Xyris difformis Chapm.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Lvs broadly linear or elliptic-linear, mostly 10–50 cm × 5–15 mm, spreading, lustrous dark green, anthocyanic at the dilated, soft, thin, keeled base; scapes 1.5–7 dm, terete and twisted below, straighter above and somewhat compressed, with 2 broad thin ridges that may be collectively as wide as the body; spikes 0.5–1.5 cm at maturity, ovoid to subglobose, blunt or acute; lateral sep shortly included, the broad keel lacerate in its upper half; pet-blades cuneate, 4 mm, yellow, unfolding in the morning; seeds 0.5–0.6 mm, broadly ellipsoid, very finely ribbed; 2n=18. Wet, low, often sandy places, often in river-swamps; coastal region from s. Me. to Fla. and Tex., and less commonly inland to Mich., Ind., Wis., and Okla. Midsummer–fall. Two vars. with us, both widespread. Var. difformis is ± robust, with smooth lvs. Var. curtissii (Malme) Kral is smaller and more tufted, seldom over 2 dm, the lf-surfaces evidently papillate. (X. bayardii; X. curtissii; X. papillosa)