The oak, in its many variations, has...

The oak, in its many variations, has played a key role in the culture and history of California.

The tree is the essence of form and function. Throughout the centuries, both wildlife and humans have used the oak for food, shelter and shade. It has been a valuable source for fuel and tools. And not the least of its qualities is sheer beauty.

“Oaks cover millions of acres from one end of the state to the other, yet there is widespread concern that many of California’s native oak landscapes are in trouble,” reads the foreword to a 1991 book, “Oaks of California.” Among the culprits, the book says, are “urbanization, conversion of wildlands to agriculture and fragmentation of natural habitats in rural areas.”

On Tuesday , at the Rancho Santa Ana Botanic Gardens in Claremont, Bruce M. Pavlik, a Mills College associate professor and expert on the state’s plant life, will lecture on oaks and sign copies of “Oaks of California.” Pavlik was lead author of the 184-page, color-illustrated book.

His talk and slide show is scheduled to start at 7 p.m. at the Plant Science Center Auditorium of the garden, at 1500 N. College Ave.

There is no admission charge. But due to limited seating, reservations must be made by calling (714) 625-8767.