Does anyone know what this is…?

It appears to be some sort of a pod. There are several dozen of these attached to the bottoms of numerous leaves on a tree of unknown variety that is in my yard.

At first I thought it was some sort of an insect pod. I was ready to start researching pesticides to wipe out whatever awful creature it might be. Eventually, though, curiosity got the better of me and I decided to split one open. I carefully sliced it with surgical precision using my brother’s old license plate, which happened to be sitting on my back step.

I didn’t snap a photo of the cross-section, but it appeared to have a small green seed-like inner core, surrounded by a grape-like material. The skin was also grape-like. It didn’t smell like a grape, though. And if it is a grape– which I seriously doubt– it is the first grape I have ever heard of that grows as a parasite on a mature tree.

So, any takers on what this might be?