LINDAU in his monograph of the family in the first edition of ENGLER & PRANTL distinguished four subfamilies: Nelsonioideae, Mendoncioideae, Thunbergioideae and Acanthoideae. The first three subfamilies afterwards were united by VAN TIEGHEM and separated from the Acanthaceae under the name Thunbergiaceae. WETTSTEIN agreed with VAN TIEGHEM in so far that he too accepted a nearer affinity between the first three subfamilies, but instead of regarding the whole as a family distinct from the true Acanthaceae he considered them as a subfamily Thunbergioideae, reducing the three subfamilies of LINDAU to tribes. In this way, however, he had, apparently unwittingly, returned to the standpoint taken in by NEES, whose Anechmatacantheae and Echmatacantheae correspond exactly with WETTSTEIN’s Thunbergioideae and Acanthoideae. The difference between the various systems lies therefore in the rank assigned to the groups for which LINDAU used the names Nelsonioideae, Mendoncioideae and Thunbergioideae. They agree with each other in considering these groups as fundamentally distinct from what we might call the typical Acanthaceae or, in LINDAU’s nomenclature, the Acanthoideae.