Humbertia madagascariensis (PROTA)

Humbertia madagascariensis Lam.

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Timber
Conservation status

Protologue: Encycl. 2: 356, t. 103 (1786).

Family: Convolvulaceae

Vernacular names

Bois de fer (Fr).

Origin and geographic distribution

Humbertia madagascariensis is endemic to Madagascar, where it is restricted to the south-eastern part of the island, from Manakara south to Taolañaro.

Uses

The wood from this tree, most commonly known as ‘endranendrana’ but also as ‘fantsinakoho’, is used for purposes where extreme durability and strength are required, mainly for heavy construction, outdoor and indoor joinery, poles, naval construction, wharves and bridges. Its nice polish makes it suitable for sculptures and turning. It is also suitable for heavy-duty and luxury parquet flooring, mine props, vehicle bodies, railway sleepers, sporting goods, toys, novelties and agricultural implements. However, it is little used because it is extremely difficult to saw and work.

Properties

The heartwood is pinkish creamy-white to pinkish pale brown, and distinctly demarcated from the greyish yellow sapwood. The grain is usually wavy, texture very fine. Fresh wood has a strong turpentine smell, but the odour has also been described as close to that of sandalwood.

The wood is extremely heavy, with a density of 1260–1300 kg/m³ at 12% moisture content, and extremely hard. The shrinkage rates during drying are moderate for such a heavy wood, from green to oven dry 4.4–6.6% radial and 6.8–7.9% tangential. Once dry, the wood is unstable in service. At 12% moisture content, the modulus of rupture is 168–276 N/mm², modulus of elasticity 14,100–23,540 N/mm², compression parallel to grain 91–108 N/mm², shear 6–9.5 N/mm², cleavage 18.5–19.5 N/mm and Chalais-Meudon side hardness 29–30.5.

The wood is very difficult to saw, work and plane; high power is needed and the wood causes severe blunting of saw teeth and cutting edges. It takes an excellent polish. Nailing is impossible because of its hardness. The wood glues and paints well. It is extremely durable, being resistant to fungal, insect and marine borer attacks. The heartwood is not treatable with preservatives.

Some sesquiterpenes have been isolated from the heartwood, including humbertiol.

Adulterations and substitutes

The wood of Phylloxylon spp. and Dialium unifoliolatum Capuron is used for similar purposes, although that of the latter species is less hard.

Description

Medium-sized tree up to 30 m tall; bole usually straight and cylindrical, up to 200 cm in diameter, often with small buttresses; bark surface grey to brown, finely cracked, inner bark with white bands; twigs with distinct leaf scars, reddish hairy when young. Leaves alternate, clustered at ends of twigs, simple and entire; stipules absent; petiole 0.5–1.5 cm long; blade obovate, 3–10.5 cm × 1.5–4 cm, cuneate at base, obtuse to slightly notched at apex, leathery, glabrous, pinnately veined with 6–9 pairs of lateral veins. Flowers axillary in leaf axils at ends of twigs, solitary or few together, bisexual, slightly zygomorphic, 5-merous; pedicel 1–1.5 cm long; sepals nearly free, obovate to rounded, c. 1 cm long, with membranous margins; corolla campanulate, c. 1.5 cm long, hairy outside, creamy white with membranous margins; stamens inserted on the corolla tube, c. 4.5 cm long; ovary superior, c. 4 mm long, hairy near apex, 2-celled, style slender, c. 4 cm long. Fruit an ellipsoid-ovoid berry c. 1.5 cm long, fruit wall slightly fleshy, smooth, brownish, indehiscent, 1–2(–4)-seeded. Seeds ovoid, c. 7 mm long, grooved on one side, beige, glabrous.

Other botanical information

Humbertia comprises a single species. It is considered a primitive genus of Convolvulaceae and has been placed in the tribe Erycibeae together with genera from America and Asia, but also in a separate family Humbertiaceae and in a subfamily Humbertioideae within Convolvulaceae. The latter view is most supported at present.

