One to three feet high. Leaves, - Opposite, large, ovate, toothed, pointed. Flowers. - Yellowish, lemon-scented, clustered loosely. Calyx. - Two-lipped, the upper lip three-toothed, the lower two-cleft. Corolla. - Elongated, somewhat two-lipped, the four upper lobes nearly equal, the lower large and long, toothed or fringed. Stamens. - Two (sometimes four, the upper pair shorter), protruding, diverging. Pistil. - One, with a two-lobed style.

In the damp rich woods of midsummer these strong-scented herbs, with their loose terminal clusters of lemon-colored, lemon-scented flowers are abundant. The plant was introduced into England by the amateur botanist and flower-lover, Collinson, after whom the species is named. The Indians formerly employed it as an application to wounds.