Stems: scape glabrous, tall. Leaves: from three to seven in a rosette at the base of the scape, entire, ovate, obtuse. Flowers: one-flowered; calyx five-parted; corolla bilabiate, the upper lip two-cleft, the lower one three-cleft, base of the corolla saccate and contracted into a nectariferous, acute, nearly straight spur.

At first sight the Butterwort looks like a lovely large purple violet, but a second glance reveals its rosette of very pale green leaves, with their involute margins, and the traveller at once recognizes the Pinguicula, its name being derived from the Latin pinguis, " fat," and referring to the horrible slimy greasy secretion with which its leaves are coated, and which renders them most repulsive to the touch.

The Butterwort is carnivorous like the Sundew, and by means of the colourless fluid secreted by the glandular hairs covering the leaves it catches insects and the irritation thereby set up causes the glands to exude an increased supply which becomes very acid and capable of digesting the animal matter entrapped. Later the dissolved nitrogenous matter is absorbed and assimilated by the plant. The Butterwort resorts to these evil insectivorous practices in order to obtain sufficient nitrogen for its nutriment, as it usually grows in places where the soil is deficient in this respect.

The flowers are of a rich purple colour, and are two-lipped, the upper lip being cleft into two and the lower lip into three lobes. These lobes are delicately veined and the lower ones are covered with white hairs. The corolla terminates behind in a long straight spur. The Butterwort always grows near water, and usually in swamps or other very moist places.