Ball?

This evening I decided to walk a nature trail that bikes are not allowed to use. When I first saw this ball I thought it was a giant puff ball. Later when I saw others in the undergrowth, they looked like a child's bouncy ball. However, they turned out to be giant mushroom balls.

Here's what it looks like on the inside. (I didn't break it open. I found it that way.)

 It hasn't rained at all in October but there must still be plenty of moisture in these wooded areas. I thought these mushrooms looked like something out of a fairy tale.