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 caulescent herbs, with hirsute-pubescent foliage. Leaves opposite; blades entire or pinnately divided, all or some of them auricled at the base, sessile. Flowers in terminal spikes. Calyx of 5 partially united sepals. Corolla purple or rarely white; tube broadly dilated at the throat; lobes spreading. Stamens 4, didynamous, included; filaments glabrous or nearly so; anthers awnless, those of the shorter stamens much smaller than those of the longer. Style slender. Stigma entire. Capsule oval or globose-oval, often minutely pointed. Seeds angled. [Greek, meaning lobed leaf.]
Two species in eastern North America. Type species: Gerardia auriculata Michx.
Leaf-blades, or some of them, with 2 auricles at the base; corolla 8"-10" long; capsules over 5" long.
1. O. auriculata.
Leaf-blades parted into 3-7 linear segments; corolla 1'-1 1/4' long; capsules about 1/4' long.
2. O. densiflora.
G. auriculata Michx. Fl. Bor. Am. 2: 20. 1803. Otophylla auriculata Small, Fl. SE. U. S. 1075. 1903.
Annual, scabrous; stem slender, simple, or branched above, hirsute, 1°-2° high. Leaves lanceolate or ovate-lanceolate, acuminate at the apex, sessile, mostly rounded and 2-lobed at the base, or quite entire, 1'-2' long, the basal lobes oblong or lanceolate, obtusish, short; flowers solitary in the upper axils, sessile, purple, 8"-10" long; calyx 5-cleft, its lobes lanceolate, acute, slightly unequal, as long as or longer than the tube; corolla densely puberulent outside, glabrous within; filaments glabrous; anther-sacs obtuse at the base; capsule oval-oblong, about ¥ high, a little shorter than the calyx.
In moist open soil, Pennsylvania to Illinois, Minnesota, North Carolina and Kansas. Adventive at Woodbridge, N. J. July-Sept.
G. densiflora Benth. Comp. Bot. Mag. 1: 206. 1835. Otophylla densiflora Small, Fl. SE. U. S. 1075. 1903.
Annual, scabrous and short-hispid; stems stiff, erect, branched, or simple, 1°-21/2° high, very leafy. Leaves sessile, ovate in outline, ascending, about 1' long, pinnately parted nearly to the midvein into 3-7 narrowly linear acute rigid segments less than 1" wide; flowers l'-l 1/4' long, rose purple, sessile in the upper axils; calyx 5-cleft, its lobes linear, acuminate, ciliate, about as long as the tube; corolla glabrous both outside and within; filaments glabrous or villous; capsule about i' high, shorter than the calyx.
On dry prairies, Kansas to Texas. Aug.-Oct.