Perennial herbs; rhizome slender. Stem to 30 cm, simple or rarely sparsely branched. Leaves dimorphic. Submerged leaves petiolate, translucent, upper usually opposite, alternate below, elliptic or narrowly elliptic, apex obtuse to acute, base cuneate, shorter or longer than petiole, with 11−19 longitudinal veins and many fine cross-veins visible against light, herbaceous. Stipules free, mostly decaying at flowering, acute, up to 3.5 cm long. Floating leaves petiolate, lanceolate to ovate-lanceolate or broadly elliptic, 3.5−8.5 x 1.5−4 cm. Peduncles stiff, tapering slightly upward, 3−13 cm. Flowers green-brownish in dense spikes, 1.5−5 cm. Carpels 1−2 per flower. Drupelets 3−4 mm long, broadly obovoid, usually with 3 wavy keels, lateral keels prolonged into tubercles at top and bottom, medium with tubercle only at base, ventral face curved, dorsal face semicircular, beak less than 0.5 mm.

 Distribution:  Nepal, E Himalaya, Tibetan Plateau, E Asia, SE Asia, Pacific Island.

Altitudinal range: 900−3000 m. 

Ecology: Occurs in ponds, pools, marshes and slow running rivers, also as a weed of rice field. 

Flowering and fruiting time: July−October. 

Potamogeton acuminatus Schumach.

Perennial submerged herbs; rhizome slender to robust. Stem terete, elongated, sparsely branched. Leaves submerged, sub-sessile to shortly petiolate, translucent,  elliptic or obovate-elliptic to narrowly elliptic-oblong, cuneate at the base, apex acute or acuminate or cuspidate, more or less distinctly serrulate, 7−9 x 1.5−1.8 cm, with regularly ascending secondary veins (occasional leaves reduced to phyllodes), midvein thickened and conspicuous, without rows of lacunae bordering midvein. Petiole 0.5−1.5 cm. Stipules axillary, large and conspicuous, herbaceous, to 4 cm, free from leaf base. Peduncles to 5 cm, stiff, thickened upwards. Spikes to 3 cm, densely flowered, with many whorls of somewhat opposite flowers. Carpels 4, free. Drupelets ovoid or obovoid-rounded, lateral sibs obscure, 3−4 mm, abaxial keel distinct, beak short.

 Distribution: Nepal, Tibetan Plateau, Assam-Burma,  E. Asia, SE. Asia, N Africa, Europe.

 Altitudinal range: 2300−3400 m.

 Ecology: Submerged in lakes and ponds.

 Flowering & fruiting time: May–August.

     Potamogeton affinis Boenn. ex Cham. & Schlecht.

 Perennial herbs; rhizome slender to robust. Stems to 40 cm, slender to robust. Leaves dimorphic. Floating leaves alternate, translucent, up to 4−8 x 1.6−3.6 cm, ovate to elliptical or lanceolate, cuneate to sub-cordate at the base; petiole often longer than the lamina, up to 10.5 cm long with a discolored flexible joint and distinct angle at the top of petiole, immediately below the lamina. Submerged leaves less than 3 mm wide, reduced to narrowly linear, obtuse, without expanded blade, often disappearing early. Stipules free large, up to 5 cm, closely veined, often fibrous-persistent. Peduncles 3−8 cm, stiff. Flowers many in spikes, 2−3 cm. Perianth segments 4, suborbicular, clawed. Stamens 4. Carpels 4. Drupelets 2−4 mm, dorsally convex, keeled, beak short, stout.

Distribution: Nepal,  E Himalaya, Tibetan Plateau, Assam-Burma, SW Asia, N Asia, Europe, and North America.

Altitudinal range: 900−4400 m.

 Ecology: Occurs in pond.

 Flowering time: June−July. Fruiting time: July−September.

     Potamogeton indicus Roxb.

 Perennial herbs; rhizome slender with apical dormant buds. Stem to 35 cm, simple or rarely sparsely branched. Leaves floating, upper usually opposite, alternate below, elliptic, oblong-ovate, elliptic-suborbicular or elliptic-lanceolate, apex obtuse to acute, base cuneate or rounded, 3.7−12 x 2−4 cm, shorter or longer than petiole, with 11−16 longitudinal veins and many fine cross-veins visible against light, coriaceous. Petiole up to 8 cm. Stipules free, mostly decaying at flowering, acute, to 4 cm long. Peduncle stiff, tapering slightly upward, 3−10 cm. Flowers in dense spikes, 3.5−5.5 cm. Perianth segments 4, suborbicular, entire, obtuse, clawed. Stamens 4. Carpels 4. Drupelets obliquely ovoid, 3−4 mm long, usually with 3 wavy keels, lateral keels prolonged into tubercles at top and bottom, medium with tubercle only at base, ventral face curved, dorsal face semicircular, beak less than 0.6 mm.

