Nakai, Journal of Japanese Botany 17: 203. 1941.
Members of Costaceae are perennial, rhizomatous, non-aromatic herbs, usually terrestrial or more rarely epiphytic. Stems are terete, most often unbranched, leafy, sometimes spirally contorted; when branched, then secondary branches break through the leaf sheaths (Tapeinochilus). Leaves are spirally arranged, with the sheaths closed and tubular; libule is present and the petiole short; pulvinus is absent; lamina are narrowly to broadly elliptic, rolled up from one side to the other in bud. The inflorescence a strobilaceous spike, terminal on the leafy shoot or on a separate, short, leafless shoot, or flowers solitary, axillary (Monocostus). Flowers are epigynous, perfect, and zygomorphic; the calyx is tubular, shortly 2-3 lobed; corolla is 3-lobed, with the lobes basally fused, imbricate in bud and unequal. Labellum is petaloid, staminodial, opposite to the stamen, as long as or much longer than the corolla, ± 3-lobed, often with crisped margin; basal part of stamen and labellum are united into a papillate tube. (From Kubitski, et al., p. 128)