I ordinarily try not to be crass online, but sometimes you’ve just gotta use a certain phrase. There’s not a lot this squishy, brown, suspiciously cylindrical fungus resembles more than, ahem, dog poop, especially when you step on it (I bet you can guess how I know). The brown color is so strong that yarn makers dye wool with it (it’s also known as the dyemaker’s puffball or dyemaker’s mushroom).
This interesting fungus is mycorrhizal — it grows in mutually beneficial association with plant roots, particularly conifers and oak trees. Horticulturalists even deliberately inoculate plants’ roots with the fungus to make them stronger prior to transplantation.
The really funny part is when I searched for it online (“mushroom looks like poop”), this page came right up! I’m not the only one with a filthy mind, apparently. (Or a filthy backyard.) Other cultures agree: other common names include the “horse dung fungus”, “dead man’s foot”, and the “Bohemian truffle”, which suggests a terrible, terrible prank pulled at a dinner party.
Mushroomexpert.com (which is certainly smarter than I am) seems to think that the official Latin name for this fungus is, in fact, Pisolithus arenarius, because the name P. tinctorius has actually already been used for a different species in the Canary islands, but we unwashed heathens in the U.S. seem to be calling this P. tinctorius so I’ll just mention both names here and go hide under my hat.
Also, because this fungus is just delightful and seems to delight people who write about it, I shall link this lovely article by The Artful Amoeba at Scientific American.