M.B. BAYER
Department of Agricultural Development
Winter Rainfall Region, Elsenburg (RSA).
ABSTRACT
The genus Oxalis, as it occurs in South Africa, is discussed generally in relation to the revision by T.M. Salter (1944). A brief account is given of Salter’s collecting activities, the distribution and variability of the species, and the problems of classification. Some new combinations are made. Particular attention is paid to the section Pardales Salter, and all the 11 species recognised by Salter (many described by him) are combined in one species, namely Oxalis pardalis Jacq. Two species, Oxalis dentata Jacq. and Oxalis lateriflora Jacq., are reduced under O. livida Jacq. Similarly Oxalis urbaniana Schltr. and Oxalis callimarginata Weintr. are reduced under Oxalis goniorrhiza Eckl. & Zey.
Keywords: Oxalis, taxonomy, speciation.
Oxalis is particularly well represented in South America, and the species are also a very prominent component of the flora of the Mediterranean region of South Africa. This region extends from Luderitz in Namibia, southeastwards to near East London on the southeast coast (Bayer, 1974). Annual precipitation over this area varies enormously from as little as 100 to over 1400mm/annum. The area is divided by Rutherford and Westfall (1986) into four distinct biomes on the basis of summer aridity, seasonal distribution of rainfall and on plant growth forms. Both geology and topography vary enormously so that landscape heterogeneity and soil forms provide great habitat contrasts over short distances. These factors, together with historical events, probably account for the richness of the Cape flora. Despite the potential and realised weediness (for example: O. pes-caprae L. and O. caprina L.), many species are spectacularly colourful in autumn and winter and are useful and interesting as horticultural subjects. T.M. Salter (1944) revised the genus on the basis of his own intensive collecting. His interest in fact started in 1931, and, although he collected until 1957, serious attention to Oxalis continued only until 1942.