Plant: plant 0.3-9 dm, annual, biennial, taprooted, hairy, generally simple or few-branched Leaves: petiole 4-15 cm; blade 3-10.5 cm, oblong, pinnately dissected; segments 1-5 mm, linear, acute, entire, ± bristly INFLORESCENCE: umbels compound; peduncles 1-4.5 cm, bristles reflexed to spreading; rays many, 0.4-4 cm; pedicels 2-9 mm; bracts conspicuous, generally pinnately lobed; bractlets entire to toothed Flowers: many, small, outer sometimes ± bilateral; calyx lobes 0 or evident; petals wide, white, tips narrowed, unequally 2-lobed; stamens 5; pistil 1, ovary inferior, 2-chambered, generally with a ± conic, persistent projection or platform on top subtending 2 free styles Fruit: 2 dry, 1-seeded halves that separate from each other but generally remain attached for some time to a central axis, 3-5 mm, oblong, compressed front-to-back; ribs 10, primary thread-like and bristly, secondary winged and prickly; oil tubes 1 beneath each secondary ribs; fruit axis entire or notched at tip Misc: Rocky or sandy places; 0-1500 m.; Apr-Jun References: Kearney & Peebles. Arizona Flora.J.C. Hickman, ed. The Jepson Manual. A. Cronquist. An integrated system of classification of flowering plants. ASU specimens.