AILANTHUS (more correctly ailantus, from ailanto, an Amboyna word probably meaning "Tree of the Gods," or "Tree of Heaven"), a genus of trees belonging to the family Simaruba ceae. The best known species, A. glandulosa, Chinese sumach or tree of heaven, is a handsome, quick-growing tree with spread ing branches, and large compound leaves, resembling those of the ash, and bearing numerous pairs of long pointed leaflets. The small greenish flowers are borne on branched panicles; and the male ones are characterized by having a disgusting odour. The fruits are free in clusters, and each is drawn out into a long wing with the seed in the middle. The wood is fine grained and satiny. The tree, which is a native of China and Japan, was introduced into England in 1751 and is a favourite in parks and gardens. It has been extensively planted in the eastern United States where it is one of the few trees which will grow in smoky manufacturing districts. Two other species, A. imberiflora and A. punctata are important Australian timber-trees ; A. excelsa is common in India.