Now, you know, when the plants pull carbon dioxide to pieces, they keep the carbon and return the oxygen to the air. In this way we get it to breathe.
But there is more than this to the matter in hand. We are all the time breathing out carbon dioxide as an impurity; so are all the millions upon millions of animals in the world.
The air might in time contain enough carbon dioxide to kill us if there were not some way of getting rid of it. You know what that way is.
The plants use it up. So by giving oxygen into the air and taking out carbon dioxide, the plants keep the air fit for us and all animals to breathe.
But there is more than this we have to thank them for.
They shade the earth and regulate the rainfall and the water supply.
Where forests grow there are always streams of water, and the large water courses are kept full the year round.
The Mississippi River depends upon the far-away forests for its broad stream.
The spreading crowns of the trees shade the earth and prevent the water which falls as rain or dew from evaporating rapidly. It collects into streams and flows through the land, keeping the earth fresh and beautiful.