A pretty plant, with an erect, leafy stem, six inches to two feet tall, springing from running rootstocks, and pale green, more or less downy, leaves, finely cut into numerous, small, narrow lobes, so that they look like rather dry little ferns. The delicate flowers are the usual Evening Primrose shape, about an inch across, in the axils of the leaves, with pure white petals, greenish at the base and turning pink in fading, and a calyx-tube two inches long, with turned-back, pinkish-green lobes. The anthers are brown, the pistil green, the throat of the corolla is closed by a fringe of white hairs, the buds are drooping and the capsule is oblong and hairy. This is common on prairies and plains, from Nebraska to Utah, and south to New Mexico, reaching an altitude of nine thousand feet.
There are several kinds of Onagra, differing from Anogra in having yellow flowers and in the arrangement of the seeds; with stems; leaves alternate, with wavy or toothed margins; buds erect; flowers night-blooming, in terminal clusters; calyx-tube long; petals four; stamens eight, equal in length; stigma four-cleft; capsule four-angled, more or less tapering.