Myxomycetes, or slime moulds

They are also known as slime moulds. For definitions and background see the article in Wikipedia: "Slime moulds .. are peculiar protists that normally take the form of amoebae, but under certain conditions develop fruiting bodies that release spores, superficially similar to the sporangia of fungi."

Plasmodium of a yellow slime mould on the dead stump of an ash tree, possibly 'scrambled egg slime', Fuligo septica.