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Pterygota macrocarpa K.Schum.

Engl., Monogr. afrik. Pflanzen-Fam. 5: 135 (1900).
Sterculiaceae (APG: Malvaceae)
Chromosome number
2n = 36
Vernacular names
African pterygota (En). Koto, erable d’Afrique (Fr).
Origin and geographic distribution
Pterygota macrocarpa occurs from Sierra Leone east to Congo, DR Congo and Cabinda (Angola). It may also occur in the drier parts of northern Gabon.
The wood (trade names: koto, pterygota) is used for veneer, plywood, interior panelling, interior joinery, moulding, furniture, block board, fibre board, particle board and light carpentry. It is also used for staircases, light flooring, wood-frame houses, glued-laminated timber, matchboxes, boxes and crates. The wood is also used for fuel.
In Côte d’Ivoire Pterygota macrocarpa is occasionally retained as a shade tree in cacao plantations. The large leaves are used as temporary thatch and for wrapping food. In Nigeria a decoction of the leaves is drunk against stomach, bladder and urinary problems and against flatulence.
Production and international trade
The timber of Pterygota macrocarpa is important in Côte d’Ivoire, Ghana and Cameroon. In 1995 Côte d’Ivoire exported 2000 m³ of rotary veneer and 2000 m³ of sliced veneer at a price of US$ 406/m³ and US$ 963/m³, respectively, in addition to 5000 m³ of logs at an average price of US$ 567/m³. In 2004 Côte d’Ivoire exported 32,000 m³ of sawn wood at US$ 397 /m³, and in 2005 it exported 25,000 m³ at US$ 439/m³. Ghana exported rotary veneer, sliced veneer and jointed veneer in 1995, at average prices of US$ 510/m³, US$ 900/m³ and US$ 1250/m³, respectively. It also exported 9000 m³ of sawn wood at an average price of US$ 440/m³ and 1000 m³ of logs at US$ 165/m³. In 2001 Pterygota macrocarpa timber represented 5% of the timber exports of Ghana, but was among the 3 most important sources of plywood for export; the export price of face veneer was about US$ 300/m³. In 2004 Ghana exported 5000 m³ of sawn wood at an average price of US$ 560/m³, 5000 m³ of veneer at an average price of US$ 693/m³, and some plywood at US$ 327/m³. In 2005 it exported 4000 m³ of sawn wood at an average price of US$ 487/m³, and 6000 m³ of veneer at an average price of US$ 627/m³, and some plywood at US$ 375/m³. According to ATIBT statistics, Cameroon exported 1325 m³ of logs in 2003, 535 m³ in 2004, and 2250 m³ in 2006. It exported 2460 m³ of sawn wood in 2003, 980 m³ in 2004 and 3185 m³ in 2006.
The heartwood is creamy white to yellowish, sometimes attractively flecked on quartersawn surfaces. It is not demarcated from the up to 10 cm wide sapwood. Fresh wood has an unpleasant odour. The grain is straight or occasionally shallowly interlocked, texture moderately coarse.
The wood is medium-weight, with a density at 12% moisture of 480–660(–750) kg/m³. The wood dries fairly easily with little risk of surface checking or twisting, but with some risk of extension of shakes. The rates of shrinkage from green to oven dry are high: 3.9–6.0% radial and 8.8–12.6% tangential. Once dry, the stability in service is medium.
At 12% moisture content the modulus of rupture is 85–153 N/mm², modulus of elasticity 9200–14,800 N/mm², compression parallel to grain 43–58 N/mm², shear 6–9 N/mm², cleavage 17–19 N/mm and Janka side hardness 4190 N.
The wood can be worked with normal hand and machine tools. The blunting effect on cutting edges is medium. Sawing is satisfactory, but the tendency to breaking out at the bottom of the cut may be pronounced. For planing quartersawn surfaces, a reduction of the cutting angle to 20° is recommended and cutters should be kept sharp. For good surface finishing, a filler is needed. The nailing and screwing properties, as well as the peeling and slicing properties are satisfactory to good. Bending properties are variable, but in general the wood buckles.
