Description from Flora of China
Pentasacme G. Don.
Herbs perennial, erect, often growing in or near flowing water. Leaves opposite, narrow. Cymes racemelike or umbel-like. Pedicel threadlike. Calyx with basal glands. Corolla rotate or subcampanulate; tube short; lobes narrow, longer than tube, twisted to right. Corona lobes 5, inserted on corolla tube, apical appendages denticulate or lobed. Filaments connate into a short tube; anthers erect, apex membranous and inflexed on base of stigma head; pollinia 2 per pollinarium, erect, ovoid, apex with a small translucent beak. Stigma head conical or flat, apex 2-cleft. Follicles cylindric-lanceolate, smooth.
Four species: Bangladesh, Bhutan, China, India, Malaysia, Myanmar, Nepal, Singapore, Thailand, Vietnam; one species in China.