A PECULIAR NEGATIVE CORRELATION IN 

 OENOTHERA HYBRIDS. 



BY GEORGE HARRISON SHULL. 



Station for Experimental Evolution, of the Carnegie Institution 

 of Washington, Cold Spring Harbor, Long Island. 



WITH all the careful attention which has been given to the 

 Oenotheras by students of genetic phenomena, there is no other group 

 of organisms in which these phenomena seem so far from a satisfactory 

 interpretation. Fundamental difficulties are encountered whenever 

 attempts are made to apply to the Oenotheras rules of genetic behavior 

 which are readily demonstrated in other groups of organisms. Equal 

 confusion has arisen by the application of genetic experiences with the 

 Oenotheras to species in which typical Mendelian phenomena appear. 

 A hereditary mechanism must exist in Oenothera fundamentally 

 different from that which distributes the Mendelian unit-characters. 

 It becomes increasingly clear that the data on record are inadequate for 

 the discovery of the essential features of this mechanism. It is con- 

 ceivable that different mechanisms for the distribution of the hereditary 

 characters may exist in different sections of the genus and that this 

 may partly account for the slowness with which a comprehensive view 

 of the genetic phenomena in this field has been made possible. Under 

 these circumstances there is demanded a large amount of purely 

 inductive work by the strictest pedigree methods and individual 

 analysis. Before we can hope to explain the phenomena we must 

 know what phenomena are presented for explanation. As a modest 

 contribution to our knowledge of the genetic facts in Oenothera which 

 need interpretation the following data are presented. 



Early in June 1912 I received from Dr. A. F. Blakeslee, Storrs, 

 Connecticut, three rosettes grown from unguarded seeds of Oenothera 

 rubricalyx Gates, the seeds having been received by him from 

 Dr. R. R. Gates, the discoverer of this particularly beautiful form. 



62 



