Isoglossa glandulosissima (Acanthaceae, Ruellieae), a New Species from Southern Africa

Material of a common and widespread species of Isoglossa Oerst. in southern Africa keys to I. stipitata C. B. Clarke in Clarke's 1901 taxonomic account in Flora Capensis. However, this material does not match either the type or the description of that species. Thus, a new species, I. glandulosissima K. Balkwill, is described for the Acanthaceae, Ruellieae. The critical distinction between I. glandulosissima and I. stipitata within the genus is the combination of a densely glandular bract with an acute tip that is either equal to or longer than the calyx in the terminal inflorescences. The new taxon occurs in a range of habitats, is not threatened, and is considered to be of Least Concern (LC) according to IUCN Red List criteria.