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.

erect to ascending, ± quadrangular to pentagonal or broadly elliptic, sometimes sulcate, (1.9–)4.2–8.6 cm (extraterritorial plants to 12 cm) × 0.2–0.4 mm, soft.

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

distal leaf sheaths persistent or fugaceous, pale brown or red-brown sometimes spotted or streaked red-brown, translucent, membranous, apex acute.

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.

basal spikelets absent; never proliferous, ovoid, ellipsoid or obovoid, laterally compressed when young, but terete at maturity, 1.9–4 × 1–3 mm, apex acute, proximal scale empty, deciduous, amplexicaulous or nearly so, similar to floral scales, 0.6–2.5 × 0.8–1.2 mm, midrib sometimes slightly prolonged beyond lamina;

subproximal scale with a flower;

floral scales distichous or spirodistichous, (2–) 4–10, 3–5 per mm of rachilla, pale brown, spotted or streaked red-brown, ovate or elliptic, 1.7–2.2 × 0.4–0.7 mm, membranous, midrib green, spotted red-brown, prominent, apex rounded.

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 6, red-brown, equaling to much exceeding tubercle;

spinules sparse, retrorse, sharply acute;

stamens 3;

anthers 0.5–0.7 × 0.1 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.

whitish or pale brown, circular in outline, ellipsoid, or obovoid, trigonous, angles prominent, 0.6–0.8 × 0.5–0.6(–0.7) mm, apex constricted proximal to tubercle, smooth.

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

white or red-brown, pyramidal, trigonous, 0.2–0.4 × 0.3–0.4 mm.