Catharanthus makayensis L. Allorge, Phillipson & Razakamal. (Apocynaceae), a new species from Madagascar

Catharanthus makayensis L. Allorge, Phillipson & Razakamal. (Apocynaceae), a species new to science from Madagascar is described and illustrated. It differs from all other species in the genus by the hexagonal cross-section of its stems, and by a combination of flowering and fruiting characters. Its 5-6 mm long filiform sepals are clearly much narrower and longer than all other species with the exception of Catharanthus coriaceus Markgr., but the latter species is highly distinct with its pendulous fruits, as opposed to erect fruits of Catharanthus makayensis and all other species of the genus. Catharanthus makayensis and Catharanthus roseus (L.) G. Don are the only species to have a magenta, rather than white to pale yellow eye. The corolla lobes and the flower buds of Catharanthus makayensis are pure white or tinted pale pink whereas Catharanthus roseus typically has pink lobes. The relationships of the new species with the eight other species of Catharanthus G. Don are discussed and an identification key to the Malagasy species of the genus is provided.