Camissonia arenaria (A. Nelson) P. H. Raven; Oenothera arenaria (A. Nelson) P. H. Raven; O. cardiophylla Torrey var. longituba Jepson; O. cardiophylla var. splendens Munz &I. M. Johnston

Herbs perennial, sometimes facultative annual, villous, sometimes also sparsely glandular puberulent in inflorescences. Stems well branched, 25–180 cm. Leaves cauline, often mostly toward base; petiole 3–6 cm; blade cordate-deltate, 2.5–4(–6) × 2.5–4(–6) cm, smaller distally, margins coarsely dentate. Racemes nodding, open. Flowers: floral tube 18–40 mm, finely pubescent inside; sepals 8–15 mm; petals bright to pale yellow, 8–20 mm; filaments 5–9 mm, anthers 5–8 mm; style 30–58 mm, stigma exserted beyond anthers at anthesis. Capsules ascending, cylindrical, 30–44 mm; pedicel 2–5 mm. Seeds 0.5–0.7 mm. 2n = 14.

Flowering Mar–Apr. Sandy washes, rocky slopes, desert scrub in Sonoran Desert shrublands, usually with Ambrosia dumosa, Carnegiea, Larrea tridentata, and Prosopis; -50–500 m; Ariz., Calif.; Mexico (Sonora).

Chylismia arenaria is known from the foot of the Needles in Mohave County, Arizona, and from the north end of the Salton Sea, Riverside County, California, southeastward to the Tinajas Atlas Range, Arizona, and Sonora, Mexico. P. H. Raven (1962, 1969) determined C. arenaria to be self-compatible, but primarily outcrossing.