2n = c. 28

Leaves of two kinds: submersed, narrow-elliptic, ± translucent; floating, often long-petiolate, mostly broad-oval, firm and opaque, longitudinal nerves c. 11-(13). Spike (1)-2-2.5 cm long, dense. Achenes flattened with 3-ridged keel, green to brown.

Rhizome sparsely branched, rooting at nodes and producing mostly simple lfy branches that reach up to surface of water. Stipules membr., free, open. Submersed lvs us. rather distant, us. shortly petiolate; lamina c. 4–6–(10) × (0.5)–1–1.5 cm., elliptic, entire, subacute, delicate and translucent, longitudinal nerves c. 5–(11), joined by irregular cross veins. Floating lvs often long-petiolate; lamina (2)–3–4 × (1)–1.5–2.5 cm., broad oblong-oval, entire, us. quite obtuse, firm and opaque, longitudinal nerves c. 11–(13) in all, laterals emerging from petiole rather than from midrib. Peduncles in axils of floating lvs, stout, erect, us. projecting several cm. above surface of water at fl., submersed in fr. Spike (1)–2–2.5 cm. long, dense. Achene c. 2.5 × 1.5 mm., moderately flattened with rather strongly 3-ridged keel and short straight beak.