Ophiorrhiza saxatilis (Rubiaceae), a new species from Guizhou, China

Ophiorrhiza saxatilis M.T.An & G.L.Li, sp. nov ., a new species of the genus Ophiorrhiza (Rubiaceae) discovered in the karst regions of Guizhou, China, and provides its taxonomic basis from a morphological perspective. The new species is morphologically similar to Ophiorrhiza lignosa , but differs from the latter by having an inflorescence in that its young branches are uniformly pubescent (vs. bifariously pubescent in O. lignosa ); the abaxial leaf surface is pubescent (vs. puberulent only along the midrib and secondary veins in O. lignosa ); the bracteoles are 5–6 mm long (vs. 1.5–3 mm long in O. lignosa ); the petioles are 2–5.8 mm long (vs. 6–20 mm long in O. lignosa ); the stamens are inserted at the base of the corolla tube (vs. inserted near the middle of the corolla tube in O. lignosa ); the flowers are distylous (vs. monomorphic with pin flowers in O. lignosa ), and the styles of long-styled flowers are 6–8 mm long (vs. 10–11 mm long in O. lignosa ). These stable and significant morphological differences, combined with a comprehensive and detailed morphological description of the new species and a comparison of diagnostic characters with similar species, firmly support the recognition of Ophiorrhiza saxatilis as a distinct new species.