Ceratophyllum demersum Rigid Hornwort

A submerged, rootless, perennial aquatic plant with toothed forked filamentous leaves that are divided 2 or 3 times at their tips (see photo). It grows in neutral or alkaline mesotrophic and eutrophic water and can be abundant in slow-flowing water courses such as canals where it may form dense mats at the surface. Plants are monoecious and the water-pollinated flowers are tiny but produced infrequently. Consequently, seed production is rare and it reproduces mainly by vegetative fragmentation. It is widespread and common in much of the southern half of Britain but it is scarce and largely coastal in much of Wales and absent from the uplands. It has a scattered distribution in West Glamorgan where it is locally abundant in canals.

Native