Pterolepis xaxa (Melastomateae, Melastomataceae), a new haplostemonous species from Bahia, Brazil

We describe Pterolepis xaxa (Melastomateae, Melastomataceae), a new species collected in “caatinga rupestre” at Licínio de Almeida, Bahia, Brazil. Pterolepis xaxa resembles the recently described Pterolepis haplostemona , both representing the only two species in the genus that are haplostemonous (i.e., with the stamens equal in number to the petals). Apart from flowers with a single whorl of stamens, P. xaxa can also be recognized by intercalycine projections consisting of a very short central axis topped with 2–3 trichomes, and white petals (vs. intercalycine projections lacking trichomes at the apex and magenta or lilac petals in P. haplostemona ).