Each year one ring of this sapwood develops.

This process of growth may continue until the annual layers amount to 50 or 100, or more, according to the life of the tree.
One can tell the age of a tree by counting the number of annual rings.

Sometimes, because of the interruption of normal growth, two false rings may be produced instead of a single true ring.
However, such blemishes are easy for the trained eye to recognize.

Heartwood does not occur in all varieties of trees.

In some cases, where both heartwood and sapwood appear, it is difficult to distinguish between them as their colors are so nearly alike.