Tom Volk's Fungus of the Month for May 2008
TomVolkFungi.net for the rest of Tom Volk's pages on fungi
This month's fungus is Disciotis venosa, an interesting, but not particularly common cup fungus. At first it looks like just another brown cup fungus, until you look much more closely at it. Most other brown cup fungi are very smooth on the inside, but Disciotis venosa has raised vein-like ridges, as its name would suggest. These veins may serve to increase the surface area for bearing asci with their ascospores, but not by much. We'll talk more abut those veins later.
I have only seen this species once, in Missouri in the Spring of 1996 with my friend Ken Gilberg. Although I had never seen it before, I knew immediately what it was because of the veins and its size. It's also relatively large for a cup fungus, about 6-7 inches (18-20 cm) in diameter. The only other brown cups that I know to be that large are Peziza repanda, which grows on wood in the forest and Peziza domiciliana, which grows on wood in houses. Since this fungus was growing on the ground in the forest, I knew it was not one of those Peziza species. The size, color, habitat and veined morphology led me to an easy identification. However, when I picked it up, there was one more surprise in store-- this fungus smells like a morel ! I also noticed when I picked it, that it also had the same brittle yet rubbery texture of a morel. Then I remembered-- the closest relative to Disciotis is Morchella! Some people who have eaten Disciotis say that it tastes like a morel. Microscopically, the ascospores even look like morel ascospores-- they are borne eight to an ascus and lack large oil droplets like those found inside the ascospores of Helvella and Gyromitra. However, fresh ascospores of both Morchella and Disciotis usually have several tiny oil droplets stuck to the outside of the ascospores, particularly around the "poles" of the spores. Unfortunately I did not have the equipment to take pictures of the Disciotis spores in 1996, but to the right are some intact asci of Morchella.
So, what about those veins we talked about earlier? There is a hypothesis that explains these veins as the beginnings of folds to create the pitted surface of a morel. However, the veins are on the inside of the cup of the Disciotis while the pitted surface of a morel is on the outside of the fruiting body. This could be explained by the inversion of the cup to make a morel. I have crudely illustrated this to the left. "A" represents a typical cup fungus, such as Disciotis or Peziza. "B" represents a cup that grew an elongated stalk, In "C" the cup has begun to invert, and in "D" the cup has fused back to the hollow stalk, as in a morel. Thus you can see how the veins might end up on the outside. Although I know of no scientific evidence for this hypothetical progression, this is what makes the most sense to me.
In this photo I have backlit the fruiting body so that you can better see the veins.
I hope you enjoyed learning about Disciotis venosa, the veined cup fungus. If you've found this and eaten it, let me know what you think. But please don't go around eating random brown cup fungi-- be sure of your identification!
If you have anything to add, or if you have corrections, comments, or recommendations for future FotM's (or maybe you'd like to be co-author of a FotM?), please write to me at
This page and other pages are © Copyright 2008 by Thomas J.
Volk, University of Wisconsin-La Crosse.
Learn more about fungi! Go to Tom Volk's Fungi Home Page --TomVolkFungi.net
Return to Tom Volk's Fungus of the month pages listing