We found a whole lot of these beautiful toadstools while on a walk above Loch Lomond today.
After reaching maturity, the cap breaks down into a black liquid - a process known as auto-digestion. The picture below shows four stages in the process. At bottom right is a perfect specimen. The ones in the middle have just started to widen and turn to liquid at the margins. Those on the left are half way through the process, and those at top right have completely liquified.