No. 561] GENETIC AL STUDIES ON OENOTHERA 



567 



the type-form of the species. No species of (Enothera 

 is perhaps so free from suspicion as to its gametic purity. 

 It Stomps can obtain mutations from tested material of 

 the Dutch biennis grown in pure lines he will have the 

 basis of a strong argument, but this seems to me lacking 

 in the conclusions drawn from his cross of biennis with 

 cruciata. 



I do not believe it at all probable that the Dutch biennis 

 will be found to "mutate" under normal conditions to a 

 degree worthy of serious consideration for the mutation 

 theory of De Vries. The plant has already been made 

 the subject of extensive cultures and its characters are 

 known to a number of workers with Oenotheras. Yet I 

 am far from taking the stand that environmental condi- 

 tions may never induce a modification of germinal con- 

 stitution and still leave the organism vigorous. The 

 possibility of direct modification of germ plasm, inde- 

 pendent of sexual mixing, presents one of the most in- 

 viting fields of genetical research. However, if such re- 

 search gives affirmative conclusions we should be most 

 cautious in applying them to the conditions that normally 

 surround a species and to the process of organic evolu- 

 tion. 



6. The Problem of the Origin of (Enothera 

 Lamarckiana De Vries 

 As stated in the introduction to this paper, we are no 

 longer in our problem of the origin of (Enothera La- 

 marckiana De Vries concerned with Lamarck's plant 

 (CE. Lamarckiana Seringe, 1828) of about 1796. This 

 plant (Davis, '12b) was with little doubt a form of (E. 

 grandifora Solander, 1789, introduced at Kew in 1778. 

 It had no relation to the cultures of Carter and Company, 

 of about 1860, which were the starting point for the dis- 

 tribution among seedsmen of the plants known in cultiva- 

 tion as Lamarckiana (an incorrect determination of 

 Lindley) from some of which De Vries 's material was 

 derived. 



