Moulds

Nostoc
This is a genus of blue-green algae or cyanobacteria. They are prokaryotic and perform photosynthesis. They are often found on tree trunks. They are also found as an algal component of lichens in certain bryophytes. They are capable of nitrogen-fixing and perform photosynthesis. They are also present as an endosymbiont to fungus.

Nostoc are prokaryotic and are grouped with bacteria. The cell lacks membrane-bound organelles and genetic material is found dispersed in the cytoplasm. They are kept in cyanobacteria as they are photosynthetic.

Must agree with Pam's ID, @trevorpreston, this fluffy white stuff is appearing all through our local forests atm, usually on soil but it often overlays onto small twigs, stones and partially buried branches.

I think you might be right. @Teresa what do you think?

Though I'm not particularly familiar with either myxomycetes or jelly fungi, I suspect this is a slime mould rather than a fungus due to the substrate.

Chromelosporium is very common & late fruiting fungi in earth throughout our local forests