98 BOTANICAL GAZETTE [February 



In 0. pratincola In mut. nummularia 



The hairs of the calyx segments and The hairs of the calyx segments and 

 hypanthium are about i mm. long hypanthiimi are less than 0.5 mm. 

 and all belong to the thick-walled, long and belong to two types: (i) 

 acute type with multicellular, tuber- acute, thick-walled hairs without 

 culate bases. multicellular, tuberculate bases, and 



(2) thin-waUed, roimd-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 quaUtative 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. nummularia marks an evolutionary 

 advance over O. pratincola. A priori it seems to be a safe prediction 

 that mut. nummularia will prove to be a progressive mutation of 

 even more striking individuaUty than 0. 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 Fi 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 stiU 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 tj^ical 0. pratincola 

 contains well over 300. Until plants of the mutation shall have 

 developed imder more favorable conditions than those to which 

 the first season's plants were subjected, it will be impossible to say 



