Aerial Roots, roots produced in the air, which mostly also take in nourishment from atmospheric moisture. They are accordingly almost confined to tropical plants. The roots put out by the climbing stems of ivy serve to attach the plant and take in water that may trickle down the trunk on which it grows. Most aerial roots, such as those of the banyan (Ficus indica), are produced adventitiously from the branches; but in mangroves they are tap-roots produced by the germination of seeds in fruits still hanging on the parent tree. In both these cases the aerial roots grow to the ground or mud, acquire a thick cork, and resemble stems externally. Many tropical orchids are epiphytes, attached to the boughs of trees by green aerial roots which never reach the ground.