Classification of Lichen - Types of Lichen

Lichens are slow growing, long living organism formed by the symbiotic association between algae and fungi that form a unique morphology distinct from both partner.

• The fungal partner is called mycobiont
• The algal partner is called phycobiont

Lichens are classified on the basis of 1) habitat, 2) the group of fungal partner,  3) thallus structure and 4) the distribution of algal component in the thallus
I. Based on habitat
1. Saxicolous: Rock dwellers eg: Peltigera

2. Corticolous: Bark livers eg: Parmelia
3.Terricolous: Soil livers eg: Cladonia floerkeana
4. Lignicolous: Wood livers eg: Cyphellum
II. Based on the group of fungal partner
1.Ascolichen: Fungal partner is an ascomycete
A: Gymnocarpae: Fruiting body apothecium eg: Usnea
B. Pyrenocarpae: Fruiting body perithecium eg: Verrucaria
2. Basidiolichen: Fungal partner is a basidiomycete eg: Dictyonema
III. Based on thallus structure
1.Leprose lichen: minute scales attached superficially to the substratum eg: Lepraria
2. Crustose: crust like, closely attached to the substratum at several points.
eg: Graphis

3.Foliose: flat leaf like lobed thallus attached to the substratum at one or many points.
eg: Parmelia

4. Fruticose: branched, erect or pendulous with a bushy appearance. Attached to the substratum by a basal disc. eg: Usnea

IV. Based on distribution of algal component in the thallus
1.Homoisomerous thalli: algal cells and fungal hyphae are uniformly distributed in the thalllus eg: Collema
2. Heteromerous thalli: Algal cells forms a distinct layer or algal zone and fungal hyphae in different layer eg: Parmelia. Learn more on the structure of heteromerous thallus