This is Evernia prunastri or oak moss lichen, one of the fruticose lichens. It's native to Europe and North Anerica, and has been collected in Europe for its use in making perfumes and other high quality cosmetics. The Wayne's Word website says, "This remarkable lichen occurs in California, but air pollution has eliminated it throughout most of its former range in Southern California." These pictures were taken at the Santa Rosa Plateau Ecological Reserve in Riverside County where it grows on the old stems of many of the larger shrubs and trees such as Quercus, Rhamnus and Adenostema.
