Thursday, 10 July 2008
Family of the week:
EUPHORBIACEAE (Spurge Family)
Large and extremely variable family cosmopolitan in distribution except in arctic region but they are most abundant in tropical region. In India round 61 genera and 336 species mostly in tropical and subtropical Himalayas and in mountains of south India; while all over the world 7500 species.
The family shows great range in vegetative as well as floral forms. The plants are mostly shrubs or trees and rarely herbs sometimes succulent and cactus-like. The plants often contain a milky latex or sap in special laticiferous vessels.
The leaves are mostly alternate but may be opposite or whorled and they are simple, or compound, or sometimes highly reduced. Stipules are generally present but may be reduced to hairs, glands or spines. In cactus like habits the leaves fall off early and the photosynthesis is carried out by green stems.
Inflorescence and flowers:
The inflorescence is complex. The first branching is usually racemose and the subsequent branching is cymose.
A specialized type of miniature inflorescence called a cyathium occurs in about 1,500 species comprising the genera Euphorbia and Chamaesyce. The cyathium consists of a single naked pistillate flower surrounded by cymes of naked staminate flowers, each consisting of a single stamen.
These flowers are all enclosed in a cup-like involucre that typically is provided with peripheral nectaries and petaloid appendages such that the whole aggregation closely resembles a single flower. In other members of the family the flowers and inflorescences are more ordinary in appearance, with male and female flowers typically bearing a 5-merous calyx and corolla of distinct segments, although the corolla is sometimes absent. In these forms the androecium most commonly consists of 5, 10 or sometimes numerous distinct or monadelphous stamens. The gynoecium of female flowers consists of a single compound pistil of typically 3 carpels, an equal number of styles or primary style branches, and a superior ovary with typically 3 locules, each bearing 1 or 2 collateral, axile-apical pendulous ovules.
The flowers are monoecious;both male and female flowers are naked in Euphorbia whereas in Anthostema both have a tubular perianth. The flowers are unisexual, actinomorphic and hypogynous or rarely perigynous as in Bridellia.The flowers show considerable variation.
The number of stamens in male flowers ranges from one to numerousThe filaments are free or united in the form of a coloumn. A rudimentary ovary is often present in male flowers.An intrastaminal disc is present in flowers with many stamens.
The gynoecium is tricarpellary and syncarpous with a superior and trilocular ovary.The styles are three, often bipartite, free or more or less united. At the base of the ovary a nectiriferous disc is present which is annular or of separate glands.
Fruits and seeds:
Fruit is usually a three chambered schizocarpic capsule.Rarely a drupe or a berry.
Pollination is by insects.Seed dispersal is by explosion of capsule or through water or by birds aor animals.
Manihot esculanta (Cassava)
Manihot glaziovii(Manicoba rubber)
Hevea brasiliensis(Para rubber tree)
Ricinus communis(Castor bean,Erand)
Mallotus philippinensis(Kamela tree)
Jatropha curcas (Purging nut)
Hura crepitans(Sandbox tree)
Posted by SATISFIED at 14:18