This section is from the "The New Student's Reference Work Volume 5: How And Why Stories" by Elinor Atkinson.
Did you ever see a squirrel gathering acorns and nuts in the autumn? All summer long squirrels eat their food as they find it, bring up their babies, grow fat themselves and play a great deal. But when the first frost sends the nuts rattling to the ground, they know winter is coming. So they lay away a good store of food, in some safe place, to last them through "hard times." Wise little brother of the tree tops! How busy he is, and how hard he works!
Plants are just like squirrels. They eat and grow all summer, feed their flower babies until they are ripe seeds, then they store food to last them until the Spring. It is not so easy to catch plants at work, as it is to catch squirrels, but if you have very sharp eyes and minds you can do it. All plants above the fungi, earn their own living. In all green plants the roots get food from the earth, and the leaves get food from the air. The two kinds of food come together in the leaves, and the sun mixes and changes them into plant cells.
In the story about water you learned that water never runs up hill. Then how does water get from far down in the ground to the top of a tree? It doesn't run up; it is pumped up. Get a basin of water. Hold your handkerchief so just the hem on one side of it is in the water. That becomes wet at once. Hold it there. See the water climb, thread by thread! In a little while the handkerchief is wet to the top. You know a wet piece of cloth dries rapidly in the sun. As the water in the handkerchief passes into the air as vapor, more water is drawn from the basin. After awhile it is all soaked up. The basin is empty, and soon afterwards the handkerchief is dry.
This drawing of water up by threads, is called capillary attraction. A lump of sugar has it. Hold a lump of sugar with one tiny corner of it just touching the top of a cup of coffee. Soon the whole lump is brown and wet. A plant is like a big handkerchief full of threads that run from the root hairs to the leaves. The sun draws the water, in vapor, from the leaves, and more water is pulled up just as long as the roots can find any in the earth. Those little wood-fibers that you found in bundles in the stems of fern leaves, are not only bones, they are blood vessels, too.
Those little tubes are so small that they cannot carry anything but liquid food. The sap of trees looks like clear water, but it has a great many things melted in it. The sap of maple trees has sugar. Some saps are puckery, some spicy. In the earth are many things that melt in water. Water will take up and hold, salt, sugar, lime, iron and many minerals. When clear well water is boiled in a
tea-kettle, it coats the inside of the kettle with lime. If you melt salt in water and then put it in the sun, the water will pass away as vapor, but the salt will be left in the glass.
Minerals will not burn. If you burn wood you have a little heap of ashes left. The ashes are the minerals that were in the wood. Plants do not like rain-water as they do well-water. They must have water that has gone down into the earth and taken up minerals. That is the reason why plants are so made that they get all their water through the roots.
You might think that plants drink the rain that falls on their leaves and stems. They don't. They merely use rain to wash their faces. They need to wash the dust out of their skin pores, just as you do. Ask them if this is not true. Leaves will talk, as they are supposed to do in fairy stories, if you know their language. This is one way to ask leaves if they drink through their leaf-pores, or through their roots.
Take a leafy branch. Lay it across the mouth of a jar of water, so some of the leaves dip into the water. In another jar put the stems of leaves in the water. These stay fresh several days, and drink the water, as you can see by the smaller amount in the jar. The others soon wilt and wither, and do not use the water in the jar. The work of the leaves is to do the air-breathing for the plants. They do it just as you do, through lungs. Their lungs are more like the pores of your skin. There are little open mouths at the ends and crossings of the little tubes that come up from the roots. In net-veined leaves, like the rose and apple, they are scattered over the under surface. They open little mouths, breathe out the vapor of the water from the roots, and breathe in the air.
 
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