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.