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.

1. Megapterium Missouriènse (Sims) Spach. Missouri Primrose

Fig. 3062

Oenothera missouriensis Sims. Bot. Mag. pl. 1592.

1814. Oenothera macrocarpa Pursh, Fl. Amer. Sept.

734. 1814. Megapterium missouriense Spach, Hist. Veg. 4:

364. 1835.

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.

In dry soil, Missouri to Nebraska, Colorado and Texas. May-July.

2. Megapterium Fremòntii (S. Wats.) Britton. Fremont's Primrose

Fig. 3063

Oenothera Fremontii S. Wats. Proc. Am. Acad.

8:587. 1873. Megapterium Fremontii Britton, Mem. Torr. Club 5: 236. 1894.

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.

3. Megapterium Oklahomènse Norton. Oklahoma Primrose

Fig. 3064

Megapterium oklahomense Norton, Ann. Rep. Mo. Bot. Gard. 9: 153. 1898.

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.