Studies on the Variability and Heritability of Pigmentation in Oenothera. 369 
there would be no dominance in the case of O. rubricalyx. The fact 
of alternative inheritance in O. Lamarckiana >< O. rubricalyx and its 
reciprocal, shows the non-universality of Mendelian behavior, and there 
is at present no reason for supposing that in crosses between closely 
related biotypes or pure lines, alternative inheritance will ultimately 
be found any less common than Mendelian dominance and splitting. 
The fact of alternative inheritance, i. e., a “split’”’ in the first generation, 
both types breeding true in later generations, has never yet received 
an explanation which is even theoretically satisfactory, though the 
occurrence of such a type of behavior is well-established, especially in 
crosses between O. Lamarckiana and its mutants. 
Summary. 
I. Variations in the extent of the red color pattern on the sepals 
in Oenothera rubrinervis and other forms, follow Quetelet’s law in 
general, though the slope of the curve is more abrupt on one side 
than on the other. This is true for the buds considered en masse 
as a population, and also for the buds of each individual, though in 
the latter case the mode falls in different classes in different individuals. 
Usually the mode of an individual does not shift during the season. 
The variation of this color pattern is definite in O. rubrinervis and 
most other Oenotheras in which it occurs, the variants forming a reduction 
series, in which the anthocyan retreats from each margin of the sepal 
towards the median longitudinal ridge of the sepal (See plate VI). This 
is evidently due to the fact that the median ridge contains a single 
vascular bundle which acts as an irrigation system, bringing materials 
(sugars, tannins, glucosides or enzymes) which take part in the formation 
of anthocyan. The area nearest the vascular bundle is therefore that 
in which anthocyan is most likely to appear, and if the supply from 
this “irrigation system“ is sufficient, red pigment may appear at some 
distance on either side of the ridge, and even out to the margin of 
the sepal. This furnishes a simple explanation of the definiteness of 
this variation series. 
2. The same conditions of variability hold for several other mutants 
of O. Lamarckiana and for various other races of Oenothera. In a race 
known in my cultures as No. 25, from the English coast, near Liverpool, 
having characters intermediate in certain respects between O. rubrinervis 
and O. grandiflora Ait., the modal condition for the whole population 
of buds is found to be the same as in O. rubrinervis, but the plus 
Induktive Abstammungs- und Vererbungslehre. IV. 24 
