Aizoaceae

The Aizoaceae Martynov, nom. cons. (fig-marigold family) is a large family of dicotyledonous flowering plants containing 135 genera and about 1800 species. They are commonly known as ice plants or carpet weeds. They are often called vygies in South Africa and New Zealand. Highly succulent species that resemble stones are sometimes called mesembs. The family Aizoaceae is widely recognised by taxonomists. It once went by the botanical name 'Ficoidaceae', now disallowed. The APG II system of 2003 (unchanged from the APG system of 1998) also recognizes the family, and assigns it to the order Caryophyllales in the clade core eudicots. The APG II system also classes the former families Mesembryanthemaceae Fenzl, Sesuviaceae Horan. and Tetragoniaceae Link under the family Aizoaceae. The common Afrikaans name 'vygie' meaning 'small fig' refers to the fruiting capsule, which resembles the true fig. Glistening epidermal bladder cells give the family its common name 'ice plants'. Most species (96%, 1782 species in 132 genera) in this family are endemic to arid or semiarid parts of Southern Africa in the Succulent Karoo. Much of the Aizoaceae's diversity is found in the Greater Cape Floristic Region, which is the most plant-diverse temperate region in the world. A few species are found in Australia and the Central Pacific area. Most fig-marigolds are herbaceous, rarely somewhat woody, with sympodial growth and stems either erect or prostrate. Leaves are simple, opposite or alternate, and more or less succulent with entire (or rarely toothed) margins. Flowers are perfect in most species (but unisexual in some), actinomorphic, and appear singularly or in few-flowered cymes developing from the leaf axils. Sepals are typically five (3-8) and more or less connate (fused) below. True petals are absent. However, some species have numerous linear petals derived from staminodes. The seed capsules have one to numerous seeds per cell and are often hygrochastic, dispersing seeds by 'jet action' when wet. The radiation of the Aizoaceae, specifically the subfamily Ruschioideae, was one of the most recent among the angiosperms, occurring 1.13-6.49 Mya. It is also one of the fastest radiations ever described in the angiosperms, with a diversification rate of about 4.4 species per million years. This diversification was roughly contemporaneous with major radiations in two other succulent lineages, Cactaceae and Agave. The family includes many species that use crassulacean acid metabolism as pathway for carbon fixation. Some species in the subfamily Sesuvioideae instead use C4 carbon fixation, which might have evolved multiple times in the group. Several genera are cultivated. Lithops, or 'living stones', are popular as novelty house plants because of their stone-like appearance.