1. Sicyosperma gracile A. Gray, Smithsonian Contr. Knowl. 5(6): 62. 1853.
Leaf blades 2–7 cm wide, lobe apex rounded to acute. Inflorescences: each flower loosely enclosed within 2 bracts; peduncle hispid, hairs retrorsely curved. Flowers: petals apically 2-fid, corolla 2–3 mm diam. Pepos 4–5 mm, loosely enclosed by persistent bracts.
Flowering Aug–Oct(–Nov). North slopes, cliff bases, canyon bottoms, stream sides, riparian scrub, willow-ash, cottonwood-willow, hackberry-acacia, oak woodlands; 1000–1700 m; Ariz., N.Mex.; Mexico (Chihuahua, Sonora).
Sicyosperma gracile is recognized by its annual duration, minute salverform corollas with white, apically bifid petals, each flower enclosed within a pair of basally cordate bracts, and relatively small, 1-seeded, dry, indehiscent, unarmed pepos loosely enclosed by bracts. Specimens sometimes show only staminate inflorescences, but apparently this is an artifact of collection rather than an indication that the plant is unisexual.