Talk about Lichens.

Symbiotic association between fungus and green photosynthetic unicellular or filamentous algae or cyanobacteria, partner (mycobiont) is most often Ascomycete, although it is sometimes Basidiomycete, while green algae are the photosynthetic partner (photobiont) (bios=life) Fungus gives lichen its shape. Tissues made by hyphae represent most of lichens mass, fungus provides algae with ideal environment for growth and absorb essential minerals from air or rain. Aalgae constitutes in general from the internal layer providing food to Eumycetes. Cyanobacteria fix atmospheric N2 and convert it into organic, play role in nitrogen giving for ecosystem