05/09/2026
Two completely different organisms in these images, and they’re worth separating because their biology is wildly different.
The big yellow cushion: Fuligo septica — Dog Vomit Slime Mould (a.k.a. Scrambled Egg Slime). This is not a fungus, not a moss, not even technically a plant or animal. It’s a plasmodial slime mould (Myxomycete), which is a protist — a giant amoeboid single-celled organism with millions of nuclei sharing one cell membrane, slowly crawling over rotting wood and engulfing bacteria, yeasts, and fungal spores by phagocytosis. What you’re photographing is the aethalium — the spore-producing fruiting stage that forms when the plasmodium runs out of food or moisture. Within a day or two it’ll harden, darken to grey-brown, and crumble into a cocoa-powder dust of spores.
Composition is fascinating:
• Pigment: fuligorubin A (a tetramic acid derivative) gives the yellow colour and acts as an electron-transport molecule in the plasmodium
• Calcium carbonate: deposited as microscopic granules in the peridium and capillitium — gives it that slightly gritty, foam-like texture
• Heavy-metal concentrator: famously sequesters zinc and other metals (often >20,000 ppm zinc in dry weight) — has been studied for bioremediation
• Slime moulds also exhibit primitive “intelligence” — Physarum polycephalum, a close relative, can solve mazes and reproduce the Tokyo subway map by optimising nutrient flow between food sources
The yellow dusting on the bark itself is something else entirely — almost certainly Chrysothrix candelaris (Gold Dust Lichen) or a close relative. That’s a leprose lichen — no proper thallus, just a powdery crust of fungal hyphae enclosing single-celled green algae (Trentepohlia or similar). The yellow comes from calycin and pulvinic acid derivatives, secondary metabolites the fungus produces as UV screens and antimicrobials. The fine grey-green frilly bits nearby are fruticose lichens (likely Ramalina sp.), which often share the same dead-wood substrates in Knysna’s humid forests.
So in one photo you’ve got a protist, two lichens, and a moss-covered hardwood stump — a nice cross-kingdom snapshot.