Bobby Elliott, age 14* of Forest, Miss., for `his question:

What are lichens?

You have seen them like pastel rosettes painted on the bare face of a barren rock. Some you may have mistaken for toadstools clinging in thick frills to a growing tree trunk. Others, like carpets of small, sprouting tendrils, may be mistaken for mosses. We find them in shady woods, in open fields and high up the mountain slopes where even mosses could not survive, We even find them under the snow of the Arctic.

They are lichens, the first living things to occupy land newly drained from the sea, the first to brave the charred land left by a forest fire.

Whether it looks like a carpet of moss, a toadstool or a green‑grey rosette on a rock, you would say that a lichen is a plant, Actually, you are only half correct. For a lichen is really two different plants living together in a partnership of give‑and‑take. Its basic body is a fungus plant made from a host of spongy threads, Between the threads are algae, the simplest of all green plants. The two plants can live together where neither of them could live alone and certainly where no other plants can live at all,

We call this kind of partnership symbiosis. A fungus plant has no chlorophyll, the green substance most plants use to make their food, It depends upon food prefabricated by other plants, which is why we find toadstools growing around the roots of trees and mushroom rings in the rich, organic soil from an old rotting tree stump. Algae have no roots to take up moisture from the soil and most of them are water plans, The fungus is handicapped when it comes to getting food, the alga is handicapped when it comes to getting water.

In the symbiosis of the lichen, the two plants get together and solve each others problems. The alga uses its green chlorophyll to make enough food for both itself and the fungus.

The fungus traps and holds the needed moisture among its spongy threads. Together# the two plants thrive where neither could live alone. A new lichen starts from a wad of cells blown on the wind. It contains algae and fungi cells from the parent plant and it can start growing where no other plant would dare to venture. Lichens tend to form acids which break down bare rocks and often this is the first step in soil formation, In the far north, moss‑like lichen provide food for reindeer dnd yin ice.. land certain starch‑rich lichens are used to make bread.

Throughout the world we know of some 15,000 different lichens and they are classified according to their shapes. Those that resemble mosses are called folicose lichens, those that resemble shells are the crustose lichens. The folicose lichens, naturally, resemble foliage.