The present study is the result of combining genetics with taxonomy in the investigation of a polymorphic group of wild plants. It shows a degree of multiformity which was hitherto unsuspected in the genus. All the early genetical work on
Oenothera
was done with species which had been naturalized in Europe and whose North American home was unknown. Later, de vries (1913) introduced various American forms into cultivation and used them in genetic experiment, but without full taxonomic descriptions. Bartlett was mainly concerned in describing about twenty-five new species from wild plants of eastern North America brought into cultivation, and the present writer has previously described five, all but one of them from Eastern Canada. Professional taxonomists have paid little attention to the
Onagra
section of the genus except for the occasional description of a new species from western North America, and the whole number of species now recognized and described is about 70, not counting the 17 new species and 15 new varieties described in the present paper. The reason for the neglect of the taxonomists, even after the mutation work concentrated a great deal of attention on the genus, was no doubt the difficulty that many of the characters are not well shown in ordinary herbarium material. Indeed, cultures are necessary in order to study adequately the characters of these forms ; but, on the other hand, species once clearly delimited in this way can be recognized in the field, at least when well-developed plants are available, and frequently from the rosette stage alone.
VIII - Genetical and taxonomic investigations in the Genus
Oenothera
