Ice hairs on dead wood in the Bugey region. An unusual winter phenomenon that has long remained a mystery: under the effect of frost, extremely fine (0.02mm), curved ice fibers grow several centimeters from the pores of dead wood on a branch, provided the wood is colonized by a saprophytic fungus, Exidiopsis effusa, whose presence prevents the formation of crystals. As soon as the first rays of sunlight appear, these hairs .France