Whilst initially looking like ice crystals or coral, it is actually a slime mould – which is not a fungi but belongs to the kingdom Protozoa – single-celled organisms.
This colony was found covering a large area of a fallen and decaying tree trunk.
Although many slime mold species fruit on wood they do not form a penetrating and absorptive mass of hyphae in the wood substrate, but form structures called plasmodia which are naked (without cell walls) masses of protoplasm which can move and engulf particles of food in an amoeboid manner. Slime mold plasmodia creep about over the surfaces of materials, engulfing bacteria, spores of fungi and plants, protozoa, and particles of nonliving organic matter. At some point, plasmodia convert into spore-bearing structures.