2. Aldrovanda Linnaeus, Sp. Pl. 1: 281. 1753.
Herbs perennial, aquatic, carnivorous, apparently without roots, freely floating during growing season, forming a bulb at shoot tip during winter. Leaves whorled, exstipulate, united at base; petiole cuneate, with 4-8 laciniate bristles; leaf blade articulated at base into 2 segments forming a trap for small, aquatic animals. Stem simple or sometimes branched, with sensitive hairs and numerous digestive glands. Flower axillary, solitary on short scape 0.5-1.5 cm. Sepals 5, united at base, ovate-elliptic to elliptic-lanceolate, 2-4 × 1-1.5 mm. Petals 5, white or greenish white, oblong. Stamens 5, 3-4 mm; filaments subulate. Ovary superior, subglobose, 5-carpellate; styles 5; stigma multifid. Capsule subglobose, indehiscent. Seeds 5-8 or fewer, ovoid-globose.
One species: Africa (including Madagascar), E, N and SE Asia, C and S Europe, N Pacific Islands.