I've just noticed that the Buddleia in our garden is absolutely covered in these:
According to Wikipedia, Auricularia auricula-judae, the Jew's ear fungus, grows especially well on elder. Both its common and scientific names are said to derive from the belief that Judas Iscariot hanged himself from an elder tree; the common name Judas's ear eventually became Jew's ear. But I always take folk etymology with a pinch of salt.
A weird, and pleasing fungus, though.