Aerial roots form on above-the-ground structures, such as a leaf or stem, instead of the roots in soil. They serve different functions in different species; for example, the banyan tree (Ficus benghalensis) and red mangrove (Rhizophora mangle) have aerial roots called prop roots since they support the plant. The aerial roots of ivy (Hedera helix) and Spanish moss (Tillandsia usneoides) cling to the surface of an object, providing support for the stem.