When Is Fuligo septica Purple? Not Very Often!

I was out with Ruby last summer when I spotted an unusual patch of colour in the distance, a pale, pretty, pinkish violet perched atop a moss-covered oak log. As Ruby and I got closer, it became obvious that it was not a wayward bit of plastic or a spent balloon, it was something special.

Ruby with Daedaleopsis confragosa
and Hypoxylon fragiforme

Now, Ruby is a fabulous foray companion — not only does she make me laugh, I can also count on her to give me warning of approaching wildlife, such as bears, when I’m silently concentrating on fungal marvels. Now that she’s outgrown her jubilant puppy habit of pouncing directly on top of whatever exciting specimen I happen to be focusing my camera on, she is almost perfect.

Ruby is a log-walker.

Almost, but not quite. Her one remaining flaw (besides, like most dogs, occasionally rolling in something nasty - see my last post), is that she is a log-walker. There’s nothing Ruby loves more than to scramble up onto a fallen tree and elegantly walk it from one end to the other, as sure-footed as a balance-beam gymnast — a problem if I’m trying to photograph or collect a specimen from said log.

I knew I had to distract her, so I gathered a few sticks and began throwing them until I reached my quarry. What I found was a large patch of not-quite-set, but fully-formedslime mold, Fuligo septica, but a F. septica that was, of all things, a beautiful lavender instead of bright or dull yellowish.

Immature violet Fuligo septica 

I managed to keep Ruby at bay long enough to collect a sample and took it home. I set it aside to mature and produce spores and started reading. I took more pictures. I looked at under the microscope. I read some more.

Immature violet Fuligo septica showing pale pink plasmodium 

I found a reference to a F. violacea, (Persoon, C.H. 1801. Synopsis methodica fungorum), but little information about it other than the original Latin description which refers to a yellow outer shell. Mycobank clumps F. violacea together with numerous other synonyms of F. septica.  

Violet Fuligo septica two days later

Having reached the limit of what I could find on line, I sent photos to Michael Warnock, one of the myxomycete aficionados of my local club, the Mycological Society of Toronto.  Michael replied with the suggestion that my specimen might be a F. septica that had been attacked by the myxomycophagist (slime mold eater), Nectriopsis violacea. I’ve actually found this curious character before. It looks completely different than what I’d found.

Nectriopsis violacea, an ascomycete, feeds on Fuligo septica.

The perithecia of Nectriopsis violacea are royal purple when moist.

N. violacea is an ascomycete that specifically targets F. septica. It’s not terribly common — I’ve only seen it twice, both times at the Cain Foray near Algonquin Park in Ontario — but it’s unmistakable. Its colour ranges from dark purple to purplish white (not pinkish lavender), peppered with minute darker pimples, the perithecia through which its spores are released. Not what I had found.

A squash-mounted perithecium of Nectriopsis violacea 
along with globose spores of Fuligo septica

F. septica, known for centuries as Flowers of Tan because of its proclivity to colonize the piles of tannin-filled wood chips used in the leather tanning industry, has several commonly found forms. The dull beige version that can sometimes produce massive fruitings on hay or straw or compost piles has been fondly called Dog Vomit Slime (self-explanatory). In Scandinavian folklore, it's identified as the vomit of troll cats, a creature I want to see. 
In my neck of the woods, I more often encounter a yellower, more compact version that matures from sometimes startlingly yellow, huge masses of plasmodium, a stage that gave rise to another descriptive moniker, Scrambled Egg Slime. This plasmodium sometimes matures into large, dull-yellowish amorphic patches on logs and trunks of trees. Other times it separates into much smaller, individual, deep cadmium yellow pillows. All of the above forms contain dark purplish brown masses of globose, minutely spiny spores that all look the same microscopically. None of these forms are pinkish violet. Not even close. But I did read that the final colour can have a connection to the acidity of the substrate on which its aethalia (pillow-shaped fruiting bodies) have chosen to form.

A metre-wide patch of Fuligo septica plasmodium,
also known as Flowers of Tan

Under the microscope, I found another anomaly — the spores of mine all contained oil droplets of various sizes. So did I actually have a different species? Or did my sample have some kind of weird infection?

Spores of violet Fuligo septica showing oil droplets

I found an old paper describing techniques for propagating F. septica and decided — in my completely amateur way — to try to grow mine. I put some spores on a sprinkling of ground-up oatmeal on a damp coffee filter in a covered container. Within a couple of days, the spores produced a flash of pigmented growth. The first day it was a bright, deep fuchsia, which then settled down to more of a pale pink, like the interior of the original immature aethalia. My experiment then stagnated and did nothing until it began to smell. I threw it out.

My spore-growing experiment produced brief pigmented growth.

Still, there had been no sign of the usual bright yellow pigment that F. septica commonly produces, so what did I have? I decided to go to the top of the myxomycete food chain and emailed Frederick W. Spiegel at the University of Arkansas, a specialist in Mycetozoans, a grouping of slime molds that include the genus Fuligo. He, in turn, forwarded my message and photos to his colleague, Steven L. Stephenson, author of numerous publications, including the indispensable Myxomycetes: A Handbook of Slime Molds, noting that Steven had likely seen more F. septica fruitings than any other human being.

Normal egg-yolk yellow Fuligo septica plasmodium

Steven, at first unable to open my image files, suggested once again that I had a found a F. septica specimen that was being consumed by N. violacea. Once he was actually able to see my photos, though, he informed me that he had once come across F. septica approaching the colour of mine, possibly in Alaska. He also said that oil droplets and other inclusions are found in a lot of myxos. His final word was that, as F. septica is almost certainly a species complex, what I had found could only be called that until such time that someone decides to make the effort to sequence a series of collections. As per his suggestion, I have frozen my collection for future study. Any takers?


Many thanks to Michael Warnock, Frederick W. Spiegel, and Steven L. Stephenson!

Three stages of a pale yellowish beige Fuligo septica

The colour of Fuligo septica can vary enormously.

References & Resources

Steven L. Stephenson, Myxomycetes : a handbook of slime molds, Timber Press, 1994.

Patricia M. Scholes: Some Observations on the Cultivation, Fruiting and Germination of Fuligo septica, J . Gen. Microbiol. (1961), 29, 137-148 

Tom Volk's entertaining Fuligo septica page

Some fun Fuligo septica history from Historical and Literary Botany: Containing the Qualities, Anecdotes, and supperstitions, relative to trees, plants, and flowers, which are mentioned in sacred and profane history - Volume 3 By Eliza P. Reid 1826 

Great series of photos from Wayne’s World of the different stages of pale version of F. septica plasmodium growing on wood chip mulch

The Myxomyceticolous Species of Nectria: Gary J. Samuels Source: Mycologia, Vol. 65, No. 2 (Mar. - Apr., 1973), pp. 401-420

An amazing BLUE Fuligo!!!