Systematics of the southern African genus Ixia L. (Iridaceae): 5. Synopsis of section Ixia, including five new species

•All species of sect. Ixia L. (Iridaceae) are reviewed.•Five new species of Ixia L. are described.•Ixia alticola and I. angelae are endemic to the Cederberg.•Ixia sarmentos is widespread along the West Coast.•Ixia helmei is known from one location near Bot River.•Ixia roseoalba is restricted to the western Langeberg.

The southern African winter-rainfall genus Ixia L., with almost 100 species, is divided into four sections, with sect. Ixia distinguished by a filiform perianth tube closely clasping the style, and filaments that occlude the mouth of perianth tube and are sometimes partly united but never decurrent in the tube. The section was last revised by G. J. Lewis in 1962, at which time it included 18 species and several varieties. Five species have since been described, I. atrandra Goldblatt & J.C. Manning, I. calendulacea Goldblatt & J.C. Manning, I. frederickii M.P. de Vos (subsequently reduced to synonymy in I. dubia Vent.), I. mostertii M.P. de Vos and I. superba Goldblatt & J.C. Manning. One more, I. purpureorosea G.J. Lewis, was later transferred to sect. Hyalis (Baker) Diels. Here we provide a revised key and synopsis of sect. Ixia as the final contribution in our series of systematic studies in the genus, which already includes revisions of sects. Dichone (Salisb. ex Baker) Goldblatt & J.C. Manning, Hyalis (Baker) Diels and Morphixia (Ker Gawl.) Pax. We recognize a total of 29 species in sect. Ixia, including five new species: I. alticola Goldblatt & J.C. Manning and I. angelae Goldblatt & J.C. Manning from the central Cedarberg; late-flowering I. helmei Goldblatt & J.C. Manning from near Bot River; I. roseoalba Goldblatt & J.C. Manning from the western Langeberg; and yellow- or pink-flowered, usually stoloniferous I. sarmentosa Goldblatt & J.C. Manning from marshes and seeps at low elevations in Western Cape. We also recognize white-flowered I. leucantha Jacq. (currently a synonym of I. polystachya L.), I. fuscocitrina Desf. ex DC. (currently a variety of I. maculata L.), and elevate I. polystachya var. longistylis M.P. de Vos to species rank as I. longistylis (M.P. de Vos) Goldblatt & J.C. Manning. I. patens var. linearifolia G.J. Lewis and I. viridiflora var. minor M.P. de Vos are reduced to synonymy in their respective species.