特徵描述
作者
YANG, Yuen-Po
型態特徵
Submersed freshwater herbs. Roots fibrous, from the lower nodes. Stems terete or slightly compressed. Leaves biseriate, alternate or rarely opposite, often two types on same plant: submersed leavesusually sessile; floating leaves linear or lanceolate, leathery, petiolate, lanceolate to ovate or elliptic. Stipules membranaceous, usually fused to form a sheath with two conspicuous veins and many small parallel veins. Spikes pedunculate, contained within stipules in bud. Flowers bisexual; perianth-segments 4, free, rounded, short clawed, valvate. Stamens 4, inserted on base of claw of sepals; anthers sessile, 2-celled, extrorse. Carpels 2-4, free, sessile; stigmas mostly sessile, slightly compressed, usually keeled; ovule solitary, attached to adaxial angle of carpel, fruiting carpel rupaceous, 1-seeded, indehiscent. Seeds without endosperm.
屬
One genus with about 100 species, cosmopolitan.
