Lichens grow on hard surfaces such as trees, paths, drives and rocks. They are not plants but are symbiotic combinations of fungi and algae or cyano-bacteria.
Lichens are flat tough patches of often circular leaf-like thallus on hard surfaces. They are symbiotic combinations of fungi and algae or cyanobacteria. The fungi are able to extract nutrients for the substrate and the algae or cyanobacteria produce food by photosynthesis.
Lichens can be regarded as unsightly when growing on paths, drives or tree trunks. They do not usually cause any disease or damage when growing on trees. They can be of many different colours; common forms are grey, green, black, orange, yellow.
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