"Life in the garden takes many shapes and sizes but one of the strangest is galls. Galls are abnormal growths on a plant caused by a parasite.

I found these galls on a fallen oak leaf today. The doughnut shaped ones are Silk Button Galls (Neuroterus numismalis) and the green-coloured ones are Common Spangle Galls (Neuroterus quercusbaccarum). They are tiny. The diameter of the Silk Button is about 3 mm.

They are created when the tiny Cynipid wasp lays eggs on the oak leaf. The grub matures inside the gall." from http://english-country-garden.blogspot.com/2...