Page:TheTreesOfGreatBritainAndIreland vol02B.djvu/386



trees belonging to the order Juglandeæ, with large, alternate, compound, imparipinnate leaves; leaflets serrate; stipules absent. Buds scaly or naked, the lateral ones often multiple, two to three in a vertical row above the insertion of the leaf. Pith chambered. Flowers monœcious, numerous in long pendent catkins. Male catkins usually several, arising singly in the leaf axils; in some species (caucasica, stenoptera) lateral on the preceding year's shoots, with an occasional catkin on the current year's shoot; in other species (rhoifola, Paliurus) all on the new shoots. Stamens nine to eighteen in several series on the axis of a three- to six-lobed scale, to which a bract is adnate on the back, the scale representing two bracteoles and one to four perianth segments. Female catkins solitary, terminating the young shoot. Female flowers with a bract and two bracteoles at the base; perianth four-lobed, adnate to the ovary, which contains one ovule, and is surmounted by a short style, divided above into two papillose stigmatic divisions. Fruit catkins long, with numerous nut-like fruits, which have in most species two lateral wings, in one species a single orbicular wing all round, due to the enlarged bracteoles of the flower, the bract persisting little changed at the base of the fruit. Nutlet, with a thin pericarp and a hardened endocarp, the latter divided below into four imperfect cells, and containing one seed, which is four-lobed below. Cotyledons bi-partite, each division being again deeply divided, forming four linear segments; carried above ground in germination.

Pterocarya and Juglans have similar foliage, and agree in the chambered pith of the twigs. They are readily distinguished when in fruit, that of Pterocarya being always small and winged. When specimens in leaf only are obtainable, the best mark of distinction lies in the buds, which in Pterocarya are either without scales or are enclosed in a long conical beaked funnel-like covering, composed of membranous scales—differing in either case from the short buds of Juglans with two to three external scales,

Seven species of Pterocarya are known, occurring in Persia, the Caucasus, China, Tonking, and Japan. A hybrid species has been obtained in cultivation, which will be described under P. caucasica. The seven species which occur in the wild state may be arranged as follows:—