Flora of North America species comparison

often branched, to 0.6 m. Turions present, ± brown, narrowly cylindrical, with gradual transition from foliage leaves to highly reduced turion leaves, (4–)7–12(–20)× 0.5–2(–3) mm, apex rounded to truncate;

leaves often pectinate proximally and entire to 3-fid distally, strongly appressed to axis, lanceolate to narrowly elliptic or ovate in outline, (1.5–)2–4(–6.5) × (0.2–)0.3–2(–2.5) mm;

segments 0–6(–10), longest segment 0.5–2 mm, basal segment less than or equal to 1/2 central axisof leaf, apex ± acute or rounded, brown, long-necked, ascidiate trichomes in axils present.

often branched, to 1 m. Turions absent.

opposite or in whorls of 3(or 4), heteromorphic;

petiole 0–9 mm; submersed leaves usually pectinate, sometimes 2- or 3-lobed, ovate to widely ovate or trullate in outline, (1.3–)5–22(–26) × (0.3–)3–28(–35) mm, segments(0–)4–12(–14), distinctly alternate, lobed to linear-filiform, longest segment (0.5–)2–20(–25) mm; emersed leaves usually linear, spatulate, or 2- or 3-lobed, sometimes pectinate proximally, (1.7–)2.5–9(–10.5) × 0.3–3.5(–5) mm, segments (0–)2–8(–12), lobed to linear-filiform.

usually in whorls of (3 or)4, often subverticillate or irregular, sometimes alternate, heteromorphic;

petiole 0–5 mm; submersed leaves pectinate, ovate to obovate in outline, (9.5–)12–28(–33) × (7–)10–20(–25) mm, segments 6–12(–13), linear-filiform, longest segment (5–)8–15(–20) mm; emersed leaves linear-lanceolate, margins lobed to serrate, pectinate to pinnatifid, (4–)6–17(–19) × 1–6.5 mm, segments (0–)3–10.

to 12 cm;

flowers usually unisexual, rarely bisexual;

bracteoles cream to stramineous, lanceolate, elliptic, ovate, or obovate, (0.2–)0.3–0.7(–0.9) × (0.1–)0.2–0.4(–0.5) mm, margins entire, irregular, dentate, glandular, or lobed.

to 20 cm;

flowers proximally pistillate, medially bisexual, distally staminate;

bracteoles cream, ovate to triangular or deltate, 0.5–0.8 × 0.2–0.5 mm, margins serrate to irregularly lobed.

sepals cream, elliptic to lanceolate, 0.5–0.7 × 0.2–0.5 mm;

petals persistent, cream, sometimes apically suffused with purple, widely oblanceolate, 1.2–2.5 × 0.7–1.2 mm;

stamens 8, filaments to 1.4 mm, anthers 0.9–1.8 × 0.2–0.4 mm.

sepals cream to stramineous, elliptic to linear-lanceolate or narrowly triangular, 0.1–0.3(–0.4) × 0.1–0.2 mm;

petals persistent, cream to purple, elliptic to obovate, 0.7–1.7(–1.9) × (0.4–)0.5–0.8(–1) mm;

stamens 4, filaments to 1.4 mm, anthers 0.7–1.5 × 0.2–0.5(–0.7) mm.

sepals and petals rudimentary or absent;

pistils to 0.7 mm, stigmas white, to 0.3 mm.

sepals cream, triangular, 0.1–0.2 × 0.1–0.2 mm;

petals usually caducous, rarely persistent, cream, elliptic to obovate, 1–2 × 0.5–0.7 mm;

pistils 0.8–1.2 mm, stigmas red to ± purple, to 0.5 mm.

subglobose, 4-lobed.

ovoid, cruciate.

brown, obovate, 0.8 × 0.6 mm, abaxial surface rounded, minutely tuberculate, wings and ribs absent.

tan to brown, cylindric to ovoid, (1–)1.2–1.8 × 0.6–0.8(–1) mm, transversely elliptic, flattened, abaxial surface sharply 2-angled, flattened to concave, papillate, sometimes minutely tuberculate, with 2 distinct longitudinal ridges, ridges with prominent, membranous, undulating wings, wings erect to reflexed, with 6–12 perpendicular ribs.

= [14] 21.