98 BOTANICAL GAZETTE 
In O. pratincola 
The hairs of the calyx segments and 
hypanthium are about 1mm. long 
and all belong to the thick-walled, 
[FEBRUARY 
In mut. mummularia 
The hairs of the calyx segments and 
hypanthium are less than o.5mm. 
long and belong to two types: (1) 
acute type with multicellular, tuber- 
culate bases. 
acute, thick-walled hairs without 
multicellular, tuberculate bases, and 
(2) thin-walled, round-pointed clavate 
or cylindrical hairs. 
The calyx segments separate in pairs. The four calyx segments remain 
united when the flower opens. 
The difference in the rupture of the calyx is shown in fig. 8. The 
writer is inclined to believe that the clear-cut qualitative dis- 
tinction between the calyx pubescence of the parent form and 
that of the mutation will provide an absolute criterion for deter- 
mining whether or not mut. nmummularia marks an evolutionary 
advance over O. pratincola. A priori it seems to be a safe prediction 
that mut. xummularia will prove to be a progressive mutation of 
even more striking individuality than O. gigas. 
It is unfortunate that data on reciprocal crosses between 0. 
pratincola and mut. nummularia will not be available until next 
year. The first flowers of the original mutations were, of course, 
self-pollinated, and further work was prevented by the loss of the 
plants. This year (1914) the writer has numerous plants of mut. 
nummularia (primary mutations as well as F; plants) with which to 
make the necessary crosses. 
The heritability of mut. nummularia 
The three individuals of mut. nummularia which bore seeds 
were nos. 2, 17, and 21. Even these, however, wilted and dried 
up while still in flower, so that very few capsules were obtained. 
As in the case of many somewhat self-sterile Oenotheras, the cap- 
sules were small and contained few good seeds. From each of 
several capsules only one or two seeds were obtained, and the 
best had but 30, whereas a large capsule of typical O. pratincola 
contains well over 300. Until plants of the mutation shall have 
, developed under more favorable conditions than those to which 
the first season’s plants were subjected, it will be impossible to say 
