Walnut is the fruit of the walnut tree (Juglans regia), a plant native to Asia (slopes of the Himalayas), introduced in Europe in ancient times, which can reach 20 meters in height; the walnut is formed by a seed, called gheriglio, covered with a skin and sandwiched between two woody shells (which form the endocarp) of brown color, wrapped in a green casing called mallo, which when ripe opens. In Italy its cultivation is of some importance only in the Campania region. Among the varieties of general interest are: Sorrento: it is the most widespread variety in Italy, it produces medium fruits, oval in shape, one with elongated, regular, slightly pointed shell (with "lace") at the apex and beveled at the base and the other round and smaller, of good quality. The shell is light in color, not very wrinkled, thin, so much so that it breaks with a slight pressure. The gheriglio is creamy white in color, not very oily (therefore able to preserve well for a certain time), substantial, tender and crunchy. Franquette: French, produces large fruits, oval in shape, of excellent quality. Hartley California: produces large fruits, suboval in shape, of good quality. Others such as: Malizia, selection of Sorrento, Feltrina, Bleggiana, Cerreto and Midland.