Annual rings

Annual rings, rings of dark and light wood seen across the trunk of a tree that has been cut down. The lighter rings are formed during the spring and are made up of cells with large cavities. The darker rings are formed during the summer, when less new wood is laid down and the cells have smaller cavities. In hot countries the rings represent dry and wet seasons. The size of the rings tells a great deal about the conditions under which the tree was growing, and the number of rings can be used to measure the age of the tree. The science of dating things by counting annual rings is dendrochronology.