Alder Tongue

Always one of my favourite finds - the Alder Tongue gall, a distortion of the female Alder catkins induced by the fungal pathogen Taphrina alni. I spotted at least a dozen of these on this morning's walk with the spaniel along the banks of the river Ouse. At the moment they are relatively small and mostly yellow/green in colour. As they mature they will become larger and turn red.