Flora of North America species comparison

taproots or fibrous, and then often with adventitious nodal roots;

rhizomes sometimes present [stolons in some Haloragis].

often branched, to 3 m. Turions absent.

erect, ascending, decumbent, or prostrate, cylindric to 4-ribbed, glabrous or scabrous to pubescent, hairs uniseriate and multiseriate, glands present or absent.

present or absent, lateral and/or terminal.

mostly in whorls of (3 or)4(or 5), sometimes opposite to subopposite, heteromorphic;

petiole 0–4 mm; submersed leaves pectinate to lobed (basalmost leaves opposite to subopposite, reduced, margins entire), ovate to obovate in outline, (3–)5–25(–35) × (2–)3–18(–20) mm, segments (2 or)3–9(–11), linear, ± applanate, longest segment (7–)8–15(–17) mm; emersed leaves pinnatisect to lobed or entire, ovate to oblong in outline, 2–9 × 1–6 mm, margins dentate to minutely serrate.

opposite, alternate, or subverticillate to whorled, simple, often heteromorphic in Myriophyllum and Proserpinaca;

stipules absent;

sessile or petiolate;

blade lobed, unlobed, or pinnatifid to pectinate, margins entire or serrate, surfaces glabrous or scabrous.

to 8 cm;

flowers proximally pistillate, medially bisexual, distally staminate;

bracteoles cream, deltate, 0.5–1 × 0.2–0.6 mm, margins dentate to serrate, with glandular tip.

terminal or lateral in axils of bracts or leaves, determinate or indeterminate, dichasia (Haloragis and Proserpinaca), or simple racemes (Myriophyllum);

bracts and bracteoles present.

bisexual or unisexual, staminate and pistillate usually on same plant, sessile or pedicellate (sometimes sessile in pistillate flowers of Myriophyllum);

perianth and androecium epigynous;

hypanthium subglobose;

sepals persistent, (3 or)4, sometimes rudimentary (Myriophyllum), petals often caducous, sometimes persistent, (3 or)4, or 0 or rudimentary (Proserpinaca), keeled, cucullate, often distally cupulate;

stamens 3–8 (1 or 2 times as many as sepals);

anthers basifixed, dehiscing longitudinally;

pistil 1, 3- or 4-carpellate;

ovary 1, inferior, 1–4-locular;

placentation axile;

styles 1 per locule;

stigmas 1 per locule, clavate, capitate, fimbriate;

ovules 1(or 2, in Haloragis and Proserpinaca), anatropous, bitegmic, crassinucellate.

sepals green to cream, ovate to deltate, (0.2–)0.3–0.5(–0.7) × (0.1–)0.2–0.4(–0.5) mm;

petals persistent, ± purple, oblong, 2–3 × 0.5–1.5 mm;

stamens 8, filaments to 0.6 mm, anthers 1.8–2.5 × 0.2–0.6 mm.

sepals cream, deltate, 0.2–0.5 × 0.1–0.4 mm;

petals ± persistent, cream, ± cucullate, elliptic, 0.1–0.5 × 0.2–0.3 mm;

pistils 1.1–2.2 mm, stigmas cream to ± purple, to 0.6 mm.

cylindric to oblong, 4-lobed.

a nutlet, indehiscent, or schizocarp, splitting into (2–)4 mericarps;

exocarp glabrous, scabrous, rugose, tuberculate, or papillate, sometimes with ribs, ridges, or wings.

1 per locule;

embryo straight, cylindric;

endosperm ± copious and fleshy.

tan to olive-brown, cylindric to ovoid, 1.5–1.8 × 0.6–0.8 mm, transversely elliptic, abaxial surface rounded, smooth, sometimes with a shallow, longitudinal ridge, wings and ribs absent.

= 42.