Family 4. Juglandifloræ.
This family resembles the Quercifloræ in the catkin-like inflorescences, the imperfect, unisexual flowers, the epigynous perianth and the woody shoots with scattered leaves, etc., though it is in other respects very dissimilar; one point of difference is the presence of aromatic compounds, but a more important divergence is found in the structure of the gynœceum, which is formed of two carpels with one loculus and has one basal, orthotropous and erect ovule, which, as in the Quercifloræ, does not become developed until after pollination; the fruit too is very different, being generally a drupe. Endosperm absent.
Fig. 337.—Juglans regia: A ♂-flower seen from below with bract (cover-scale) (b), bracteoles (α and β), perianth-leaves (p); B the same from the front; C lateral view of the same; D diagram of A; E ♀-flower with bract, the bracteoles are united with the ovary, their edge being visible as an indented line below the perianth; F 2 ♀-flowers at the end of a foliage-shoot; G fruit (without the fleshy covering) in longitudinal section; H transverse section of the same.
Order 1. Juglandaceæ (Walnuts). Leaves scattered, imparipinnate, rich in aromatic compounds. Stipules absent. Flowers unisexual. Monœcious. The ♂-catkins are lateral, generally on naked branches of the previous year, cylindrical, pendulous, many-flowered; the two bracteoles and the 2–4-leaved perianth of the ♂-flower unite with the subtending bract; the ♂-flower has indefinite stamens (6–20 in Juglans, Fig. [337] A-D). The ♀-catkins are terminal, generally on branches of the same year, few-flowered (Fig. [337] F); the ♀-flowers have a superior, 4-leaved perianth, a bicarpellate gynœceum, two styles with stigmas on the internal surface. The ovary, bracteoles and bract all unite together (Fig. [337] E). The fruit is generally a green or black drupe,[34] whose flesh (outer soft portion) in Carya and Juglans ruptures more or less irregularly, and frees the stone (“Walnut”).—The stone in Juglans is divided internally by one true (Fig. [337] H) and by several false, low partition walls into several incomplete compartments, so that the two large cotyledons become lobed and incised to fit like a cast into the irregularities of the inner surface of the stone; the embryo is exendospermous and covered with a thin testa.—The leaf scars are large and cordate with 3 groups of vascular bundles. The PITH in Juglans and Pterocarya is divided into chambers. The stone ruptures, on germination, along the dorsal suture into 2 valves; the cotyledons remain underground. In Juglans regia a long row of accessory buds is found on the lowest internode (epicotyl) above the axils of the cotyledons. Pollination by the wind. Both protogynous and protandrous examples of Juglans regia occur.—33 species, mostly in temperate North America.—Uses. Walnuts are obtained from J. nigra and regia; Hickory from North American species of Carya. The oil-containing seeds of several species are edible. Pterocarya and others are cultivated as ornamental plants.
Fig. 338.—Myrica gale: a young fruit; × the bracteoles with numerous glands; b longitudinal section of fruit.
Order 2. Myricaceæ. To this order belong shrubs or trees which have penninerved, simple, at most lobed or pinnatifid leaves, with or without stipules, and with yellow, aromatic, resin glands (Fig. [338] a). The flowers, situated in catkin-like spikes, are unisexual and naked, and supported by scale-like floral-leaves. ♂-flower: 4–6 (–16) stamens with short filaments; ♀: generally situated singly. The gynœceum has a short style with 2 long stigmas, and unites with the bracteoles, which form wing-like outgrowths on the ripe drupe as in Pterocarya in the Juglandaceæ (Fig. [338]). Cotyledons fleshy (Fig. [338] b).—Myrica; Comptonia.
40 species; Temperate.—Myrica gale (Sweet-gale, Bog-myrtle) has been used in the preparation of beer (Sweet-willow beer) on account of its resinous essential oil. M. cerifera (N. America) and species from the Cape, M. quercifolia and others, form wax on the fruit which is used in the preparation of candles.