Nomenclature etc. STERCULIACEAE. Species included in the description: Pterospermum acerifolium Willd., P. canescens Roxb., P. elongatum Korth., P. javanicum Jungh. Not protected under CITES regulations.
Description based on 4 specimens. Tree. Geographic distribution: Burma, Thailand, Laos, Vietnam, Cambodia, and Indomalesia.
General. Growth ring boundaries distinct and indistinct or absent. P.elongatum, P.javanicum: growth ring limits microscopically indistinct. Heartwood basically brown. Sapwood colour similar to heartwood colour and distinct from heartwood colour. Odour indistinct or absent.
Vessels. Vessels present. Wood diffuse-porous. Vessels arranged in no specific pattern, in multiples, commonly short (2–3 vessels) radial rows, radial rows of 4 or more, and in clusters. Vessel outline rounded. Two distinct vessel diameter classes absent. Average tangential vessel diameter 80–130–230 µm; diameter of vessel lumina: large. Average number of vessels/mm² (3–)5–12; vessels per square millimetre few. 3–4 vessels per mm² in P. elongatum. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 4–8 µm, small, 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 present and absent, thinwalled. Other deposits in heartwood vessels present and not observed, tyloses and reddish brown gums in vessels of P.javanicum.
Tracheids and fibres. Vascular or vasicentric tracheids sporadic to absent. Fibres very thin-walled and 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 marginal (or seemingly marginal), fine, up to three cells wide. Axial parenchyma apotracheal and paratracheal. Apotracheal axial parenchyma diffuse and diffuse-in-aggregates. Paratracheal axial parenchyma scanty and vasicentric. Axial parenchyma as strands. Average number of cells per axial parenchyma strand (3–)4(–5). Unlignified parenchyma absent. P.elongatum und P.javanicum: no banded parenchyma observed.
Rays. Rays present, 6–12 per tangential mm, multiseriate (also if only few), 1–2–3(–6) cells wide, narrow (2–3 seriate), of medium width (3–5 seriate), and wide (5–10 seriate). Rays with multiseriate portions as wide as uniseriate portions absent. Aggregate rays absent. Rays of two distinct sizes and of one size. 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. Sheath cells absent. Tile cells present. Perforated ray cells absent. Disjunctive ray parenchyma end walls indistinct or absent. P.elongatum and P.javanicum with rays of two different size classes.
Storied structures. Storied structure present, all rays storied and some rays storied, some not, axial parenchyma storied, vessel elements storied, fibres storied. Arrangement of tiers regular (horizontal or straight) and irregular. Storied structure conspicuous in P.canescens and P.acerifolium, irregular in P.elongatum and P.javanicum.
Secretory structures. Oil and mucilage cells absent. Intercellular canals absent. Laticifers or tanniniferous tubes absent.
Cambial variants. Included phloem absent. Other cambial variants absent.
Mineral inclusions. Crystals present, prismatic, located in ray cells and axial parenchyma cells. Crystal-containing ray cells upright and/or square, upright and/or square ray cells chambered and not chambered. Crystal-containing axial parenchyma cells not chambered. Number of crystals per cell or chamber one and more than one. Crystals in one cell or chamber of the same size. Crystal containing cells of normal size. Cystoliths absent. Crystals in chambered ray cells observed only in P.elongatum. Silica not observed.
Physical and chemical tests. Heartwood fluorescent. Water extract fluorescent; basically colourless to brown or shade of brown. Heartwood extractives not leachable by water. Ethanol extract not fluorescent. Colour of ethanol extract colourless to brown or shade of brown. Chrome azurol-S test negative. Froth test negative. Splinter burns to partial ash. Ash white to grey.
Illustrations. • Transverse section. Pterospermum javanicum. • Tangential section. Pterospermum canescens. • Radial section. Pterospermum elongatum. Pterospermum-type tile cells in rays (PTC). PTC. PTC.
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. http://delta-intkey.com’.