Chamaexeros longicaulis (Dasypogonaceae), a new species from Walpole, south western Australia, with additional notes on Chamaexeros

The new species is described and illustrated with photographs. Chamaexeros longicaulis is most closely related to C. serra but differs in several characteristics including three unique in the genus: elongated stems, elongated rhizomes resulting in vegetative reproduction, and thickened vertical rhizomes which presumably provide for storage of reserves. The species is of conservation interest owing to the small number of populations known, and is listed among conservation priority taxa for Western Australia. A revised key to the species of Chamaexeros is presented. Features of the ovary, capsule and seed are clarified for this genus. Floral measurement data are given for all species. A range extension is noted for C. serra.