Acer negundo; box elder, ash-leaved maple [Sapindaceae]  Small to medium sized, weak-wooded tree.  Leaves pinnately compound with 3-7 coarsely toothed or shallowly lobed leaflets.  Staminate flowers in drooping clusters on separate trees from pistillate flowers, which occur in drooping racemes.  Seeds are U-shaped, winged, 1½-2" long and persistent on the tree.  Mature bark is gray-brown and deeply furrowed.  Native to moist forests, box elder has become quite common in disturbed uplands such as abandoned fields, fence rows, and untended urban sites.  [097]