Commercial Timbers


H. G. Richter and M. J. Dallwitz

Bixa arborea Huber (Urucú da mata)

Nomenclature etc. BIXACEAE. Including Bixa orellana (shrub). Trade and local names: urucú, u. bravo, u. da mata (BR); arnato, achiote, bija, bixa, urucú (sAm); anatto (GB); roucou (FR); Orlean-strauch (DE). Not protected under CITES regulations.

Tree and shrub. Geographic distribution: Mexico and Central America to tropical South America.

General. Growth ring boundaries indistinct or absent. Heartwood basically brown and yellow white or grey, without streaks. Sapwood colour similar to heartwood colour. Odour indistinct or absent. Density 0.228–0.35 g/cm³. Wood of commercial potential, or of no commercial potential.

Vessels. Wood diffuse-porous. Vessels arranged in no specific pattern, in multiples, commonly short (2–3 vessels) radial rows or radial rows of 4 or more. Average tangential vessel diameter 90–150(–190) µm. Average number of vessels/mm² 4–8. Average vessel element length 340–430–630 µm. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 3–5 µm, vestured. Vessel-ray pits with distinct borders, similar to intervessel pits. Helical thickenings absent. Tyloses in vessels absent. Other deposits in heartwood vessels not observed.

Tracheids and fibres. Vascular or vasicentric tracheids commonly present (vasicentric). Fibres very thin-walled. Average fibre length 720–1100–1900 µm. Fibre pits common in both radial and tangential walls, simple to minutely bordered or distinctly bordered. Helical thickenings absent. Fibres non-septate.

Axial parenchyma. Axial parenchyma not banded. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse-in-aggregates. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 2–4. Unlignified parenchyma absent.

Rays. Rays 8–12 per tangential mm, multiseriate (also if only few), 1–3 cells wide. Rays with multiseriate portions as wide as uniseriate portions absent. Aggregate rays absent. Rays of one size. 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. Sheath cells absent. Tile cells absent. Perforated ray cells present. Disjunctive ray parenchyma end walls indistinct or absent. Rays contain perforated ray cells and horizontally oriented vascular elements, interspersed with parenchymateous cells (see Chalk & Chattaway 1933, Carlquist 1960, 1988).

Storied structures. Storied structure present, all rays storied, axial parenchyma storied, vessel elements storied, fibres storied. Arrangement of tiers regular (horizontal or straight), or irregular. Number of ray tiers per axial millimetre 3–4. Longitudinally fused rays extend over several stories.

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

Cambial variants. Included phloem absent. Other cambial variants absent. Occasionally with small groups of non-perforated vascular elements without contact to vessels, embedded between fibres and axial parenchyma strands.

Mineral inclusions. Crystals not observed. Silica not observed.

Illustrations. • Transverse section. Bixa orellana.. • Tangential section. Bixa orellana.. • Radial section. Bixa orellana..

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.’.