Lichen

Definition:

Lichen is a plant-like growth that is actually a result of a fungus and algae living together.

It grows very slowly, lives for a long time, looks like moss or a crusty dry leaf and can grow on bare rock or soil.

Lichen is an important food source for caribou.

Source: INAC Glossary 

More:
Foliose lichens on a tree trunk Foliose lichens on a tree trunk

Source: UW-Madison Department of Botany 

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