COSTACEAE
Perennial, often large-sized herbs, with +/- fleshy rhizomes, non-aromatic. Stems usually simple, terete, straight or spirally contorted (twisted or bent out of normal shape), leafy. Leaves spirally arranged, simple; leaf sheaths tubular, closed; ligule truncate or 2-lobed; petiole short; leaf blade narrowly to broadly elliptic, rolled longitudinally in bud, margin entire. Inflorescence a spike, terminal on a leafy stem or sometimes on separate leafless shoots arising from rhizomes, very rarely flowers solitary axillary; bracts imbricate, often brightly coloured, coriaceous to herbaceous, with linear nectariferous callus below apex, 1- or 2-flowered; bracteole 1, folded or tubular. Flowers bisexual, epigynous, zygomorphic. Calyx tubular, usually 3-lobed or 3-toothed. Petals 3, proximally connate into tube, lobes unequal. Staminodes 5, united into a labellum, equalling or much exceeding corolla, tubular or horizontally spreading; fertile stamen 1, filament broad and petaloid, anther 1, usually attached at middle, dehiscence longitudinal, introrse. Ovary inferior, 2-3-locular with 2 septal nectarial glands towards apex, placentation axile, ovules many, anatropous; style 1, filiform, lying close to stamen and embraced by thecae (usually enclosed between thecae); stigma 1, 2-lamellate with a 2-lobed appendage or cup-shaped and unappendaged. Fruit a capsule, crowned by persistent calyx, 2-3-valved and dehiscing loculicidally or irregularly and tardily. Seeds many, angular-ovoid, black, shining, with a white aril.
8 genera and about 130 species
