Nature Bulletin No. 131 November 15, 1947
Forest Preserve District of Cook County
William N. Erickson, President
Roberts Mann, Supt. of Conservation
When winter comes with its fogs, rains, and melting snow, the lichens
flourish. In the country we find them on the bark of trees, boulders and
patches of barren earth, but rarely in cities because they are very
sensitive to poisonous gases in the smoky air. In Iceland and
Greenland, and the vast tundras of the arctics, they are the dominant
forms of plant life.
A lichen is the partnership of a colorless plant and a green one: a
fungus and an alga. The two exchange food materials. Fungus has
remarkable power to absorb and store moisture. The alga, using that
water, and using carbon dioxide from the air, manufactures food. The
fungus absorbs the excess food and produces an acid which eats into
the earth or wood or rock upon which it grows, anchoring it firmly in
Lichens grow very, very slowly. Many are merely flat, gray-green,
crust-like plants. A few are bright yellow or orange. other lichens are
low erect plants with branch-like growths. One, called " Reindeer
Moss", forms a thick carpet in the arctic tundras. Another, called "Old
Man's Beard", hangs in tufts of gray-green threads from the limbs of
spruces in our northern forests. But most of them are very small; gray-
green or black. Many are weirdly beautiful when studied under a hand
lens, resembling miniature forests of dead trees. One, called the
"British Soldier", has tiny stalks capped with scarlet.
Of about 10,000 species, most are bitter and inedible due to the acids
they produce, but "Iceland Moss" can be used in soups, and the manna
of the Israelites was the lichen of Africa and Asia that the desert tribes
grind into meal for bread. Lichens were used by the ancient Greeks,
Romans and Hebrews, and are still used as a source of brown, blue and
They are the pioneers of the plant world, the first living things to
colonize barren earth or a rocky area. First come lichens, then moss,
then grass and other flowering plants, and finally forest vegetation.
Without lichens, much of the earth today might be as bare and lifeless
as it was hundreds of millions of years ago.
Don't despise the lowly lichen.
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Update: June 2012