Dig deeper at SERNEC, a consortium of southeastern herbaria.
Spermatophytes (seed plants): Angiosperms (flowering plants): Eudicots: Core Eudicots: Asterids: Lamiids: Gentianales
Manual of Vascular Plants of NE US & Adjacent Canada (Gleason & Cronquist,1991)
The Genera of Cinchonoideae (Rubiaceae) in the southeastern US (Rogers, 1987)
Diffuse-branched Bluet, Narrow-leaved Houstonia