STUDIES IN TERATOLOGICAL PHENOMENA 
35 
dominance of the normal, although never approaching that state. 
The pistillody was absolutely recessive. 
4. Discussion and Summary 
1. Nicotiana plants showing petalody were selfed and progeny 
grown from them. In one race the abnormal character was extremely 
variable, some plants showing a large expression, other plants showing 
it only to a slight degree. This race varied in many other characters, 
proving the mother plant to have been very heterozygous. In another 
race, the abnormality was reproduced in all the progeny to the same 
degree as in the mother plant. With the exception of pollen color, no 
variation in other characters occurred in this race. 
2. Pistillody originated as a discontinuous variation and was 
inherited in the same manner, crosses with the normal in one case 
giving in F2 a progeny closely approximating a simple 3 : i ratio. 
In two hybrid Fi families, it was completely recessive, while in what 
appears to be another hybrid Fi family, it is wholly dominant. The 
first two families differ from the last family in a large number of char- 
acters, as the ancestry of the latter involves another species. 
3. The catacorolla race of Nicotiana originated from a discon- 
tinuous variation. When crossed with normal races, the Fi progeny 
were either intermediate in character or absolutely normal, though 
the individual Fi progeny from each cross showed no variation among 
themselves. Great variation existed between the different pollen 
parents of many of these Fi individuals. 
As a whole, the data secured from hybridizing races of normal 
plants with those possessing the three abnormalities discussed above 
support the view that dominance and recessiveness are not in any way 
attributes of the factor or "character" in itself, but are the result of 
the factor expression plus the modifying influence of the environment, 
whether genotypical or external (soil, climate, etc.). The variability 
in the expression of catacorolla in the 119 Fi plants of -4-1 A crossed 
with the 119 different normals is strong supporting evidence that this 
conception of dominance is the most tenable of those recently ad- 
vanced by geneticists. 
LITERATURE CITED 
Bateson, W. Mendel's Principles of Heredity, Cambridge Univ. Press, pp. 1-396. 
1909. 
Castle, W. E. The Origin of a Polydactylous Race of Guinea-pigs. Contrib. from 
Zool. Lab. of Mus. Comp. ZooL, Harvard Univ., No. 176, pp. 17-29. 1905. 
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