Marcella Burek, age 11, of Utica, N.Y., or her question:

How does a hollow tree staff alive?

The largest living thing is a tree and the oldest living thing is a tree. General Sherman, giant of Sequoia National Park, California, holds the world’s record for size. This elegant monarch is as tall as a 25­ story buildings his topmost twigs are 272 feet above the ground. There is enough redwood in his mighty trunk to build a small town. The General is 3,500 years old. But certain bristlecone pines, also growing in the California Sierra, could call him Juniors One of these ancient stubby trees is 4600 years old and quite a few were 1000 yours old whoa the General was a sapling.

When it comes to size and age, trees have rules of their own. A horse grows just so big and then, barring accidents, lives out his normal life span. This is true for most animals and also for people. A tree disregards these rules, or it may disregard them if it is lucky. An oak tree goes on growing as long as conditions are right for it. It must stay well rooted in rich, moist earth. Its trunk must remain sturdy enough to hold its leaves high in the sunny air.

When these factors are right, the tree adds now growth to its trunk every year. This is necessary for the tree to stay alive. For the sap anal vital tree fluids are carried only in this new wood. And these vital new cells are added around the outside of the tree trunk, ring by ring each year.

The wood in the center of the trunk was made years ago when the tree was young. The cells no longer carry precious sap to and fro. When this work was done, they became hard woody cells. Their job then was to support the leafy arms of the tree. Rings of new cells grew around the trunk year by year to fetch and carry.

In time these outer cells were buried under new rings. They, too, lent their strength to supporting the tree. The inner heartwood of the trunk became very old and hard and dry. It was a temptation to wood eating insects and to bacteria and fungus plants that feed on wood.

The center of the tree was attacked and its dry old heartwood was chewed to powder. The trunk of the tree became hollow. But there was still a sturdy band of wood around the hole. An owl built his nest in the hollow and a squirrel used it as a hiding place. A woodchuck used the floor as a bedroom. And the hollow in the tree grew bigger.

Each year, rings of new cells wore added around the trunk and last year’s cells became woody supports. Each year moisture was drawn up from the ground and a crop of green leaves made enough plant food for growth to continue.

The tree did not miss the strong support from the center of the trunk. It went on growing for many, many years. But at last it failed. During a fierce storm, the hollow trunk was unable to hold up the lofty branches. A loud crash mingled with the thunder as the ancient tree toppled. The same storm brought down a slender sappling, too weak to stand in the face of the gale. Both trees were done for. They no longer had an unbroken chain of new woody cells to carry moisture from roots to twigs, their broken trunks could no longer support their leafy boughs in the sunny air.