Ailanthus Desf.

Tall, fast-growing, sometimes deciduous, dioecious trees. Branches thick, pithy; leaf-scars large. Leaves large, imparipinnate or paripinnate (with a prolonged rachis), sometimes on a single tree, more or less tufted at the ends of the twigs, multijugate, base of petiole often shrunken when dry; leaflets opposite or subopposite, oblique, usually acuminate, (in Mal.) entire, rachis and petiole terete, pithy, nearly always with some glands on the undersurface, usually near the base; midrib and lateral nerves prominent on the undersurface; petiole, rachis, petiolules, and branchlets of the panicles usually striate when dry. Flowers in axillary panicles, 5(-6)-merous. Calyx small, 5(-6)-lobed or closed in bud and later irregularly dehiscing (often 2-lobed) to the base, rarely cupular. Petals 5(-6), induplicate-valvate in bud, concave, oblong to narrowly oblong, still enlarging during anthesis. Stamens 10, in male flowers inserted below the outer margin of the disk, in female flowers either of subnormal size (but without pollen) or vestigial or absent; anthers oblong to broadly oblong, latrorse to extrorse, filaments dorsally attached halfway, the 2 cells free in their lower half. Carpels 2-5, free, flat, in the male flowers vestigial or absent; styles 2-5, free or connate, inserted above the middle on the adaxial side; ovule 1, epitropous, anatropous, adaxially attached in the middle. Fruit a linear or oblong-lanceolate samara. Seed flat, orbicular or obovate or somewhat triangular, exalbuminous; testa thin; cotyledons 2, flat, planoconvex, radicle pointing upwards.

In Malaysia both in the rain-forest and in monsoon forest, below 1000 m, on the whole rather uncommon and never gregarious, in valleys, along streams, and in open places.

Uses. See under the species.