Disa introrsa sp. nov. (Orchidaceae) from the Western Cape of South Africa, with notes on the phylogeny of Disa sect. Disella

Disa introrsa Kurzweil, Liltved and Linder (Orchidaceae - Orchidoideae - Diseae) is described from the Ceres District of the Western Cape of South Africa, and is placed in sect. Disella Lindl. The species is so far known from only two collections. Flowering is strongly stimulated through the effects of fire which may account for the apparent rarity of D. introrsa. Possible phylogenetic relationships among the species of D. sect. Disella are outlined.