Huernia humpatana (Apocynaceae), a new species from southern Angola

A new species, Huernia humpatana Bruyns (Apocynaceae–Ceropegieae), closely related to H. similis N.E.Br., is described from the Chela Mountains of Huila Province in southern Angola. The two species are distinguished by the 5-angled and erect stems with more prominent tubercles up to 6 mm long joined into clear angles and separated by V-shaped grooves in H. humpatana as opposed to very obtusely 4-angled stems with tubercles only 2 mm long and only indistinct grooves between the angles in H. similis. Furthermore, in H. similis the nodding corolla is ± 9 mm in diameter with sepals ± 2 mm long, while in H. humpatana the horizontally facing corolla is 18–20 mm in diameter with sepals 4–6 mm long.