This name is a synonym of Philadelphus microphyllus subsp. pumilus (Rydb.) C.L. Hitchc..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50106125) with original publication details: N. Amer. Fl. 22(2): 173 1905.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:192851-2.
This name was in version 1 of The Plant List, record tro-50106125, and has not been changed.