This name is a synonym of Apocynum × floribundum Greene.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 329909) with original publication details: Atti Reale Accad. Lincei, Mem. Cl. Sci. Fis. Va, 9: 717 1913.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:16604-2.
This name was in version 1 of The Plant List, record kew-329909.