Taphrina alni

Taphrina alni is a fungal plant pathogen that causes alder tongue gall, a chemically induced distortion of female alder catkins (Alnus glutinosa). Taphrina alni produces a distinctive tongue-like growth which derives mainly from the ovarian tissues of the alder catkin or from the bracteoles. These alder pseudocones may carry several tongue galls, each of which usually appear to come from the same position; those curling down usually come from the bracteoles tissues and those projecting upwards usually come from ovarian tissues....read more on Wikipedia.