a polyphore fungus
If I had to make a guess as to species, I'd say either Phellinus igniarius (click for information and photos here and here), which is often found on willow as I believe is shown above, or Phellinus pomaceus. As I was trying to locate a common name for these fungi, I discovered P. igniarius is sometimes called false tinder polyphore. Of course, I had to look up this unusual name. Come to find out there are true tinder fungus and false tinder fungus of various spp., which were primitively used for creating, keeping, and transporting fire. No kidding! Two sites I found with interesting, albeit somewhat contradictory, information about this tinder ability are Tinder Fungi of Illinois and Wildwood Survival.