Lichen

Lichens are a type of living organism that consists of two different types of organisms living together. One type is a fungus, which is like a plant but doesn't have roots and stems or leaves. The other type is an alga, which is a tiny plant that usually grows in moist, wet places like ponds and streams. The fungus and alga work together to get food and everything else they need to survive. The fungus gives the alga protection and a place to live and in return, the alga provides the fungus with food. Lichens can grow almost anywhere and look like warts or very small patches of moss.