Acanthaceae

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iAcanthaceae

Flowers of Odontonema cuspidatum

Scientific classification

Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Lamiales
Family:	Acanthaceae Juss.

Type Genus

Acanthus
L.

Genera

See text.

The family Acanthaceae (or Acanthus family) is a taxon of dicotyledonous flowering plants containing almost 250 genera and about 2500 species.

Most are tropical herbs, shrubs, or twining vines; some are spiny. Only a few species are distributed in temperate regions, the four main centres of distribution are Indo-Malaya, Africa, Brasil and Central America. The representatives of the family can be found in nearly every habitat, e.g. in dense or open forest, in thickets, on wet fields and valleys, at the sea coast and in marine areas, swamps and as an element of mangrove woods.

Image:Starr 021122 0083 justicia aurea.jpg

Plants in this family have simple, opposite, decussate leaves with entire (or sometimes toothed or lobed) margins. The leaves may contain cystoliths, seen as streaks in the surface. The flowers are perfect, zygomorphic to nearly actinomorphic, these arranged in an inflorescence that is either a spike, raceme, or cyme. Typically there is a colorful bract subtending each flower; in some species the bract is large and showy. The calyx is usually 4-5 lobed; the corolla tubular, 2-lipped or 5-lobed; stamens either 2 or 4 arranged in pairs and inserted on the corolla; and the ovary superior, 2-carpellate, with axile placentation. The fruit is a two-celled capsule, dehiscing somewhat explosively. In most species, the seeds are attached to a small, hooked stalk (a modified funiculus called a jaculator) that ejects them from the capsule. Seeds non-endospermous with large embryos.

A species well-known to temperate gardeners is Acanthus mollis or Bear's breeches, a herbaceous perennial plant with big leaves and flower spikes up to 2 m tall. Tropical genera familiar to gardeners include Thunbergia and Justicia.

Avicennia, usually placed in Verbenaceae or in its own family, Avicenniaceae, is included in Acanthaceae by the Angiosperm Phylogeny Group on the basis of molecular phylogenies that show it to be associated with this family.