Sleumeria (Icacinaceae): A New Genus from Northern Borneo

A new genus of Icacinaceae, Sleumeria, is described from northern Borneo. The only known species, Sleumeria auriculata, is a large woody scrambler with spirally arranged leaves with entire margins and prominent reticulation, hairs that dry a distinctive yellow-brown, and racemose or compound racemose inflorescences. The habit, leaf arrangement, and inflorescence type place Sleumeria in a group of climbing Icacinaceae near to Sarcostigma, but it is distinguished from that and other closely related genera by the combination of distinctly pedicellate flowers arranged singly or in pairs along the inflorescence rachis, swollen sagittate anther connectives, and a spherical ovary with a distinct filiform style with an unlobed stigma. Investigation of the stem anatomy confirms the relationship with Sarcostigma, especially the presence of successive cambia, but the new genus differs, amongst other anatomical characters, in lacking islands of included phloem within the xylem.