Euphorbiaceae-Spurge family

Euphorbiaceae-Spurge family

321 genera, 7,770 species (including Phyllanthaceae) Distributed widely in tropical and subtropical regions, with few species in temperate regions.

Salient features:

Plants usually with milky latex, leaves alternate, flowers unisexual, carpels 3, ovary superior, 3-chambered, ovule with a caruncle.

Major genera:

Euphorbia (2100 species), Cro-ton (720), Phyllanthus (500), Acalypha (350), Glochidion (300), Antidesma (140), Manihot (160) and Jatropha (140).

Description:

Herbs (some species of Euphorbia, Phyllanthus) shrubs (Acalypha) or trees (Hevea) with often milky or coloured latex, sometimes succulent and cactus-like, usually poisonous.

Leaves:

alternate rarely opposite (some species of Euphorbia; Excoecaria) or whorled (Mischodon), some- times modified into spines, simple or palmate compound, venation pinnate or pal- mate, reticulate, stipules present, sometimes modified into spines (Euphorbia milii) or glandular, rarely absent.

Inflorescence

Inflorescence of various types, commonly a cup shaped cyathium (Euphorbia) having a cup-shaped
involucre with usually 5 nectaries along the rim and enclosing numerous male flowers (arranged in scorpioid cymes, without perianth and represented by a single stamen) and single female flower in the centre; sometimes a raceme (Croton) or panicle (Ricinus).

Flowers

Flowers unisexual (monoecious or dioecious), actinomorphic, hypogynous.

Perianth

Perianth usually with 5 tepals (representing sepals, petals absent), rarely 6 in two whorls (Phyllanthus) or absent (Euphorbia), petals usually absent but present in Jatropha and Aleurites, free or connate.

Androecium

Androecium with 1 stamen (Euphorbia), 3 with fused filaments (Phyllanthus), 5 (Bridelia) or many (Trewia), sometimes polyadelphous (or with repeatedly branched filaments) as in Ricinus, anthers bithecous (sometimes monothecous in Ricinus due to splitting of filament), dehiscence longitudinal.

Gynoecium

Gynoecium with 3 united carpels, carpels rarely 4-many, ovary superior, trilocular with 1-2 ovules in each chamber, placentation axile, styles usually 3.

Fruit

Fruit a schizocarpic capsule, a regma (Ricinus), rarely a berry or drupe (Bridelia); seed often with conspicuous fleshy outgrowth called caruncle, embryo curved or straight, endosperm abundant or absent.

Figure Euphorbiaceae. Euphorbia milii. A: Branch with umbellate cyathia and spines; B: Vertical section of cyathium to depict showy scarlet bracts, single female flower and numerous male flowers, and nectaries along the rim of cyathium. E. hirta. C: Portion of plant showing opposite leaves and cyathia in heads; D: Cyathium with female flower protruding out and only 4 nectaries, showy bracts absent; E: Vertical section of cyathium. Phyllanthus fraternus. F: Portion of plant with flowers; G: Male flower with monadelphous stamens; H: Female flower; I: Vertical section of female flower. Croton bonplandianum. J: Portion of plant with flowers and fruits; K: Male flower with many stamens; L: Female flower; M: Vertical section of female flower.

Economic importance:

The family includes a number of valuable plants. Hevea brasiliensis (Para rubber tree) is the source
of natural rubber. Rubber is also obtained from Manihot glaziovii (ceara rubber). Thick roots of Manihot esculentus (cassava or tapioca) are important source of starch in tropi-cal regions. The leaves of Cnido-scolus chayamansa are used as vegetable.

The fruits of Antidesma bunias are also edible. Aleurites moluccana (candlenut tree) and A. fordii (Tung tree) are sources of oils used in the manufacture of paints and varnishes. Oil similar to tung is also obtained from the species of Vernicia. Castor oil obtained from Ricinus communis is used as purgative.

The common ornamentals include Euphorbia pulcherrima, E. milii, Acalypha hispida, Jatropha pand-uraefolia and Codiaeum variegatum. The fruit of Phyllanthus emblica (‘amla’) is very rich source of vitamin C. The greasy tallow surrounding the seeds of Sapium sebiferum (Chinese tallow tree) is used for
making soaps and candles.

 

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Ramzan

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