Vegetative key to the families

Submerged plants rooted in mud. Leaves submerged or floating on the surface or sometimes the leaf blades held erect above the water surface. Freshwater or marine (Amphibious plants are not included in this group)
Leaves opposite or whorled on an elongated stem
Leaves entire or toothed or almost pinnatifid
Broad stipules present. Leaves 2–7 cm long. Salt water plants (Halophila) Hydrocharitaceae
Stipules small or absent. Fresh or brackish water plants