Discover Nature this week and a natural mystery called lichen. "United we stand, divided we fall". And so it is with lichens. A lichen is made up of two unrelated organisms: a fungus and an algae. If the fungus and the algae were divided, the lichen would no longer exist. The fungus gives the lichen form and shape -- it also holds water and slows evaporation. The algae, a green plant, provides food for the fungus. Lichens look like nature's living carpet and are often seen covering rocks and