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 Oe¢nothera Lamarckiana, O. 
biennis, and O. pratincola cannot be attributed to heterozygosis. 
BuREAU OF PLANT INDUSTRY 
WASHINGTON, D.C. ‘ 
