- hornwort - any aquatic plant of the genus Ceratophyllum; forms submerged masses in ponds and slow-flowing streams
--1 is a kind of aquatic plant, water plant, hydrophyte, hydrophytic plant
--1 is a member of Ceratophyllum, genus Ceratophyllum- hornwort - liverworts with slender hornlike 2-valved capsules
--2 is a kind of liverwort
--2 is a member of Anthocerotales, order Anthocerotales - hornwort - liverworts with slender hornlike 2-valved capsules