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.

branched or unbranched, to 3 m. Turions present, becoming brown to red-brown at maturity, clavate to obdeltoid, with abrupt transition from foliage leaves to reduced turion leaves, (6–)11–37(–52) × (3–)4–6(–9) mm, apex ± rounded, lateral turions with several whorls of minute, brown prophylls, entire proximallyand toothed to lobed distally, ovate to elliptic or lanceolate in outline;

leaves pectinate, strongly appressed to axis throughout, narrowly flabelliform in outline, 4.5–7.5 × 1.2–1.8(–4) mm;

segments 8–12(–18), flattened, linear-lanceolate, longest segment 1.5–6 mm, basal segment usually greater than or equal to 2/3 central axis of leaf, apex ± acute, trichomes usually 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.

in whorls of (3 or)4, heteromorphic;

petiole to 6 mm; submersed leaves pectinate, ovate to elliptic in outline, (7–)12–30(–46) × 9–24(–40) mm, segments (9–)12–22(–34), linear-filiform, longest segment (2–)6–19(–29) mm; emersed leaves pectinate, lanceolate to elliptic to ovate in outline, 2–5(–15) ×0.9–2.6 mm, segments (9–)12–20, greater than 0.5 mm.

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 25 cm;

flowers proximally pistillate, medially bisexual, distally staminate, in whorls of 4;

bracteoles cream, ovate, 0.3–0.6(–1) × 0.1–0.6(–1.3) mm, margins deeply dissected into irregular lobes.

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, narrowly triangular to deltate, 0.5–0.7(–0.9) × 0.4–0.6(–0.8) mm;

petals persistent, cream, sometimes apically suffused with purple, elliptic to obovate, 1.8–2.2(–2.4) ×0.7–1.5 mm;

stamens 8, filaments to 2 mm, anthers 0.8–1.7 × 0.3–0.6 mm.

sepals and petals rudimentary or absent;

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

sepals greenish to cream, elliptic to triangular, 0.2–0.7 × 0.2–0.7 mm;

petals often caducous, sometimes persistent, cream to purple, elliptic to obovate, 0.4–0.7(–0.9) × 0.3–0.5(–0.8) mm;

pistils (1.3–)1.8–2.7 mm, stigmas red to± purple, to 0.8 mm.

subglobose, 4-lobed.

globose, shallowly 4-lobed.

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

olive-green to brown, subglobose to globose, 2–2.7(–3) × (0.9–)1.1–1.3(–1.7) mm, transverselywidely obovate, abaxial surface broadly rounded to moderately flattened, smooth, often with 2 shallow longitudinal ridges, wings and ribs absent.

= [14] 21.

= 28.