Look at a lichen (LIE-kin) and you'd probably guess it's some kind of weird plant. But lichens aren't plants. They aren't animals, either. Instead, they're two kinds of lifeforms living together. The two lifeforms are called fungi (FUNJ-eye) and algae (AL-jee).
Think of a lichen as a fungus farmer growing a crop of algae. The two work together. First, the fungus gives the algae a good place to live--sort of like a farmer giving seeds a good place to grow. The fungus also collects water and minerals and protects the algae from getting too much sunlight.
Meanwhile, the algae make food from water and carbon dioxide in the air. And that feeds both the algae and the fungus.
LICHENS LURK IN LOTS OF PLACES
Loads of Lichens
There are at least 15 thousand different species (kinds) of lichens. And they come in lots of different shapes, sizes, and colors. Lichens range in color from bright orange, red, or yellow to dull gray or green.
Looking for Lichens
Want to find some lichens near you? Start by looking at the lichens on these pages. Next, go to a library and find a book about lichens. Then grab a magnifying glass and go outside!
Here, There, Everywhere
Lichens can grow on almost any solid surface. You'll find most of them on trees and rocks. But they also grow on gravestones (1), on wrecked cars (2), and even on old jaw bones (3).
Lichens can be found from seashores to mountaintops, and from very hot places to very cold ones. Some grow in deserts where temperatures reach 120 F (49 C). Others survive in Antarctica (4) at temperatures way below zero!
What Lichens Don't Like
Even though lichens can grow in all sorts of places, there's one thing they can't survive: pollution. Air pollution and acid rain quickly kill lichens. So when lichens start to disappear from an area, it's a clue that the air is getting too polluted.
Lichens Come First
Lichens are often the first lifeforms to grow on a bare surface. For example, by growing on a rock, they may make it easier for plants to grow there too. Here's how:
Tiny root-like threads grow from a lichen and reach down into tiny spaces in the rock. Slowly the threads break off small rock pieces. Meanwhile, the lichen also makes acids that dissolve the rock. After many years, little hollows appear in the rock where windblown soil and seeds can collect. The soil holds moisture, which allows the seeds to sprout. Soon a mini-garden is formed.
Most lichens grow less than half an inch (12 mm) a year. (And you thought it took you a long time to grow!) But some lichens grow for a long time--as long as four thousand years!
Want a Date? Ask a Lichen!
Because some types of lichens live so long, scientists use them to date (figure out the age of) old buildings and other objects. First the scientists find out how much a certain kind of lichen usually grows in a year--let's say it's 2 millimeters. Then they measure the largest lichen of that kind growing on an old building. Let's say it's 100 millimeters from its center to the edge. To figure the lichen's age, they divide 100 millimeters by 2 millimeters to get 50. The building, then, has to be at least 50 years old.
LOOK WHO USES LICHENS
Lichens for Rudolph
Most folks don't want to munch on lichens--many kinds just taste too bad. But long ago, some Native Americans used to eat lichens steamed with berries and onions. And Canadian trappers sometimes ate a kind of lichen called "rock tripe" when they ran out of other food. It kept them alive. Today, some people in Japan still eat rock tripe.
Not many animals eat lichens either. But in the cold northern forests and the Arctic tundra, caribou eat reindeer lichens (left) all winter long. Sometimes flying squirrels, deer, and elk also eat lichens.
For centuries, lichens have been used to make medicines. In the old days, doctors picked lichens that looked like parts
of the human body. Then they'd use the lichens to treat those parts. For example, the lungwort lichen looks like a lung, so it was used to treat lung disease.
That way of treating people never worked. But lichens are still used in medicine. Some kinds of lichens are made into ointments that kill germs.
If you look carefully, you can see a grizzled mantid hiding on the lichen above. Like many other insects, the mantid has colors and patterns that match lichens almost perfectly. This helps the mantid hide from its enemies. And some lacewing insects actually have lichens growing on their backs!
Lichens are sometimes used to make dye, which puts color into cloth. Some very famous kinds of cloth are dyed with lichens-- including the kind that Navajo people use to add color to their blankets.
There's a lot to learn about these strange forms of life. So keep looking--you may take a lichen to them!
Lichens can look really different. The cup-like ones (1) are called pixie cups. The hairy-looking lichen (2) is old man's beard. Long ago, it was used to treat baldness. (It didn't work.) And these British soldier lichens (3) were named after soldiers in the British Army, who once wore red coats.
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|Date:||Sep 1, 1995|
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