Lichens

LICHEN. On places like tree trunks, rocks, old boards, and also on the ground grow strange splotches of various-colored plant life called lichens. They are of great scientific interest because they are not single plants; instead, each lichen is formed of a fungus and an alga living together so intimately as to seem a single plant. The lichens are one of the best illustrations of symbiosis, the intimate living together of two different kinds of …

…in the most unfavorable and desolate places. In such exposed situations the fungus could not live because it depends upon other organisms, and the alga could not live because it would dry out quickly. But the two can live together. Certain kinds of lichens, such as the ones called Iceland moss and reindeer moss, are used as food by reindeer and even by humans. Other kinds are used to produce dyes, drugs, and other products.