Lichens

Lichens are unusual creatures. A lichen is not a single organism the way most other living things are, but
rather it is a combination of two organisms which live together intimately. Most of the lichen is composed of
fungal filaments, but living among the filaments are algal cells, usually from a green alga or a
cyanobacterium.
In many cases the fungus and the alga which together make the lichen may each be found living in nature
without its partner, but many other lichens include a fungus which cannot survive on its own it
has
become dependent on its algal partner for survival. In all cases though, the appearance of the fungus in
the lichen is quite different from its morphology as a separately growing individual.