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In summer the Ailanthus is readily distinguished from all other trees cultivated in England by its large pinnate leaves, which have at the base of the leaflets on each side one or two glandular teeth. The black walnut, butternut, and Cedrela sinensis have somewhat similar foliage; but in these the glandular teeth are wanting. The bark of Ailanthus is quite peculiar, and when once seen cannot be confounded with that of any other tree.

In winter Ailanthus is easily recognised by its bark in trees of a certain size; but in all stages of growth it is well marked by the characters of the buds and branchlets.

The buds are alternate, uniform in size, small and hemispherical, and show externally 2 or 3 brown tomentose scales. The buds are set obliquely on the twigs just above the leaf-scars. The latter are large, heart-shaped, and slightly concave; and on their surface may be seen about 7 little elevated cicatrices which correspond to the vascular bundles of the fallen leaves. No true terminal bud is formed; and at the apex of the twig there is an elevated small circular scar, which marks the spot where the tip of the branchlet fell off in summer. The twigs are very coarse, glabrous, or finely pubescent, shining and brown in colour, with a few plainly visible lenticels. The pith is large, buff or yellowish in colour, showing clearly on section the medullary rays. In Cedrela there is a large terminal bud, and the leafscar has 5 cicatrices. The chambered pith of Juglans will readily distinguish the black walnut and butternut.

Several varieties are mentioned in books; aucubæfolia, pendulifolia, rubra, and flavescens being recognised by Schelle; but it is doubtful if any of these are sufficiently marked to deserve recognition. The Ailanthus flavescens of gardens was determined by Carrière to be Cedrela sinensis. A form with variegated leaves is mentioned by Koch, but it is exceedingly rare. The Kew Hand-list only admits one variety, pendula, a form somewhat weeping in habit.

Ailanthus glandulosa has been only found truly wild on the mountains of the province of Chihli in Northern China; but it is cultivated in most parts of China, and doubtless was once a constituent of the forests of the northern coast provinces, most of which have been destroyed by the Chinese. I never saw it wild in any of the mountain forests of Central or Southern China. When first introduced