This Native Plant Trust class on October 19 begins at 10:30 am, with a morning in which you compare lichen collections at Garden in the Woods in Framingham to study the features that distinguish species. An afternoon visit to a local site, the Sudbury Center cemeteries, offers an opportunity to study the diversity of lichens commonly found growing on rock walls and the factors that influence lichen colonization and growth.  Elizabeth Kneiper leads, and the class is $75 for NPT members, $90 for nonmembers. Register at http://www.nativeplanttrust.org/events/lichen-diversity/