You may have seen the small, moss-like plants called lichens covering rocks or the branches of old trees. Though you’d never guess it from looking at these plants, lichens are really two plants in one: a fungus and an alga.
The fungus and alga in a lichen live so closely together that you’d need a microscope to tell them apart. The relationship of this fungus and alga in a lichen is called symbiotic, which means that both the fungus and alga help each other survive.
The lichen’s fungi send branchlike pieces into rocks or pieces of wood from which they absorb moisture and minerals. The algae make food by photosynthesis, the process that all green plants use to make food from sunlight, minerals, and water.
So, the fungus “waters” the alga, and the alga “feeds” the fungus.
