Argostemma cordatum (Rubiaceae), a new species from Vietnam

Argostemma cordatum , a new species of Rubiaceae, is described and illustrated. The species was discovered in 2014 during a botanical survey of the Chu Yang Sin National Park (Dak Lak province, Southern Vietnam). Argostemma cordatum possesses a solitary large leaf per plant (along with one very small leaf). The new species differs from morphologically similar species mainly by the small size of the enlarged leaf and cordate base of the enlarged leaf. It is also characterized by the following features: plant completely glabrous, stipules minute and reduced to papillate warts, inflorescence with all axes elongated, anthers coherent into anther cone and dehiscent by longitudinal slits, style slightly exserted. An extended description of the vegetation in the area inhabited by A. cordatum is provided.