Aquatic herb.. Rhizomes slender to robust, terete, pink to orange brown, perennial, abundantly branched, with internodes up to 8 cm long; with apical scaly turions.. Stem terete, up to 1 m long, mostly unbranched, rooting along the nodes, annual.. Submerged leaves decaying early, generally not present on adult plants, rarely 1 or 2 at the fruiting stage; petiole (10– )45– 180 mm long, 0.2– 1.8 times as long as the lamina; lamina bright green to dark green, lanceolate to oblong, sometimes almost reduced to phyllodes, 80– 200 mm long, 5– 27 mm wide, 5– 13 times as long as wide, 5– 9(– 15)-veined, with narrow rows of lacunae bordering the midrib, entire at margins, narrowly cuneate at base, gradually narrowed towards an obtuse apex, never mucronate.. Intermediate leaves often present; floating leaves always present on adult plants; petiole 18– 110(– 200) mm long, (0.3– )0.6– 3 times as long as the lamina, often with a discoloured section at the junction with the lamina, though sometimes only on some leaves or not apparent; lamina green, brownish green to dark green, or ± pinkish, elliptical to oblong-ovate, 30– 80(– 124) mm long, (11– )20– 40(– 48) mm wide, 1.6– 3.5(– 5) times as long as wide, opaque, coriaceous, 11– 25-veined, broadly cuneate to rounded at base, broadly acute at apex, entire at margins; stipules axillary, robust, convolute, 25– 40(– 60) mm long, translucent, persistent as grey fibres after decay.. Peduncles inserted in the axils of floating leaves, 50– 100 mm long, 2– 3.5 times as long as the fruiting spike, as thick as the stem or slightly thinner, a little pale brown tinged; spikes emergent, cylindrical, sometimes crooked, 30– 50 mm long in fruit, contiguous.. Flowers numerous; tepals pale green; anthers white to yellowish; carpels 4.. Fruitlets green to pale brown, (3.2– )3.9– 5.2(– 5.5) mm long, 2.1– 3.3 mm wide, ventrally straight, dorsally convex, distinctly 3-keeled.. Stem anatomy: stele of trio type, endodermis of U-type, interlacunar bundles present in (1– )2(– 3) circles, subepidermal bundles mostly present, pseudohypodermis present, 1-layered.. Fig. 4 (p. 14).
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Floating leaves always present on adult plants, which never flower and fruit in the absence of floating leaves; lamina coriaceous, light green to deep green or sometimes olive green, occasionally slightly shiny, sometimes brownish or secondarily blackish (when dried slowly), oblong to broadly elliptical, mostly rounded or sometimes broadly cuneate at base; petiole sometimes narrowly winged towards the lamina, often with a discoloured section on its upper end at the junction with the lamina, though sometimes only on some leaves or not very apparent. Intermediate leaves, similar in shape to floating leaves, sometimes develop just below the water surface. Submerged leaves decaying early, generally not present on adult plants, rarely one or two are present at the fruiting stage, often partly rotten, short to long petiolate; lamina membraneous, narrowly oblong to linear-lanceolate, sometimes almost reduced to phyll-odes, mid green to blackish, 5-9(-15)-veined, gradually narrowed towards a narrowly obtuse apex, never mucronate; petiole often narrowly winged towards the lamina, mostly 5-15 cm long, exceptionally up to 23 cm long, 0.3-2 times as long as the lamina. Stipules robust, widest near the base and gradually narrowing towards the apex, persistent grey fibres remain after they decay. Peduncle as thick as or sometimes even thinner than the robust stem. Fruits (3.7-)3.9-5.2(-5.5) mm long, ochre brown to pale brown or seldom dark blackish brown or greenish brown, rarely with reddish-brown tinge, with acute and high distinct dorsal keel and often with a pair of low lateral keels or ridges.
Perennial, aquatic herb, up to 1 m high. Leaves with petioles of two kinds: submerged leaves disappearing early, not present in mature plant; floating or aerial leaves with blade elliptic to oblong-ovate, margins smooth, leathery, veining indistinct, usually with a discoloured section at junction of petiole and blade. Flowers: in many-flowered spikes; Nov.-Mar. Fruit 4-5 mm long.
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