Azollaceae >

Leaves minute, up to 1.5 mm long. Whole plants 0.8–6 cm long. Rhizome with numerous roots, bearing leaves in two alternate rows Azollaceae
Roots simple. Plants irregularly pinnate. Massulae of the microsporangia spherical, with numerous barbed processes borne on all sides. Megasporangia each with 3 apical swimming floats. Widespread. Floating on slow-moving or stagnant water Azolla filiculoides