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Wonderful Things: The Hidden Beauty of the Horse Dung Fungus

The views expressed are those of the author and are not necessarily those of Scientific American.

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Note: This is the third installment in the “Wonderful Things” series.

What you are about to see is a truffle-like (although it seems to fruit above-ground) fungus called Pisolithus tinctorius. It has many names, but in the United States it sometimes goes by “dyemaker’s puffball”. From the outside, it sits on the ground like an unassuming horse biscuit (it is called “the horse dung fungus” in Australia). But on the inside, it is a work of art.

The roundish objects are locuoles, packets of ripening spores that you can see in successive stages of readiness from the bottom (center) of the fungus to the top, where they metamorphose into powdery puffs of cinnamon spores. Pisolithus literally means “pea stone”, and I think you can see how it got that name. They are embedded within a black matrix, through which they appear to bubble up like air in an aquarium in a beautiful textural mosaic of color. The black matrix is the stuff that dyers use to color cloth a shade of reddish brown or black, according to Volk, giving the fungus its common name.

Here’s one that’s a bit further along in the spore-making process (note how many more of the locules have assumed their mature cinnamon color). This video also nicely shows what P. tinctorius looks like from the outside.

P. tinctoirus grows in mutually beneficial association with plant roots that scientists call “mycorrhizal“. It’s not very picky about who it grows with (it has been recorded to partner with nearly 50 tree species), and as a result, horticulturalists may innoculate landscaping plants’ roots with the fungus to fortify them for transplant to an inhospitable new home, especially if said new home is hot, dry, and/or nutrient-poor.

And in fact, that was where the fungus in the photograph at the top of the page was found last week during the Mycological Society of America Foray in Austin, Texas — sitting on the ground among the landscaping of the office park where our bus was parked. Unlike the fungi in the forest, which were universally baked and hard under the scorching August sun, the fresh puffball may have had access to a fungal creature comfort: sprinklers.

According to mycologist Bryce Kendrick’s book “The Fifth Kingdom”, P. tinctorius has been sometimes called “the ugliest fungus in the world”. I think that’s a bit unfair given its spectacular internal appearance and rather bland (although indisputably scatalogical) facade. I can think of several arguably more deserving fungi. He also notes that the puffballs can be used in “a hot-weather version of a snowball fight” . Which, in my opinion, may well be the nerdiest snowball fight in the world.

Jennifer Frazer About the Author: Jennifer Frazer is a AAAS Science Journalism Award-winning science writer. She has degrees in biology, plant pathology/mycology, and science writing, and has spent many happy hours studying life in situ. Follow on Twitter @JenniferFrazer.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Heteromeles 4:44 pm 08/24/2013

    Oh good grief. How could you sell Pisolithus tinctorius so short?

    For one thing, to be specific, it’s ectomycorrhizal, which means it grows with things like oaks, pines, or eucalypts, not with grasses. For the second, it’s one of the most generalist ectomycorrhizal fungi known, to the extent that, back in the 1970s, it was viewed as something of a wonder fungus.

    The annoying part is that (if I recall properly) the spores can stain clothes, so you have to be a little careful about handling sporing ‘carps. Otherwise, it’s a neat fungus that deserves more props than it gets.

    Link to this

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