The pith could easily have been reduced to dust during this long period of life, since the core of a tree, botanically dead, has a tendency to deteriorate. But that tree lives on, producing an infinity of new cells year after year.
The roots of a tree, too, have vital functions to perform. They anchor the tree. They search for water, without which the tree cannot survive. In dry areas, roots range far and wide, hunting water. Many hardy trees like the oak have a main root, called a taproot, which plunges deep into the earth. Others like the beeches and willows have instead many smaller roots which reach in all directions, fairly close to the surface.
In each growing season in temperate zones, a tree adds on a layer of wood—a growth ring. The record of all that the average tree has witnessed and endured is written in its growth rings. They tell by their number how old the tree is. They help to pinpoint when droughts, floods, fire and insects ravaged the land and when life-giving rain fell in abundance. During difficult growth periods, the rings of some trees are so narrow and close together that it is almost impossible to count them.
A. Outer Bark—The protective skin of a tree. The way bark expands characterizes the species of the tree: some scale off, some create fissures, and some seem almost elastic in their smoothness.
B. Phloem—The sugars produced by the leaves are conducted to the roots and the trunk through this layer.
C. Cambium Layer—Produces new wood and bark by the creation of cells.
E. Heartwood—The bulk of the tree, composed of cells no longer carrying vital juices—essentially dead. In some instances, the heartwood decays, leaving the tree a living shell.
F. Early Growth—Fast growth of the tree in its youth. This heartwood is often knotty and therefore inferior.
G. Pith—Where it all started.