A discussion of the relationship between Ophiorrhiza exigua and O. michelloides (Rubiaceae) with the description of a new species

Through field observations, studies of herbarium specimens and relevant literature, Ophiorrhiza exigua and O. michelloides, two long‐controversial species are shown to be two different species. Meanwhile, our results supported O. nanlingensis L. Wu & Q. R. Liu as a new species, previously confused with O. exigua. Ophiorrhiza nanlingensis is morphologically similar to O. exigua and O. michelloides, but differs from the former in its monostylous flowers and corolla tube without a ring of hairs inside, and from the latter in pubescence of most vegetative organs with unicellular trichomes which are generally shorter than 0.3 mm and inflorescence nutant when young and then erect. We provide a detailed morphological and habitat description, as well as colour photographs and illustrations of the new species.