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
Leaves 1–3 cm long. Whole plants 5–20 cm long. Rhizome rootless, bearing leaves in whorls of three, the third leaf of each whorl being finely dissected and serving as a root Salviniaceae