This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial pubescent or tomentose herbs, some species shrubby, with dentate or crenate leaves, and small bracted flowers in axillary clusters. Calyx tubular-funnelform, 10-nerved, 5-10-toothed, the teeth dilated at the base, or sometimes connate into a spreading limb. Corolla-tube about as long as the calyx, provided with a ring of hairs within, the limb strongly 2-lipped; upper lip erect, concave, emarginate, lower lip spreading, 3-lobed, the middle lobe emarginate or obcordate. Stamens 4, didynamous, ascending under the upper lip of the corolla, the anterior pair the longer; anther-sacs divergent at maturity. Ovary deeply 4-lobed; style 2-cleft at the summit. Nutlets ovoid, smooth. [The Greek name.]
About 30 species, natives of the Old World, most numerous in the Mediterranean region, the following typical.
Ballota nigra L. Sp. Pl. 582. 1753.
Herbaceous, puberulent or pubescent, ill-scented; stem usually branched, erect, 1 1/2°-3° high, its hairs mostly reflexed. Leaves slender-petioled, ovate, or the lower nearly orbicular, acute or obtuse at the apex, coarsely dentate, thin, narrowed, truncate or subcor-date at the base, 1'-2' long; clusters numerous, several-flowered, dense; bractlets subulate, somewhat shorter than the calyx; calyx about 4" long, its teeth lanceolate, sharp, bristle-pointed, spreading in fruit; corolla 6"-9" long, reddish-purple to whitish, its upper lip pubescent on both sides; nutlets shining.
In waste places, eastern Massachusetts to Pennsylvania. Naturalized from Europe. June-Sept. Black archangel. Hairhound. Henbit. Bastard-hoarhound.