Nomenclature etc. JUGLANDACEAE. Trade and local names: J. regia: Nussbaum, Gemeiner Walnussbaum, Französisch -, Italienisch-, Kaukasisch-, Nepal-, Persisch-, Türkisch Nussbaum (DE); noyer commun (FR), walnut (GB, US), Europees noten (NL), noce (IT), geviz (TR), dié (HU), nogal (ES); J. nigra: Amerikanischer Nussbaum, black walnut, Schwarznuss (DE), oresák cerny (CZ), noyer noir (FR), American walnut (GB), American black walnut, Eastern black walnut (US), noce nero (IT), oreh crni, oreh crni (CS), Amerikaans noten (NL), nuc negru (RO), orech tschornyi (RU), fekete diá (HU). Not protected under CITES regulations.
Tree. Geographic distribution: Europe, excl. Mediterranean and North America.
General. Growth ring boundaries distinct. Heartwood basically brown to yellow (J. regia) brown to purple (J. nigra), with streaks. Sapwood colour distinct from heartwood colour. Density 0.45–0.64–0.74 g/cm³.
Vessels. Vessels present. Wood semi-ring-porous (to sometimes diffuse porous). Vessels in multiples, commonly short (2–3 vessels) radial rows. Average tangential vessel diameter 75–135–210 µm. Average number of vessels/mm² 3–14. Perforation plates simple. Intervessel pits alternate, average diameter (vertical) 9–13 µm. Vessel-ray pits with reduced borders or apparently simple. Helical thickenings absent. Tyloses in vessels present, thinwalled. Other deposits in heartwood vessels so called "reticulate" thickenings were observed in J. nigra (Miller 1976), only in small latewood vessels.
Tracheids and fibres. Fibres of medium wall thickness. Average fibre length 1000–2000 µm. Fibre pits mainly restricted to radial walls, simple to minutely bordered. Fibres non-septate.
Axial parenchyma. Axial parenchyma present, banded (rarely). Axial parenchyma bands marginal (or seemingly marginal), scalariform, fine, up to three cells wide. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse-in-aggregates. Axial parenchyma as strands. Average number of cells per axial parenchyma strand (3–)6–8.
Rays. Rays 6–8 per tangential mm, multiseriate (also if only few), (1–)3–5 cells wide. Rays composed of a single cell type (homocellular), or two or more cell types (heterocellular) (J. regia: homocellular; J. nigra: weakly heterocellular); homocellular ray cells procumbent. Heterocellular rays with square and upright cells restricted to marginal rows, mostly 1 marginal row of upright or square cells.
Storied structures. Storied structure absent.
Secretory structures. Oil and mucilage cells absent.
Mineral inclusions. Crystals present, prismatic, located in axial parenchyma cells. Crystal-containing axial parenchyma cells chambered, or not chambered. Number of crystals per cell or chamber one. Crystal containing cells of normal size, or enlarged (idioblasts). Crystals observed only in J. nigra. Silica not observed.
Illustrations. • Macro images. Juglans regia. Transverse. Tangential. • Transverse section: J. regia. Juglans regia. • Tangential section: J. regia. Juglans regia. • Radial section: J. regia. Juglans regia. • Transverse section: J. nigra. Juglans nigra. • Tangential section: J. nigra. Juglans nigra. • Radial section: J. nigra. Juglans nigra. (Inset: large prismatic crystals in axial parenchyma cells (absent in Juglans regia)).
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’.