In winter, on a wet day, sometimes you see something coloured like egg yolk up in a tree. It is a mushroom, Witches' Butter (Tremella mesenterica), a yellow gelatinous mass (no, it is not like butter) on a dead branch in an oak tree. In this picture the branch is covered in green lichens.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3QehJfmeIgiDDPDP9wSXxBj-Zio8OEJs4i2NJEmeI6fhdFLlMr8OAn5SC6s5NgmhrlRLfCcjZIaQa-fHb60kro93Ym-QXp5vjKPvFXUPjOfCMi5W9gK0Q8bjn8XKenUnHptmBpqQ-UwU/s400/tremella+mesenterica-114785a-l-600-8s.jpg)
The Witches' Butter lives in an indirect way from dead wood, it is a parasite and lives on the mycelium of another mushroom that grows in the dead branch.