The wood is not durable, being susceptible to attack by borers, termites and fungi. It is very prone to blue stain. However, it is easily impregnated with preservatives. The energy value of the wood is 18,170 kJ/kg.
Adulterations and substitutes
The wood of Pterygota macrocarpa is very similar to that of Sterculia oblonga Mast. (‘eyong’), which is also medium-weight and used for similar purposes.
Deciduous, medium-sized to fairly large tree up to 35 m tall; bole cylindrical, up to 120 cm in diameter, with very large, thin and wavy buttresses, bark surface greyish, smooth with raised hoops and small lenticels, inner bark with green outer layer, white with vertical lines; crown small, dense, branchlets hairy, glabrescent. Leaves alternate, simple; stipules lanceolate, c. 5 mm long, greyish hairy; petiole 5–18 cm long; blade ovate to orbicular, sometimes slightly lobed, 5–30 cm × 10–25 cm, base cordate, apex short-acuminate, brownish hairy when young but glabrescent, shiny, with 5–7(–9) veins from the base and 2–4 pairs of lateral veins. Inflorescence a few-flowered, terminal panicle 6–14 cm long, reddish brown hairy. Flowers usually unisexual, regular; pedicel 5–6 mm long, jointed below the middle; calyx campanulate, 5–6 lobed, lobes lanceolate, 13–20 mm × 3–6 mm, densely reddish stellate hairy outside; corolla absent; male flowers with staminal column c. 8 mm long, thin, with 8–10 anthers at apex and surrounding 5 rudimentary carpels; female flowers with superior ovary consisting of 5 carpels fused at base, each carpel with a c. 2.5 mm long style and small stigma, surrounded by rudimentary anthers. Fruit consisting of 1–5 ellipsoid to globular follicles 12–18 cm × 10–13 cm, woody, with 1.5–4.5 cm long stipe, many-seeded. Seeds 9–11 cm long including a wing of 6.5–7 cm × c. 3 cm. Seedling with epigeal germination; epicotyl 4–6 cm long, hypocotyl 2–3 cm long; cotyledons oblong, c. 3 cm × 2 cm; first leaves opposite, simple, blade 8–11 cm × c. 7 cm, cordate at base, long-acuminate at apex.
Other botanical information
Pterygota is a pantropical genus comprising 15–20 species, of which about 10 occur in tropical Africa and the Indian Ocean islands. It is closely related to Sterculia.
Pterygota bequaertii De Wild. occurs from Côte d’Ivoire east to Cameroon and south to Cabinda (Angola) and DR Congo. It is a deciduous large tree up to 50 m tall, with a bole branchless up to 35 m and up to 100 cm in diameter, with winged buttresses up to 2 m high. Its leaves are smaller than those of Pterygota macrocarpa. Its wood is similar in appearance and properties to that of Pterygota macrocarpa. It is traded as ‘koto’ or ‘akodiokédé’. In DR Congo the wood is traditionally used for making bells for hunting dogs, honey containers, canoes and drums. The sticky fruit is used as an adhesive paste. The dried pulverized root is applied as poultice against chest pain and intercostal pain. Pterygota bequaertii is included as vulnerable in the IUCN Red list.
Wood-anatomical description (IAWA hardwood codes):
Growth rings: 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)); 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; 46: 5 vessels per square millimetre; (47: 5–20 vessels per square millimetre). Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 69: fibres thin- to thick-walled. Axial parenchyma: (83: axial parenchyma confluent); 85: axial parenchyma bands more than three cells wide; 92: four (3–4) cells per parenchyma strand; (93: eight (5–8) cells per parenchyma strand). Rays: 98: larger rays commonly 4- to 10-seriate; (102: ray height > 1 mm); (103: rays of two distinct sizes); 107: body ray cells procumbent with mostly 2–4 rows of upright and/or square marginal cells; 110: sheath cells present; 114: 4 rays per mm; (115: 4–12 rays per mm). Storied structure: 120: axial parenchyma and/or vessel elements storied. Secretory elements and cambial variants: 131: intercellular canals of traumatic origin. Mineral inclusions: 136: prismatic crystals present; 137: prismatic crystals in upright and/or square ray cells; 141: prismatic crystals in non-chambered axial parenchyma cells.
