MUTANTS AND HYBRIDS OF THE OENOTHERAS. 



49 



Darwin performed a large number of experiments to test the 

 effect of self and cross fertilization, but his object was to determine the 

 advantages or disadvantages as measured by height, productivity, etc., 

 rather than the effect on variability. The number of specimens used by 

 him in each species studied was hardly sufficient to allow conclusions 

 of value regarding variability , but he infers that variations are primarily 



Fig. 12. Correlation table of length and width of leaf in Onagra rubrinervis. 

 Width of leaf subject, length relative ; p = 0.6604 0.0119. 



due to differences of environmental conditions, and that cross-fertiliza- 

 tion tends to produce uniformity when these variations are slight, and 

 to increase the diversity when the variations are considerable. These 

 questions need thorough reinvestigation, and their discussion is futile 

 until such investigation is made. (Darwin, 1876, p. 452.) 



If the Onagra mutants are not the result of selection and isola- 

 tion, acting within the field of applicability of known laws of 

 variation and heredity, but are really, as they have been called by 

 certain German writers, ' ' correlation-breakers, ' ' may not the increased 



