Potamogeton L. >
Inflorescence usually more than 2-flowered. Carpels 4. Mature fruit ± sessile Potamogeton
Leaves sessile or nearly so, all alike, submerged, membranous
Leaves lanceolate or oblong to linear. Spikes ± interrupted. Flowers few. Fruiting carpels distinctly beaked
Leaves almost or quite flat, with entire margins, linear to narrow-oblong. Fruit with a beak shorter than the fruit.
Leaves up to 1 mm wide; ligule long, obtuse. Spikes interrupted, with the flowers in few-flowered globular groups, 2–5 cm long. Widespread. Fl. spring–aurumn Potamogeton pectinatus