Geograph - photograph every grid square

Fly agaric (Amanita muscaria) is the classic toadstool often depicted in illustrated stories with a toad (or a pixie) perched on it - something I can honestly say I've never witnessed for any fungus!
Three are seen here; nearest the camera a partly slug-eaten immature specimen; on the left a damaged fully grown example leans over to reveal its bright white gills. On the right a fully grown fine example showing its white "warts" which are remnants of the universal veil, the egg-like structure that encased the entire fruiting body when first produced. The fungus has a membranous ring near the top of its stem, though as can be seen from this photo, that may not always be obvious. Also, after heavy rain, the warts may be washed off the cap leaving it plain red (which may also fade considerably) - it can then be easily confused with any one of the larger red-capped Russula species. But normally, as here, it is the most easily identified of all fungi.
A. muscaria is, perhaps surprisingly, not particularly poisonous - but that is not to say that it should ever be eaten. It contains the psychoactive alkaloid, Muscimol (aka Agarin or Pantherine) which can cause hallucinations or other psychotic effects. Note that despite its latin name, it contains very little of the drug Muscarine - this specific name coming from the Latin for Fly (musca).
Another naming confusion is the "Agaric" in its common English name - because this fungus belongs firmly in the Amanita, not the Agaricus genus.
Some distance away I found a just-emerging young specimen - see SP9208 : Amanita muscaria (Fly Agaric) - immature emerging
Wikipedia article here Link