Commercial timbers

H. G. Richter and M. J. Dallwitz

Hymenolobium spp.

Nomenclature etc. PAPILIONACEAE. Species included in the description: Hymenolobium elatum Ducke (1), Hymenolobium excelsum Ducke (2), Hymenolobium flavum Kleinh. (2), Hymenolobium petraeumi0 Ducke (3). Status of protection under CITES regulations: not protected.

Description based on: 8 specimens. Tree. Geographic distribution: tropical South America.

General. Growth ring boundaries indistinct or absent. Heartwood basically brown and yellow, with streaks. Sapwood colour 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 and in clusters. Vessel outline rounded. Two distinct vessel diameter classes absent. Vessels often with radial multi-vessel tails. Average tangential vessel diameter 135–230–325 µm. Average tangential diameter of vessel lumina very large. Vessels per square millimetre very few. Perforation plates simple. Intervessel pits scalariform, average diameter (vertical) 6–10 µm, medium, 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, brown to black deposits.

Tracheids and fibres. Vascular or vasicentric tracheids sporadic to absent. Fibres very thick-walled. Fibre pits mainly restricted to radial walls, simple to minutely bordered. Helical thickenings absent. Fibres non-septate.

Axial parenchyma. Axial parenchyma present, banded. Axial parenchyma bands not marginal (or seemingly marginal), bands much wider than rays, coarse, more than three cells wide. Banded parenchyma less developed in H. excelsum. Axial parenchyma paratracheal. Paratracheal axial parenchyma aliform and confluent. Aliform parenchyma lozenge. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 4(–5). Unlignified parenchyma absent.

Rays. Rays present, multiseriate, also if only few, 2–3–5 cells wide, 2–3 cells wide and commonly 3–5 cells wide. 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 rays square and upright cells restricted to marginal rows. Number of marginal rows of upright or square cells 1. Sheath cells absent. Tile cells absent. Perforated ray cells absent. Disjunctive ray parenchyma end walls indistinct or absent. Wood rays 2–3 cells wide in H.elatum, H. flavum and H. petraeum; 3–5 cells wide in H.excelsum.

Storied structures. Storied structure present, all rays storied, axial parenchyma storied, vessel elements storied and not storied, fibres not storied. Arrangement of tiers regular (horizontal or straight) and irregular. Number of ray tiers per axial millimetre 2. Storied structure (rays) less obvious in H. flavum.

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 axial parenchyma cells. 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 fluorescent. Water extract fluorescent. Water extract basically colourless to brown or shade of brown. Heartwood extractives not leachable by water. Ethanol extract fluorescent. Ethanol extract basically red or shade of red. Water extract with yellow, ethanol extract with whitish fluorescence. Chrome azurol-S test negative. Froth test negative. Splinter burns to partial ash. Ash bright white.