I came across these in the New Forest on Sunday. These pink domes are the spore containing stage, or fruiting body, of Lycogala epidendrum, the Wolf’s Milk Slime Mould. If punctured, they ooze a pink toothpaste-like material.
Usually this organism exists as red coloured and microscopic amoeba-like cells which move around on a substrate, such as a rotting log, and feed on bacteria. If conditions are appropriate, these unicellular organisms will start to mate, to eventually form a large multinucleated monocellular organism known as a plasmodium, which can grow into mat up to a metre in diameter. I’m not certain, but the yellow plasmodial form of a slime pictured here, and also found at the same location, might be that of Lycogala epidendrum. In any case, the plasmodium is also mobile and can move towards food and also away from harm. Eventually, if environmental factors change for the worse, the plasmodium may transform into the spore containing and pink fruiting bodies also seen here.