Stems: slender. Leaves: lanceolate, sessile, coarsely serrate-dentate, acute, bracts ovate, incised-dentate, the teeth acuminate. Flowers: in terminal, one-sided, leafy-bracted spikes, and solitary in the upper axils; calyx much inflated, conspicuously veiny in fruit; corolla very irregular, two-lipped; the galea compressed, arched, minutely two-toothed below the entire apex, the lower lip three-lobed, spreading.
The name Yellow Rattle has been given to this plant on account of the way in which the ripened seeds, which lie loose in the capsules, rattle whenever the wind shakes them to and fro. It is a firm erect plant, usually growing from six to ten inches high, and chiefly conspicuous by reason of its inflated green flower-cups and bright yellow blossoms, the lips of which frequently are spotted with purple.