Wolffia Horkel ex Schleid.

Roots absent Wolffia
Cladode widest just below the water surface, globular to ovoid, less than twice as deep as wide, up to 0.7 mm long, green at the edge and paler in the centre, usually with less than 25 stomata on the upper surface, flat near the apex, acute at the edges. Widespread. Still water Wolffia globosa