Flora of North America species comparison

floating or creeping and ascending to erect, terete, 10–100(–300) cm, simple or branched, glabrous or sparsely to densely villous, hairs sometimes viscid on emergent distal stem.

prostrate or decumbent and ascending at tips, slightly ridged, often well branched, 5–70 cm, glabrate to sparsely strigillose, denser on distal parts.

stipules broadly ovate-deltate, 0.6–1.6 × 0.4–1 mm, succulent, apex acute or obtuse, gland-tipped, rarely divided into 3 parts;

petiole flattened or narrowly winged, 0.2–6 cm;

blade narrowly oblong or elliptic to ovate, broadly obovate, or orbiculate, (0.4–)1–10 × 0.4–4 cm, base narrowly cuneate or attenuate, margins entire, apex obtuse or rounded to acute, sometimes mucronate or glandular-mucronate, surfaces of floating leaves glabrous, those of emergent leaves glabrous to sparsely or densely strigillose at least adaxially;

bracts scarcely reduced.

opposite;

stipules narrowly deltate or ovate, 0.05–0.15 × 0.05–0.1 mm; submerged stems: petiole 0–0.2 cm, blade narrowly linear, 1.9–4 ×0.1–0.25 cm;

emergent stems: petiole 0–0.2 cm, blade narrowly elliptic or narrowly oblanceolate-elliptic to linear, 0.6–1.8 × 0.2–0.5 cm, base narrowly cuneate, margins entire, apex acute, surfaces glabrous or sparingly strigillose on margins and abaxial midveins;

bracts reduced.

on emergent stems sometimes in leafy racemes, flowers solitary in leaf axils;

bracteoles (rarely absent), deltate, squamate, 0.5–1 × 0.5–1 mm, apex acute, attached near base or on lower 1/2 of ovary.

in racemes or spikes, well-formed on ascending stems, not on prostrate stems;

bracteoles attached at base of ovary or 1.5–8 mm proximally on pedicels, sublinear to very narrowly elliptic, 1.4–5 × 0.2–0.8 mm, apex acute, surfaces minutely strigillose.

sepals narrowly deltate or lanceolate, 3–12 × 1.5–4 mm, apex acute or acuminate, surfaces glabrous or sparsely to densely hirtellous;

petals yellow, obpyramidal,7–24 × 4–13 mm, apex mucronate or emarginate, up-curved;

stamens 10(or 12), in 2 unequal series, bright yellow, filaments suberect or reflexed, shorter ones 1.4–4.2 mm, longer ones (1.9–)3.3–6 mm, anthers oblong, 0.5–2.2 mm;

ovary subcylindric or truncate, 6–20 × 1.5–3 mm, apex somewhat broader, glabrous or sparsely to densely hirtellous;

nectary disc slightly raised on ovary apex, 2–2.5 mm diam., lobed, glabrous or fringed with long hairs;

style (1.9–)2.4–7.3 mm, glabrous or sparsely to densely hirtellous on proximal 1/2, stigma flattened-globose, 0.9–1.2 × 1–2.5 mm, sometimes shallowly or deeply 5-lobed, as long as or exserted beyond anthers.

sepals reflexed or spreading, green, lanceolate-deltate, 5.2–10 ×1.5–2.7 mm, with 3 prominent parallel veins, margins entire and minutely strigillose, apex acute or elongate-acuminate, surfaces minutely strigillose abaxially;

petals rarely caducous, elliptic-obovate to spatulate-obovate, 7–11 × 4.5–8 mm, base attenuate, apex rounded;

filaments initially spreading, becoming erect, yellow, 2.5–4.5 mm, anthers 1.3–2 × 0.7–1.1 mm;

pollen shed in tight tetrads;

ovary cylindric to funnelform, 4–5.5 × 1.5–2.8 mm;

nectary disc elevated 0.6–1 mm on ovary apex, 1.5–2.6 mm diam., bright yellow, with 4 distinct domed lobes, minutely strigillose between lobes or glabrous;

style yellow, 2.3–4(–4.8) mm, glabrous, stigma yellow, broadly capitate, 0.3–0.6 × 0.6–1.8 mm, as long as or exserted beyond anthers.

cylindric, subterete to obscurely 5-angled, straight or curved, 10–40 × 2–4 mm, with thick woody walls, irregularly and tardily dehiscent, pedicel 7–60(–90) mm.

clavate, subterete, sometimes slightly curved, 5.5–10 × 2.3–4 mm, hard-walled, irregularly dehiscent, pedicel (12–)17–45 mm.

embedded in elongated piece of endocarp, 1–1.5 × 0.9–1.3 mm.

light to dark brown, elliptic-oblong, 0.5–0.7 × 0.3–0.4 mm, surface cells transversely elongate.

= 16.

= 32.