The coast redwood tree is an evergreen conifer and a member of the cypress family. Its scientific name is Sequoia sempervirens. It is sometimes called the California redwood, but most often it is simply referred to as the redwood. No one knows exactly when or where the redwood entered the history of life on earth, though it is an ancient kind of tree, and has come down to our world as an inheritance out of deep time. A redwood has furrowed, fibrous bark, and a tall, straight trunk. It has soft, flat needles that become short and spiky near the top of the tree. The tree produces seeds but does not bear flowers. The seeds of a redwood are released from cones that are about the size of olives. The heartwood of the tree is a dark, shimmery red in color, like old claret. The wood has a lemony scent, and is extremely resistant to rot.

Redwoods grow in valleys and on mountains along the coast of California, mostly within ten miles of the sea. They reach enormous sizes in the mild, rainy climate of the northern stretches of the coast. Parts of the North Coast of California are covered with temperate rain forest. A rain forest is usually considered to be a forest that gets at least eighty inches of rain a year, and parts of the North Coast get more than that. A temperate rain forest has a cool, moist, even climate, not too hot or cold. Redwoods flourish in fog, but they don't like salt air. They tend to appear in valleys that are just out of sight of the sea. In their relationship with the sea, redwoods are like cats that long to be stroked but are shy to the touch. The natural range of the coast redwoods begins at a creek in Big Sur that flows down a mountain called Mount Mars. From there, the redwoods run up the California coast in a broken ribbon, continuing to just inside Oregon. Fourteen miles up the Oregon coast, in the valley of the Chetco River, the redwoods stop.

The coast redwood is the tallest species of tree on earth. The tallest redwoods today are between 350 and close to 380 feet in height-thirty-five to thirty-eight stories tall. The crown of a tree is its radiant array of limbs and branches, covered with leaves. The crown of a supertall redwood has a towering, cloudy, irregular form, and the crowns of the tallest redwoods can sometimes look like the plume of exhaust from a rocket taking off.

Botanists make a distinction between the height of a tree and its overall size, which is measured by the amount of wood the tree has in its trunks and limbs. The largest redwoods, which are called redwood giants or redwood titans, are usually not the very tallest ones, although they are still among the world's tallest trees-they are typically more than three hundred feet tall. Today, almost no trees of any species, anywhere, reach more than three hundred feet tall, except for redwoods. The main trunk of a redwood titan can be as much as thirty feet in diameter near its base.

Many people who are familiar with coast redwoods have seen them in the Muir Woods National Monument, in Marin County, just north of the Golden Gate Bridge. The Muir Woods, which is visited by nearly a million people every year, is a tiny patch of virgin, primeval redwood forest, and it is like a small window that reveals a glimpse of the way much of Northern California looked in prehistoric times. Though the redwoods in the Muir Woods are hauntingly beautiful trees, they are relatively small and are not very tall, at least for redwoods. The redwoods you can see in the Muir Woods are nothing like the redwood titans that stand in the rain-forest valleys of the North Coast, closer to Oregon. They are the dreadnoughts of their kind, the blue whales of the plant kingdom.

Nobody knows the ages of any of the living giant coast redwoods, because nobody has ever drilled into one of them in order to count its annual growth rings. Drilling into an old redwood would not reveal its age, anyway, because the oldest redwoods seem to be hollow; they don't have growth rings left in their centers to be counted. Botanists suspect that the oldest living redwoods may be somewhere between two thousand and three thousand years old-they seem to be roughly the age of the Parthenon.

Excerpted from The Wild Trees by Richard Preston Copyright © 2007 by Richard Preston. Excerpted by permission of Random House, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.