Ceratophyllum

Ceratophyllum (commonly known as coontails) are a cosmopolitan genus of flowering plants commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. It is the only extant genus in the family Ceratophyllaceae, itself the only extant family in the order Ceratophyllales. They are often called "hornworts", although the second name is also used for Anthocerotophytes (which have a distinctive horn-like sporophyte). Coontails lack anything resembling a horn, so to avoid confusion, calling them "hornworts" is strongly discouraged. Ceratophyllum grows completely submerged, usually, though not always, floating on the surface of the water. The plant stems can reach 1–3 m in length. At intervals along nodes of the stem they produce rings of bright green leaves, which are narrow and often much-branched. The forked leaves are brittle and stiff to the touch in some species, softer in others. Roots are completely absent and are missing even in the embryonic stage, but sometimes they develop modified leaves with a rootlike appearance, which anchor the plant to the bottom. Stomata are not present on any species.