Cycnogeton rheophilum (Aston) Mering & Kadereit

Perennial aquatic herb. Rhizome woody, fibre-covered, 4–14 mm thick. Tubers usually elongated, 11–102 mm long, 2–11 mm diam.; terminating roots c. 2.5–18 cm long. Leaves linear, usually submerged and isolateral and trailing in fast-flowing water, 41–450 cm long, 2–16 mm wide, thin-textured; basal sheath tapered; T.S. c. 3 cm below sheath summit linear to thinly plano-convex, with width of central portion c. 4.5–21 times its thickness and with sheath margins narrow, usually less than 1/4 of leaf width, mostly tightly inrolled, never meeting across blade face; leaves sometimes dorsiventral and glossy above when stranded. Scape at fruiting submerged, trailing, often semi-flattened, 14–79 cm long, 2–18 mm diam. Infructescence a raceme, 5–36 cm long, 15–35 mm diam.; pedicels 2.5–9 mm long. Fruits c. 20–232 per infructescence, ± ellipsoid, 9–16 mm long, 5–9.5 mm diam. Carpels 6 (or 7), normally all maturing; central axis absent; mature carpels attached along 63%–70% of length, straight or sometimes twisted, with a prominent, narrow-convex, dorsal ridge and 2 broad-convex lateral ridges, the latter sometimes absent.

Inhabits clear flowing fresh water to 1 m deep in permanent, often rocky, streams and rivers usually subject to severe flooding; typically in wet sclerophyll forest with thick shrub understorey. Recorded to c. 970 m alt.

The tubers are roasted and eaten. They can be pounded to a paste. The young green seeds are eaten. The leaf stems are baked with fish.