Spiradiclis lui, a new species of Rubiaceae from Guangxi, China

Spiradiclis lui, a new species of Rubiaceae growing inside limestone caves and on wet shaded limestone walls in Guangxi, southwestern China is here described as most similar to S. umbelliformis, but differing from the latter in its glabrous stems, ovate or oval leaf blades, and the position of stamens and stigmas inside corollas. The conservation status of the novelity is asessed as Vulnerable' (VU) according to the IUCN red list categories and criteria. A diagnostic key to the species of Spiradiclis with corolla tubes longer than 12 mm is also provided.