Ceratophyllum demersum L.
hornwort
Delicate submerged or floating aquatic herb; stems 30-150 cm long. Lvs whorled, dark green, stiff, 1-2× forked, 10-30 mm long; segments filiform to linear, denticulate, bristle-tipped. Nut black, 4-5 mm long; face smooth; basal spines 2, reflexed; terminal spine (style) 4-6 mm long.
N.: Northland, Auckland, Waikato, Hawke's Bay, Wellington.
Cosmopolitan 1969
Drains, lakes, lagoons, slow-moving rivers.
Hornwort may be confused with Myriophyllum spp. which it superficially resembles. However in Myriophyllum the lvs are pinnate whereas in Ceratophyllum they are dichotomously forking. The reduced fls are specialised for underwater pollination and the pollen is smooth, thin walled and inaperturate.
