A well-known, perennial herb, formerly esteemed as a remedy in dog-bites. It was also used as a family medicine for nervous disorders of every description. This species grows commonly in moist, shady places, along ditches and ponds, where it raises its slender, smooth, square, leafy, and much-branched stalk a foot or two high. The thin, coarsely toothed, slender-stemmed leaves are pointed oblong to lance shaped, and are arranged in opposite alternating pairs. The several or many small, tubular, blue flowers are two lipped. The upper lip is arched and the spreading lower one is notched at the apex. The two-lipped calyx has a small, helmet-like appendage on the upper lip, which is an easy means for identifying the genus. The flowers spring from the axils of the uppermost leaves, on one-sided, terminal branches, from July to September. This species ranges from coast to coast, and from the British possessions south to Florida, New Mexico and Washington.