This name is a synonym of Oenothera cespitosa subsp. purpurea (S. Watson) Munz.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50104079) with original publication details: Botany (Fortieth Parallel) 108 1871.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:173170-2.
This name was in version 1 of The Plant List, record tro-50104079.