Mycologia 97(4): 861. 2005.
Photo: Growing on a moss covered log.
Common Name: cramp balls
Synonym: Hypoxylon thouarsianum (Lév.) Lloyd (Myc. Writ. 5: 26. 1919.)
Misapplied name: Daldinia grandis
Fruit body annual, sessile, 1.0-5.0 cm broad, up to 3.0 cm in height, compressed-globose to hemispheric, occasionally lobed; surface dark-brown to black, carbonaceous, dull or varnished, densely pimpled with perithecia, the tips encircled by a flat, sometimes sunken disc; context fibrous-woody, radially lined to faintly concentrically-zoned grey and brown, sometimes appearing silky-lustrous; odor and taste not investigated.
Spores 15.0-21.0 x 4.5-6.0 µm, smooth, inequilateral, narrowly elliptical to slightly fusoid or cucumber-shaped with a curved and flat side, the latter with a germ slit; spores light to medium-brown mounted in water; spore deposit not seen.
Scattered to clustered on bark of hardwoods, especially Quercus agrifolia (coast live oak) and Lithocarpus densiflora (tanbark oak); fresh sporocarps developing after the fall rains, often persisting through the following season; common, often mistaken for Daldinia grandis (see Comments)
Few fungi are more familiar yet so consistently confused as Annulohypoxylon thouarsianum with Daldinia grandis and Daldinia loculata. These Ascomycetes produce the distinctive charcoal-like fruiting bodies one sees on downed hardwoods. Historically they've been lumped under the name Daldinia grandis. Since there are no collections of Daldinia grandis in the Thiers Herbarium at San Francisco State University, it's occurrence in California is questionable. A closely related species, Daldinia loculata, occurs only sporadically on various hardwoods and is separated from Daldinia grandis by spore size. What is found abundantly on Quercus agrifolia (coast live oak), and Lithocarpus densifora (tanbark oak), is Annulohypoxylon thouarsianum.
Annulohypoxylon thouarsianum can be distinguished from Daldinia grandis and Daldinia loculata by comparing the sporocarp surface and context (see pictures). In Annulohypoxylon thouarsianum the surface is conspicuously pimpled, the tips surrounded by a small, flat disc, visible with a hand lens, while in Daldinia grandis and a sister species, Daldinia loculata, the surface is relatively smooth, the pimples lacking a disc. The context of Annulohypoxylon thouarsianum is radially fibrous, sometimes appearing silky-lustrous, occasionally faintly concentrically zoned in shades of grey and brown, while that of Daldinia grandis and Daldinia loculata is strongly zoned grey to brown, the concentric layers alternating in density from pithy to loculate, especially in age.
Based on molecular evidence, the new genus Annulohypoxylon was recently created for members of Hypoxylon section Annulata, which includes Hypoxylon thouarsianum (See Hsieh et al., Mycologia 97, 2005).
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Hsieh, H.-M. , Ju, Y.-M. & Rogers, J.D. (2005). Molecular phylogeny of Hypoxylon and closely related genera. Mycologia 97(4): 844-865.
Ju, Y.-M. & Rogers, J.D. (1996). A Revision of the Genus Hypoxylon (Mycologia Memoir No. 20). APS Press: St. Paul, MN. 365 p.
Rogers, J.D. (1979). The Xylariaceae: Systematic, Biological and Evolutionary Aspects. Mycologia 71(1): 1-42.