The Afro-Madagascan Aristea Ait., only genus of Iridaceae subfam. Aristeoideae Goldblatt, comprises some 58 species of rhizomatous, evergreen perennials. The genus is currently subdivided into three subgenera: two of them, subg. Aristea (18 spp.) and subg. Pseudaristea (Pax) Goldblatt (9 spp.) are restricted to the southern African winter-rainfall zone in the southwest of the subcontinent (Goldblatt 2012), whereas subg. Eucapsulares (Goldblatt) Goldblatt (31 spp.) occurs widely across sub-Saharan Africa, where we now recognize 24 species. There are also eight species in Madagascar, one of them, A. goetzei Harms, shared with highlands of southern Tanzania (Goldblatt et al. 2013). Five species are shared between tropical and southern Africa, five are exclusively tropical African, and 13 species are restricted to southern Africa, three of them restricted to the southern African winter rainfall zone (Table 1).

The systematics of Aristea is relatively well understood in tropical Africa as a result of accounts of the genus for Flora Zambesiaca (Goldblatt 1993), Flora of East Tropical Africa (Goldblatt 1996a), Flora of Ethiopia (Goldblatt 1997) and Flore d'Afrique Centrale (Geerinck 2005). Nevertheless, some taxa require comment and clarification. Aristea djalonis Hutch., from the West African highlands, has been confused with A. angolensis Baker (e.g. Hepper 1968), but we consider it quite distinct from that species and most likely more closely related to the eastern and southern African A. torulosa Klatt (better known by its later synonym A. woodii N.E.Br.).

The taxonomy of a second species, A. abyssinica Pax, requires modification: A. bequaertii De Wild. was treated as a subspecies of A. alata Baker by Weimarck (1940) in a revision of the genus, but Geerinck (2005) included it without comment in A. abyssinica. We agree that A. bequaertii is more closely related to A. abyssiniica than to the East African A. alata, but some features of the taxon suggest it is better treated as a separate species. The types of A. bequaertii and of A. homblei De Wild. share with A. abyssinca and A. alata a stem consisting of a long basal internode, but whereas the latter two species have a single subterminal leaf subtending the single or pair of inflorescences (always binate rhipidia in the genus but called flower clusters here), A. bequaertii consistently has two cauline leaves, one inserted a short distance below the upper. This feature is not seen in A. abyssinica and in conjunction with some unusual floral features indicates to us that these plants represent a separate species.

Lastly, Aristea gerrardii Weim. (Weimarck 1940), recognized by Goldblatt (1993) in his account of the genus in Flora Zambesiaca, is, we now conclude, a later name for A. compressa Baker (1877), and we accordingly reduce it to synonymy under that species. The two taxa share a multi-branched compound inflorescence and compressed, 2-winged stems, and cited differences between them, especially in spathe and bract size, seem to us negligible once features of a third species, A. parviflora Baker, which was mistakenly included in A. compressa by Weimarck (1940) and Vincent (1985), are removed from consideration....