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 strings of cells, and can be easily separated and studied under a microscope.

There were some seaweeds that did not have a chance to become green. They grew far down in the deep sea, under tons of dark, almost airless water. They lay on rocks, flat and motionless and sluggish. They grew slowly but were hard to kill. They learned to live in colonies, to cling, to spread, and to grow spore buds, so they were a little above the fungi. By and by they were lifted, with the rocks they grew on. You know earthquakes lift the ocean floor. Parts of the deep ocean floor have been lifted suddenly into rocky islands. When that happened these colorless seaweed colonies were lifted, too, and shipwrecked in the air. They were just like Robinson Crusoe.

They wanted to live. If you were lost in the woods you would hunt roots and berries and nuts. You would strike stones together to make a spark and start a fire. You would make a bed of leaves in a cave. You would do your very best to live, wouldn't you? Robinson Crusoe was lost on an island a long time. He had to do many things he had never done before, and he changed so much that his best friends wouldn't have known him. If those deep-water seaweeds had been lifted slowly, to the air and sunlight, but still kept under the water, they would have become green algae. But they were castaways on the land before they got far enough along to be algae.

Most of them, millions and billions of them died. But those that died, decayed, mixed with the sand or rock waste and made the first soil that covered the bare rocks. Some of the water weeds managed to live by clinging to the rocks and decaying plants. But, like Robinson Crusoe, they had to learn new ways of living, and they grew to be very different from the algae, their water cousins, and different from the fungi, their ancestors.

For one thing, they became very dry and gray. They spread in broad scales to turn as many cells as possible to the air and rain. But they never turned green. You may find such plants today, on the rocks of the highest mountains, under the snows of cold countries, where grass will not grow, on dead or dying trees and fence rails, and on old house shingles. And, scientists tell us, they are to be found on the deepest rocks in the sea. They are called lichens, (li'kens). Some people think lichens are dry mosses, but they are not. They are plants between the fungi of the yeast and