Viola umphangensis (Violaceae), a new species from Thailand

Viola umphangensis S. Nansai, Srisanga & Suwanph., a new species from Thailand, is described and illustrated. Morphological, anatomical and palynological characters of V. umphangensis are compared with a similar species, V. betonicifolia Sm.. An amended key to the Viola species in the Flora of Thailand account is provided.