on other plants like cornstalks. Alfalfa is more bushy, and with smaller leaflets than the clovers. The acacia, the sensitive plant, and locust have long, feather-veined fern-like leaves.
Beside the bees, the pod-seeded plants have another animal friend. He lives in the ground, on the roots. He is so small you can not see him except with a very good microscope. But you can find the house he lives in with hundreds of his family. Find a fine field clover or alfalfa plant, and soak the ground around it with water until you make a very deep mud puddle. Then pull, loosening the root gently, so as to get as many rootlets as possible. Wash the earth away from the root in a tub of water. All over the root-fibres you will find funny little brown wart-like knots and swellings.
Those knots are the houses of little animals called bac-te'ria. This is how they help the plants. All kinds of plants need a food called nitrates. There is some in most soils, and some is supplied by animal manures that you often see spread on gardens in the spring. In the air is a great deal of gas called nitrogen. The leaves of plants cannot use that gas. They send it back to the roots. Clovers and other pod-seeded plants have these little animal friends that fasten themselves in colonies on the roots, and use that nitrogen gas to make nitrates. So those little swellings are really nitrate factories full of busy workers. They make more nitrates than the plants they grow on can use, and leave some in the soil for wheat and other crops. So, you see, the clovers are soil-makers, and bring good crops and good luck to the farmers.
If you see pussy prowling around a clover field, leave her alone. Pussy eats field mice. Field mice eat baby bumble bees. If the mice were so many that they ate all the bumble bees, the clover would have no help in making seeds. Then bossy cow would have no clover to eat, and couldn't make as good milk. And we wouldn't have as sweet yellow butter to put on our bread.
Isn't that just like the house that Jack built? Dear, dear, out this is a nice, mixed-up, friendly old world, where everybody helps everybody else, and has a fine time doing it.
Sometimes, clover will not grow in a field at all. Men who make a study of plants found out that this was because there were no nitrates in the soil, and no nitrate making bacteria to help the plants make them. So the farmer's department of our big country, in Washington City, began to hatch bacteria in liquid baths. Cotton is soaked in this bath and dried. This cotton is sent to farmers who
