Hydrocharitaceae is a flowering plant

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

 family that includes a number of species of aquatic plant

Aquatic plant

Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...

, broadly called the Tape-grasses, and includes the well known Canadian Waterweed and Frog's Bit.

The family includes both fresh and marine aquatics. They are found throughout the world in a wide variety of habitats, but are primarily tropical.

The species are annual

Annual plant

An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...

 or perennial

Perennial plant

A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...

, with a creeping monopodial rhizome

Rhizome

In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

 with the leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 arranged in two vertical rows, or an erect main shoot with root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s at the base and spirally arranged or whorled leaves. The leaves are simple and usually found submerged, though they may be found floating or partially emerse. As with many aquatics they can be very variable in shape - from linear to orbicular, with or without a petiole

Petiole (botany)

In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...

, and with or without a sheathing base.

The flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s are arranged in a forked, spathe-like bract

Bract

In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...

 or between two opposite bracts. They are usually irregular, though in some case they may be slightly irregular, and either bisexual or unisexual. The perianth

Petal

Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...

 segments are in 1 or 2 series of (2-)3 free segments; the inner series when present are usually showy and petal-like. Stamen

Stamen

The stamen is the pollen producing reproductive organ of a flower...

s 1 - numerous, in 1 or more series; the inner ones sometimes sterile. Pollen

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

 is globular and free but in the marine genera (Thalassia

Thalassia

Thalassia may refer to:*Thalassia, Greece, a prefecture in Greece*Thalassia , a genus of seagrass commonly known as "turtle grass"*Thalassia , a queen of Characene...

and Halophila

Halophila

Halophila is a genus of seagrasses in the family Hydrocharitaceae, the tape-grasses. The number of its contained species, and its own placement in the order Alismatales, has been subject to revision by botanical authors....

) - the pollen grains are carried in chains, like strings of beads. The ovary

Ovary (plants)

In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...

 is inferior with 2 - 15 united carpels

Gynoecium

Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...

 containing a single locule

Locule

A locule is a small cavity or compartment within an organ or part of an organism ....

 with numerous ovules on parietal placentas which either protrude nearly to the centre of the ovary or are incompletely developed. Fruit

Fruit

In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

s are globular to linear, dry or pulpy, dehiscent

Dehiscence (botany)

Dehiscence is the opening, at maturity, in a pre-defined way, of a plant structure, such as a fruit, anther, or sporangium, to release its contents. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent...

 or more usually indehiscent and opening by decay of the pericarp

Fruit anatomy

Fruit anatomy is the internal structure of fruit, the mature ovary or ovaries from one or more flowers. In fleshy fruits, the outer and often edible layer is the pericarp, which is the tissue that develops from the ovary wall of the flower and surrounds the seeds. Some edible "vegetables" such as...

. Seed

Seed

A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s are normally numerous with straight embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

s and no endosperm

Endosperm

Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...

.

Pollination can be extremely specialised.

Some botanists divide this family into three subfamilies

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 - Hydrocharitoideae, Thalassoideae (Thalassia

Thalassia

Thalassia may refer to:*Thalassia, Greece, a prefecture in Greece*Thalassia , a genus of seagrass commonly known as "turtle grass"*Thalassia , a queen of Characene...

) and Halophiloideae (Halophila

Halophila

Halophila is a genus of seagrasses in the family Hydrocharitaceae, the tape-grasses. The number of its contained species, and its own placement in the order Alismatales, has been subject to revision by botanical authors....

).

Uses

Some species have become established ornamental plant

Ornamental plant

Ornamental plants are plants that are grown for decorative purposes in gardens and landscape design projects, as house plants, for cut flowers and specimen display...

s, and subsequently serious weeds in the wild (such as Elodea

Elodea

Elodea is a genus of aquatic plants often called the waterweeds. Elodea is native to North America and is also widely used as aquarium vegetation. The introduction of some species of Elodea into waterways in parts of Europe, Australia, Africa, Asia, and New Zealand has created a significant problem...

).

Genera