Peniophora rufa

Peniophora rufa is a distinctive crust fungus that forms small, bright red, cushion-shaped structures on the dead but still bark-covered branches and trunks of aspens, including quaking aspen and big-toothed aspen. Although a microscope is probably not needed in order to identify Peniophora rufa successfully, the fungus has fascinating microscopic features, including prominent gloeocystidia.