Partially or wholly submerged herbs, sometimes marine Hydrocharitaceae
Ovary inferior; male flowers with more than 1 stamen
Fresh water plants
Leaves all basal arising from a rootstock growing on the bottom of a stream or pond
Leaves linear, ribbon-like. Flowers unisexual; petals in female flowers rudimentary Vallisneria
Leaves elliptic. Flowers bisexual; petals larger than the sepals Ottelia