Tom Volk's Fungus of the Month for October 2000

This month's fungus is Tremella mesenterica, witch's butter

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Tremella mesenterica, witch's butteranimated witchIt's Halloween month again! If you've been following my web pages, you know that for previous Octobers' Fungus of the Month features I've had Omphalotus olearius (the Jack-O-Lantern mushroom) and Claviceps purpurea (cause of ergotism-- and likely contributor to the Salem Witch Trials), so the next fun choice for this October's fungus is the jelly fungus Tremella mesenterica, better known as witch's butter.

Why the curious name for such an innocuous-looking fungus? Well according to some eastern European legends, this fungus appears on your gate or on the entrance to your house when you have been put under a spell by a witch! The only way to get rid of the hex is to prick the witch's butter with straight pins, which makes the inner juices of the fruiting body leak out, killing the fungus, thus allowing you to live your life witch-free once again. I'm guessing the witch's butter hex is probably not a true story, but I'm not taking any chances...

Tremella mesenterica is not your typical looking mushroom, but appears rather like someone stuck a spoon into a jar of orange marmalade and splattered it across a log. There are a number of these jelly fungi, many of which have the texture of a Gummi BearTM. They're surprisingly tough. All of the jelly fungi are members of the Basidiomycota, although there are also jelly-like Ascomycota, so you'll have to check microscopically to be sure sometimes. The jelly fungi are found in three orders: the Tremellales, Auriculariales and the Dacrymycetales. All unusual types of basidia; the Tremellales have vertically septate basidia, the Auriculariales have transversely septate basidia (these are both types of phragmobasidia-- phragmo means fragmented) and the Dacrymycetales have tuning fork basidia. Most mushrooms that you are familiar with have basidia that are not septate (holobasidia-- holo means whole or entire).

Tremella basidia Tremella mesenterica and other members of the Tremellales have vertically septate or cruciate septate basidia, depending on what angle you look at them. "Cruciate" means in the shape of a cross (from the same root word as crucify), and this can most easily be seen looking at the tops of the immature basidia on the lower left panel of the picture. The basidium to the far left in that panel shows the septa particularly well. When the basidia mature, four elongate sterigmata form to bear the spores (upper right), but the cross can still be seen (or at least imagined...). The picture on the upper left shows a side view of a basidium with sterigmata-- you can also see one of the vertical septum. The lower right picture shows the mature basidium with four sterigmata, but the septa cannot be seen, since the picture is focused on the outside of the basidium. I have been unable to capture a good view of these basidia with spores attached, as they fall off very easily in the preparation of the specimens, which involves much "chowdering" of the specimens to expose single basidia-- they're usually deeply embedded in a gelatinous matrix and only the spores are exposed on the surface of the fruiting body.(I learned to use the word "chowdering" from students in my basidiomycete workshop on the coast of Maine last summer. Mmmmm, good chowder...)

Incidentally, these pictures were taken with my digital camera (Nikon CoolPix 950) through the eyepiece of a normal microscope, without any attachments and without removing the eyepiece. It's so easy. Make sure the automatic flash is turned off. Try it yourself!

Tremella on Stereum Typically you can find Tremella mesenterica on woody substrates, but that's really quite deceiving. All members of the genus Tremella are reported to be parasitic on wood decay fungi, such as Stereum or Aleurodiscus! Most of the time Tremella species are parasitic only on the mycelium (the hyphae) of these wood decay fungi, but in rare cases, such as shown here, you can actually see the two fungi fruiting together, with the Tremella appearing to grow right on the Stereum fruiting body. I can recall seeing this configuration only twice in all the time I've been collecting fungi. Tremella species are often difficult to culture, since many of them have a yeast phase in the absence of their wood decay host. This yeast is often mistaken for a contaminant and the culture is discarded. Even if you recognize this as the correct culture. it seems to be difficult to keep these in culture for very long without their host.

Tremella basidia There are a number of other common species in the Tremellales, some of which can grow to be quite large. In the picture to the left A is Tremella foliacea, with my 2 inch (5 cm) lens cap on top of it. B is Tremella fuciformis, cultivated in China and served as a dessert. When cultivated, the host fungus is inoculated into the log first, then this parasitic fungus. That's very different from other edible mushrooms that are grown as a monoculture. C is Tremella reticulata, a hollow jelly fungus often found apparently fruiting on the ground, and D is Phlogiotis (=Tremiscus) helvelloides, the apricot jelly fungus. All of them are fun to find in the woods, playing an important role in keeping certain wood decay fungi in check. Some of them are quite edible. Even if none of them have a delicious flavor, it's the texture that's important here.

I hope you enjoyed this month's fungus. Be on the lookout for these jelly fungi. I hope you will try to look at some member of the Tremellales under the microscope next time you find one. They're all quite beautiful to look at and even more beautiful and unusual under the microscope. Remember, there's always a story behind every fungus.

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This page and other pages are © Copyright 2000 by Thomas J. Volk, University of Wisconsin-La Crosse.

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