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..
Annual herbs, with petioled purple or discolored leaves, and small flowers in loose bracted racemes. Calyx campanulate, 10-nerved, 5-cleft, nearly regular in flower, enlarging, declined and becoming 2-lipped in fruit, the upper lip 3-toothed, the lower 2-cleft, the throat not bearded. Corolla-tube not longer than the calyx, the throat obliquely campanulate, the limb 5-cleft, the lower lobe slightly the larger. Stamens 4, nearly equal, or the posterior pair shorter, erect, divergent; anthers 2-celled. Style deeply 2-cleft; ovary 4-parted. Nutlets globose, reticulated. [The native name in India.]
One or 2 species, natives of Asia, the following typical.
Purple or purple-green, sparingly pubescent; stem stout, erect, much branched, l°-3° high, leafy. Leaves long-petioled, broadly ovate, acuminate at the apex, narrowed at the base, coarsely dentate or incised, 3'-6' long and nearly as wide; racemes terminal and axillary, many-flowered, 3'-6' long; pedicels spreading, 1 1/2"-3" long in fruit; calyx minute in flower, much enlarged, gibbous at the base and densely pilose-pubescent in fruit; corolla purple or white, 1 1/2" long, with a woolly ring within.