Argostemma ehuangzhangense (Rubiaceae), a new species from Guangdong, China.

Argostemma ehuangzhangense, a new Rubiaceae species from E'huangzhang Nature Reserve, Guangdong Province, China, is here described and illustrated. A morphological comparison between the new species and its putative relatives, A. lamxayanum, A. laotica and A. verticillatum, is presented. The new species is mostly similar to A. laotica, but they can be distinguished from each other since Argostemma ehuangzhangense presents solitary flower (vs. 2-flowered inflorescences), flower lobes 4 (vs. 5) and anthers opening by longitudinal slits (vs. apical pores). In a preliminary IUCN Red List status of Argostemma ehuangzhangense this species is assigned as Vulnerable (VU). [ABSTRACT FROM AUTHOR]