Erect annual. Stems glabrous or sparsely hairy, simple or with a few lower branches, up to c. 50 cm high. Lvs alternate, glabrous, exstipulate, sessile, serrate toward apex, obovate and long-cuneate to base, usually rounded at apex, rarely subacute, (10)-20-40-(60) mm long. Terminal umbel 3-5-rayed, usually with no axillary rays below on each stem; lvs subtending umbel similar to stem lvs but usually broader and less cuneate; rays often secondarily branched and then forming compound dichasia; lvs subtending ray-branches and cyathia similar to stem lvs but much smaller and less cuneate, sometimes elliptic, conspicuous yellow-green. Glands elliptic, entire. Capsule smooth, deeply grooved, with keel rounded or slightly ridged. Seeds reticulate-rugose, rounded, dark brown, c. 2 mm long.