This fungus is actually rather common but usually goes unnoticed. Within the last few weeks it has been reproducing rather extensively on the trunks of some juniper and cypress trees in the Washington Park Arboretum. This type of fungus, often called a resupinate, produces spores in a fertile layer that covers the underlying wood substrate. In the photo the white fringes of the fertile layer are growing out onto additional substrate while the brownish area towards the center is producing spores. Coniophora puteana occurs on wood in natural habitats but also is common on timbers and other wood construction and is often called the "cellar fungus." It causes a brown rot but also has been reported as a wet or soft rot fungus.
Coniophora puteana is part of the Burke Museum's Featured Fungi 2009 series.