456 BOTANICAL GAZETTE [DECEMBER 
2. The phenomenon is known in two species of Oenothera: O. 
Reynoldsti, in which it was first described, and O. pratincola, the 
subject of this paper. 
3. It cannot be explained by HERIBERT-Nitsson’s Mendelian 
hypothesis. 
4. The mutations of the mass mutant strain of O. pratincola are: 
(A) common to other strains of the species; the non-characteristic 
mutations are not produced in unexpected numbers and show mass 
mutability superposed upon their ordinary behavior in heredity; 
(B) characteristic of the mass mutant strain. 
5. The characteristic mutations are constant in that they do 
not throw the type form of the species, but, except in the case of 
the most reduced member of the group, are themselves highly 
mutable. 
6. As far as tested, the characteristic mutations adhere to the 
following scheme of inheritance: 
mutation mutation-—> mutation 
mutation parent-—> mutation 
parent X mutation —> parent 
7. They belong to a group with certain structural characters 
in common, but do not seem to form a linear reduction series. 
8. They seem to result from the mutative modification in the 
female gametes of factors which have no counterparts in the male 
gametes. 
9g. Mass mutation is associated with a high tks of sterility, 
which manifests itself in the production of a greatly reduced number 
of seeds or in the production of many empty seeds. 
UNIVERSITY OF MICHIGAN 
