Costus 閉鞘薑屬
型態特徵
Stems erect from rhizome, covered with bladeless sheaths near base, unbranched when young, later brached, secondary branches breaking through leaf-sheaths. Leaves spirally arranged, base of blade usually attached to sheath by a short stalk, articulated at junction; sheath tubular, closed; ligule short. Inflorescence dense, globose or ellipsoid, terminal on leafy stems or on short leafless shoots; bracts in a series of parastichies, usually broad and overlapping at base, with 1 or 2 flowers per bract; bracteoles smaller, laterally flattened; calyx tubular, +/- deeply 3-lobed, lobes often acute, anterior one usually broader than lateral ones; corolla tube shorter or longer than calyx, lobes overlapping; staminode none; labellum large, obovate, thin, edges often crisped, never deeply lobed, often brightly colored. Stamen with a broad petaloid filament which usually curves forward and closes entrance to tube of flower, with an upturned tip. Anther attached below apex of stamen, only slightly raised above its surfaces, with two depressions that secrete nectar. Ovary trilocular, ovules many, in 2 rows. Capsule triangular, loculicidal, opening by 3 slits, but not splitting to apex. Seeds angular, usually with a white fleshy aril.
Four genera and ca. 120 species; one genus and one species in Taiwan.
