Tenacious Lichens

Q: What is lichen?

A: Lichen is a plant community: a big guy and a little guy who depend on each other and develop as a single structure. It often looks like a crusty brown, orange, black, yellowish, or grey moss that grows on trees and bare rock. But, because of its dual nature, it can look bizarre. Click here for lichen pictures.

A lichen can contain as many as three members of the plant kingdom. The partners are as different as plants can get: a fungus (the dominant one, a yeast, mold, mushroom kind of plant), alga, and cyanobacterium (formerly called blue-green alga).

The fungus farms the other partner(s) because it can't make food and they can. What do the algae get out of it? Water, mainly, and protection. The spongy fungus partner shares its stored water with the algae and weaves a sheltering web about them.

The tough combination can shut down its metabolism and survive long periods, barely alive. Handy in the Arctic and other forbidding places where it grows.

Further Surfing:

Lichens of North America

(Answered Nov. 1, 2002; updated Oct. 10, 2007)