This name is a synonym of Rhododendron eudoxum var. mesopolium (Balf. f. & Forrest) D.F. Chamb..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 12304746) with original publication details: Notes Roy. Bot. Gard. Edinburgh 13(65): 258–259 1922.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:332375-1.
This name was in version 1 of The Plant List, record tro-12304746, and has not been changed.