Aquatic, floating submerged herbs. Stem (stolons) monomorphic, branched, up to 1.7-2.5 cm long, terete, glabrous. Leaves filiform usually with 2 primary segments, internodes 5-9 mm, pinnately divided; segments capillary, denticulate, bearing solitary or fasciculate setulae on each tooth. Bladders dimorphic, ovoid, stalked, 1.5-3 mm long, with simple forked antennae. Inflorescence erect, 8-20 cm long; peduncle filiform, terete, glabrous; scales 2-3, 1.9-3 mm long, ovate, basifixed, apex acute-obtuse. Bracts basifixed, c. 4 mm long, ovate, base auriculate. Flowers 4-12; pedicel filiform, terete, 10-15 mm long, erect, deflexed in fruits. Calyx lobes ± subequal, ovate. Corolla yellow, externally glabrous; upper lip ovate, apex refuse; lower lip darker with reddish brown lines and spots ± flat, reniform, margins spreading; palate glabrous; spur broadly conical at base, c. 6 mm, longer than wide, inner distal half with internal glands on both adaxial and abaxial surfaces. Filaments curved c. 2 mm long. Stigma upper lip short, lower lip semicircular, ciliate. Ovary globose, glandular. Seeds prismatic, 4-6-angled, narrowly winged.

Fl. Per.: August-October.

Holotype: Australia: New South Wales, between Hawksbury and Paramatta, R. Brown s.n. (BM).

Distribution: Europe (except far north), temperate Asia to China and Japan, tropical and south Africa, tropical Asia, Australia and New Zealand.

For complete synonymy see Taylor in Kew Bull. Add. ser. 14. 1989.

A planktonic species commonly occurs in still, shallow water of ditches, lakes and rice-swamps.