Annuals. Stems few to several from base, erect, branched distally, (0.7-)1-6(-7) dm. Basal leaves: petiole (0.5-)1-4(-5) cm; blade lanceolate, oblanceolate, or ovate, (1.2-)2-5(-6) cm × (5-)10-20 (-30) mm, base cuneate, margins usually dentate, sinuate, rarely pinnatifid. Cauline leaves (distal) shortly petiolate or sessile; blade ovate, lanceolate, or oblong, 1-4(-5) cm × (3-)10-20(-30) mm, base cuneate, margins entire, dentate, or repand. Racemes considerably elongated in fruit. Fruiting pedicels 1.5-2.5 mm. Flowers: sepals purple to lavender, linear, (6-)7-9(-10) × 0.8-1.2 mm; petals white to pale lavender, (10-)12-15 × (1.5-)2-3 mm; filaments 6-7 mm; anthers 1.5-2(-2.5) mm. Fruits: valves transversely ovate to suborbicular, 3.5-5 (-6) × 4-6(-7) mm, base and apex rounded, pubescent, trichomes clavate, simple, papillate (branched trichomes rarely present on fruit margin); style 0.1-0.5(-1) mm. Seeds 3-4 × 1.5-2.5 mm. 2n = 20. Flowering (depending on elevation) Mar-Oct. Sandy deserts, sand dunes; 50-1400 m; Ariz., Calif., Nev.; Mexico (Baja California, Sonora). Dithyrea californica is known in Arizona from Maricopa, Mohave, and Yuma counties and in Nevada from Clark and Lincoln counties. In material with immature fruits and lacking the proximal portion of stems, the species is readily distinguished from D. maritima by the presence of clavate trichomes, quite visible even on the ovaries of developing fruits. By contrast, D. maritima has branched instead of clavate trichomes.

Plant: Annual canescent; bases of cauline leaves, pedicels with paired glands; stems arising below leaf clusters, decumbent to erect, 1-7 dm; branches 0 below, sparse or 0 above Leaves: not fleshy, canescent; basal 3-15 cm, oblanceolate to widely obovate, dentate to shallowly lobed, tip obtuse; basal and lower cauline petioled; middle and upper cauline petioles 0 or short; cauline 1-4 cm, widely oblong to ovate INFLORESCENCE: raceme; bracts 0 Flowers: bisexual, fragrant; sepals 4, free overlapped; petals 12-15 mm, free, prominently 3-veined, erect, narrowly tongue-shaped, whitish to light lavender; stamens generally (2,4)6, generally 4 long, 2 short; ovary 1, superior, chambers generally 2, septum membranous, connecting 2 parietal placentas, style 1, stigma simple or 2-lobed Fruit: Fruit: capsule with 2 deciduous valves, indehiscent, flat perpendicular to septum; 1-seeded halves ± round, each bordered by a raised rim; hairs simple, club-like or not; pedicel spreading; Seed 3-4 mm widely oblong, flat; wing 0; embryonic root at edges of both cotyledons Misc: Sandy places, washes, scrub; < 1400 m.; Mar-May