Small diffuse or tufted herbs, with mostly opposite and entire leaves, scarious stipules, and a 4-5-toothed or parted coriaceous persiatent calyx. Petals wanting. Stamens perigynous, as many as the lobes of the calyx and opposite them, or fewer. Style 2-cleft at the apex. Fruit a 1-seeded utricle.
P. sessiliflo'ra, Nutt. Flowers terminal, solitary, sessile. Stems densely matted or tufted, from a woody root. The dry, silvery stipules 2-cleft. Sepals oblong-linear, concave, awned at the apex. - N. W. prairies.