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Millettia laurentii De Wild.

Protologue
Belg. Colon. 30: 378 (1904).
Family
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Vernacular names
Wenge, awong, grey ebony (En). Wengé, wengué, awong, bois de fer, bois noir, palissandre du Congo, faux ébénier (Fr). Wenge, pau ferro (Po).
Origin and geographic distribution
Millettia laurentii is restricted to a limited area in Central Africa, from the eastern parts of Cameroon, Equatorial Guinea and Gabon to the western parts of the Central African Republic and DR Congo.
Uses
The wood (trade names: wenge, wengé) is commonly used for heavy flooring, interior and exterior joinery, interior and exterior panelling, cabinet work, furniture, carving, turnery and sliced veneer. It is also suitable for heavy construction, mine props, vehicle bodies, implements, sporting goods, toys, novelties, boxes, crates and railway sleepers. It is in high demand for decorative furniture and parquet flooring. It is also used for high-quality musical instruments, especially guitars; it is said to give a good and strong tone. It is popular for the production of sculptures, masks and drums.
In traditional medicine a bark decoction is used to treat liver complaints, diabetes, hernia, skin diseases, constipation, fever and rheumatism. The bark is also applied as an expectorant and emetic, and to treat epilepsy, smallpox, oedema, sores and abscesses. It is used as fish poison, an insecticide, vermifuge and arrow poison. Flowering trees provide nectar to honey bees, and edible caterpillars feed on the leaves. Millettia laurentii is planted as an ornamental and roadside tree. Stem cuttings are planted as a live fence.
Production and international trade
According to ITTO, Congo exported 2000 m³ of sawn wenge timber in 2003, with an average price of US$ 409/m³, and 1000 m³ of plywood, with an average price of US$ 354/m³. In 2004 the export of sawn timber from Congo was 4000 m³ with an average price of US$ 383/m³, and of plywood 2000 m³ with an average price of US$ 334/m³. According to ATIBT, Congo exported 4500 m³ of logs, 1900 m³ of humid lumber and 100 m³ of dry lumber in 2004. The annual export of wenge logs from Gabon averaged 4700 m³ in 2000–2004. Cameroon exported 500 m³ and 600 m³ of sawn wenge in 2003 and 2004, respectively. In Cameroon logs are banned from export. Other countries (Central African Republic, Equatorial Guinea and DR Congo) also export this timber.
Properties
The heartwood is yellow when freshly sawn but darkens on exposure to dark brown or black-brown, with black streaks, and is sharply demarcated from the pale yellow, 2–5 cm thick sapwood. The grain is straight, texture medium to coarse.
The wood is heavy, with a density of 750–960 kg/m³ at 12% moisture content. The wood air-dries slowly, with slight risk of distortion and high risk of checking. The rates of shrinkage are rather high, from green to oven dry 4.5–6.2% radial and 8.6–10.0% tangential. Once dry, the wood is moderately stable in service.
The wood is hard and elastic, but with a tendency to split. At 12% moisture content, the modulus of rupture is 123–246 N/mm², modulus of elasticity 16,500–22,400 N/mm², compression parallel to grain 69–100 N/mm², shear 11–12 N/mm², cleavage 13–22 N/mm and Chalais-Meudon side hardness 7.5–11.1.
The wood saws and works well, but force is required and sawteeth and cutting tools may blunt rapidly; stellite-tipped sawteeth and tungsten-carbide tipped cutting tools are recommended. It is difficult to polish and the use of a finishing wax is recommended. Pre-boring before nailing and screwing is needed. The wood slices well. It can also be rotary cut, but intensive steaming is then needed. The gluing and varnishing properties are poor due to the presence of resin cells, but the use of a filler improves the results considerably.
