Glabrous annual herbs with small taproots. Leaves (1–)3–4-pinnatisect, often ternately dissected. Inflorescence a leaf-opposed compound umbel; bracts and bracteoles usually absent; rays and pedicels slender. Flowers bisexual; sepals inconspicuous; petals elliptic to broad-ovate, sometimes inflexed, often shortly apiculate. Fruit ovoid-globose to c. globose, glabrous or rarely shortly bristly; mericarps with 5 prominent ribs; carpophore shortly divided.
1–3 species, native to America; 1 widely naturalised in Australia.