A species of slime mould that I have not yet been able to identify. It was on a downward-facing side of a decaying log. A few centimetres away from these white sporangia were the following brown and black ones, which I presume are more mature versions of the same species.
The white in the background to this photo, might possibly be the plasmodium of this species. I shall check this out next time I am up there.
Photos taken in Whiteknights Park, Reading University grounds, Reading, UK, on 2010-03-02.