Maples are distinguished by opposite leaf arrangement. The leaves in most species are palmate veined and lobed, with 3 to 9 (rarely to 13) veins each leading to a lobe, one of which is central or apical. A small number of species differ in having palmate compound, pinnate compound, pinnate veined or unlobed leaves. Several species, including "Acer griseum" (paperbark maple), "Acer mandshuricum" (Manchurian maple), "Acer maximowiczianum" (Nikko maple) and "Acer triflorum" (three-flowered maple), have trifoliate leaves. One species, "Acer negundo" (box-elder or Manitoba maple), has pinnately compound leaves that may be simply trifoliate or may have five, seven, or rarely nine leaflets. A few, such as "Acer laevigatum" (Nepal maple) and "Acer carpinifolium" (hornbeam maple), have pinnately veined simple leaves.