"Oh, no," I thought, as I pulled into the parking area at The Nature Conservancy's Jepson Prairie. Preserve. "This is a vernal pool?" Throughout the drive from Berkeley to California's Central Valley I'd been repeating the musical words: "vernal pool, vernal pool, vernal pool." Though I'd never seen one, the name evoked something small and green, nestled in a mossy hollow, far from the madding crowd. But in the parking area, reality intruded. Olcott Lake, the biggest of the pools on the 1,600-acre preserve, looked more like a huge puddle of milky coffee than an emerald jewel. On this wet spring day it measured a quarter-mile wide by a half-mile long, and maybe two feet deep. And the maddening crowd was uncomfortably close: big-bellied C-141s took off from and landed at a nearby air force base, and a stream of 18-wheelers roared down an adjacent road. I could barely suppress the heretical thought that Jepson Preserve was just--well--some puddles in a pasture. Later, when I confessed my reaction to Oren Pollak, a Nature Conservancy biologist, he chuckled indulgently. "You have to get up close to the pools to understand them," he said. "But I guarantee that to know this place is to love it."