A taxonomic study of Cryptolepis (Apocynaceae) in southern Africa

A taxonomic revision of Cryptolepis R.Br. (Apocynaceae, Periplocoideae) in southern Africa is presented. This revision comprises investigations into the micromorphology of pollen, translators, leaf anatomy, leaf epidermal surfaces and seed coat surfaces; macro-morphology of the plant parts; nomenclature, geographical distribution and ecological characteristics of the six species indigenous to southern Africa. The investigations resulted in descriptions with appropriate nomenclature and the compilation of an identification key for the six species. All available type specimens related to Cryptolepis in southern Africa were studied. Where holotype specimens could not be located lectotypes were designated from available isotypes or syntypes. Where no isotypes or syntypes could be located, neotypes were declared. In cases where only syntypes had been given by authors of species names, lectotypes were declared. Cryptolepis is widely distributed throughout the northern parts of southern Africa, with the largest concentration of species in the north-east of the region. Some species, such as C. oblongifolia, are common, while others have very restricted distribution ranges. C. delagoensis, for instance, is known from only six localities in southern Africa. Only C. decidua occurs in the desert and semi-desert habitats in the north-west of southern Africa, while the other five species inhabit savannah, sand forest, riverine -, afromontane - and coastal vegetation in the eastern parts of the region. In southern Africa Cryptolepis consists of slender climbers, occasionally small suffrutices or branching shrubs with white latex and interpetiolar ridges with dentate colleters. Leaves are opposite, decussate or rarely fascicled. A combination of leaf anatomy and leaf surface characteristics proved to be taxonomically useful for distinguishing the southern African species. The fruit consists of paired follicles. Seeds of Cryptolepis are adapted to anemochoric dispersal through a com