Horned Gall

@ Dan, These seem to be Horned galls caused by the " Callirhytis wasp"

Horned galls are the most common spiked variety on oaks. Caused by the Callirhytis wasp, these galls are seen on pin, black and water oaks. The galls vary in size and are covered in hornlike projections. Xanthoteras gall wasps cause spiny vase galls, which resemble small pitchers or vases. This variety is covered in very small red or yellow spikes and they appear in the fall. The hedgehog gall, initiated by Acraspis erinacei, occurs on the leaves of white oaks and has numerous short spines. http://www.ehow.com/info_7961505_spiky-balls-hang-oak-trees.html

@ Dan ,this is really interesting.

Great sequence of shots, showcases it really well!