What kind of mushroom/fungus is the one shown in the photos?
Description: Looks similar in size (~4-5 cm as I remember) and shape to a puffball. It is not hard to the touch, unlike typical mushrooms that grow on trees. Several balls were growing individually (not in clusters) from the 2-3 m tall stump of a broken tree, at multiple locations from the bottom to the top. They were breaking through the bark from the inside.
Time and location: Saxony, Germany, in a mixed forest. Early September.