Listera R. Br.
雙葉蘭屬
SU, Horng-Jye and HU, Chia-Ying
Terrestrial perennial herbs with fibrous roots and short rhizome. Stems simple, erect, slender, with 2 leaves near middle, usually puberulous, turning into peduncle above leaves, glabrous below leves. Leaves opposite or subopposite, nearly sessile, deltoid, ovate-semiorbicular or orbicular-ovate, acute, mucronate or obtuse at apex, truncate or cordate at base, entire or slightly wavy, mainly 3-7-nerved, with reticulate veinlets. Raceme terminal, with few to many flowers; peduncle and rachis more or less puberulous; bracts ovate-lanceolate or broadly ovate; pedicel and ovary straight or curved, glabrous or slightly puberulous. Flowers usually greenish, sometimes tinged with red-purple on lip; sepals and petals subequal, free, spreading or reflexed, dorsal sepal ovate or lanceolate, lateral sepals obliquely ovate or falcate, petals linear-lanceolate or linear-oblong; lip spreading, undivided or with 2 terminal lobes, sometimes with 2 auricles at base or 2 lateral lobes near base, cuneate, elongate-cuneate or rectangular, entire, incised or ciliate along margins, spurless, disc glabrous or shortly puberulous, flat or sometimes with raised calli or keels, often with shallow nectary of various forms near middle or base; column either short and stout, or slender and elongate, short one nearly sessile, consisting of anther, clinandrium and stigma, without distinct stalk, elongate one consisting of dilated and incurved top, slender neck and slightly dilated stalk at base; anther terminal, nearly erect or inclined, 2-loculed; pollinia 2, unequally 2partite, soft and mealy; stigma entire, concave under rostellum; rostellum, ovate or rectangular.
About 30-40 species, widespread in temperate regions of the northern hemisphere. Nine species in Taiwan.
