Stems slender, 3-10 dm, not much thickened at base and sometimes without thickened roots; lvs all cauline, with linear or very narrowly lanceolate, sparsely and saliently dentate to entire lfls or segments to 5 mm wide; umbels rarely to 5 cm wide, often none, surpassed by the leafy shoots; fr rarely matured, orbicular, 1.5-2 mm, the lateral ribs separated by a constriction at the commissure; 2n=22. Swamps and marshes; Nf. to Alas., s. to Pa., W.Va., Ky., Kans., and Oreg., and at higher altitudes to Va. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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From Flora of Indiana (1940) by Charles C. Deam
Restricted to the lake area of the northern part of the state. Miry, mucky, or sandy borders of lakes, ponds, and swamps. Infrequent. Grows in wetter situations than does the next species [Cicuta maculata].