Mossy Willow Catkin Gall
We have lots of Pussy Willow/Goat Willow in our garden and other willows on the boundary. I also visit a nature reserve with many willow trees. So I have had plenty of opportunities to find one of these but today is the first time I have noticed one.
They are probably caused by a virus and are about the size of a walnut.
The stereos are crosseye.
Olympus EM-1, (aperture priority), Olympus 4/3 50mm f2 macro, f8, hand-held.