Lichens are the symbiotic association of algal and fungal part so, are closely associated with each other.so, that they provide single body structure. Algal part is known as phycobiont. It prepares food for itself and for the fungal part also. Fungal part is known as mycobiont. It absorbs water and minerals and provides protection to the thallus. Thallus structure is irregular and variously coloured like black, brown, white, red, orange.
They have a wide range of occurrence. They are found in a various type of habitat like a tree trunk, branches of trees, fallen leaves, wall and leaf on the surface of a rock.
There are various types of lichens. They are as follows;
Crustose lichens are very thin and closely attached to substratum so, it is difficult to separate it from the substratum. They bear fruiting body, apothecia on the upper surface. Eg; Lecanora, Graphis. Lecanora, Graphis.
Foliose lichens are much branched and folded and it forms leaf-like appearance. They are attached to substratum with the help of rhizine.
They are much branched, erect, and pendulous structure. They bear fructose body at the tip of branches. Eg; Clodonia unsea