Flora of North America species comparison

acutely trigonous;

spikelet-bearing culms 16–70 cm × 0.7–0.9 mm; when submersed plants often forming numerous, filiform, flaccid culms without spikelets, sometimes with whorls of slender branches, 0.1–0.3 mm wide;

soft, sometimes septate-nodulose when aquatic, internally spongy, transverse septa incomplete.

greatly compressed, 4–10 times wider than thick, often with 1 or 2 sharp ridges on 1 side, (8–)20–35 cm × 0.7–2.3 mm, hard, finely striate, spongy.

distal leaf sheaths persistent or decaying, membranous, apex obtuse to acuminate.

distal leaf sheaths persistent, not splitting, proximally red or stramineous, distally green to stramineous, inflated, papery, apex dark brown, broadly obtuse to subtruncate, callose, tooth absent.

sometimes proliferous (when submerged), 9–33 × 1.5–3 mm;

rachilla joints bearing prominent winglike remnants of floral scales;

proximal scale with a flower, amplexicaulous, (5–)6–9.8 mm;

floral scales 4–18, 0.5–1 per mm of rachilla, stramineous to pale brown, often minutely dotted reddish, without or rarely with darker submarginal band, narrowly ovate to lanceolate, 5–7.8 × 2–3 mm, thickly papery, membranous toward margins, apex narrowly rounded to acute.

ovoid, 4–9 × 2.5–4 mm, apex acute;

proximal scale clasping 2/3–3/4 of culm, apex 2-fid;

subproximal scale empty or with a flower;

floral scales spreading in fruit, 30–60, 6–9 per mm of rachilla, medium or pale brown, midrib region often paler, ovate-lanceolate, 2.5–3.5 × 1.5 mm, apex 2-fid, carinate in distal part of spikelet.

perianth bristles 6–7, stramineous to reddish brown, proximally slightly flattened, subequal to equal, much exceeding to rarely shorter than achene, 3–5 mm, retrorsely spinulose;

anthers yellow to reddish, 1.6–3.2 mm;

styles 3-fid.

perianth bristles 0(–5), stramineous to pale brown, 1/2 of to equaling achene length;

stamens 3;

anthers orange-brown, 0.7–1.5 mm;

styles 3-fid.

stramineous or medium brown, biconvex or compressed trigonous, narrowly obpyriform, 1.9–2.6 × 1–1.4 mm, adaxial face with 15–22 rows of rectangular, transversely elongated or nearly isodiametric cells, clearly sculptured at 10–15X, apex usually conspicuously constricted to short neck 0.4–0.7 mm wide, usually wider at tubercle base.

falling with scales, yellow-brown to medium brown, obovoid to obpyriform, nearly equilaterally trigonous, cross section circular to slightly compressed, angles obscure or evident, 0.9–1.1 × 0.6–0.75, neck usually very short, finely rugulose at 10–30X, 20 or more low, blunt horizontal ridges in vertical series.

stramineous to medium brown, high-pyramidal, 0.5–1.1 × 0.3–0.7 mm.

brown, depressed-pyramidal, often rudimentary, 0.1–0.25 × 0.2–0.3 mm.