I've no idea what these are but they are growing on a silver birch log that Mrs S brought in from the woodshed this morning. They weren't evident when she brought the wood in at around 8am but they were very much there when I came to stoke up the fire at around 6pm... obviously the heat of the house brought them out. They are quite delicate and each fungi looked like a small white butterfly with its wings folded. Isn't nature wonderful?