Potamogeton cheesemanii

Emergent herb; stem erect; branches flattened, up to c. 2 m long. Leaf sheath free, up to 4 cm long, soon torn; ligule absent. Submerged leaves different from emergent ones. Submerged leaves thin and translucent, sessile or very shortly petiolate; lamina lanceolate to elliptic, 5–10 cm long, 0.5–2.5 cm wide; base rounded to gradually tapered; margin flat or slightly undulate; apex obtuse to tapering; 5–12 principal longitudinal veins, with finer transverse secondary veins; distal submerged leaves more like emergent leaves, but with petiole much longer than for emergent leaves. Emergent leaves floating, ± thick and leathery, petiolate; lamina ovate to lanceolate, 1.5–5.0 cm long, 1.5–3.5 cm wide, dull; base rounded to cordate; apex obtuse to apiculate; margin flat; 10–20 principal longitudinal veins, with transverse secondary veins indistinct. Inflorescence c. 12–24 flowered. Infructescence 1.0–2.5 cm long (excluding non-fruiting part of axis). Fruiting carpels 2–3 mm long (including distal point), dorsal surface with a ± prominent, smooth to crenulate  keel and 2 smooth lateral ridges that are sometimes low or not developed, distally with a ± straight to curved point up to c. 0.7 mm long. Flowers and fruits Sep.–Apr.