This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", 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..
Low perennial herbs with stout sparingly branched stems. Leaves numerous, alternate, narrow, entire or slightly toothed. Flowers perfect, few, but large and showy, axillary, yellow. Calyx-tube much elongated, dilated toward the throat; calyx-segments narrow, the tips free in the bud. Petals 4, spreading. Stamens 8, the alternate ones longer; filaments filiform; anthers linear. Ovary 4-celled, 4-angled or 4-winged; united styles filiform; stigma 4-cleft; ovules few, sessile in rows. Capsules broadly 4-winged. Seeds few, crested. [Greek, broad-winged.]
About 4 species, in North America and Mexico. Type species: Megapterium Nuttallianum Spach.
Flowers 3'-6' broad; capsules suborbicular, 2'-2 1/4' long.
Flowers 1' - 2' broad; capsules oblong, 9"-14" long.
Densely finely canescent.
Oenothera missouriensis Sims. Bot. Mag. pl. 1592.
734. 1814. Megapterium missouriense Spach, Hist. Veg. 4:
Tufted, stems decumbent or ascending, finely and densely canescent, 6-12' long. Leaves thick, linear-lanceolate or oblong-lanceolate, acuminate or acute at the apex, narrowed at the base info a slender petiole or the uppermost nearly sessile, entire or remotely denticulate, 2'-6' long, 2"-8" wide; flowers 3'-6' broad; calyx-lobes broadly lanceolate, spreading, the tube 2'-6' long, 6-12 times the length of the ovary; capsule short-stalked, nearly orbicular, very broadly winged, finely canescent, or glabrate when mature, 1-3' long.
Tufted, stems mostly simple, ascending, 2'-6' high, densely appressed-pubescent or canescent. Leaves linear-lanceolate to somewhat oblanceolate, acuminate at the apex, narrowed at the base into a slender petiole, entire or very nearly so, silvery canescent, 1 1/2'-3' long, 2"-4" wide; flowers 1'-2' broad; calyx-lobes broadly lanceolate, acuminate, spreading, the tube canescent, very slender, 4-5 times the length of the ovary; capsule ovate, canescent, broadly winged, rounded at the summit, about 8" long and 6" wide, short-stalked.
Plains, Kansas to Texas. Summer.
Glabrous throughout, even when young; stems decumbent or ascending, 1° long or less; leaves firm in texture, lanceolate, acuminate at the apex, narrowed at the base, remotely toothed or entire-margined, 2 1/2'-4' long; flowers 1 1/2-2' broad; calyx-lobes linear-lanceolate, purple-spotted; capsules oblong, short-stalked, about 1' long, its wings 3"-4" wide.
Kansas and Oklahoma. Summer.