Studies on the Variability and Heritability of Pigmentation in Oenothera. 341 
forming a reduction series. In extreme reduction one finds only a few 
red spots or blotches scattered along-side of the central portion of 
the median ridge, often forming a more or less irregular row on either 
side (plate VI fig. 1). More rarely one finds a bud, mature and ready 
for flowering, without even a trace of the red color pattern. 
Plate VI is an accurate natural size reproduction of selected in- 
dividual buds of O. ruérinervis, chosen to represent the range of color 
variation in the sepals. They form a series numbered from I to 8 
and have been used in cataloguing the data of variability. Fig. 1 
represents a condition of extreme reduction, in which only a few 
small red areas appear in series on either side of the median ridge 
in its central portion. Fig. 2 shows an increase in the area of this 
pigment. In fig. 3 the pigment is in definite bands extending out 
from the median ridge toward the margin of the sepal. Fig. 5 re- 
presents the commonest type of color pattern in O. rubrinervis, the 
color band extending from the median ridge nearly to the margin of 
the sepal, and from the free sepal tips to the cone. Fig. 4 has the 
same extent of color pattern, but differs in being of a much paler 
shade of red. Fig. 6 also has the same extent of red color pattern 
as in fig. 5, but differs in that the median ridge and the margin of 
the sepal are greenish instead of yellowish. In fig. 7 there is a slight 
increase of red, so that it comes nearer the margin than in fig. 6. 
This is the extreme condition in O. rubrinervis. The series I—7 is 
absolutely continuous, with all possible intergrades, the figures merely 
representing more or less equidistant points in this continuous series. 
In fig. 8 there is a great increase in the amount of anthocyanin 
present, and there are no forms to bridge the gap between figs. 7 
and 8. Not only are the sepals red almost to the extreme margin, 
but the whole hypanthium is red, and the median longitudinal ridge 
instead of green is even deeper red than the rest of the sepal. The 
sepal tips remain green, however, and also certain areas at the base 
of the bud cone. In 1907 there appeared in my experimental garden 
at the University of Chicago, in a culture of about one thousand 
O. rubrinervis plants of various pedigrees, a single individual all of 
whose buds were exactly like fig. 8. The only preceptible variation 
in the coloring of these buds (the plant bore over fifty flowers), was 
in the size of the small triangular green areas at the base of the cone. 
The extent of the red color pattern of these buds was otherwise in- 
variable, and there was no variation in the depth of the shade. I have 
since called this form O. rubricalyx (GATES, 1909, p. 133). It evidently 
