These three diligent layers of cells perform all the intricate science and engineering needed to keep a tree alive, and the efficiency with which they do it is one of the wonders of life. Without noise or fuss, every tree in a forest lifts massive volumes of water—several hundred gallons in the case of a large tree on a hot day—from its roots to its leaves, where it is returned to the atmosphere. Imagine the din and commotion, the clutter of machinery, that would be needed for a fire department to raise a similar volume of water.
