The class Lemnetea includes species-poor aquatic vegetation of free-floating macrophytes, which are not rooted in the bottom. They can be either natant (floating on the water surface) or submerged. Natant species include small lemnids, aquatic ferns and liverworts, but there are also large floating species such as Hydrocharis morsus-ranae and Stratiotes aloides. Submerged floating macrophytes include Lemna trisulca, species of Ceratophyllum, Utricularia and liverworts. This vegetation occurs in eutrophic to mesotrophic water bodies. It is widespread all over the world including the tropics. In the Czech Republic it is common, especially at low to middle altitudes.