Najas tenuifolia

Herb up to 1 m long; monoecious. Leaves 14–27(–50) × 0.2–1(–3) mm, length to width ratio 30–62; sheath with auricle triangular to narrowly triangular; lamina margin with teeth up to c. 0.1 mm long, dorsal surface without teeth; leaf-sheath scales narrowly triangular to linear-triangular. Flowers 1–3 together. Male flowers with outer cup-like structure 2–3.8 mm long. Female flowers (1–)1.5–3.5(–4) mm long; stigmas 2. Flowers Jan.–Mar., or irregularly.