Kewa acida
Kewa acida is one of the eight species currently recognized in the genus "Kewa", the sole genus in the family Kewaceae. It is a bushy grey-leaved annual or short-lived perennial plant, with white flowers, endemic to St Helena, where it has been called the "salad plant". It is regarded as Critically Endangered. The succulent leaves are high in Vitamin C and were used by sailors in the past as a scurvy preventative. Description. "Kewa acida" is an annual or short-lived perennial, growing up to tall by about wide. It has a spreading, bush-like habit , with stems that may be woody at the base. The succulent leaves are narrow, usually long by wide, but occasionally longer, and are smooth, with a bluish-grey waxy coat. The inflorescence is a false umbel with two to seven flowers, each on a stem (pedicel) up to long. The white flowers are about across. The flower has five tepals arranged in a single whorl. Characteristic of the genus "Kewa", the outer two appear to be sepals, being green; one appears to be half sepal and half petal; and the inner two appear to be petals, being white with a  green stripe on the back. The stamens are arranged in two whorls: ten paired in one whorl alternating with five single in the other. The ovary is superior (visible inside the tepals). The fruit is yellowish-brown, dehiscent, containing small black seeds. Taxonomy. "Kewa acida" was first described by Joseph Dalton Hooker in 1868, as "Pharnaceum acidum". In 1908, Konrad Müller transferred it to the genus "Hypertelis", as "H. acida". Müller placed "Hypertelis" in the family Aizoaceae, but it was subsequently placed in Molluginaceae. Molecular phylogenetic studies in the 21st century showed that most of the species placed in "Hypertelis  did not belong there, and in 2014 a new genus, Kewa", was established for eight species, including "K. acida". Distribution, habitat and conservation. "Kewa acida" is endemic to the mid-Atlantic island of St Helena. It is found in hot, dry coastal regions, up to in elevation. It tends to be annual and hence smaller in drier areas, but can become perennial and shrubby where there is more moisture. Occurring only on a single island in an area of about , the species is considered to be Critically Endangered, i.e. at a high risk of extinction. It is threatened by introduced  animals, such as mice and rabbits, which eat the highly palatable leaves, and also by competition from introduced plants. Efforts have been made to exclude grazing animals. Seeds are stored at the Millennium Seed Bank, Kew. Uses. On St Helena, "Kewa acida" has been called the "salad plant". Its leaves have a salty acid taste and are high in vitamin C, so were used by sailors to prevent scurvy. Cultivation. "Kewa acida" is in cultivation at Kew Gardens, originating from seeds collected in 2009. It is grown in a porous, low-nutrient potting compost, and kept at a minimum temperature  of at night, higher in the daytime. It can be propagated by seeds or by cuttings.