TLDR: lichens are not a symbiosis between a fungus and an alga; they are a symbioses between two fungi and an alga. It's a very nice article that explains how

TLDR: lichens are not a symbiosis between a fungus and an alga; they are a symbioses between two fungi and an alga. It's a very nice article that explains how this was discovered. If you like biology, read the article; you'll like it.