Ig15] BARTLETT—MUTATION IN OENOTHERA 85 
It is shown in this paper (1) that the phenomena of mutation 
are as characteristic and as easily observed in ‘one of the wild 
small-flowered self-pollinating Onagras as in Oenothera Lamarckiana; 
(2) that the mutations show characters unlike those of any other 
form with which the parent could have crossed; and (3) that the 
mutations cannot be ascribed to Mendelian segregation as at 
present understood. It therefore seems in the highest degree 
probable that mutation is a phenomenon which is independent of 
hybridization, and that the evidence of mutation which DE VRIES 
has found in. Oenothera Lamarckiana is just as valid as though 
that species were known as a wild plant and not suspected of 
having had a horticultural origin. 
Differential germination 
Several of the most interesting mutations which were observed 
during the season of 1913 were found quite by chance. One lot 
of potting soil, in which the seeds of several strains were sown, 
proved to be a very stiff clay on which a hard crust formed. 
Germination was go poor that in several cases less than a dozen 
seedlings resulted from sowing perhaps a thousand or more seeds. 
It was afterward found that the seeds showed the usual per- 
centage of germination when sown in good soil. In three different 
species the small progenies obtained when the seeds were planted 
under unfavorable conditions disclosed striking mutations, which 
had survived as a result of differential or selective germination. 
These mutations might easily have been overlooked in a seed pan 
containing several hundred seedlings, of which only a few were to 
be retained and grown to maturity. 
The three mutant species were from widely separated localities. 
The seeds of one, from Plymouth, Massachusetts, were sent by 
Professor B. M. Davis; the others were collected by the writer at 
White Sulphur Springs, W.Va., and Lexington, Ky., respectively. 
The mutations of the two funnier species were lost before they 
matured. It will be useless, therefore, to give an account of their 
characters or of the cultures in which they appeared until they 
shall have been found again. In the case of the third species, 
