This name is a synonym of Populus deltoides subsp. monilifera (Aiton) Eckenw..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50295594) with original publication details: Fl. Colorado 91 1906.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:776796-1.
This name was in version 1 of The Plant List, record tro-50295594.