As a young artist Giuseppe Penone was associated with the Arte Povera movement, but his lifelong association has been with trees, which stand upright as humans do. “The bifurcations of the trees,” he has said, “appear so intimately human to us.” Working in bronze, stone, and marble, Penone explores this intimacy, as well as the codependence of man and nature, in sculptures and installations of mysterious eloquence. —L.J.