Subclass Alismatidae is a taxonomic group that includes aquatic and marsh plants such as water lilies and arrowheads. Synonyms for this term include the Alismatanae subclass and the Alismataneae order. Other related taxonomic categories within this group include the family Alismataceae, which contains many of the plants traditionally referred to as water lilies. These plants are characterized by their large, showy flowers and broad, floating leaves. While the term subclass Alismatidae may not be widely recognized outside of botanical circles, it is an important classification for researchers studying the diversity and evolution of aquatic plants.