Studies on the Variability and Heritability of Pigmentation in Oenothera. 339 
forms which overstep in this regard any imaginary line which may 
be drawn between the two species. 
2. Conspicuous bands of red on the sepals and the valves of 
the unripe fruits. O. Lamarckiana sometimes shows an almost equally 
conspicuous color pattern on its sepals, though usually the amount 
is considerably less or extremely slight. The unripe fruits of O. Lamarc- 
kiana usually show a longitudinal red band on each valve, but this 
is less conspicuous than in O. rudrinervis. 
3. Increased brittleness of the stem and branches. DE VRIES 
found this to be due mainly to the thinner walls of the bast fibres 
of the stem. 
4. A greater tendency in O. rudrinervis to produce side branches. 
5. A. tendency for the stem in O. rudrinervis to be zigzag. 
Of these differences the color pattern in O. rubrinervis exhibits 
a wide range of variability, which made it an exceptionally interesting 
character for study. Similar studies on the color pattern of the sepals 
have since been carried out on several other forms. The studies with 
O. rubrinervis were undertaken with the aim of determining the mode 
for various individuals, and then by growing the offspring of indivi- 
duals with their modes in different classes, to find out whether the 
mode of the offspring showed any effect of their parentage. Also by 
crossing individuals whose modes were in different classes, to determine 
whether there is any discoverable quantitative pigment inheritance. 
My seeds for these purposes in the second generation failed to germinate 
in sufficient numbers to furnish adequate evidence, but so far as the 
evidence goes, it indicates that in ordinary cases there is no such 
inheritance. 
The details of the observations concerning this color pattern in 
O. rubrinervis may now be taken up. (See plate VI). The sepals are 
four in number and the edges of the adjacent sepals cohere closely, 
forming four lines of contact, and thus completely enclosing the bud 
in a tight covering. The usual length of this part of the sepal is 
about 26—30 mm. Each sepal has a free tip, cylindrical or awl 
shaped, extending beyond the tip of the bud. These free tips are 
6—7 mm. in length in the mature bud nearly ready for opening, the 
four lying more or less parallel and forming a close group at the end 
of the bud. The hypanthium is a slender tube about 25-34 mm. in 
length, connecting the calyx and ovary. Its length is very variable 
as shown by the statistical studies of SHULL (1907) and under certain 
abnormal conditions to be mentioned later it fails to develop at all. 
22* 
