Revision of the genus Rennellia Korth. (Rubiaceae-Rubioideae)

In this revision of the genus Rennellia Korth. four species are recognized: R. elliptica Korth., R. amoena (Bremek.) J.T. Johansson comb, nov., R. speciosa (Wall, ex Kurz) J.D. Hooker, and R. morindiformis (Korth.) Ridley. Rennellia includes shrubs and small trees with white to pale bluish or pale violet flowers in panicle-, umbel-, or spike-like cymes. The pedicels and ovaries are nearly always connate. Rennellia is confined to tropical rain forests in SE Asia, Sumatra, and Borneo. The genus is closely related to Gentingia, Motleyia, and Prismatomeris, but differs from these genera in, e.g., inflorescence morphology and colour of the flowers. A key to the species is presented, and all species are illustrated with line drawings and their distributions mapped.