Commercial Timbers


H. G. Richter and M. J. Dallwitz

Koompassia excelsa (Becc.) Taub. (Tualang)

Nomenclature etc. FABACEAE-CAESALPINIOIDEAE. Trade and local names: tualang (ID, MY). Not protected under CITES regulations.

Description based on 6 specimens. Geographic distribution: Thailand, Laos, Vietnam, Cambodia and Indomalesia.

General. Growth ring boundaries indistinct or absent. Heartwood basically brown and red, without streaks. Sapwood colour distinct from heartwood colour. Odour indistinct or absent. Density (0.57–)0.8–0.9(–1.12) g/cm³. With interlocked grain.

Vessels. Vessels present. Wood diffuse-porous. Vessels arranged in no specific pattern, in multiples, commonly short (2–3 vessels) radial rows and radial rows of 4 or more. Vessel outline rounded. Two distinct vessel diameter classes absent. Average tangential vessel diameter (90–)200(–290) µm; diameter of vessel lumina: large and very large. Average number of vessels/mm² 3–5; vessels per square millimetre very few. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 6–8 µm, medium, not vestured. Vessel-ray pits with distinct borders, similar to intervessel pits, of uniform size or type, of the same type in adjacent elements, located throughout the ray. Helical thickenings absent. Tyloses in vessels absent. Other deposits in heartwood vessels present, reddish brown organic deposits.

Tracheids and fibres. Vascular or vasicentric tracheids sporadic to absent. Fibres of medium wall thickness. Fibre pits mainly restricted to radial walls, simple to minutely bordered. Helical thickenings absent. Fibres non-septate.

Axial parenchyma. Axial parenchyma present, banded and not banded. Axial parenchyma bands not marginal (or seemingly marginal), bands much wider than rays, coarse, more than three cells wide. Axial parenchyma paratracheal. Apotracheal axial parenchyma diffuse-in-aggregates. Paratracheal axial parenchyma aliform and confluent. Aliform parenchyma winged. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 6–10. Unlignified parenchyma absent.

Rays. Rays present, 5–7 per tangential mm, multiseriate (also if only few), 2–3 cells wide, narrow (2–3 seriate). Rays with multiseriate portions as wide as uniseriate portions absent. Aggregate rays absent. Rays of one size. Height of large rays up to 500 µm. Rays composed of two or more cell types (heterocellular). Heterocellular rays with square and upright cells restricted to marginal rows, mostly 1 marginal row of upright or square cells and mostly 2–4 marginal rows of upright or square cells. Sheath cells absent. Tile cells absent. Perforated ray cells absent. Disjunctive ray parenchyma end walls indistinct or absent.

Storied structures. Storied structure present and absent, all rays storied, axial parenchyma storied, vessel elements storied, fibres not storied. Arrangement of tiers irregular. Number of ray tiers per axial millimetre 2. Storeying of rays more or less developed in different specimens.

Secretory structures. Oil and mucilage cells absent. Intercellular canals absent. Laticifers or tanniniferous tubes absent.

Cambial variants. Included phloem present, diffuse. Other cambial variants absent.

Mineral inclusions. Crystals present, prismatic and druses, located in ray cells and axial parenchyma cells. Crystal-containing ray cells upright and/or square, upright and/or square ray cells chambered. Crystal-containing axial parenchyma cells chambered. Number of crystals per cell or chamber one. Crystal containing cells of normal size. Cystoliths absent. Silica not observed.

Physical and chemical tests. Heartwood not fluorescent. Water extract fluorescent (yellow); basically colourless to brown or shade of brown. Ethanol extract not fluorescent. Colour of ethanol extract colourless to brown or shade of brown. Froth test negative (froth test weakly positive). Splinter burns to partial ash. Ash bright white.

Illustrations. • Transverse section. Koompassia excelsa. • Tangential section. Koompassia excelsa. • Radial section. Koompassia excelsa. • Crystals in rays and aial parenchyma. Koompassia excelsa. Druses in marginal ray cells + prismatic crystals in chambered axial parenchyma cells under normal (left) and polarized (right) light.

The interactive key allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting specified attributes, summaries of attributes within groups of taxa, and geographical distribution.

Cite this publication as: ‘Richter, H.G., and Dallwitz, M.J. 2000 onwards. Commercial timbers: descriptions, illustrations, identification, and information retrieval. In English, French, German, Portuguese, and Spanish. Version: 25th June 2009.’.