The genus Cystacanthus was established by Anderson (1867: 457) and placed in tribe Ruellieae Dumortier (1829: 23) when published. In fact, it is closely related to Phlogacanthus Nees von Esenbeck (1832: 76, 99) and differs only in the corolla shape and indumentum. Thus, many authors merged Cystacanthus with Phlogacanthus (Benoist 1935, Imlay 1939, Brummit 1992, Mabberley 2008). But it was still...
