Calyx conspicuous, the outer 2 sepals subulate, ± 0.75 mm., longer than the inner 3.
Umbels on ± 2.5–7 cm. peduncles, 4–9-rayed, the rays ± 8–18 mm., usually minutely scabrid above; involucre absent; partial umbels ± 9–20(–25)-flowered; pedicels very short, ± 1–2 mm.; involucel of ± 6–8 narrowly linear bracteoles 1.5–3 mm. long, not exceeding the flowers.
Lower leaves with the lamina deltoid in outline, ± 3–7 × 3–6 cm., pinnate with the lower leaflets deeply incised or frequently bipinnate with 2–3 pairs of pinnae of which the lower are stalked, pinnules 1–2 pairs; leaflets ovate to oblong-ovate, obtuse to subacute, ± 5–20 × 3–15 mm., frequently some incised on one side (or the apical on both), serrate with very shortly mucronate teeth; sheaths narrowly oblong, striate, rounded or auriculate above, ± 1–1.5 cm., with broad, pale-membranous margins; petiole ± 0.5–2.5 cm.; upper leaves similar but sessile and usually the uppermost simply pinnate only.
Ascending, glabrous perennial herb with the lower part of the stem long-prostrate and rooting in the mud, ± 0.25–0.7 m. from the uppermost rooting node to the tip of the plant.
Stem fistular, succulent, coarsely ribbed and furrowed, with 0–few branches; internodes to ± 12 cm.
Fruit oblong-ovate, ± 3 × 2 mm., rather tumid, the marginal ribs much broader and blunter than the dorsal 3, curving round on to the commissure; stylopodia small, discoid; styles slender, ± 1–1.25 mm.; vittae 8, 1 in each dorsal vallecula and 2 beneath each marginal/commissural rib.