AS THE MORNING mist evaporates, a pale rock becomes visible in the garden. It invites a passing bird that perches on its crest. Before flying off again, the bird drops a few seeds that it was carrying in its beak. They skitter down the smooth face of the rock and find a comfortable spot at its feet. Shaded from the hot sun during the day and warmed by the rock’s mass radiating stored heat at night, the seeds find conditions right to germinate. They sprout and send forth a fragile stem and a first set of tiny leaves. Before long, the plant is taller than the rock, but no matter how tall it is, the rock still shares its shade and moisture with the plant’s roots.