Commercial Timbers


H. G. Richter and M. J. Dallwitz

Autranella congolensis (de Wild.) A. Chev. (Mukulungu)

Nomenclature etc. SAPOTACEAE. Trade and local names: elang, elanzok (CM); bouanga (CF); mfua (CG); kungulu (AO); mukulungu (CD). Not protected under CITES regulations.

Description based on 4 specimens. Tree. Geographic distribution: tropical Africa.

General. Growth ring boundaries distinct to indistinct or absent. Growth ring limits often marked by the abruptly changing distance between parenchyma bands. Heartwood basically brown to red, without streaks. Sapwood colour distinct from heartwood colour. Odour indistinct or absent. Density 0.82–0.95 g/cm³.

Vessels. Wood diffuse-porous. Vessels arranged in diagonal and/or radial pattern and no specific pattern, in multiples, commonly short (2–3 vessels) radial rows to radial rows of 4 or more. Vessel outline rounded. Two distinct vessel diameter classes absent. Radial orientation of vessel multiples more or less evident. Average tangential vessel diameter 100–150 µm; diameter of vessel lumina: large. Average number of vessels/mm² 10–15; vessels per square millimetre few. Average vessel element length 400–800 µm. Average vessel element length medium. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 8–10 µm, medium, not vestured. Vessel-ray pits with distinct borders and with reduced borders or apparently simple, similar to intervessel pits and different from intervessel pits, rounded or angular and horizontal to vertical, of two distinct sizes or types in the same ray cell, of the same type in adjacent elements, located throughout the ray. Helical thickenings absent. Tyloses in vessels present, thinwalled.

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 marginal (or seemingly marginal) or not marginal (or seemingly marginal), reticulate, fine, up to three cells wide. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse to diffuse-in-aggregates. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 6–9. Unlignified parenchyma absent.

Rays. Rays 7–11 per tangential mm, multiseriate (also if only few), 1–3 cells wide, narrow (2–3 seriate). 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). Heterocellular rays with square and upright cells restricted to marginal rows, mostly 2–4 marginal rows of upright or square cells. Sheath cells absent. Tile cells absent. Perforated ray cells absent. Disjunctive ray parenchyma end walls distinct to indistinct or absent. Uniseriate rays composed exclusively of square and/or upright cells.

Storied structures. Storied structure absent.

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. Crystalliferous chains very short (3–5 crystals). Silica present, as grains, in rays cells and in axial parenchyma. Silica in rays typically restricted to marginal rows.

Physical and chemical tests. Froth test positive.

Illustrations. • Transverse section. Autranella congolensis . • Tangential section. Autranella congolensis. • Radial section. Autranella congolensis. • Mineral inclusions. Autranella congolensis. Small spherical silica particles in rays (primarily in marginal cells) and axial parenchyma cells (rare). Prismatic crystals occasionally in chambered and non-chambered axial parenchyma cells.

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.’.