A lichen is a composite organism that arises from algae or cyanobacteria (or both) living among filaments of a fungus in a symbiotic relationship. The combined life form has properties that are very different from the properties of its component organisms. Lichens come in many colours, sizes, and forms. The properties are sometimes plant-like, but lichens are not plants.
Lichens may have tiny, leafless branches (fruticose), flat leaf-like structures (foliose), flakes that lie on the surface like peeling paint (crustose), or other growth forms. Lichens do not have roots that absorb water and nutrients as plants do, but like plants they produce their own food by photosynthesis using sunlight energy, from carbon dioxide, water and minerals in their environment. When they grow on plants, they do not live as parasites and only use the plants as a substrate.
This post is part of the Wordless Wednesday meme,
and also part of the ABC Wednesday meme,
and also part of the Nature Notes meme.