Mystery oak gall, soft and spongy, on leather oak. Pepperwood Preserve near Dwight Center.
about 20 feet tall. at first I thought it was a toyon but the fruit isn't growing in clusters like toyon.
On Valley Oak (Quercus lobata).
According to the sign, these abundant and regularly-spaced knots on the branches of California-grown quince trees are bacterial galls. Found an old book describing them and saying the cause wan't well-determined yet:
Lots of these in the zinnias.