MUTANTS AND HYBRIDS OF THE OENOTHERAS. 



47 



ters are shown in figs. 12 and 13. The lesser correlation of the for- 

 mer isapparent to the eye in the more scattered distribution of the 

 variates. The coefficients of correlation are as follows : Onagra la- 

 marckiana, 0.7916 ± 0.0090; Onagra rubrinervis, 0.6604 ± 0.0119. 

 This is simply another way of expressing the fact that the leaf-form of 

 O. rubrinervis is more variable than that of its parent-species. 



If increased variability and decreased correlation be, as here indi- 

 cated, a general feature of those characters in which a mutant departs 

 markedly from the parental condition, how is it to be interpreted? It 

 is hinted by Weldon ('02) that these mutants are possibly the result of 

 selection and isolation. No one can deny that there has been selec- 

 tion and isolation in their culture, but it may be questioned whether 



35-26 27-28 29-30 31-32 33-34 35-36 37-38 3'J— 10 11-42 



Fig. 10. Variation in the mean width of leaves of Onagra rubrinervis and O. 

 lamarckiana. Curve for O. rubrinervis shaded with lines rising to the right. Kange : 

 O. rubrinervis, 25.93 to 32.53 mm.; O. lamarckiana, 33.71 to 41.64 mm. 



these processes have been carried on to such an extent as to explain 

 the peculiar behavior of the mutants as compared with that of an 

 extreme variate. This question will not be satisfactorily answered 

 until a newly arisen mutant shall be subjected to various conditions 

 of cross and self fertilization, and the results are studied statistically. 

 It seems fair to assume that there has been a more discriminating 

 selection in the case of the several mutants than in O. lamarckiana. It 

 is therefore something of a surprise, if Weldon's suggestion be true, 

 to find the latter less variable in nearly every character studied. This 

 surprise is due to what may be a false assumption, namely, that selec- 

 tion necessarily operates to lessen variability. Is it not conceivable 