(L.N. Banak, H. Beeckman & P.E. Gasson)
Growth and development
Pterygota macrocarpa is classified as a non-pioneer light demander. Seeds are produced in large numbers and released at the beginning of the rainy season. They are dispersed by wind. In Côte d’Ivoire trees had a mean annual bole diameter growth of 1.7–1.9 cm/year at 14 years after planting. In unthinned natural forest diameter growth was estimated at 0.4 cm per year, in thinned natural forest at 0.9 cm per year.
Pterygota macrocarpa occurs in dense and humid semi-deciduous forest and gallery forest. In Ghana it is equally common in logged as in undisturbed forest. It prefers drier, base-rich soil.
Propagation and planting
The 1000-seed is about 1 kg. Germination starts after 8 days. Large numbers of seedlings are sometimes found near mother trees. Seedlings tolerate shade and wet, leached soils. However, light shade is preferred, and saplings are more abundant in forest affected by logging damage than in undisturbed forest, whereas germination is depressed in large gaps. In Ghana seedling regeneration is highest in burnt forest, but trees with a bole diameter over 5 cm were found to be less abundant in burnt than in unburnt forest.
In southern Cameroon the species density has been estimated at 0.28 stems per ha, of which 30% had a bole diameter larger than the minimum extractable diameter of 80 cm. The allowable cut was estimated at 0.008 m³/ha/year.
The minimum felling diameter is 60 cm in Côte d’Ivoire and Liberia, and 110 cm in Ghana.
Handling after harvest
After felling, logs need to be extracted rapidly to avoid insect damage and fungal attack, or they should be treated with preservatives.
Genetic resources
Pterygota macrocarpa is common, but is locally under pressure of exploitation. In Ghana it needs control of its exploitation and some protection. It is included in the IUCN Red list as vulnerable because of habitat loss and high levels of exploitation.
The wood of Pterygota macrocarpa can be easily treated with preservatives and is then a good general purpose timber for indoor use. With proper management its export volumes can still be expanded, although it has become locally vulnerable. Because of its fast growth, clear straight bole and small crown, Pterygota macrocarpa has been recommended for plantation and enrichment planting.
Major references
• ATIBT (Association Technique Internationale des Bois Tropicaux), 1986. Tropical timber atlas: Part 1 – Africa. ATIBT, Paris, France. 208 pp.
• Aubréville, A., 1959. La flore forestière de la Côte d’Ivoire. Deuxième édition révisée. Tome deuxième. Publication No 15. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 341 pp.
• CIRAD Forestry Department, 2003. Koto. [Internet] Tropix 5.0. afr/koto.pdf. Accessed July 2008.
• Dupuy, B., 1998. Bases pour une sylviculture en forêt dense tropicale humide africaine. Document Forafri 4. Cirad, Montpellier, France. 328 pp.
• Durand, P.Y., 1978. Propriétés physiques et mécaniques des bois de Côte d’Ivoire: moyennes d’espèce et variabilité intraspécifique. Centre Technique Forestier Tropical, Abidjan, Côte d’Ivoire. 70 pp.
• Farmer, R.H., 1972. Handbook of hardwoods. 2nd Edition. Her Majesty’s Stationery Office, London, United Kingdom. 243 pp.
• Germain, R. & Bamps, P., 1963. Sterculiaceae. 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 10. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 205–316.
• Parant, B., Boyer, F., Chichignoud, M. & Curie, P., 2008. Présentation graphique des caractères technologiques des principaux bois tropicaux. Tome 1. Bois d’Afrique. Réédition. CIRAD-Fôret, Montpellier, France. 186 pp.
