This section is from the "The New Student's Reference Work Volume 5: How And Why Stories" by Elinor Atkinson.
Did you ever find a four-leafed clover? It's good luck to find one. With a four-leafed clover in your shoe you can walk right in among goblins and witches in any fairy story, and they can't play tricks on you. Long, long ago people thought any clover leaf was a charm. Most clover leaves have three leaflets, and three is a lucky number. Besides, many of the leaflets are marked with white, daintily penciled horseshoes, and everybody knows a horseshoe is lucky. But ask any farmer and he will tell you that clover is a good luck plant, whether it has three leaflets or four, or is marked with a horseshoe or not. When you read this story you will find out why.
Clover is one flower that you can always find in June, and June is the leafy month when there are few flowers. The Spring blossoms are gone, the orchards are done blooming? But there are acres and acres of purple-pink clover heads in blossom, all over the land, and more acres of the violet-purple clusters of alfalfa, a first cousin of the clovers. The round buttons of the white, creeping clover dot every green lawn, and the blood red cones of the crimson clover grow along many a wayside.
How far one can smell a field of clover! It is a breath of the country as sweet as the perfume of orchards in bloom. Over a clover field there is always a pleasant hum of bumblebees and honey bees, and the glimmer of wings of gay little butterflies. When the feast of the clover is spread all the winged world goes to the party. Let us go, too.
Look out for Mr. Bumble Bee in a clover field! Big, fuzzy, black and yellow worker, he isn't thinking about you at all. But he blunders about, bumping into things, and he thinks human beings are enemies, as they very often are. He's a good friend of the red clover, and he often makes his nest in the ground near the roots. He drops on a fine flower head and pokes his long honey-sucker mouth to the bottom of the flower tubes. Pull one of those flowers yourself, and suck the base of it. You get a sweet drop, don't you? The white clover is sweet, too, but the honey bee feeds on that. The tubes of the white clover are short, and the bumble bee has a regular fishing pole of a mouth, too long for such shallow pools of nectar.
White clover is called the honey suckle of the grass, and bee keepers often plant whole fields of it.
Because it has so many flowers on one head, you may think the clover is a cousin of the dandelion. It isn't. The flowers are not crowded into a green vase, they just grow very close together on the swollen end of a stem. Pull the colored tubes from a clover head, and you will see that you have left behind every one some tiny upright threads. Those are the seed-making parts. Put a pink tube under a microscope and see how it widens, at the top, into pouting lips something like a sweet-pea blossom. Clover and Alfalfa are really cousins of the peas and beans and peanuts, and other plants that ripen their seeds in pods. You know the pods of peas and beans that you can split to shell out the seeds? Clover seed, too, grow—one or two, in a fairy pod below the tubular blossom. It is hidden, for the flower tube dries and turns brown on the head. The pod of the peanut is a woody, papery shell that grows on buried stems like potatoes. The seed-pods of alfalfa are coiled in snail-like spirals, and the teeny weeny seeds of green or yellow are exactly the shape of kidney beans.
How much a sweet-pea blossom looks like a butterfly. One of the names of this class of plants is a long Latin word that means butterfly. You can always know them by the blossom, although some of them are low creepers and some are beautiful trees. Do you like liquorice candy? Liquorice is a cousin of the clover and peanut. It is a woody shrub sometimes called the sweet root, for it is from its root that the liquorice juice is made. The sensitive plant, whose leaves go to sleep if you touch it, is one of this family, too; and the indigo shrub that gives us our beautiful blue dye. Another very tall relation is the beautiful honey locust tree, with its clusters of pink butterfly blossoms. It grows in many parts of our country. The clovers are members of a very big, important family, aren't they? They are all great honey makers.
All of these butterfly-blossomed, pod-seeded plants have strong, fibrous roots. There is a central root-stock with many branches, and a bush of rootlets, like a leafless shrub turned upside down and buried. This gives them a strong hold on the soil and many water suckers. Their stems are very zig-zaggy, branching in a twisty kind of way, as if they didn't quite know whether to be vines or not. The white clover, and the dear little Shamrock of Ireland, spring from creeping, vine-like stems. Many peas and beans climb on poles, or 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.