III. Sailor Plants and Robinson Crusoes
The first little plants were sailors. As they floated about in the water, the living drop of jelly or protoplasm, soaked food through the thin walls of the cells. One cell budded from another, and broke away to start a new family, or clung to the parent cells in a bead-like string, or in a knot that floated together. Then they budded all around the sides and formed mats and flat net-works of cells, held together by a gelatine in the cell walls.
Some of these nets and mats floated on rocks, in quiet places where the motion of the water was not strong enough to float them off again. As the rocks sheltered them, the plants were not so easily torn apart. The cells that lay on the rocks could not gather so much food, so they learned to cling. The free, floating cells gathered food, and budded and spread into feathery, leaf-like fronds. The plants lived in a colony, you see. So, by and by, they divided the labor just as people do in a village. It was the business of some plants, or cells, to cling to the rocks. Others waved in the water and gathered food. It wasn't necessary, any longer, and there wasn't room, for each cell to bud, although it could have done so. Certain cells began to collect budding material, in little raised dots on the fronds. When these dots ripened they were washed off. These bud dots were spores. They were not seeds, they were just the hints of seeds; and the cells that clung to the rocks were hints of roots; and the cells that spread out and floated were hints of leaves. All together they formed—seaweeds! Seaweeds belong to a family called algae. Algae are higher plants than fungi. But these colonies of cells did not deserve to go into a higher class until something else happened.
Some of these plants were born near the surface of the water where there was more air and sunlight. The sunlight turned them green. A green plant can take raw material like earth, air and water and, with the aid of sunlight, make its own food. Algae are found in oceans, rivers, lakes, ponds, marshes and warm springs, everywhere. Some of them are very beautiful, in a great variety of forms and colors. The very commonest algae that you can all find, almost everywhere, is the green scum that forms on quiet ponds and swamps. Scum is all broken up into single plants, or knots and
