Slime mold is one of those things you encounter when you wander around in the woods, like moss and lichens.

I always thought it was a fungus.

But now I read this article by Chet Raymo, [UPDATE: original story now disappeared, sorry] and it turns out that slime mold isn’t a fungus, but . . . well, something else entirely.

For part of its life cycle it lives as “free-roaming amoebas, single-celled organisms, grazing on bacteria” — during this stage it’s invisible to the naked eye.

If the supply of bacteria runs out, however, some of the organisms “secrete a chemical called acrasin, after Acrasia, the cruel witch in Spenser’s Faerie Queen who attracted men and turned them into beasts. It is a call. A signal.” This caused the organisms to clump into the slime form — at which point the mass is able to move by sliding, say, down a log — and then, when it reaches a suitable spot, organisms within the mass organize to form fruiting bodies.

Raymo gives details of this process in a very readable way, so click through if you enjoy that sort of thing. Incredible stuff.

Raymo then writes that it’s “now widely agreed”

that slime molds are neither plant nor animal nor fungus but members of the kingdom Protoctista, which encompasses some of the most ancient single-celled organisms . . . in their curious life cycle slime molds recapitulate that episode in the history of life, which occurred about 700 million years ago, when single-celled microorganisms, having lived on their own for 3 billion years, came together to form multicellular organisms. Invisible life became gloriously visible, and wonderfully diverse. Creatures individually smaller than the point of a pin piled themselves together to become, in the fullness of time, brontosauruses and blue whales.

Something to muse upon the next time you see a splotch of “dog vomit fungus” in your perennial bed.