Euphorbiaceae

From Freepedia

Spurge family

Image:Aleuritesmoluccana1web.jpg
Candlenut tree (Aleurites moluccana)

Scientific classification

Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Malpighiales
Family:	Euphorbiaceae Juss.

Subfamilies

For a full list of genera, see
Taxonomy of the Euphorbiaceae.

The Spurge family (Euphorbiaceae) is a large family of flowering plants with 280 genera and around 6,000 species. Most are herbs, but some, especially in the Tropics, are also shrubs or trees. Some are succulent and resemble cacti.

This family occurs mainly in the Tropics, with the majority of the species in the Indo-Malayan region and tropical South America a good second. However, Euphorbia also has many species in non-tropical areas such as the Mediterranean, the Middle East, South Africa and southern USA.

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. A milky sap or latex is a characteristic of the subfamilies Euphorbioideae and Crotonoideae. This milky sap is poisonous in the Euphorbioideae, innocuous in the Crotonoideae. White mangrove (Excoecaria agallocha), or Blind-Your-Eye Mangrove sap causes blistering on contact and temporary blindness if it contacts the eyes. Other common names are Milky Mangrove, Buta Buta (Malay), Gewa (Bangladesh).

The radially symmetrical flowers are unisexual, with the male and the female flowers usually occurring on the same plant. As can be expected from such a large family, there is a wide variety in the structure of the flowers. They can be monoecious or dioecious. The stamens (the male organs) can number from 1 to 10 (or even more). The female flowers are hypogynous, that is, with a superior ovary.

Image:Chamaesyce cyathia.jpg

The genera, Euphorbia and Chamaesyce, show a highly specialized form of inflorescence called a cyathium. This is usually a small cup-like involucre consisting of peripheral horseshoe-shaped nectaries 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, sometimes a drupe. A typical schizocarp is the regma, a capsular fruit with three or more cells, each of which splits open at maturity into separate parts and then breaks away explosively, scattering the small seeds.

Uses

A number of plants of the Spurge family are of considerable economic importance. Prominent plants include manioc, the Castor bean, and the Para rubber tree. Many are grown as ornamental plants, such as poinsettia (Euphorbia pulcherrima).

Taxonomy

The Euphorbiaceae is a complex family with a notoriously difficult circumscription. It is divided into four subfamilies: the Acalyphoideae (by far the largest), the Crotonoideae, the Euphorbioideae, and the Oldfieldioideae. A former fifth subfamily (the Phyllanthoideae) has been separated from the Euphorbiaceae as a result of lineage analysis and now is treated as the Family Phyllanthaceae. This latter's circumscription is nearly coincident with that of former Subfamily Phyllanthoideae, with the exception that Tribe Drypeteae is now the Family Putranjivaceae.

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