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 3 mm wide or wider; ligule acuminate. Spikes dense, 2–3 cm long. Widespread. Fl. spring–summer Potamogeton ochreatus