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 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.

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.

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.

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 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.

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 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 and petals rudimentary or absent;

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

subglobose, 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.

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

= [14] 21.