Isoetes eludens (Isoetaceae), a new endemic species from the Kamiesberg, Northern Cape, South Africa

Isoetes eludens, a new, highly localised, endemic species from the Kamiesberg, Northern Cape is described. The aquatic species grows in a shallow temporary gnamma or !gau (rock pool) in Kamiesberg gneiss at an altitude of 1,284 m. It is characterised by a short, strongly 3-lobed stem, relatively short, and broad estomate sporophylls, a complete velum, the presence of an outer sporangium sack (a feature not previously reported for the genus), graphite-black, laevigate megaspores with a narrow, but tall laesura, microspores with near smooth proximal surfaces but with a papillate distal surface, the absence of a ligule and labium, and simple roots with few root-hairs. The systematic relationship of the species is difficult to determine as a result of convergent evolution in the genus. The sporangium sack does not support an affinity with any of the known species. Further surveys are needed to establish the geographical extent and conservation status of this remarkable local endemic. © The Board of Trustees of the Royal Botanic Gardens, Kew 2009.