Monilophyta >

Sporangia scattered over the lower surface of the lamina, or 2-3(-4) fused into synangia in the axils of 2-lobed scale-like or leaf-like appendages, or rarely in terminal strobili, then the sporangia hanging from a peltate structure. Monilophyta
Whole plants floating with the roots or root-like submerged leaves suspended in the water
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