Yesterday (Jan 30th) I noticed that the lower parts of the yellow slime mould (probably Badhamia utricularis), that I found a week ago, is now covered in small black fruiting bodies, or sporangia. I cannot remember seeing these on my previous visit the day before (Jan 29th), but it is possible that they were there and I missed them because they were just on the lower part of one log. I had to bend down quite low to get a clear view of them. Looking back at the photos I took on Jan 29th, in one of them there does seem to be lots of little yellow lumps which might be the first signs of the developing sporangia:
Most of the photos of B. urticularis sporangia out on the web show them as an ashy light grey colour, but this is probably only their colour when they are relatively mature and nearly ready to release their spores. Some photos show B. utricularis with bright yellow sporangia. I suppose that it is possible that yellow is the natural colour of the new sporangia, and that the black colour in the above photo is just a result of a frost (-2C) that occurred on the previous night.
I will try to keep an eye on how this slime mould develops over the next few days.
Photo taken in Whiteknights Park, Readng University grounds, Reading, UK, on 2010-01-30.