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.

subterete to sometimes compressed, to (2–)3 times as wide as thick, often with (4–)5–10 ridges or angles, 5–90 cm × 0.3–0.8 mm, firm to soft, spongy.

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

distal leaf sheaths persistent, not splitting, proximally dark red, distally green to stramineous or red, thinly papery to membranous, apex usually red-brown, obtuse to subacute, often callose, tooth to 0.5 mm usually present on some culms.

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, 3–8 × 2–3(–4) mm, apex obtuse (to acute);

proximal scales amplexicaulous, apex entire;

subproximal scale with a flower;

floral scales spreading in fruit, 10–30, 5–7 per mm of rachilla, medium to very dark brown, midrib region often paler, ovate, 1.7–3 × 1–1.5 mm, apex rounded to obtuse (or acute), entire or shallowly notched (emarginate) or sometimes cut to 0.5(–0.7) mm deep, apical colorless hyaline part at least as wide as long, 0.2–0.7 mm, 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 absent or rarely 1–3, pale brown, to 1/2 of achene length, sparsely retrorsely spinulose;

stamens 3;

anthers orange-brown, 0.8–1.7 mm;

styles 3-fid or some 2-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.

persistent after scales fall, usually lemon yellow or dark yellow, orange, or medium brown, rarely greenish, obpyriform, nearly equilaterally to compressed-trigonous, often some biconvex, angles evident to prominent, 0.7–1.2 × 0.6–0.9 mm, neck short or absent, finely to coarsely rugulose at 10X, 12–20 horizontal ridges in vertical series, usually finely cancellate at 10–20X.

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

brown to whitish, greatly depressed, apiculate, sometimes pyramidal, 0.1–0.25 × 0.25–0.45 mm.

= 38.