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 teakettle, 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.
The leaves are little plant-food factories. In them they have water and minerals from the roots, and oxygen, nitrogen and carbon-dioxide from the air. Oxygen is a purifier. We use oxygen to purify the blood in our lungs. Carbon is the wood-fiber maker. It
