THE 



AMERICAN NATURALIST 



Vol. XLVI July, 1912 No. 547 



GENETICAL STUDIES ON OENOTHERA. Ill 



Further Hybrids of (Enothera biennis and 0. grandi- 

 flora that resemble 0. Lamarckiana 1 



DR. BRADLEY MOORE DAVIS 

 University of Pennsylvania 



The following paper will describe my cultures of 

 (Enothera, grown during the season of 1911, which bear 

 upon the working hypothesis announced in a previous 

 contribution (Davis,' 11) to the effect that (Enothera 

 Lamarckiana arose as a hybrid between types of 0. 

 biennis and 0. grandiflora. The cultures of 1911 gave 

 results much more striking than those of 1910 and 1909 

 and marked progress has been made towards the synthe- 



so similar to Lamarckiana as to be practically indistin- 

 guishable by the usual taxonomic tests. 



The problem before me seems to be chiefly that of find- 

 ing and selecting among the various strains or races of 

 biennis and grandiflora the most favorable types with 

 which to work. As the study has progressed I have been 

 surprised at the wealth and variety of forms which 

 taxonomically are included in the species 0. biennis, but 

 which can be readily differentiated in "pure line" cul- 



l An abstract of this paper was presented before the American Society 

 of Naturalists on December 28, 1911. 



377 



