationstheorie, ' ' 1901-1903. 



Aside from his claim of direct proof of the origin of 

 mutations from (Enothera Lamarckiana, De Vries offers 

 a considerable body of indirect evidence of the sort pre- 

 sented in Darwin's "Variation of Animals and Plants 

 under Domestication," and in that extensive and very 

 carefully sifted account of Bateson, "Materials for the 

 Study of Variations," 1894. However, much of this in- 

 direct evidence of De Vries deals witli the origin of 

 "sports" from domesticated forms or with the origin 



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