define lichens and give two examples .
Lichens are the "dual or composite"organisms formed by the symbiotic associationbetween "algae and fungi".
They are the simple slow-growing plant that typically forms a low crusty, leaf-like or branching growth on rocks, walls and trees.
Example:
Peltigera Canina,Cristatella, Cretariaislandica,Parmelia(genus)