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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, Mediterranean incl. N. Africa and Middle East, temperate Asia, India, Pakistan, Sri Lanka (Juglans regia), North America (Juglans nigra).
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 in 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, different from intervessel pits, rounded or angular. Tyloses present, thinwalled. 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 banded. Bands marginal (or seemingly marginal) or not marginal (or seemingly marginal). Axial parenchyma bands forming a reticulate pattern with rays. Bands fine. Axial parenchyma apotracheal. Apotracheal axial parenchyma diffuse-in-aggregates. Axial parenchyma as strands. Average number of cells per strand: (3–)6–8.
Rays. Rays 6–8 per tangential mm, multiseriate, (1–)3–5 cells wide. Height of large rays up to 500 µm. 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. Laticifers or tanniniferous tubes absent.
Mineral inclusions. Crystals present (only in J. nigra), prismatic, located in axial parenchyma cells. Crystal-containing axial parenchyma cells not chambered. Number of crystals per cell or chamber one. Crystal containing cells of normal size, or enlarged (idioblasts) (only in some specimens). Silica not observed.
Physical and chemical tests. Heartwood not fluorescent. Water extract fluorescent (bluish green (J. regia); blue (J. nigra)); colour of water extract colourless to brown. Ethanol extract fluorescent (J. nigra: variable depending on specimen, blueish, greenish or yellowish), or not fluorescent (J. regia). Colour of ethanol extract colourless to brown. Froth test positive. Splinter burns to partial ash. Ash white to grey.
Illustrations. • Macroscopic images. Juglans regia. transverse (ca. 10x). tangential (natural size). • 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. • Crystals: J. nigra. large prismatic crystals in axial aprenchyma cells (absent in Juglans regia). Juglans nigra.
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: 9th April 2019. delta-intkey.com’.
