Nothing is so engrossing as science in the hands of a savvy wordsmith. I am thinking of astronomy as interpreted by Harry Shipman in his "Black Holes, Quasars and the Universe"; soil ecology in Peter Farb's "Living Earth"; and epidemiology in Berton Rouechehs "Eleven Blue Men" and Other Naratives of Medical Detection." The write who can explain complex physical prosesses with clarity and elan entertains without gimmicks. James Jackson is such an entertainer.

"The Biograhy of a Tree" concerns a white oak, a species common in the Washington area -- not an actual oak in a specific location, but a composite of many oaks which Jackson has evidently dently devoted years to observing. In simple but evocative prose, interspersed with dozens of excellent fullpage photos, he recounts the tree's 265 years.

One can love oaks but loathe acorns. As the story gets under way, Jackson explains why there must be so blessed many of them: Fewer than one in 10,000 makes it to treehood. Acorn weevils attack them while 'hey'-re still on the tree, squirrels make off with them after they've fallen, and dry weather makes the soil too hard to give them a purchase. Once past these obstacles, acorns stand a fair chance of rooting themselves.

Our dendro-heor manages the feat only to find itself situated in shade. As Jackson explains, "Certain trees... including the sugar maple and beech, were quite tolerant of deep shade in their youth and grew well under other trees, until maturity brought them up to crowning sunlight. The flowering dogwood survived its entire life in a shadowy realm. But not the oaks. To outgrow the seedling stage, they needed sunlight: A window to the sky was their only chance for ultimate survival." Fortunately, a nearby red oak is just then entering senility. It falls victim to lightning in the white oak's ninth year. The lightning fire spreads. In a shocking sentence redolent of Janet Leigh's early dispatch in "Psycho," Jackson observes laconically: "the shrubby white oak was reduced to a few dead, blackened sticks poking up out of bare soil."

But the white oak literally comes back from the grave. Relying on a reservoir of food in its 5-foot-long root, it reconstitutes itself. By early the next summer, it is 3-feet high. And thanks to a two-hour daily dose of sunlight, delivered through the space vacated by the red oak, it is ready to flourish. Two years later its highest sprout is man-tall.

As the white oak reaches maturity, Jackson pauses to explore selected facets of tree life. The reason a treehs lower limbs tend to die is the inability of the crown to soak in enough sunlight to fuel limbs at the bootom -- the common biological problem of poor circulation at the extremities. Trees are twiggy because their branches endlessly divide themselves in their struggle toward sunlight. And by middle age the interior of this tree has become dead heartwood. As Jackson puts it, "The living tree had grown to become a mere shell thinly circumscribing a huge pillar of dead wood which served only to support the massive crown above."

Now well into its second century and more than 100 feet twall, the tree plays unwitting host to insects, birds and squirrels. Its lowest limb, now placed some 60 feet above the ground, breaks off and lands on one of the roots -- the result of natural pruning. But this seemingly innocuous event opens a knothole in the tree's bark. Worried at by woodpeckers and squirrels, the knothole deepens into a cavity leading straight to heartwood. Then a ground fire pounces on the discarded branch and runs up to the main trunk, where it opens a long gash. These two clefts in the tree make it vulnerable for the first time since infancy. (Except, that is for its vulnerability to man. The few times that humans get close to the tree, the reader flinches. But for one reason or another, they leave it be.)

The tree is also declining in another way, this one a function of its rootedness. By now it is has extracted all of the nutrients from the soil in which it stands, and the soil can not be replenished fast enough to meet the tree's needs. Jackson phrases it nicely: "In a sense the tree was eating itself to death."

Carpenter ants and fungi get through the two openings in the tree. Eventually they would have overcome it, but its end comes somewhat more quickly. One summer night it is struck by lightning. "A chisel of 10 million volts down its massive trunk etched a groove five inches wide from the topmost limb to a large buttressing root." The resulting damage includes the rupture of many of the tree's foodlines. About seven years later, the tree succumbs in a winter storm. Weighed down with ice, it crashes to the forest floor. Its corpse fertilizes the soil for white oaks to come.

Though he has long been a naturalist and teacher, this is Jackson's first book. One way of encouraging him to write more would be to pay him the customary compliment by pronouncing this the "definite life." But that sounds stuffy, and Jackson is anything but a stuffy writer. So I'll say instead that if there were still Druids, this would be their Bible.