The Genus Scutellaria L. (Labiatae) in Tropical Africa

Abstract

Scutellaria is a large, subcosmopolitan genus of around 360 species (Paton 1990). There are 8 species in Africa; the 4 tropical species are dealt with in this paper. Three species have a North African/Mediterranean distribution: S. orientalis L. is found in the mountains of Morocco, S. columnae All. in Algeria and S. rubicunda Hornem. sens. lat. in Libya. S. racemosa Pers., originally from temperate S. America, is naturalized in South Africa. The aim of this paper is to provide a key to and describe the four tropical African species. The tropical African species of Scutellaria were previously revised by Baker (1990), who recognized 6 species. Four of these, S. schweinfurthii Briq., S. paucifolia Baker, S. livingstonei Baker and S. debeerstii Briq. differ only in leaf morphology. When developmental variation is taken into account, these differences no longer merit specific recognition and therefore only one species, S. schweinfurthii, is recognized. Forms with long, narrowly ovate or linear leaves, referable to the type of S. schweinfurthii, occur only in Ethiopia, S Sudan and NW Uganda. Specimens from further south or west tend to have smaller, broader leaves. Two subspecies are therefore recognized, subsp. schweinfurthii and subsp. paucifolia (Baker) Paton (see Map 1). Of the tropical African species, S. violascens Giirke, S. polyadena Briq. and S. schweinfurthii Briq., with glabrous nutlets, internal pericarp glands and no pericarp air spaces, belong to the 'S. violascens' species-group defined in Paton (1990). The remaining species, S. arabica, belongs in the 'S. albida' species-group. This species has hairs on the nutlet papillae, lacks internal pericarp glands and has pericarp air spaces.