Erect, slender, 2-8 dm, freely branched above; lvs 4-10 cm, pinnately dissected into filiform segments, 5-25 mm, commonly 3 divisions at a node along the rachis; umbels 2-5 cm wide, overtopping the lvs; bracts few, 1-2 cm, simple or divided into filiform segments; rays 5-15 or more; sep minute, deltoid; fr broadly ovoid, subacute, 2-3 mm; styles 0.2-0.5 mm, not strongly recurved, scarcely as long as the stylopodium; 2n=14, 28. Fresh or brackish swamps and marshes; Mass. to Fla. and Tex., chiefly near the coast in our range, n. in the interior to Ky., Mo., and Kans. June-Oct.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.