Recently my husband and I had a marvelous mushroom walk with lots of different species, including some spectacular coral, crust, and jelly fungi as well as gilled mushrooms. With the amazing morphological diversity of the fungi available, when we saw two patches of yellow goo, we didn’t pay too close of attention to the second one. On encountering the jelly in the right picture below, we said “Oh neat! More Witches’ Butter!”, snapped some photos, and moved on. (“Witches’ Butter” is the common name for a yellow jelly fungi, usually in the genus Tremella.)
But on closer inspection of my photos, I discovered that while they’re both yellow and gelatinous, these are two very different fungi!
The first thing I noticed in these photos was that the points of attachment to the log are totally different colors in each specimen. Look at the above left image image and see how the jelly is yellow all the way from tip to log. Meanwhile, on the right-hand image, the base of each glob is transparent!
The next thing that sets them apart is how the fruiting masses are growing. Our First Find had a convoluted, brainlike edge, even in the young specimen on the left. It got increasingly convoluted with age, with individual globs sort of merging in the older specimen on the right (which was on a different part of the same log).
On the other hand, our Second Find seems to have individual fruiting bodies with distinct masses that don’t really merge, at least not nearly as extensively as they do for the First Find.
Finally, there’s a third vital difference, which I didn’t realize was important until I tried identifying these jellies. First Find was fruiting on a log that still had the bark on it, while Second Find was fruiting on bark-free (“decorticated“) wood. (“Cortex” means “outer layer” in Latin, so a “decorticated” log is one with its outer layer missing.) This, combined with the color and morphological differences, confirms that they are different species. They aren’t even closely related – they’re in different genera!
Our First Find is the classic Witches’ Butter, Tremella mesenterica.
The genus name, Tremella, comes from the Latin word tremere, “to tremble” (1), probably because members of the genus are so gooey and will wobble when shaken. When we first saw this patch, the word “Tremella” popped into my head because it’s just such an evocative word. In classic Old Science fashion, the genus name comes from Latin but the species name is Greek: meso- is Greek for “middle”, like in “Mesoamerica”, and enteron means “intestine” (2). Clearly the person who first described the species thought the jelly fungus looked less like jelly and more like entrails!
While it’s growing out of a log, this jelly fungus is not actually digesting the log. T. mesenterica is a mycoparasite, meaning it feeds on other fungi. In this case, our specimen is feeding on the unseen mycelia of a Peniophora species (3) – which might be fruiting as a visible crust if it weren’t for T. mesenterica over here taking its nutrients!
Our Second Find is the species Dacrymyces chrysospermus, and to my credit, apparently it is often confused for T. mesenterica (4). This is where that decorticated wood comes in: D. chrysospermus prefers it, while T. mesenterica (or at least its lookalike and close relative, T. aurantia) can very much enjoy wood with bark still on it (4). For me though, the most distinguishing feature is the transparent base of the fruiting bodies: D. chrysospermus is “abruptly narrowed and pallid [pale] at the attachment point” (4).
The genus name Dacrymyces is named for having members with small, round or tear-shaped fruiting bodies (dacry is Greek for “teardrop”), while the species name chrysospermus tells us what color the spores (“sperma“) are: chrys means “golden” (5). That sounds like a fun spore print to have, since most spore prints I’ve got so far are different shades of brown. Maybe next time I see a D. chrysospermus (and am in a collecting area and mood) I’ll take a little sample home. Who knew “just another Witches’ Butter” would actually be so interesting!
Even though they’re exciting to spot initially, multiple jelly fungi can feel a little repetitive. It’s one yellow glob of goo, and another yellow glob of goo. But there was a completely new (to me) genus right under my nose and I almost brushed right past it. This exercise in identification has proven to me that every jelly fungus is worth a second look!
(1) Rea C. (1922). British Basidiomycetaceae. A handbook of the larger British fungi. Cambridge: Cambridge University Press. p. 799. via Wikipedia ‘Tremella‘. Wikipedia.org. https://en.wikipedia.org/wiki/Tremella, accessed 20 October 2021.
(2) O’Reilly, P. (2021). Tremella mesenterica Retz. – Yellow Brain Fungus. First-Nature.com. First Nature. https://www.first-nature.com/fungi/tremella-mesenterica.php
(3) Kuo, M. (2018, October). Tremella mesenterica. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/tremella_mesenterica.html
(4) Wood, M. and Stevens, F. (2020) California Fungi—Dacrymyces chrysospermus. The Fungi of California. MykoWeb. https://www.mykoweb.com/CAF/species/Dacrymyces_chrysospermus.html
(5) O’Reilly, P. (2021). Dacrymyces chrysospermus (Bull.) Tul. – Orange Jelly Spot. First-Nature.com. First Nature. https://www.first-nature.com/fungi/dacrymyces-chrysospermus.php