Abstract
Cleisostoma schoenorchaefolium is described as a new species from limestone karst in Lao PDR. A detailed description with photographs, line drawings and a conservation assessment are presented. Due to the presence of a combination of unique characters (namely, semi-terete leaves with a subulate apex, a two-chambered spur and a complex pollinarium structure), this species cannot be satisfactorily placed in any of the existing sections of the genus. Accordingly, a new section, Teretisculum, is proposed. To aid correct placement of this and other species in their respective sections, a key to infrageneric taxonomy of Cleisostoma is provided.