Mycotaxon 1: 59. 1974.
Synonym: Helotium sulfurinum Quél.
Apothecia 0.5-1.0 mm broad, sessile, at first urn-like, centrally concave, becoming cushion-shaped to discoid; hymenium glabrous, bright yellow to citrine, slightly translucent; exterior colored like the disc or paler; margin more or less even, lacking hairs; context soft, fleshy, yellowish; odor and taste not investigated.
Spores 8.0-11.0 (13.0) x 2.0-2.5 µm, narrowly ellipsoid to subfusoid, occasionally curved, hyaline, one-septate at maturity, some with droplets; asci eight-spored, uni to biseriate, the tips inamyloid.
On hardwoods, gregarious to clustered, fruiting in association with a pyrenomycete; seldom collected because of its size, but probably common
Edibility unknown; insignificant.
Bisporella sulfurina is a tiny, lemon-yellow discomycete unusual in that it fruits in close association with a pyrenomycete. The latter is recognized by a layer of blackish tissue found in close proximity to the brightly colored discs. Bisporella citrina is a common, larger species, not associated with a pyrenomycete. It typically fruits gregariously rather than clustered on bark-free hardwoods. Both species have two-celled ascopores at maturity, but the spores of Bisporella citrina are distinctly broader. A third Bisporella, B. pallescens, forms small, whitish cups on hardwoods, and like Bisporella sulfurina, fruits on the surface of another fungus, a conidial forming taxa called Bispora antennata.
Beug, M.W., Bessette, A.E. & Bessette, A.R. (2014). Ascomycete Fungi of North America. University of Texas Press: Austin, TX. 488 p.
Breitenbach, J. & Kränzlin, F. (1984). Fungi of Switzerland. Volume 1: Ascomycetes. Verlag Mykologia: Luzern, Switzerland. 310 p.
Dennis, R.W.G. (1981). British Ascomycetes. J. Cramer: Vaduz, Liechtenstein. 585 p.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Medardi, G. (2006). Ascomiceti d'Italia. Centro Studi Micologici: Trento. 454 p.