Hydrocharitaceae is a flowering plant household including 16 known genera with a total of ca 135 known species (Christenhusz & Byng 2016), that including a variety of species of aquatic plant, for example, that the tape-grasses, the recognized Canadian waterweed and frogbit Hydrocharis morsus-ranae.

The family includes both freshwater and aquatics. They Are tropical, although are found around the world in a selection of habitats.

Description

The species are Yearly or perennial, with a creeping monopodial rhizome using the leaves arranged in two vertical rows, or an vertical Principal shoot with roots In the bottom and spirally arranged or whorled leaves. The leaves are found underwater, even though they might be found floating or emersed and simple. Just like many aquatics they may be extremely variable in shape — from linear to orbicular, with or without a petiole, and with or without a sheathing base.

The blossoms are organized in a forked, spathe-like bract Or between two bracts. Though they could be irregular, and bisexual or unisexual, they are irregular. The perianth segments are in 1 or 2 series of (2–)3 free sections; the interior series when present are usually showy and petal-like. Stamens 1–numerous, in 1 or more series; the internal ones occasionally sterile. Pollen is globular and free but at the marine genera (Thalassia and Halophila) — the pollen grains are carried in chains, such as strings of beads. The ovary is poor with two –15 combined carpels comprising one locule with many ovules on parietal placentas which protrude nearly into the middle of the ovary or are incompletely developed. Fruits are globular to linear, dry or pulpy, dehiscent or more usually indehiscent and opening by corrosion of the pericarp. Seeds are normally numerous with direct embryos and no endosperm.

Pollination can be specialised.

The most recent phylogenetic treatment of the family recognizes four subfamilies — Hydrocharitoideae (Hydrocharis, Limnobium), Stratiotoideae (Stratiotes), Anacharioideae (Apalanthe, Appertiella, Blyxa, Egeria, Elodea, Lagarosiphon and Ottelia) and Hydrilloideae (Enhalus, Halophila, Hydrilla, Maidenia, Najas, Nechamandra, Thalassia and Vallisneria).

Uses

Some species have become established decorative plants, and then serious weeds in the wild (especially Egeria, Elodea and Hydrilla).