Oak Gall....

last year was the first time I had ever seen these round, green things on my very healthy oak tree.   A Blipper correctly identified the growth.  Well, they are back this year......  in boat loads!   Supposedly, the oak has an insect that lands on the branch.  It gives off something that causes the the tree to develope the gall, which grows and nourishes a larvae contained within it.  When the time is right, the insect will  drill it's way out of the gall and go on to it's next stage.
    As you can see, the crown of this oak is loaded with the galls.  The extra has a photo of the interior of the oak tree, also loaded with galls.  I looked, real hard today, but didn't find any galls with the pinpoint hole of the insect escaping.  I will keep looking.