A genus of about 5 species, aquatic herbs, nearly cosmopolitan.
ID notes:Zannichellia is sometimes confused with other aquatics, such as Ruppia and narrow-leaved Potamogeton. Potamogeton has at least some leaves alternate; Zannichellia and Ruppia are opposite-leaved. Zannichellia lacks the abruptly broadened sheath of Najas. Also, the seeds are flattened in Zannichellia, and toothed down one side; Najas has a cylindric or elliptic fruit. Zannichellia has longer leaves (3-10 cm long) than Najas (< 4 cm long).