Lythraceae
Lythraceae is a family of flowering plants that includes 28 genera and about 620 species of herbs, shrubs, and trees. The larger genera include Cuphea, Lagerstroemia, Nesaea, Rotala, and Lythrum. It also includes the members of the former families of the pomegranate and of the water caltrop. Lythraceae has a worldwide distribution, with most species in the tropics, but ranging into temperate climate regions as well.
The family is named after the type genus, Lythrum, the loosestrifes and also includes henna. It now includes the pomegranate, formerly classed in a separate family Punicaceae. The family also includes the widely cultivated crape myrtle trees. Botanically, the leaves are usually in pairs, and the flower petals emerge from the rim of the calyx tube. The petals often appear crumpled.
Characteristics
Lythraceae species are most often herbs, and less often shrubs or trees; the shrubs and trees often have flaky bark. Traits shared by species within the Lythraceae that distinguish them from belonging to other plant families are the petals being crumpled in the bud and the many-layered outer integument of the seed.Leaves
The leaves generally have an opposite arrangement, but sometimes are whorled or alternate. They are simple with smooth margins and pinnate venation. Stipules are typically reduced, appearing as a row of minute hairs, or absent.Flowers
The flowers are bisexual, radially or occasionally bilaterally symmetric, with a well-developed hypanthium. The flowers are most commonly quadimerous but can be heximerous, with four to eight sepals and petals. The sepals may be distinct, partially fused to form a tube, or touching without overlapping. The petals are crumpled in the bud and wrinkled at maturity, and are typically distinct and overlapping; they are occasionally absent. Usually, twice as many stamens as petals are seen, arranged in two whorls, and the stamens are often unequal in length. Occasionally, the stamens are reduced to one whorl, or are more numerous with multiple whorls. The ovary is typically superior, infrequently semi-inferior, or rarely inferior. The two to many carpels can be fused together, with two to numerous ovules in each locule, with axile placentation of the ovules.Heterostyly – the presence of two or three distinct flower morphs within a species differing in the lengths of the pistil and stamens – is common within the Lythraceae.
Fruits and seeds
The fruit is usually a dry, dehiscent capsule, occasionally a berry. The seeds are usually flattened and/or winged, with a multilayered outer integument. Epidermal hairs that expand and become mucilaginous when wet are found in about half the genera.Distribution
The Lythraceae are widely distributed, but with most species tropical and some temperate. They are absent from the Sahara and most arid regions of Australia. Many species occur in aquatic or semi-aquatic habitats. The oldest fossils of the family are pollen from the Late Cretaceous of Wyoming in western North America, around 82 to 81 million years old.Economic importance
Edible crops include the pomegranate and the water caltrop. The pomegranate is cultivated for the fleshy arils surrounding the seeds, and the water caltrop for its seeds. Henna is cultivated for the dye of the same name, derived from its leaves.Ornamentals are grown from a number of genera, including Cuphea, Lagerstroemia, and Lythrum.
Purple loosestrife is an invasive exotic weed of wetlands throughout Canada and the United States.