Tremella aurantia Schwein.
Schrift. Naturf. Ges. Leipzig 1: 114. 1822.

Common Name: Witch's Butter

Misapplied name: Tremella mesenterica

• Sporocarp

  Fruit bodies 2-10 cm broad, consisting of clustered, convoluted folds with blunt margins; surface yellow, to yellowish-orange, shiny when wet, otherwise dull; context gelatinous, drying to a stiff, hard crust, reviving after periods of moisture; odor and taste not distinctive.

• Spores

  Spores 6.0-9.5 x 6.0-7.5 µm, subglobose to ovoid, smooth, thin-walled with a conspicuous hilar appendage; basidia longitudinally septate, typically stalked, 10-14 µm broad.

• Habitat

  Gregarious on downed hardwoods in coastal forests as well as low elevations of the Sierra Nevada; parasitizing Stereum hirsutum; fruiting throughout the mushroom season; common.

• Edibility

  Edible, but without flavor.

• Comments

  Tremella aurantia resembles and is often confused with Tremella mesenterica. Both species have convoluted yellowish-orange fruiting bodies, are similar in size, occur on hardwoods, and like all Tremellas, are parasitic on other fungi. As is often the case with closely related taxa, a combination of characters is needed for identification. Here we've relied on the work of British mycologist Peter Roberts to separate the species. Tremella aurantia is most easily distinguished by its host preference, attacking the common wood rotter, Stereum hirsutum, while Tremella mesenterica parasitizes species of Peniophora, a resupinate fungus. Tremella aurantia is also somewhat larger and has a duller surface when dry. Microscopically, it has smaller spores, and stalked, not sessile basidia. The ubiquitious nature of Stereum hirsutum, helps explains its abundance. The frequency of Tremella mesenterica, on the other hand, is unclear and remains to be determined.

  Besides the above species, a third "Witch's Butter," Dacrymyces palmatus, is also regularly encountered. It typically is more orange, and unlike the Tremella species, is saprobic on conifer wood. A helpful fieldmark is a whitish attachment point to the substrate. Microscopically, tuning-fork type basidia differentiates it from the longitudinally, septate, cruciate type basidia of Tremellas.

• References

  Lowy, B. (1971). Flora Neotropica, Monograph No. 6, Tremellales. Hafner Publishing Company: New York, NY. 154 p.
  Martin, G.W. (1944). The Tremellales of the North Central United States and Adjacent Canada. University of Iowa: Iowa City, IA. 88 p.
  Martin, G.W. (1964). Revision of the North Central Tremellales. J. Cramer: Lehre. 122 p.
  Roberts, P. (1995). British Tremella Species I: Tremella aurantiaca & T. mesenterica. Mycologist 9: 110-114.

• Other Descriptions and Photos
  • Michael Wood: Tremella aurantia (CP) -- parasitic on Stereum
  • Michael Wood: Tremella aurantia (CP) -- parasitic on Stereum
  • Tom Volk's Fungus of the Month: Tremella mesenterica (D & CP)
  • Mushroom Observer: Tremella aurantia (CP)
  • Arora (1986): p. 673 (D), plate 170 (CP) [as Tremella mesenterica]
  • Arora (1991): p. 242 (D & CP) [as Tremella mesenterica]
  • Breitenbach & Kränzlin (v. 2): sp. 29 (D, I, & CP) [as Tremella mesenterica]
  • Lincoff: p. 385 (D), plate 566 (CP) [as Tremella mesenterica]
  • McKenny et al.: p. 188 (D & CP) [as Tremella lutescens]
  • Miller: sp. 379 (D & CP) [as Tremella mesenterica]
  
  

  (D=Description; I=Illustration; P=Photo; CP=Color Photo)