Stump Puffballs - Lycoperdon pyriforme
These puffballs are round when young, but become pear-shaped when mature. Also, when they are mature, they develop a central hole through which spores are liberated - usually by rain. I spotted dozens of these puffballs all growing together on rotting wood.
''Lycoperdon pyriforme'', commonly known as the pear-shaped puffball or stump puffball, is a saprobic fungus present throughout much of the world. Emerging in autumn, this puffball is common and abundant on decaying logs of both deciduous and coniferous wood. It is considered a choice edible when still immature and the inner flesh is white.