Lichens on basalt rock. Lichens consist of two organisms living in close partnership - a fungus and an alga. Single cells of the alga are enmeshed in a mass of fungal hyphae, which anchor the lichen to the rock. The fungus benefits from the alga by obtaining food produced by photosynthesis. What the alga gains is not clear, but some biologists believe it receives nutrients from the fungus as well as protection and support. Although the fungi that grow in lichens are incapable of living independently, the algae grow faster alone, which raises the question of whether the relationship is symbiotic, as is often thought, or parasitic.