This is something I have observed every summer but don't know what it is. They max out at 1.5" in diameter and the picture shows two that just fell after a thunderstorm, and others that have been on the ground for several days. They turn brown and shrink when they are left on the ground. What are these "things"?

Those look like oak galls.

http://ento.psu.edu/extension/...

Yep, that's what they are. I knew the hard-as-a-rock galls that attach firmly and often girdle small branches/twigs were galls but never knew what these more colorful, soft, marble-like growths were. I pick them up constantly during the summer months and just trash them. I am eliminating some wasps from growing into adults, but probably am not making a dent in this specific wasp population.

Thanks, Celia.

I cut one of those open and it seemed to have a little white worm inside...

I found out they are oak galls, and two specific varieties of wasps are the cause of them. That white worm you saw was a wasp larva.

I'm glad I didn't decide to taste them before I cut one open.

You and me both, porkpal.

By the way, I am sort of old fashioned. What's your first name?

Very welcome, Ken. I have a neighbor plagued with them, too.

I saw a nature show, on you tube called the most magnifscent tree or something like that. it hosts/shows the fig tree and fig wasp. watch it, its really cool

Everything I read on these galls say that there is no need to treat for them since they basically don't cause damage to the trees. The wasps are not even a problem to humans. I will just keep cutting off those hard, gray galls attached to the branches and picking up and disposing of the soft ones on the ground.

That's basically what my neighbor said. He and the tree are not bothered so he isn't worried. The tree looks fine.