1915] BARTLETT— MUTATION IN OENOTHERA 123 



5. The mutation ratio cannot be explained on Mendelian 

 grounds. 



6. Mut. nummularia is better adapted than the parent type 

 to withstand influences unfavorable to germination. In every 

 case where a progeny contained an unexpectedly large number of 

 mutations, the germination was correspondingly poor. 



7. Selective germination and differential mortality among 

 dormant seeds may be important factors in natural selection. 



8. Mutation is a distinct process from Mendelian segregation, 

 and the phenomena exhibited by Oenothera Lamarckiana, 0. 

 biennis, and O. pratincola cannot be attributed to heterozygosis. 



BuREATj OF Plant Industry 

 Washington, D.C. 



