Cookeina is a genus of cup fungi in the family Sarcoscyphaceae, members of which may be found in tropical and subtropical regions of the world. Species may be found on fallen branches of angiosperms, trunks, and sometimes on fruits.
Fungus on willow - I saw one of these on a willow for the first time this year. I never knew that a regular mushroom can grow on a live tree. I always thought that wood ears and such are the only things to grow.