4. Dryopetalon membranifolium Rollins, Contr. Gray Herb. 214: 21. 1984. TYPE: Mexico, Sinaloa, 51 km by road from Villa Union on road to Durango, 800 m, steep slopes with shrubby woods, just below oak zone, 11-12 Mar 1970, W. R. Anderson & C. Anderson 6172 (holotype, GH!; isotype, MICH).

     Herbs, annual or biennial, glabrous or sparsely pubescent below or on young leaves. Stems 2–3.5 dm, erect, often branched from above base. Basal leaves rosulate; petiole 2–5 cm; leaf blade broadly ovate, entire or dentate, 3–6 × 1.8–4 cm, cuneate to cordate at base; lower cauline leaves similar to basl, upper leaves petiolate, linear to narrowly lanceolate, attenuate to cuneate and not auriculate at base, entire or shallowly sinuate-dentate, acuminate at apex. Racemes lax, elongated in fruit; fruiting pedicels divaricate-ascending, 14–20 mm, slender, glabrous. Sepals oblong, 3–4 mm; petals white, spatulate, deeply emarginate at apex, 6–7.5 × 3–3.5 mm, entire; claw glabrous; filaments glabrous, ca. 3 mm; athers oblong, ca. 1 mm. Fruit linear, 1.5–2.5 cm × 0.7–0.9 mm, terete, straight; valves glabrous; style 0.5–0.9 mm. Seeds oblong, 1–1.3 mm, wingless; cotyledons incumbent.

Flowering: Mar.

Habitat: steep woody or shrubby slopes.

Elevation: ca. 800 m.

Distribution: Mexico (Sinaloa).