difine lychens Share with your friends Share 0 Tanzila answered this lichen is a composite organism made up of a fungus, usually an ascomycete, that grows symbiotically with an alga or a cyanobacterium and characteristically forms a crustlike or branching growth on rocks or tree trunks. 1 View Full Answer Devvrat Chaurasiya answered this Lychen is composed of fungi and algea . Both are helps to each other .And it is also known as the good pollution indicator. 0 Kulbhushan answered this a very small grey or yellow plant that spreads over the surface of rocks, walls and trees and does not have any flowers. 0