Perennials, 10-30(-60) cm (rhizomatous; aquatic to subaquatic). Stems decumbent or erect (sometimes floating), simple or branched distal to bases (terete, glabrous; internodes usually shorter than leaves). Leaves cauline; whorled (4-6 per node); sessile; blades 1-nerved, linear, margins entire (apices callus-tipped), faces glabrous or sparsely gland-dotted. Heads discoid, borne singly (peduncles ebracteate). Involucres campanulate to subhemispheric, ca. 10 mm diam. Phyllaries persistent, 22-30+ in 2-3+ series, not notably nerved, linear to broadly lanceolate, unequal to ± equal (glabrous). Receptacles conic or hemispheric, epaleate. Florets ca. 50; corollas pink-lavender to flesh-colored, throats funnelform (sparsely stipitate-glandular), lobes 5, deltate; styles: bases not enlarged, glabrous, branches filiform to linear-clavate. Cypselae prismatic, 5-ribbed, gland-dotted; pappi persistent, of 5 muticous scales. x = 15.

Heads discoid, the rather numerous fls all tubular and perfect; invol campanulate or subhemispheric, its bracts subequal; receptacle hemispheric or conic, naked; cors purplish; style-branches with short, ventromarginal stigmatic lines and an elongate, papillate, linear-clavate appendage; achenes 5-angled, atomiferous-glandular; pappus of 5 short, broad, obtuse scales; slender, rhizomatous, aquatic herbs with narrow, entire lvs verticillate in 4's to 6's, the heads rather small, naked-pedunculate, mostly solitary. Monotypic.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

©The New York Botanical Garden. All rights reserved. Used by permission.