A rather small family of aquatic plants, some of them marine and most of them native in warm or tropical regions. All of our species are dioecious and are pollinated at the surface of the water.
1. Leaves floating, blades orbicular with a ± cordate base.
1. Leaves submerged, linear.
2. Leaves very long and ribbon-like (mostly 3–11 mm wide and many times as long), in a basal rosette.
2. Leaves up to 6 (–12) cm long, opposite or whorled.
3. Leaves whorled, entire.
3. Leaves opposite, minutely denticulate to visibly toothed.
All species found in Hydrocharitaceae
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. November 21, 2017. http://michiganflora.net/family.aspx?id=HYDROCHARITACEAE.