Hypogymnia is a genus commonly known as tube lichens, bone lichens, or pillow lichens. They generally grow on the bark and wood of conifers, and they have hollow (tube-like) lobes. The two species shown here are greenish to grey.
In 15th-century Europe, Hypogymnia physodes was one component of a popular drug named "Lichen quercinus virdes." In traditional Chinese medicine, another species of Hypogymnia is used for "dim vision, bleeding from uterus, bleeding from external injury, chronic dermatitis, and sores."