When she first encounters a gravestone, it is often clogged with lichen, moss and mold ... and black mold are particularly difficult to remove from the stones, and often require extra effort.Credit ...

Portland, we’ve really taken a lichen to you. That’s why Ira Flatow is coming to the World Forestry Center for a day full of the fuzzy growths on trees, roofs and gravestones. Join Science Friday and ...