Rorippa Scop.
Fruit less than 25 mm long
Perennials. Stems procumbent, hollow, rooting below then ascending or floating in water. Leaf segments with undulate margins. Flowers in short terminal racemes. Petals white, twice as long as the sepals. Pedicels and fruits spreading or curved upwards. Fruit valves with an inconspicuous vein
Seeds in 2 distinct rows in each loculus, with c. 25 depressions on each face of the testa. Fruit 10–18 mm long. Widespread. Usually in water. Introd. from Europe and W. Asia. Water Cress Rorippa nasturtium-aquaticum
Seeds ± in 1 row in each loculus, with c. 100 depressions on each face of the testa. Fruit 15–22 mm long. Widespread. In or near water. Introd. from Europe and W. Asia Rorippa microphylla