STUDIES OF TERATOLOGICAL PHENOMENA IN THEIR 
RELATION TO EVOLUTION AND THE 
PROBLEMS OF HEREDITY 
I. A Study of Certain Floral Abnormalities in Nicotiana 
AND their Bearing on Theories of Dominance^ 
Orland E. White 
When Mendel's law was rediscovered, dominance was considered 
as essential and as important a principle as segregation. Further 
investigation soon demonstrated the phenomenon of "imperfect 
dominance," and still later studies led to a substitution of the "pres- 
ence and absence" factor hypothesis for Mendel's conception of 
contrasted character pairs. De Vries (1902), Bateson (1909), Daven- 
port (1910), Castle and others lock upon dominance as an attribute 
of the factor or determiner, and according to the last two investigators, 
variation in dominance, at least in part, is the result of variable 
potency, or variation in the power of a determiner or factor to express 
itself in ontogeny. De Vries held the racially older characters to be 
dominant over the younger, a conception which the last ten years of 
experimental investigation has not upheld. On the other hand. East 
(1912) and Emerson (1912) think of dominance as a result of the 
activities of one or more specific factors, plus the modifications pro- 
duced by the whole factorial organic complex (all the other factors 
concerned in the organism/s heredity) and by the external environ- 
ment (climate, soil, etc.). In other words, under identical genotypical 
and external environments, the factor A would always give the same 
expression, no matter how often the experiment was repeated. 
The chief value of the data which I have to present lies in its 
bearing on this important question of dominance. The abnormalities 
concerned are three in number, viz., petalody and pistillody of stamens 
and that peculiar form of corolla doubling to which c'e Vries and others 
^ Contribution from the Laboratory of Genetics, Bussey Institution of Harvard 
University. Brooklyn Botanic Garden Contributions, No. 7. Read at the Annual 
Meeting of the Botanical Society of America, Atlanta, Ga., 1913. 
23 
