Herbs, either aquatic or growing in wet soil. Leaves in the terrestrial species radical, few or rosulate, entire; in the aquatic species more or less scattered, capillary and multifid. Flowers irregular, hermaphrodite, either solitary or several on a seapiform peduncle. Calyx inferior, 2-lipped or 4–5-partite. Corolla gamopetalous, hypogynous, irregular, the tube usually produced into a spur or pouch, the limb 2-lipped, upper lip entire or 2-lobed, lower lip 3–5-lobed. Stamens 2, inserted at the base of the corolla-tube; filaments usually broad, arched; anthers 1-celled. Ovary superior, globose, 1-celled; style short and thick; stigma 2-lobed; ovules numerous, on a free central placenta. Fruit a capsule, either bursting irregularly or 2–4-valved. Seeds numerous, small; albumen wanting; embryo either undivided or with very short cotyledons.

A small but very distinct order, comprising 4 genera and about 250 species. It is remarkable on account of the roots or leaves often being provided with small bladder-like appendages, which catch minute aquatic animals. The single genus found in New Zealand is almost world-wide in its distribution.