Ailanthus Desf. (1766), in the family Simaroubaceae, contains around 5 species in tropical Asia and Australia. Description Trees to 30m, with greyish bark. The leaves are alternate, deciduous, pinnate with 11–35 leaflets, the terminal leaflet solitary. The flowers are small, usually unisexual, in branched heads, at the ends of the branches. Sepals 5, rarely 6; petals 5, rarely 6, white. Stamens 2–5 in bisexual flowers, 10 in male flowers. Ovary superior, with 5 cells and 5 styles, each cell with a solitary ovule; after pollination the cells divide into separate fruits. Pollination is by insects. The fruits are winged samaras, often reddish, with 1 seed developing in each. Key Recognition Features The alternate, pinnate leaves and winged, reddish fruit make the tree similar to a large ash. Evolution and Relationships The family Simaroubaceae is considered close to Anacardiaceae and Meliaceae, which contains mahogany, Swietenia mahogani (L.) Jacq., from the West Indies, and the ornamental Melia azedarach L. with shining, much-divided leaves, small, purple flowers, and yellow-orange berries, commonly planted around the Mediterranean. Leitneria floridana Chapman, an isolated species from southeastern North America, is now considered to belong to the Simaroubaceae, although it is wind-pollinated, unlike the other genera. Its fossils have been found in Eocene deposits near London. Ecology and Geography Found in woods in central and southwestern China. Comment Ailanthus altissima (Mill.) Swingle is commonly planted as a street tree in cities. |
