Ceratophyllum demersum

About

Ceratophyllum demersum, commonly called hornwort or coontail, is a species of flowering plant in the genus Ceratophyllum. Ceratophyllum demersum is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents except Antarctica. It is a harmful weed introduced in New Zealand. It is also a popular aquarium plant. Its genome has been sequenced to study angiosperm evolution.

Summary from Wikipedia