Daldinia concentrica (Bolton) Ces. & De Not. - King Alfred's Cakes

Distribution - Taxonomic History - Etymology - Identification - Reference Sources

Daldinia concentrica

Taxonomy

Phylum: Ascomycota

Class: Soprdariomycetes

Order: Xylariales

Family: Xylariaceae

Common referred to as King Alfred's Cakes (a reference to their burnt appearance, of course, because having been given shelter by a peasant woman Alfred, preoccupied by other concerns, was reputed to have inadvertently allowed her cakes to burn, having promised that he would watch her cakes cooking. They are also referred to as Cramp Balls (because carrying them was thought to cure attacks of cramps). These hard, inedible fungi appear most often on ash and beech wood but occasionally on other hardwood trees.

Daldinia concentrica

The pinkish-brown specimens shown on the left are young and still growing, and during this asexual stage they develop over a long period and release colorless spores known as conidia, which are whitish when seen in mass. Once fully grown the fruitbodies turn black, like those in the picture above. At this mature stage the surface becomes dotted with tiny bumps that are the openings of perithecia, the spore-producing structures located just below the surface. Ascospores, which unlike the pallid conidia are jet black, are ejected from these openings in vast numbers, soon covering the surface of the fruitbody and darkening the substrate wood (creating in effect a natural spore print) for some distance around it.

Distribution

Common and widespread in Britain and Ireland and found throughout most of mainland Europe, this saprobic fungus occurs also in North America and in many other temperate regions.

Taxonomic history

Described in 1791 by British mycologist James Bolton (1750 - 1799), who gave it the scientific name Sphaeria concentrica, this ascomycetous fungus was transferred to the genus Daldinia in 1863 by Italian mycologists Vincenzo de Cesati (1806 - 1883) and Giuseppe De Notaris (1805 - 1877). Daldinia concentrica is the type species of its genus.

Daldinia concentrica has several synonyms including Fungus fraxineus Ray, Sphaeria fraxinea With., Sphaeria concentrica Bolton, Hypoxylon concentricum (Bolton) Grev., and Stromatosphaeria concentrica (Bolton) Grev.

Etymology

Inside the fruitbody there are concentric silver-grey and black layers (pictured below), from which comes the the specific epithet concentrica.

Identification guide

Cross-section of a King Alfred's Cake showing the concentric bands.

Fruitbody

Initially brown and dense, the fruitbodies of Daldinia concentrica soon turn black, dry out and become less dense.

There is no stipe; the fruitbody is attached to the host wood by a broad, flat area underneath the cushion-shaped fruitbody.

The spore-bearing surface is the outside of the fruitbody, and spores leavce a slightly darker area of wood around the fungus.

Individual fruitbodies are typically 2 to 8cm across, but several may merge to form a much larger compound outgrowth.

 

Spores

Ellipsoidal to fusiform, 12-17 x 6- 9µm.

Spore print

Black.

Odour/taste

Not distinctive.

Habitat

Saprobic, on dead or dying hardwood, nearly always of ash trees. A very similar species occurs on beech.

Season

New fruitbodies appear from mid summer through to the end of autumn, but old, dried out fruitbodies sometimes persist for a year or two.

Similar species

Several blackish crust fungi occur on dead wood. Ustulina deusta is one example; it does not have concentric rings within its fruitbody and does not form cushion-shaped or ball shaped growths.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2011

Dennis, R.W.G. (1981). British Ascomycetes; Lubrecht & Cramer; ISBN: 3768205525.

Breitenbach, J. & Kränzlin, F. (1984). Fungi of Switzerland. Volume 1: Ascomycetes. Verlag Mykologia: Luzern, Switzerland.

Medardi, G. (2006). Ascomiceti d'Italia. Centro Studi Micologici: Trento.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.