Object: A cross section of a tree trunk, if possible (or a drawing).

Good morning, boys and girls. Most of you already know how to tell the age of a tree, don't you? That is, if the tree has been cut down. A tree grows a new layer of wood every year, so all you have to do to tell a tree's age is to count the rings--one for each year.

You can tell some other things about the tree this way. Wider rings may mean that the tree got …