 Distribution: Nepal, E Himalaya, W Himalaya, Tibetan Plateau, Assam-Burma, S Asia, E Asia, SE Asia, Africa, Europe, North and South America, Pacific islands.

 Altitudinal range: 200−3000 m.

 Ecology: Occurs in lakes and roadside pond, leaves floating on surfaces.

 Flowering and fruiting time: May−October. 

Potamogeton heterophyllus Lour.

 Annual or perennial herbs; rhizome minute or absent. Stem to 30 cm, filiform, branched. Leaves dimorphic. Floating leaves petiolate, membranous, narrowly oblong, elliptic−ovate, ovate-oblong or lanceolate, 10−35 x 3−8 mm with 5−7 longitudinal veins, coriaceous; submerged leaves narrowly linear to filiform, gradually narrowed to acute apex, under 1mm wide, 3-veined, with air spaces (pale against light) on both sides of midrib. Petiole 5-15 mm. Stipules axillary, convolute, membranous, free from leaf base. Peduncles stiff, to 2.5 cm long. Spikes to 0.5 cm, slender, densely flowered. Flowers minute. Perianth segments 4, obovoid or suborbicular, clawed. Anthers 4, adnate to claw. Carpels 4, free. Drupelets ca. 1.7 mm, subglobose, dorsal face curved with a distinct shoulder, ventral face angled, 3−keeled, all keels tubercled at base, lateral keels with additional tubercles, beak conspicuous.

Distribution: Nepal, E Himalaya, Tibetan Plateau, Assam-Burma, S. Asia, , SE Asia, Africa, Australia.

Altitudinal range: 600−3000 m.

Ecology: Occurs in pond.         

Flowering and fruiting time: July−September.

Potamogeton amplexicaulis Kar.

 Perennial submerged herbs; rhizome slender. Stems to 30 cm, branched or simple. Leaves submerged, usually alternate below, opposite above, sessile, suborbicular, ovate, broadly lanceolate or orbicular-ovate, base cordate-amplexicaul, 1.8−3 x 1−1.8 cm, margin entire or minutely denticulate, rounded to obtuse at the apex, 2−9 veined, thin, translucent. Stipules free, small, less than 1 cm long. Flowers green. Spikes to 2 cm, densely flowered. Peduncles stiff, 2−3 cm. Perianth segments 4, elliptic-obovate or suborbicular, clawed. Stamens 4. Carpels 4, free. Drupelets subglobose, 2−3.5 mm long, 1.5−2 mm broad, beaked, ventral area convex, irregular or slight, beak more or less keeled.

 Distribution: Nepal, Tibetan Plateau, S. Asia, E Asia, SE. Asia, Australia, Central and North America, Europe.         

Altitudinal range: 2800−3400 m.

Ecology: Occurs in lakes and ponds.

Flowering & fruiting time: July−September.

     Potamogeton tenuissimus Hook. f.

 Annual submerged herbs; rhizome absent. Stems to 25 cm, filiform, terete or compressed, sparsely to densely branched. Leaves submerged, sessile, narrowly linear, less than 3 mm broad, mucronate (involucral leaves sometimes slightly dilated at the apex), 3−veined, the lateral veins inconspicuous; nodal glands absent or feebly developed. Stipules axillary, free, connate, membranous and translucent, tubular towards the base. Peduncles to 3 cm, stiff. Spike 1 cm with 2−4 whorls of opposite flowers. Perianth segments 4, suborbcular, clawed. Stamens 4. Carpels 4, free. Drupelets obovoid or obliquely elliptic, 1−2 mm.

 Distribution: Nepal, E Himalaya, Tibetan Plateau, Assam-Burma, S. Asia, SW Asia, E Asia, SE Asia.

 Altitudinal range: 2100−3000 m.

 Ecology: Submerged in lakes and ponds.

 Flowering and fruiting time: July−September.