This name is a synonym of Penstemon filiformis (D.D. Keck) D.D. Keck.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 29206162) with original publication details: Univ. Calif. Publ. Bot. 16(11): 394 1932.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:187573-2.
This name was in version 1 of The Plant List, record tro-29206162, and has not been changed.