limb

noun

(L. limbus: border, edge) A branch of a tree. The expanded portion of any petal, or of a leaf, such as the expanded portion of a gamopetalous corolla above the throat. The upper part of a leaf as distinct from the leaf base. The spreading part of a synsepalous calyx or sympetalous corolla, usually referring only to the calyx or corolla lobes, sometimes to their lips. The upper, free, spreading portion of a corolla or perianth that is connate at the base.