Figs. 3.1-3.4. Fig. 3.1. Perennial canker on sugar maple caused by Eutypella parasitica. Fig. 3.2. Conspicuous infection caused by the canker rot fungus Inonotus obliquus on sweet birch. Note the typical "bowling pin" shape of the infected tree and the black mass of sterile fungus tissue in the center of the canker. Fig. 3.3. Canker caused by Urnula craterium ( anamorph = Strumella corynoidea) at the base of an oak tree. Strumella cankers are found almost exclusively near dead branch stubs. Fig. 3.4. Formation of xylem inclusions in bark (single arrow) of oak infected by S. corynoidea. Note the visible margins of the canker in the bark and xylem (double arrows). (Photographs courtesy of A.L. Shigo).