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..
Biennial or perennial herbs with branched stems which sometimes become shrubby. Leaves alternate, narrow, entire or sharply serrate. Flowers perfect, regular, axillary, yellow. Calyx-tube funnelform, shorter than the ovary; calyx-segments narrow, keeled on the back, the tips free in the bud. Petals 4, often blotched at the base. Stamens 8, equal in length; filaments filiform; anthers narrow. Ovary 4-celled, 4-angled; stigma disk-like, 4-toothed; ovules numerous. Capsules linear, 4-angled, 4-celled, sessile. Seeds longitudinally grooved. [Name unexplained.]
Three or four species of temperate North America, the following typical.
Oenothera serrulata Nutt. Gen. 1: 246. 1818.
Meriolix serrulata Walp. Repert. 2: 79. 1843.
Erect, simple or branched, canescent or glabrate, 4'-18' high. Leaves linear-oblong, lanceolate or oblanceolate, acute or acutish at the apex, narrowed at the base and usually sessile, sharply dentate or denticulate, 1'-3' long, 2"-3" wide; flowers yellow, axillary, 6"-2' broad; calyx-lobes ovate, acuminate, somewhat reflexed, the tube funnelform, silvery canescent, shorter than or equalling the ovary; petals obovate, crenulate; stigma discoid; capsule sessile, linear-cylindric, silvery canescent, 8" - 15" long, about 1" thick, slightly grooved longitudinally.
In dry soil, Manitoba and Minnesota to Wisconsin, Texas and New Mexico. Consists of several races, differing in size, shape of leaves and size of flowers. May-July.
18. GAÙRA L. Sp. Pl. 347. 1753.
Annual biennial or perennial herbs, somewhat woody at the base, with alternate narrow sessile leaves, and white, pink or red flowers in terminal spikes or racemes. Calyx usually pubescent, its tube narrow, prolonged beyond the ovary, deciduous, 4-lobed (rarely 3-lobed), the lobes reflexed. Petals 4 (rarely 3), clawed, unequal. Stamens usually 8, declined; filaments filiform, each with a small scale at the base. Ovary 1-celled; united styles filiform, declined; stigma 4-lobed, surrounded by a cup-like border; ovules usually 4, pendulous. Fruit nut-like, ribbed or angled, indehiscent or nearly so, 1-4-seeded. Seeds unappendaged. [Greek, proud, some species being showy.]
About 18 species. natives of North America and Mexico. Type species: Gaura biennis L.
Fruit sessile or very nearly so; flowers spicate.
Flowers 1 1/2"-2" broad; stigma little exserted beyond its cup.
Flowers 4"-5" broad; stigma exserted beyond its cup.
Flowers red, turning scarlet; fruit canescent.
Flowers white, turning pink; fruit villous.
Fruit pedicelled; flowers racemose.
Leaves mostly glabrous; fruit 7" long, glabrous, its stout pedicel club-shaped.
Leaves densely villous; fruit 5" long, pubescent, its slender pedicel nearly filiform.