Leaves elliptical, obovate or round, 7–30(–40) mm long, folded along mid vein, frequently overlapping, pale green to greenish brown; margins entire; apex obtuse; upper surface with elongate papillae. Plants apparently sterile, occasionally producing deformed unviable spores; when present, microsporcarps numerous, in 2 rows along lobes of submerged leaf and 2–3 megasporocarps at the base of fertile leaf segments.
VVP, VRiv, GipP. Also naturalised WA, SA, NT, Qld, NSW. Native to the Neotropics. This species has become invasive in Australia. Occurs in still or slow moving water, where it can grow rapidly, forming dense mats that cover the surface of waterways. Plants are thought to be of hybrid origin, reproducing vegetatively by fragmentation (McCarthy 1998). It should be eradicated wherever found.
