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| Commercial timbers |
Nomenclature etc. EUPHORBIACEAE. Trade and local names: hevea (GB, DE, MY, TH, IN); Gummibaumholz (DE); seringa, seringeira (BR); kayu karet (ID); arbol de caucho (sAm). Not protected under CITES regulations.
Tree. Geographic distribution: Indomalesia, tropical South America (cultivated extensively in Indomalesia and Africa).
General. Growth ring boundaries distinct. Heartwood basically yellow and white or grey. Sapwood colour similar to heartwood colour. Density 0.52–0.6–0.64 g/cm³. With unpleasant odour when fresh.
Vessels. Wood diffuse porous. Vessels arranged in no specific pattern, in multiples, commonly in short (2–3 vessels) radial rows or in radial rows of 4 or more (rarely up to 10). Average tangential vessel diameter 145–205–260 µm. Average number of vessels/mm² 1–3. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 10–12 µm, pits vestured. Vessel-ray pits with reduced borders or apparently simple, different from intervessel pits, rounded or angular. Helical thickenings absent. Tyloses present, thinwalled. Other deposits present (brown).
Tracheids and fibres. Fibres of medium wall thickness. Fibre pits mainly restricted to radial walls, distinctly bordered. Fibres non-septate.
Axial parenchyma. Axial parenchyma banded. Bands marginal (or seemingly marginal) or not marginal (or seemingly marginal). Axial parenchyma bands forming a reticulate pattern with rays. Bands fine. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse-in-aggregates (in short tangential lines). Axial parenchyma as strands. Average number of cells per strand: 4–8.
Rays. Rays 8–12 per tangential mm, multiseriate, 2–5 cells wide. Rays with multiseriate portions as wide as uniseriate portions rarely present, or absent. 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 2–4 marginal rows of upright or square cells or with more than 4 marginal rows of upright or square cells. Sheath cells absent.
Storied structures. Storied structure absent.
Secretory structures. Intercellular canals absent.
Cambial variants. Included phloem absent.
Mineral inclusions. Crystals present, prismatic, located in ray cells or axial parenchyma cells. Crystal-containing ray cells upright and/or square, upright and/or square ray cells chambered or not chambered. Crystal-containing axial parenchyma cells chambered, or not chambered. Number of crystals per cell or chamber one, or more than one. Crystals in one cell or chamber of the same size, or of two distinct sizes. Silica not observed.
Physical and chemical tests. Heartwood not fluorescent. Water extract fluorescent (light blue); colour of water extract colourless to brown, or yellow. Ethanol extract fluorescent (weakly violet). Colour of ethanol extract colourless to brown. Splinter burns to partial ash. Ash dark grey.
Illustrations. • Macroscopic images. transverse (ca. 10x). tangential (natural size). • Transverse section. • Tangential section. • Radial section.
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: 9th April 2019. delta-intkey.com’.
