No. 538] MUTATION IN (EN THEE A 



mately be given to the mutation phenomena in 0. La- 

 marckiana as an evolutionary factor. 5 



Is 0. Lamarckiana obtained from 0. grandiftora X 0. 

 biennis? — Before pursuing further the subject of the 

 cause of the imitations in 0. Lamarckiana. let us ex- 

 amine the hypothesis that 0. Lamarckiana is the result 

 of a direct cross between 0. biennis and 0. grandi flora. 

 for while, since 0. Lamarckiana must be assumed to 

 have undergone crossing in any case, it is not of vital 

 significance just what those crosses may have been, yet 

 it would be of interest if it could be shown that 0. La- 

 marckiana has arisen and can be synthesized, as the in- 

 sult of a single cross. Davis ('11) has recently at- 

 tempted to produce 0. Lamarckiana in this manner. His 

 descriptions, however, fail to state the points in the 

 characters of his hybrids, which any one who is familiar 

 with these plants would like to know. Particularly does 

 he omit to state how the bud characters of his hybrids 

 differ from those of 0. grandiflora. It is stated that the 

 hybrids are in general intermediate between the parent 

 species. This would be expected, at least as regards the 

 flower characters, from the behavior of other hybrids in 

 Oenothera, e. g., 0. Lamarckiana X 0. biennis. The 

 flower characters in this cross are nearly intermediate, 

 though resembling biennis more than Lamarckiana. I 

 have observed closely the flower characters of many 

 crosses, including hybrids between series of forms be- 

 longing respectively to 0. grandiflora and 0. La- 

 marckiana, and the flowers are usually intermediate in 

 their characters, though sometimes nearer one parent 

 than the other. If the flowers of Davis's cross are also 



"It might be assumed that 0. biennis and 0. (/rouiifiora were the original 

 forms to become naturalized on the English sand dunes, and that O. La- 

 marckiana has since appeared as the result of crossing between these races. 

 If this is the case, then 0. Lamarckiana (and many related races which 



