Agnes Nevers, age 1.1, of Fairfield, Conn., for her question:

How does water  go up a redwood tree?

General Sherman is the tallest of the sequoia redwoods and his height equals a 25‑story building. His topmost twigs tower 272 feet above the ground. And these twigs are fed with moisture from the soil at his feat. For trees do not take in moisture through their haves. The General needs tons of water every day. All of it is hauled up by his own private elevator system.

Mother Nature invented this elevator system before mankind invented buildings. The system is called osmosis and it works just as well in a humble violet plant as it does in a giant redwood.

You can sae how osmosis works for yourself with a simple experiment. You will need water, a little sugar, a jar, a long glass tube and the pool from a sausage. The peel from the sausage is animal skin or membrane.

Fill the jar about half full with plain water. Stretch the membrane over one and of the glass tube. Tie it on tightly to make a waterproof floor. Dissolve the sugar into some more water and pour this solution to about halfway up the tube. Now place the tube of sugary water in the jar of plain water. In a little while the water in the tube will be higher, the water in the jar will be lower. This magic trick is osmosis.

It happens when plain vaster and water bearing chemicals are separated by a membrane. And a weaker solution will always pass through a membrane to join a stronger solution.

General Sherman, of course, is not wrapped in sausage skin. But his roots are covered with plant membrane. His massive trunk, his boughs, his twigs and leaves are made of tiny cells. And each cell is lined with membrane. The twigs, leaves, roots and outer trunk are filled with sugary sap.

In our experiment, the glass tube of sugary water takes the place of the General. The sausage skin takes the place of the plant membranes of his roots and, cells. The winter in the ___ the place of the water in the soil. The ground water contains dissolvod chemicals. But it is a weaker solution than the sap. So it must pass from the soil through the root membranes into the tree.

Inside the true, one cell leads to another. As lower cells fill, the water pushes upwards to those above. This creates strong pressure from below. At the same time, water evaporates from the lofty loaves. This creates a pull from above. The particles of water tend to cling together and all these forces combine to keep an unbroken column of water flowing from the deepest root to the topmost twig.

Food is made in the leaves. It must be dissolved in water and distributed through the tree. The rick sap is toted around by another set of cells. The redwood tree, like all other trees, has an up‑elevator system to haul up the moisture and a down‑elevator system to distribute the rich food sap.