Found on the underside of the same white oak (Quercus alba) leaf as this gall:

These galls are supposed to be deciduous, and most had dropped off, leaving the leaf covered with scars like the one to the right of the center of the frame. I suspect that the ones that are still attached to the leaf are parasitized or otherwise nonviable. From my first look at Weld's descriptions, I think these galls are caused by a species of Neuroterus.