Petiole varying greatly in length according to depth of water; leaf blade wholly submerged, varying greatly in shape and size, usually broadly ovate, ovate-elliptic, suborbicular, cordate, or sometimes lanceolate, ca. 20 × 18 cm or more, membranous. Flowers bisexual or plants occasionally dioecious-polygamous. Spathe 2.5-4 × 1.5-2.5 cm, 2- or 3-lobed at apex, with 3-6 longitudinal wings. Flowers solitary, sessile. Petals white, slightly purple, or bluish. Stamens 3-9(-12); filaments glandular hairy; anthers narrowly oblong, 3-4 mm. Ovary subglobose, with 3-9(or 10) carpels; styles 6-10, deeply 2-lobed. Fruit 2-5 × 0.8-1.8 cm. Seeds fusiform, 1-2 mm, densely hairy. Fl. and fr. Apr-Oct. 2n = 44.
Leaves submersed; blade lanceolate to widely ovate, to 17 ´ to 20 cm, margins entire to crisped. Inflorescences 1-flowered; spathes 3--10-winged. Flowers: sepals10--15 ´ 2--9 mm; stamens 3--12; ovary 1, 3--9-carpellate. Fruits 15--40 mm. Seeds to 2000.
Monoecious, dioecious or hermaphrodite, annual or perennial.
Nodal scales 4–10 per leaf, ovoid to conical.
Mature leaves petiolate; blade submerged or floating, elliptic to widely ovate, 8–17 cm. long, 5.7–20 cm. wide, acute to obtuse or rounded, cuneate to cordate or somewhat involute at base, smooth, with 2–10 prominent longitudinal veins connected by cross-veins, together with many smaller longitudinal veins; leaf-margins entire or denticulate.
Juvenile leaves linear to obovate or spathulate.
Stems corm-like, simple or rarely forked.
Ovary of 3–10 carpels, narrowly ellipsoid, 0.7–2.2 cm. long, ± 0.7 cm. wide; perianth-tube 0.6–0.8 cm. long, styles 3–10; stigmas 6–20, up to 6 mm. long, yellowish.
Fruit ellipsoid to ovoid, rarely cylindric, 1.5–4(–5) cm. long, 1–2 cm. wide, opening by decay of the pericarp.
Petals ovate to orbicular, 1.8–3 cm. long, 0.5–1 cm. wide, rounded or obcordate, white, white with yellow base, yellow, pink to purple.
Stamens 3–12; anthers 2.5–4.5 mm. long, yellowish; filaments up to 6 mm. long; staminodes filiform or 2-lobed, up to 4.8 cm. long.
Seeds narrowly cylindric, 0.9–1.3 mm. long, 0.3–0.5 mm. wide, dark purple to black, with longitudinal striations.
Male flowers several per spathe, with pedicels up to 7 cm. long; ♀ and hermaphrodite flowers sessile.
Sepals narrowly triangular to ovate, 0.6–2.4 cm. long, 1.8–5.7(–9) mm. wide, subobtuse to rounded, green, the margin often hyaline.