Partially or wholly submerged herbs, sometimes marine Hydrocharitaceae
Ovary inferior; male flowers with more than 1 stamen
Fresh water plants
Leaves cauline, opposite or whorled, on elongated occasionally branched submerged stems with adventitious roots. Flowers unisexual, axillary
Leaves serrulate, often crisped on the margins. Styles undivided, free to the base Hydrilla
Leaves with entire or minutely denticulate margins. Styles in female flowers lobed or notched