Commercial timbers

H.G. Richter and M.J. Dallwitz

Parashorea spp. (Urat mata, white seraya, gerutu)

Nomenclature etc. DIPTEROCARPACEAE. Light weight timbers: Parashorea macrophylla, P. malaanonan, P. tomentella; heavy timbers: P. aptera, P. densiflora, P. lucida, P. parviflora, P. smythiesii, P. stellata. Trade and local names: light weight timbers: Weißes seraya, w. lauan (DE); white seraya, urat mata (MY-sab); seraya puteh (MY-sar); white lauan, bagtikan (PH); pendan (ID). heavy timbers: heavy white seraya, urat mata batu (MY-sab), gerutu, meranti gerutu (MY); khai kheo, khiansai (TH); thinkadu, tavoy wood (MM); cho chi (VN); may nao (LA); comment: this timber group is not to be mixed up with the trade timber 'white meranti' (Shorea/anthoshorea). Not protected under CITES regulations.

Tree. Geographic distribution: Myanmar (Burma), Thailand, Laos, Vietnam, Cambodia, Indomalesia.

General. Heartwood basically white or grey and brown (light-weight timbers light brown with pinkish hue), green and brown (heavy timbers olive brown); heavy timbers only with streaks. Sapwood colour similar to heartwood colour, or distinct from heartwood colour. Density 0.35–0.63 g/cm³ (light-weight timbers), or 0.6–0.8 g/cm³ (heavy timbers).

Vessels. Wood diffuse porous. Vessels in multiples, commonly in short (2–3 vessels) radial rows. Average tangential vessel diameter 180–280 µm. Average number of vessels/mm² 3–7. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 5–7 µm, pits vestured. Vessel-ray pits with distinct borders or with reduced borders or apparently simple, similar to intervessel pits or different from intervessel pits, rounded or angular (round to oval). Tyloses present, thinwalled.

Tracheids and fibres. Vascular or vasicentric tracheids commonly present. Fibres of medium wall thickness. Fibre pits common in both radial and tangential walls, distinctly bordered.

Axial parenchyma. Axial parenchyma banded (axial resin canals embedded in parenchyma bands) or not banded. Bands fine or coarse. Axial parenchyma apotracheal, or paratracheal. Apotracheal axial parenchyma rare diffuse, or diffuse-in-aggregates. Paratracheal axial parenchyma vasicentric, aliform, confluent, and unilateral. Aliform parenchyma of the winged type. Axial parenchyma as strands. Average number of cells per strand: 4.

Rays. Rays 4–6 per tangential mm, multiseriate, (2–)4–7 cells wide. Height of large rays commonly 500 to 1000 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 or mostly 2–4 marginal rows of upright or square cells. Sheath cells only Parashorea lucida present, or absent.

Storied structures. Storied structure present, rays not storied, axial parenchyma storied.

Secretory structures. Intercellular canals present, oriented axially or oriented radially (only P. smythiesii), axial intercellular canals in long tangential lines or in short tangential lines.

Mineral inclusions. Crystals present, prismatic, located in ray cells or axial parenchyma cells. Crystal-containing ray cells procumbent, upright and/or square ray cells chambered or not chambered. Crystals in procumbent ray cells in radial alignment, or not in radial alignment. Crystal-containing axial parenchyma cells chambered, or not chambered. Number of crystals per cell or chamber one, or more than one. Silica not observed.

Physical and chemical tests. Heartwood not fluorescent. Water extract not fluorescent; colour of water extract colourless to brown. Ethanol extract not fluorescent. Colour of ethanol extract colourless to brown. Splinter burns to partial ash. Ash white to grey.

Illustrations. • Macroscopic images. transverse (ca. 10x). radial (natural size). • Transverse section. Parashorea sp. axial intercellular canals (IC) generally present (left) but often missing in a given specimen (right). IC. • Tangential section. Parashorea malaanonan. • Tangential section. Parashorea smythiesii. radial intercellular canals exclusively in this particular species, in all others absent. • Radial section. Parashorea tomentella. • Crystals. Parashorea sp. prismatic crystals in all species: scarce to abundant in both rays (left) and axial parenchyma (right).