The heartwood is very durable, being resistant to fungal, dry-wood borer and termite attacks and moderately resistant to marine borers, but the sapwood is susceptible to attack by powder-post beetles. The heartwood is resistant to impregnation with preservatives, but the sapwood is permeable. Contact with fine sawdust produced during processing may cause occupational asthma and allergic dermatitis in workers. A quinone (2,6-dimethoxy-1, 4-benzoquinone) has been isolated from the wood and identified as a contact allergen. Several isoflavones have been isolated from the heartwood, and several alkaloids, including guanidine alkaloids, from bark and seeds. The seeds contain about 35% oil.
Adulterations and substitutes
The wood of panga panga (Millettia stuhlmannii Taub.) from East Africa closely resembles that of Millettia laurentii and is used for similar purposes.
Description
Medium-sized tree up to 30(–45) m tall; bole cylindrical, often slightly bent, branchless for up to 20 m but usually much less, up to 120 cm in diameter, with small buttresses or fluted at base; bark surface greyish, rough by lenticels, inner bark yellowish, granular, with reddish exudate; branches drooping, twigs glabrous. Leaves alternate, imparipinnately compound with (4–)6–7(–9) pairs of leaflets; stipules absent; petiole 4–7 cm long, rachis 10–18 cm long; stipels absent; petiolules 4–6 mm long; leaflets opposite, oblong to obovate, 6–15 cm × 3–4(–9) cm, abruptly acuminate at apex, glabrous. Inflorescence a terminal panicle 20–40 cm long, with branches up to 5 cm long, short-hairy. Flowers bisexual, papilionaceous; pedicel c. 3 mm long, with 2 small bracteoles near apex; calyx campanulate, 6–8 mm long, tube as long as lobes; corolla pale purple to purplish blue, glabrous, standard orbicular, c. 12 mm in diameter, with c. 3 mm long claw at base, wings and keel c. 16 mm long; stamens 10, 9 fused, 1 free, c. 15 mm long; ovary superior, c. 10 mm long, hairy, style slender, curved, glabrous. Fruit an oblanceolate to linear flat pod 15–28 cm × 3–5 cm, with stiff wall, glabrous, finely striped, dehiscent, 2–4-seeded. Seeds oblong to lens-shaped, flattened, 22–25 mm × 18–20 mm, smooth, purplish brown. Seedling with epigeal germination; hypocotyl c. 4 cm long, epicotyl 7–12 cm long; cotyledons ovate, c. 12 mm long, fleshy; first leaves opposite and simple.
Other botanical information
Millettia comprises about 150 species, most of them (about 90) in mainland Africa, 8 endemic to Madagascar, and about 50 in tropical Asia. It is in need of revision and should be split into several genera based on molecular evidence.
Anatomy
Wood-anatomical description (IAWA hardwood codes):
Growth rings: (1: growth ring boundaries distinct); (2: growth ring boundaries indistinct or absent). Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; 23?: shape of alternate pits polygonal; 25: intervessel pits small (4–7 μm); 26: intervessel pits medium (7–10 μm); 29: vestured pits; 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 42: mean tangential diameter of vessel lumina 100–200 μm; 43: mean tangential diameter of vessel lumina 200 μm; (45: vessels of two distinct diameter classes, wood not ring-porous); 46: 5 vessels per square millimetre; 58: gums and other deposits in heartwood vessels. Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 70: fibres very thick-walled. Axial parenchyma: 83: axial parenchyma confluent; 85: axial parenchyma bands more than three cells wide; 89: axial parenchyma in marginal or in seemingly marginal bands; (91: two cells per parenchyma strand); 92: four (3–4) cells per parenchyma strand. Rays: (97: ray width 1–3 cells); (98: larger rays commonly 4- to 10-seriate); 104: all ray cells procumbent; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 115: 4–12 rays per mm. Storied structure: 118: all rays storied; 120: axial parenchyma and/or vessel elements storied; 121: fibres storied. Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.
(P. Ng’andwe, H. Beeckman & P.E. Gasson)
Growth and development
Trees in full flower are very conspicuous, being covered by purplish blue flowers. The roots have nodules containing nitrogen-fixing bacteria.
Ecology
Millettia laurentii occurs in rainforest, often in well-drained localities, but also in forest subject to regular inundation and in riverine forest and tree savanna.
Propagation and planting
