Some of Congdon’s collections are ephemeral, literally. Her stockpiles of eucalyptus leaves and pinecones, subject to rot, must be carefully preserved. That’s partly why she’s attracted to these beach rocks, which she picked up mostly on San Francisco’s Pacific shores. “I’ve been an avid collector of nature my whole life, but most of the time I’ll collect something, photograph it, and put it back. I’ve had this particular collection of flat beach rocks for years, though. I look for the most smooth, most round rocks, and if they have a white line going down the center, that’s a special perk,” she says.