Juglans 25 1 



JUGLANS REGIA, Common Walnut 



Juglans regia, Linnaeus, Sp. PI. 997 (1753); Loudon, Arb. et Frut. Brit. iii. 142 1 (1838). 



A deciduous tree, attaining 100 feet in height and 15 to 18 feet in girth. Bark 

 smooth aiid silvery grey in young trees, becoming ultimately more or less deeply 

 fissured. 



Leaves large, up to 10 inches long, coriaceous, of five to nine (rarely as many as 

 thirteen) leaflets, sub-opposite or opposite, the terminal leaflet stalked, the others 

 subsessile ; elliptic, long-ovate or obovate, shortly acuminate at the apex, tapering 

 and unequal at the base, glabrous on both surfaces, except for inconspicuous tufts of 

 pubescence in the axils of the nerves on the lower surface ; dark green above, paler 

 beneath, entire or slightly sinuate in margin ; exhaling an aromatic odour. Venation 

 pinnate, with ten to fourteen pairs of lateral nerves, which run nearly straight to near 

 the margin, where they curve forwards and join with the next vein. The leaflets 

 diminish in size from the apex to the base of the leaf. Rachis glabrous, terminal 

 leaflet not articulated. Young shoots glabrous, with yellow sessile glands and white 

 inconspicuous lenticels. 



Male catkins arising singly or in pairs (one above the other) above the leaf-scars 

 of the previous year's shoots, green, two to five inches long, sessile, pendulous, thickly 

 cylindrical and densely flowered ; flowers with stalked bracts, two to five perianth 

 leaves and two bracteoles ; stamens ten to twenty ; anthers oblong, apiculate. 

 Female flowers, one to four, at the apex of the young shoots, green, with usually 

 purple stigmas ; involucre minute, indistinctly four-toothed ; perianth green, with four 

 linear-lanceolate divisions. 



Fruit globular, about two inches in diameter ; pericarp green, smooth, glandular- 

 dotted, coriaceous, and very aromatic, splitting irregularly when mature. Nut very 

 variable in shape, wrinkled and irregularly furrowed, thin- or thick-shelled ; divided 

 interiorly by two thin dissepiments into four incomplete cells ; one dissepiment separat- 

 ing the two cotyledons, the other dissepiment dividing them into two lobes. The 

 structure of the fruit of the walnut is very complicated, and the reader is referred 

 for further details to Lubbock's paper ' on the fruit and seed of the J uglandeae. 



The common walnut, according to Kerner,^ is truly monoecious, the stigmas, 

 however, ripening several days before the pollen is shed from the anthers.' The 

 unripe male catkins have the flowers crowded together in a short thick spike 

 directed upwards. As soon as the pollen develops the spike elongates to three 

 or four times its former length and becomes loose and pendulous, the flowers 



^ Jour, Linn. Soc. (Bot.), xxviii. 247 (1890). Cf. also Lubbock, .Seedlings, ii. 506 seq. (1 902). Malformed walnuts 

 are occasionally produced, which are very curious. Cf. Gard. Chron. 1858, p. 5, and 1890, viii. 758, fig. 154. 



2 Cf. Kerner, Nat. Hist. Plants, Eng. trans, i. 742, fig. 184 (1898). 



' This is not invariable. Delpino observed that while certain trees of the common walnut were protogynous, i.e. the 

 stigmas ripening first, other trees were protandrous, the stigmas ripening after the anthers. In such cases the trees behave as 

 if they were dioecious. Cf Darwin, Diff. Forms of Flowers, 10 (1877), and Trelease, Missouri Bot. Garden Report, vii. 

 27 (1896). 



