The Wavy Marshwort is in family Menyanthaceae.
Native to Australia it is widespread over Queensland.
They are perennial (annual) aquatic herbs.
They have horizontal stems or stolons that lie along the bottom and root at the nodes.
The vertical stems arise from the stolons.
There are a few leaves at the base of the stem with petioles up to 40 cm long.
Blades of the basal leaves, 3 to 10 (15) cm across are widely ovate to circular with a heart-shaped base and blunt teeth on the edge.
Leaves alternating up the stems have shorter petioles and smaller blades that are more kidney-shaped.
The blades float on the surface of the water.
Inflorescences are lateral or terminal.
The lateral ones are a few pairs of flowers along a stem and terminal ones are clusters of up to 15 (20) flowers.
Flowers, with parts in 5’s (rarely 4’s or 6’s) are on stalks or pedicels 5 to 10 cm long.
The calyx is from 5 to 15 mm long with the triangular lobes having a pointed tip.
The petal bases are fused into a short tube.
The corolla of spreading bright yellow lobes is up to 5 cm across.
The wide wings on the lobes are deeply cut making a long fringed edge.
There is a central keel with a long fringe across the base and partly up the keel.
Flowers on a plant have styles of different lengths.
There are 5 (2 to 4) stigmas each with a wing that runs down the style.
The ellipsoidal capsules, up to 1 cm long have around 100 seeds.
The brown seeds may be smooth of have small nodules.