Now, you might see such a thing on your oak tree and ponder it's source and reason. Perhaps your oak has always felt like a peach tree inside or just maybe that nuclear power plant down the road IS leaking radiation.
At Pure Florida, I usually ponder things for about as long as it takes to get the right tool to figure out what's going on. In this case all it took was a sharp pocket knife.
This oak gall was growing with a dozen others on a young laurel oak in my woods. I was using the machete to clear my JEEP trail of encroaching branches (NO SCRATCHING THE JEEP!) when I noticed the oak festooned with these smooth greenish brown globes.
I plucked one. It was surprisingly cool to the touch. I mean noticeably cold compared to the day, the branches, and my skin. Not sure why, but it was really cool ... in a temperature sort of way. When I sliced it open, it was mostly hollow with a network of filaments running from the inside of the sphere to a fuzzy capsule in the center.
I separated the filaments and removed the fuzzy center. (I'm craving a Tootsie Pop right now ... how about you?)
When I carefully dissected the fuzzy center I found this little wasp pupating inside it.