4-18 Potamogetonaceae, pondweed family

Abstract

Only two genera form the pondweeds, numbering about 90 species worldwide. All have perfect flowers arranged in a spike or head. Perianth is absent; flowers are four-merous. Some species exhibit heterophyllous leaves. An important character is the presence or absence of lacunae, rows of colourless cells on either side of the central axis. All perennial, they are an important food source for waterfowl. Photograph use donated by Roger Lloyd, David Mazerolle, Ross Hall and Sean Blaney.