The Euphorbiaceae are a large family, the spurge family, of flowering plants. In common English, they are sometimes called euphorbias, which is also the name of a genus in the family. Most spurges such as Euphorbia paralias are herbs, but some, especially in the tropics, are shrubs or trees, such as Hevea brasiliensis. Some, such as Euphorbia canariensis, are succulent and resemble cacti because of convergent evolution. This family occurs mainly in the tropics, with the majority of the species in the Indo-Malayan region and tropical America a strong second. A large variety occurs in tropical Africa, but they are not as abundant or varied as in the two other tropical regions. However, the Euphorbiaceae also have many species in nontropical areas such as the Mediterranean Basin, the Middle East, South Africa, and the Southern United States.
Description
The leaves are alternate, seldom opposite, with stipules. They are mainly simple, but where compound, are always palmate, never pinnate. Stipules may be reduced to hairs, glands, or spines, or in succulent species are sometimes absent. The plants can be monoecious or dioecious. The radially symmetrical flowers are unisexual, with the male and female flowers usually on the same plant. As can be expected from such a large family, a wide variety exists in the structure of the flowers. The stamens number from one to 10. The female flowers are hypogynous, that is, with superior ovaries. The genera in tribe Euphorbieae, subtribe Euphorbiinae show a highly specialized form of pseudanthium called a cyathium. This is usually a small, cup-like involucre consisting of fused-together bracts and peripheral nectary glands, surrounding a ring of male flowers, each a single stamen. In the middle of the cyathium stands a female flower, a single pistil with branched stigmas. This whole arrangement resembles a single flower. The fruit is usually a schizocarp, but sometimes a drupe. A typical schizocarp is the regma, a capsular fruit with three or more cells, each of which splits open explosively at maturity, scattering the small seeds. The family contains a large variety of phytotoxins, including diterpene esters, alkaloids, and cyanogenic glycosides. The seeds of the castor oil plantRicinus communis contain the highly toxiccarbohydrate-binding proteinricin. A milky latex is a characteristic of the subfamilies Euphorbioideae and Crotonoideae, and the latex of the rubber treeHevea brasiliensis is the primary source of natural rubber. The latex is poisonous in the Euphorbioideae, but innocuous in the Crotonoideae. White mangrove, also known as blind-your-eye mangrove latex, causes blistering on contact and temporary blindness if it contacts the eyes. Other common names are milky mangrove, buta buta, and gewa. The latex of spurge was used as a laxative. Recent molecular studies have shown that the enigmatic family Rafflesiaceae, which was only recently recognized to belong to order Malpighiales, is derived from within the Euphorbiaceae.
Taxonomy
The family Euphorbiaceae is the fifth-largest flowering plant family and has about 7,500 species organised into 300 genera, 37 tribes, and three subfamilies.
found in Euphorbiaceae species include diterpenoids, terpenoids, flavonoids, alkaloids, tannins, neriifolins, cycloartenol, lectin, and taraxerol, among others.
Vulnerability
Some species, despite their medicinal benefits, are facing the risk of becoming extinct. These include the Euphorbia species E. appariciana, E. attastoma, E. crossadenia, and E. gymnoclada.