Millettia laurentii is propagated by seed and cuttings. In a trial in DR Congo, 48% of stem cuttings planted at the onset of the rainy season sprouted.
Management
In DR Congo Millettia laurentii is one of the species planted for reafforestation of formerly cultivated land.
Diseases and pests
Locally in DR Congo, planted trees have been completely defoliated by caterpillars of Rhopalocampta libeon, which are also collected as food.
Harvesting
The minimum diameter for felling is 50 cm in Cameroon and 60 cm in DR Congo.
Handling after harvest
Logs may have brittleheart. They can be left in the forest for some time without damage. However, borers may attack the green timber, making holes of about 0.5 cm in diameter and 1–2 cm long. The boles do not float and therefore cannot be transported by river. The timber is sawn locally and exported as strips or planks, often in sizes of about 250 cm × 20 cm × 5 cm.
Genetic resources
Millettia laurentii has a limited area of distribution and has been subject to overexploitation in many parts of its distribution area. Millettia laurentii is included in the IUCN Red list as endangered due to habitat degradation and overexploitation. Special permission is needed for the exploitation of Millettia laurentii timber in Cameroon.
Prospects
Wenge is one of the highly valued African timbers on the international market, but production is dwindling. In general, the exploitation level of Millettia laurentii is not sustainable, although the timber is locally harvested from sustainably managed forests. Research is needed on natural regeneration and growth rates to establish criteria for sustainable production in natural forest. The ability to use cuttings for propagation offers possibilities for the establishment of plantations, but more research on plantation management is needed. There is a need to focus on conserving this species.
Major references
• ATIBT (Association Technique Internationale des Bois Tropicaux), 1986. Tropical timber atlas: Part 1 – Africa. ATIBT, Paris, France. 208 pp.
• Bolza, E. & Keating, W.G., 1972. African timbers: the properties, uses and characteristics of 700 species. Division of Building Research, CSIRO, Melbourne, Australia. 710 pp.
• CTFT (Centre Technique Forestier Tropical), 1952. Wengé. Bois et Forêts des Tropiques 25: 329–332.
• CIRAD Forestry Department, 2003. Wenge. [Internet] Tropix 5.0. http://tropix.cirad.fr/ africa/wenge. Accessed April 2007.
• Hauman, L., Cronquist, A., Léonard, J., Schubert, B., Duvigneaud, P. & Dewit, J., 1954. Papilionaceae (deuxième partie). In: Robyns, W., Staner, P., Demaret, F., Germain, R., Gilbert, G., Hauman, L., Homès, M., Jurion, F., Lebrun, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 5. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. 377 pp.
• Mbenkum, F.T., 1986. Systematic studies in the genus Millettia Wight & Arnott. PhD Thesis, University of Reading, United Kingdom. 306 pp.
• Phongphaew, P., 2003. The commercial woods of Africa. Linden Publishing, Fresno, California, United States. 206 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan, 248 pp.
• Vivien, J. & Faure, J.J., 1985. Arbres des forêts denses d’Afrique Centrale. Agence de Coopération Culturelle et Technique, Paris, France. 565 pp.
• Wilks, C. & Issembé, Y., 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata, Guinée Equatoriale. 546 pp.
Other references
• Adjanohoun, E.J., Ahyi, A.M.R., Aké Assi, L., Baniakina, J., Chibon, P., Cusset, G., Doulou, V., Enzanza, A., Eymé, J., Goudoté, E., Keita, A., Mbemba, C., Mollet, J., Moutsamboté, J.-M., Mpati, J. & Sita, P. (Editors), 1988. Médecine traditionnelle et pharmacopée - Contribution aux études ethnobotaniques et floristiques en République Populaire du Congo. Agence de Coopération Culturelle et Technique, Paris, France. 606 pp.
• African Regional Workshop (Conservation & Sustainable Management of Trees, Zimbabwe), 1998. Millettia laurentii. In: IUCN. 2006 Red list of threatened species. [Internet] http://www.iucnredlist.org. Accessed April 2007.
• ATIBT (Association Technique Internationale des Bois Tropicaux), 2004. Tropical wood and wooden product export statistics. ATIBT Newsletter 20: 29–47.
