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Micrococca mercurialis (L.) Benth.

Hook., Niger Fl.: 503 (1849).
Chromosome number
2n = 20, 40, 60
Tragia mercurialis L. (1753), Mercurialis alternifolia Lam. (1797), Claoxylon mercurialis (L.) Thwaites (1861).
Origin and geographic distribution
Micrococca mercurialis occurs throughout tropical Africa, Yemen, India, Sri Lanka, western Malaysia and northern Australia.
In Benin and Gabon leaves of Micrococca mercurialis are eaten as a vegetable. In Uganda leaves are widely used as a vegetable and the method of preparation and popularity differs by region. They are sold in local markets, and dried and pounded to powder for storage and later use. In Congo the plant is used to treat fever in children, and plant sap is instilled into nose, eyes or ears to treat headache, filariasis of the eye and otitis, respectively.
The leaves of Micrococca mercurialis have an acid taste.
Annual herb up to 60 cm tall. Leaves alternate; stipules small, early caducous; petiole up to 3.5 cm long; blade ovate to lanceolate, 2–7.5 cm × 1–4 cm, rounded at base, apex acuminate, margin crenate, glabrescent to subglabrous, dull grey-green. Inflorescence a raceme 3–12 cm long, with flowers arranged interruptedly in clusters of 1 female flower and several male flowers. Flowers unisexual, pedicel 2 mm long, petals absent; male flowers with 3 calyx lobes less than 1 mm long, yellow-green, stamens 3–20 (in African specimens often 9), disc glands stipitate, spatulate, purple; female flowers with 3–5 calyx-lobes, lanceolate, 2 mm long, green with hyaline margin, ovary superior, 3-lobed, styles 3, 1 mm long, disc glands linear-filiform, 1 mm long. Fruit a subglobose, 3-lobed capsule 2.5 mm × 4 mm, strigose, purplish. Seeds angular-subglobose, 2 mm × 1.5 mm, pink-brown to blackish.
Micrococca comprises about 12 species, and is distributed in the tropics of the Old World. Micrococca mercurialis comprises a polyploidal complex selected by climate, which determines the duration of the growth cycle: 2n = 20 (diploid, dry sudan zone, short growth cycle), 2n = 40 (tetraploid, intermediate guinean zone), 2n = 60 (hexaploid, humid dense forest zone, long or continuous growth cycle).
Micrococca mercurialis grows in open places in woodland and bushland, along rivers and shores, commonly in ruderal habitats, sometimes as a weed, from sea-level up to 1700 m altitude.
In many places Micrococca mercurialis is not cultivated but grows as a weed in gardens and fields. However, in Uganda it is cultivated both for sale and domestic use and where it occurs naturally it usually is protected. The dried powdered leaves can be stored for over a year.
Genetic resources and breeding
Micrococca mercurialis is widespread and not in danger of genetic erosion.
Research is needed on the nutritive and medicinal values of Micrococca mercurialis, and also cultivation methods merit more research.
Major references
• Bouquet, A., 1969. Féticheurs et médecines traditionnelles du Congo (Brazzaville). Mémoires ORSTOM No 36. Office de la Recherche Scientifique et Technique Outre-Mer. Paris, France. 282 pp.
• Burkill, H.M., 1994. The useful plants of West Tropical Africa. 2nd Edition. Volume 2, Families E–I. Royal Botanic Gardens, Kew, United Kingdom. 636 pp.
• Katende, A.B., Ssegawa, P. & Birnie, A., 1999. Wild food plants and mushrooms of Uganda. Technical Handbook No 19. Regional Land Management Unit/SIDA, Nairobi, Kenya. 490 pp.
• Radcliffe-Smith, A., 1987. Euphorbiaceae (part 1). In: Polhill, R.M. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. 407 pp.
• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.
Other references
• Berhaut, J., 1967. Flore du Sénégal. 2nd edition. Editions Clairafrique, Dakar, Senegal. 485 pp.
• Champault, A., 1970. Etude caryosystématique et écologique de quelques Euphorbiacées herbacées et arbustives africaines. Bulletin de la Société Botanique de France 117: 137–168.
• Govaerts, R., Frodin, D.G. & Radcliffe-Smith, A., 2000. World checklist and bibliography of Euphorbiaceae (with Pandaceae). Royal Botanic Gardens, Kew, United Kingdom. 1620 pp.
• Radcliffe-Smith, A., 1996. Euphorbiaceae, subfamilies Phyllantoideae, Oldfieldioideae, Acalyphoideae, Crotonoideae and Euphorbioideae, tribe Hippomaneae. In: Pope, G.V. (Editor). Flora Zambesiaca. Volume 9, part 4. Royal Botanic Gardens, Kew, Richmond, United Kingdom. pp. 1–337.
• Sagun, V.G. & van Welzen, P.C., 2002. Revision of the Malesian species of Micrococca (Euphorbiaceae). Blumea 47: 149–155.
• van der Zon, A.P.M. & Grubben, G.J.H., 1976. Les légumes-feuilles spontanés et cultivés du Sud-Dahomey. Communication 65. Département des Recherches Agronomiques, Koninklijk Instituut voor de Tropen, Amsterdam, Netherlands. 111 pp.
P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

G.J.H. Grubben
Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate Editors
C.-M. Messiaen
Bat. B 3, Résidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Jansen, P.C.M., 2004. Micrococca mercurialis (L.) Benth. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.