Other references
• Aké Assi, L., 1990. Annotated WCMC list of timber species for the Ivory Coast (Côte d’Ivoire). [Internet] Accessed July 2008.
• 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), 1961. Koto. Information technique No 126. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 2 pp.
• de la Mensbruge, G., 1964. La fabrication des allumettes en Côte-d'Ivoire. Bois et Forêts des Tropiques 98: 27–36.
• de la Mensbruge, G., 1966. La germination et les plantules des essences arborées de la forêt dense humide de la Côte d’Ivoire. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 389 pp.
• Doat, J. & Valette, J.C., 1980. L’inflammabilité de quelques bois tropicaux. Bois et Forêts des Tropiques 194: 43–55.
• Fines, J.P., Ngibaot, F. & Ngono, G., 2001. A conceptual forest management plan for a medium size forest in southern Cameroon. Tropenbos-Cameroon Document 6. Tropenbos Cameroon Programme, Kribi, Cameroon, 98 pp.
• Hallé, N., 1961. Sterculiacées. Flore du Gabon. Volume 2. Muséum National d’Histoire Naturelle, Paris, France. 150 pp.
• Hawthorne, W. & Jongkind, C., 2006. Woody plants of western African forests: a guide to the forest trees, shrubs and lianes from Senegal to Ghana. Kew Publishing, Royal Botanic Gardens, Kew, United Kingdom. 1023 pp.
• Hawthorne, W.D. & Gyakari, N., 2006. Photoguide for the forest trees of Ghana. A tree-spotter’s field guide for identifying the largest trees. Oxford Forestry Institute. Department of Plant Sciences, Oxford, United Kingdom. 432 pp.
• Herzog, F., 1994. Multipurpose shade trees in coffee and cocoa plantations in Côte d’Ivoire. Agroforestry Systems 27: 259–267.
• InsideWood, undated. [Internet] Accessed May 2007.
• ITTO, 2006. Annual review and assessment of the world timber situation 2005. International Timber Trade Organisation, Yokohama, Japan. 214 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Nshimba, H.S., 2008. Etude floristique, écologique et phytosociologique des forêts de l’île Mbiye à Kisangani, RD Congo. PhD thesis, Université Libre de Bruxelles, Brussels, Belgium. [Internet] Accessed July 2008.
• Oteng-Amoako, A.A. (Editor), 2006. 100 tropical African timber trees from Ghana: tree description and wood identification with notes on distribution, ecology, silviculture, ethnobotany and wood uses. 304 pp.
• Riddoch, I., Grace, J., Fasehun, F.E., Riddoch, B. & Ladipo, D.O., 1991. Photosynthesis and successional status of seedlings in a tropical semi-deciduous rain forest in Nigeria. Journal of Ecology 79(2): 491–503.
• Terashima, H. & Ichikawa, M., 2003. A comparative ethnobotany of the Mbuti and Efe hunter-gatherers in the Ituri forest, Democratic Republic of Congo. African Study Monographs 24(1–2): 1–168.
• Veenendaal, E.M., Swaine, M.D., Lecha, R.T., Walsh, M.F., Abebrese, I.K. & Owusu-Afriyie, K., 1996. Responses of West African forest tree seedlings to irradiance and soil fertility. Functional Ecology 10(4): 501–511.
Sources of illustration
• Aubréville, A., 1959. La flore forestière de la Côte d’Ivoire. Deuxième édition révisée. Tome deuxième. Publication No 15. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 341 pp.
• Hawthorne, W. & Jongkind, C., 2006. Woody plants of western African forests: a guide to the forest trees, shrubs and lianes from Senegal to Ghana. Kew Publishing, Royal Botanic Gardens, Kew, United Kingdom. 1023 pp.
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

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:
Oyen, L.P.A., 2008. Pterygota macrocarpa K.Schum. 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, leaf; 2, male flower; 3, female flower; 4, fruit; 5, seed.
Redrawn and adapted by Iskak Syamsudin

tree habit

leaves and fruits

obtained from
Carlton McLendon, Inc.

wood in tangential section