Stems attached to stones by fleshy disks, 2-10 cm, usually branched; lvs alternate, dilated into a pair of stipule-like appendages at base, 1-10 cm, very narrow and entire or commonly ±forked into numerous narrow segments; spathe 2-3 mm, pedicels eventually to 1 cm; fr 2.5-3 mm. In rapidly flowing water; N.S. and N.B. and Me. to Ga., w. to s. Ont., W.Va., Ky., Okla., and La.; W.I., C. Amer.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.