Mutants and Hybrids of the Oenotheras 



BY D. T. MACDOUGAL 

 ASSISTED BY A. M. VAIL, G. H. SHULL,t AND J. K. SMALL 



PURPOSE AND SCOPE OF INVESTIGATIONS. 



The more important features of the investigations of De Vries in 

 which lines of descent were seen to originate, which embodied new 

 qualities and groupings of characters, constant and fully transmissible, 

 are now so familiar to all naturalists that no rehearsal is necessary in 

 the present paper. Early in 1902 the senior author received seeds of 

 the Lamarck's evening-primrose, and these, with seeds of various 

 species obtained directly from their native habitats in North America, 

 were cultivated in the New York Botanical Garden, in which the con- 

 ditions of soil and climate are, of course, widely different from those 

 of the botanical garden at Amsterdam, Holland. 



Among other primary purposes of the cultures it was deemed of 

 great importance that the mutants should be tested as to their stability 

 when grown as biennials after the predominant habit of the genus. 

 The results of this test, together with detailed descriptions of three of 

 the mutants, have already been given in an article in which occasion 

 was taken to set forth briefly the principal tenets of the mutation theory 

 as propounded by De Vries (MacDougal, 1903). It was found that 

 the mutant forms were not only physiologically differentiated, but were 

 also easily separable from one another and from the parental type when 

 tested by accepted taxonomic criteria, and by an examination of the 

 features of their life-histories. Furthermore, all the forms came true 

 to their newly assumed groupings of characters without reversions, and 



*The contents of this paper were presented before the weekly botanical con- 

 vention at the New York Botanical Garden, October 19, 1904. 



fOf the staff of the Station for Experimental Evolution of the Carnegie 

 Institution of Washington, Cold Spring Harbor, Long Island, N. Y. 