Anatomy

Wood-anatomical description (IAWA hardwood codes):

Growth rings: 2: growth ring boundaries indistinct or absent. Vessels: 5: wood diffuse-porous; 9: vessels exclusively solitary (90% or more); 13: simple perforation plates; 22: intervessel pits alternate; 26: intervessel pits medium (7–10 μm); 27: intervessel pits large (≥ 10 μm); 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 31: vessel-ray pits with much reduced borders to apparently simple: pits rounded or angular; 42: mean tangential diameter of vessel lumina 100–200 μm; 43: mean tangential diameter of vessel lumina ≥ 200 μm; 47: 5–20 vessels per square millimetre; 57: tyloses sclerotic. Tracheids and fibres: 62: fibres with distinctly bordered pits; 66: non-septate fibres present; 70: fibres very thick-walled. Axial parenchyma: 76: axial parenchyma diffuse; 78: axial parenchyma scanty paratracheal; 92: four (3–4) cells per parenchyma strand. Rays: 96: rays exclusively uniseriate; (97: ray width 1–3 cells); 104: all ray cells procumbent; (106: body ray cells procumbent with one row of upright and/or square marginal cells); 113: disjunctive ray parenchyma cell walls present; 115: 4–12 rays per mm; 116: ≥ 12 rays per mm.

(E. Ebanyenle, P.E. Gasson & E.A. Wheeler)

Ecology

Humbertia madagascariensis occurs in humid evergreen forest up to 600(–1000) m altitude.

Harvesting

Cutting Humbertia madagascariensis trees with their extremely hard wood is nearly impossible with hand tools and difficult with machine tools; special equipment is needed. Therefore they often were killed by fire and left standing after deforestation. Dead trees can stay upright for many years and fallen boles and branches remain undamaged for long periods.

Genetic resources

Already by the end of the 19^th century Humbertia madagascariensis has been reported to have become rare, and at the end of the 1940s it was considered nearly extinct, mainly because of land clearance and burning. Although populations still exist in south-eastern Madagascar, Humbertia madagascariensis is certainly threatened and protection is needed.

Prospects

The wood with its extreme durability is in demand for special purposes, especially for construction in contact with water. However, current focus should be at protection, and research on many aspects of this poorly studied species is recommended, particularly on propagation and growth rates.

Major references

• 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.

• Capuron, R., 1957. Essai d’introduction à l’étude de la flore forestière de Madagascar. Inspection Générale des Eaux et Forêts, Antananarivo, Madagascar. 125 pp.

• Deroin, T., 2001. Convolvulaceae. Flore de Madagascar et des Comores, familles 133 bis et 171. Muséum National d’Histoire Naturelle, Paris, France. pp. 11–287.

• Guéneau, P., 1971. Bois de Madagascar. Possibilités d’emploi. Centre Technique Forestier Tropical, Antananarivo, Madagascar. 75 pp.

• Guéneau, P., Bedel, J. & Thiel, J., 1970–1975. Bois et essences malgaches. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 150 pp.

• Guéneau, P. & Guéneau, D., 1969. Propriétés physiques et mécaniques des bois malgaches. Cahiers scientifiques No 2, Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 51 pp.

• Parant, B., Chichignoud, M. & Rakotovao, G., 1985. Présentation graphique des caractères des principaux bois tropicaux. Tome 5. Bois de Madagascar. CIRAD, Montpellier, France. 161 pp.

• Sallenave, P., 1964. Propriétés physiques et mécaniques des bois tropicaux. Premier supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 79 pp.

• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.

• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.

Other references

• Boiteau, P., Boiteau, M. & Allorge-Boiteau, L., 1999. Dictionnaire des noms malgaches de végétaux. 4 Volumes + Index des noms scientifiques avec leurs équivalents malgaches. Editions Alzieu, Grenoble, France.

• Deroin, T., 1993. Anatomie florale de Humbertia madagascariensis Lam. Contribution à la morphologie compareé de la fleur et du fruit des Convolvulaceae. Bulletin du Muséum national d’Histoire naturelle, 4e série, section B, Adansonia, 14(2): 235–255.

• Rakotovao, G., Rabevohitra, R., Gerard, J., Détienne, P. & Collas de Chatelperron, P., en préparation. Atlas des bois de Madagascar. FOFIFA-DRFP, Antananarivo, Madagascar.

• Sallenave, P., 1971. Propriétés physiques et mecaniques des bois tropicaux. Deuxième supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 128 pp.

Sources of illustration

• Deroin, T., 2001. Convolvulaceae. Flore de Madagascar et des Comores, familles 133 bis et 171. Muséum National d’Histoire Naturelle, Paris, France. pp. 11–287.

• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.

Author(s)

• S. Rakotonandrasana

Centre National d’Application des Recherches Pharmaceutiques, B.P. 702, 101 Antananarivo, Madagascar

Correct citation of this article

Rakotonandrasana, S., 2011. Humbertia madagascariensis Lam. [Internet] Record from PROTA4U. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 18 December 2024.

• See the Prota4U database.