• ATIBT (Association Technique Internationale des Bois Tropicaux), 2005. Statistics. ATIBT Newsletter 22: 26–47.
• 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.
• InsideWood, undated. [Internet] http://insidewood.lib.ncsu.edu/search/. Accessed May 2007.
• Kamnaing, P., Free, S.N.Y.F., Fomum, Z.T., Martin, M.T. & Bodo, B., 1994. Millettonine, a guanidine alkaloid from Millettia laurentii. Phytochemistry 36(6): 1561–1562.
• Kamnaing, P., Free, S.N.Y.F., Nkengfack, A.E., Folefoc, G. & Fomum, Z.T., 1999. An isoflavan quinone and a flavonol from Millettia laurentii. Phytochemistry 51(6): 829–832.
• Latham, P., 2004. Useful plants of Bas-Congo province, Democratic Republic of the Congo. DFID, London, United Kingdom. 320 pp.
• Latham, P., 2005. Some honeybee plants of Bas-Congo Province, Democratic Republic of Congo. DFID, United Kingdom. 167 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Ngamga, D., Free, S.N.Y.F., Fomum, Z.T., Chiaroni, A., Riche, C., Martin, M.T. & Bodo, B., 1993. Millaurine and acetylmillaurine: alkaloids from Millettia laurentii. Journal of Natural Products 56(12): 2126–2132.
• Ngamga, D., Free, S.N.Y.F., Fomum, Z.T., Martin, M.T. & Bodo, B., 1994. A new guanidine alkaloid from Millettia laurentii. Journal of Natural Products 57(7): 1022–1024.
• Normand, D. & Paquis, J., 1976. Manuel d’identification des bois commerciaux. Tome 2. Afrique guinéo-congolaise. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 335 pp.
• Pauwels, L., 1993. Nzayilu N’ti: guide des arbres et arbustes de la région de Kinshasa Brazzaville. Scripta Botanica Belgica. Volume 4. Jardin botanique national de Belgique, Meise, Belgium. 495 pp.
• Richter, H.G. & Dallwitz, M.J., 2000. Commercial timbers: descriptions, illustrations, identification, and information retrieval. [Internet]. Version 18th October 2002. http://delta-intkey.com/wood/index.htm. Accessed April 2007.
• Sabiti, K., Matatu, B. & Baboy, L., 1992. Influence de la dimension d’une tige et de son clouage sur la capacité de repousse de piquets vivants en milieu tropical. Tropicultura 10(3): 98–101.
• Schmalle, H., Jarchow, O. & Hausen, B.M., 1977. 2,6-dimethoxy-1,4-benzoquinone, a new contact allergen in commercial woods. Naturwissenschaften 64(10): 534–535.
• Tailfer, Y., 1989. La forêt dense d’Afrique centrale. Identification pratique des principaux arbres. Tome 2. CTA, Wageningen, Pays Bas. pp. 465–1271.
• Vieux, A.S. & Kabele Ngiefu, C., 1970. Etude de quelques espèces oléagineuses de la République Démocratique du Congo. Oléagineux 25: 395–399.
• White, L. & Abernethy, K., 1997. A guide to the vegetation of the Lopé Reserve, Gabon. 2nd edition. Wildlife Conservation Society, New York, United States. 224 pp.
Sources of illustration
• CTFT (Centre Technique Forestier Tropical), 1952. Wengé. Bois et Forêts des Tropiques 25: 329–332.
• Wilks, C. & Issembé, Y., 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata, Guinée Equatoriale. 546 pp.
Author(s)
A.T. Tchinda
Institut de Recherches Médicales et d’Etudes des Plantes Médicinales (IMPM), Ministère de la Recherche Scientifique et de l’Innovation, B.P. 6163, Yaoundé, Cameroun


Editors
D. Louppe
CIRAD, Département Environnements et Sociétés, Cirad es-dir, Campus international de Baillarguet, TA C-DIR / B (Bât. C, Bur. 113), 34398 Montpellier Cedex 5, France
A.A. Oteng-Amoako
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, 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
J.R. Cobbinah
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
Photo editor
G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Tchinda, A.T., 2008. Millettia laurentii De Wild. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map wild


1, base of bole; 2, flowering twig; 3, flower; 4, fruit; 5, seeds.
Redrawn and adapted by Achmad Satiri Nurhaman



flowering branches


part of inflorescence


plank
obtained from
Arnhemse Fijnhouthandel


stacked planks
obtained from
Arnhemse Fijnhouthandel


veneer
obtained from
Arnhemse Fijnhouthandel


wood


wood


wood in transverse section


wood in tangential section


wood in radial section