ocr: Air monitors After a winter rain, leafiess trees in an Oregon farming valley come alive with lichens, including the oakmoss lichen, an important ingredient in many fine perfumes, Virtually dormant when dry, lichens become bright, plump, and metabolically active when damp. Growing only where the air is very clean, Usnea longissima (right and with others at far right) was called pine gauze in: a sixth- century Chinese herbal and is still used in traditional Chinese medi- cine. Locally abundant in the Pacific Northwest, it has all but disappeared in Europe. Pollution is a serious threat: to liche ...
