Nomenclature etc. BETULACEAE. A. rubra Bong. - Syn.: A. oregona Nutt., A. rubra var. pinnatisecta Starker; A. incana (L.) Moench; A. glutinosa (L.) Gaertner. Trade and local names: A. glutinosa: Schwarzerle, Roterle, Gemeine Erle (DE), common alder, black alder (GB), aune (aulne) (FR), ontano nero (IT), elzen (NL); A. incana: Weißerle, Grauerle (DE); A. rubra: Amerikanische Roterle (DE), (Western) red alder, Oregon alder (US). Not protected under CITES regulations.
Tree. Geographic distribution: Europe, excl. Mediterranean, or Mediterranean incl. N. Africa and Middle East, or temperate Asia, or North America.
General. Growth ring boundaries distinct. Heartwood basically brown to red to yellow to white or grey. Sapwood colour similar to heartwood colour. Density 0.38–0.49–0.6 g/cm³. Frequently with pith flecks.
Vessels. Wood diffuse-porous. Vessels arranged in no specific pattern, in multiples, commonly short (2–3 vessels) radial rows and radial rows of 4 or more. Vessel outline angular. Average tangential vessel diameter 40–60–90 µm. Perforation plates scalariform, with 15–26 bars. Intervessel pits opposite or alternate, average diameter (vertical) 5–6 µm. Vessel-ray pits with distinct borders, similar to intervessel pits, restricted to marginal rows. Vessel-ray pits smaller (ca. 3 µm) than intervessel pits.
Tracheids and fibres. Fibres very thin-walled. Average fibre length 300–1010–1650 µm. Fibre pits mainly restricted to radial walls or common in both radial and tangential walls, simple to minutely bordered or distinctly bordered.
Axial parenchyma. Axial parenchyma present. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse and diffuse-in-aggregates. Axial parenchyma as strands. Average number of cells per axial parenchyma strand 4–8.
Rays. Rays 12–18 per tangential mm, exclusively uniseriate. Aggregate rays present. Rays composed of a single cell type (homocellular). Within aggregate rays up to 3-seriate.
Mineral inclusions. Crystals not observed. Silica not observed.
Illustrations. • Macro images. Transverse. Radial. Alnus glutinosa. • Overview. Alnus viridis. • Transverse section. Alnus viridis. • Tangential section. Alnus viridis. • Radial section. Alnus viridis.
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’.