Daldinia concentrica
Description
Tiny fire-lighters with an embarrassing story, King Alfred’s cakes are named after the king’s poor baking skills. Spot them growing in broadleaf woodland where they can last for years.
This mushroom look like hard, roundish lumps of coal stuck to the surface of decaying wood. The older they get, the darker they become. They don’t rot away quickly but can remain on deadwood for years.
When cut in half you can see concentric layers that represent each season of reproduction. The color ranges from black, dark brown to purple tones.
Common names: King Alfred’s Cakes, Carbon Balls, Cramp Balls, Coal Fungus.
Mushroom Identification
Fruitbody
Individual fruitbodies (formally referred to as stroma) of Daldinia concentrica are typically 2 to 8cm across, growing over several seasons (hence the growth rings), but several may merge to form a much larger compound outgrowth.
Initially brown and dense, the fruitbodies 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 a series of tiny chambers called perithecia, which are embedded within the outside of the fruitbody, and ejected spores leave a slightly darker area of wood around the fungus.
Each season a new fertile outer layer develops with new perithecia, inside which the next season's ascospores are produced. Large stroma is therefore much older than small ones.
Perithecia
The picture on the left is a greatly magnified view of a perithecium, the dark chamber within which the asci form and spores are produced. As with other ascomycete fungi infertile paraphyses are separating the asci.
Once the spores inside an ascus have reached maturity, the ascus expands lengthways, guided by the surrounding paraphyses, until its tip extends outside the neck of the perithecium; then water pressure built up inside the ascus bursts open the tip of the ascus and the ascospores are forcibly ejected. The ascus shrivels leaving the opening clear for the next set of eight spores to be expelled.
Asci
Each ascus contains eight ascospores. Asci are typically 200µm x 10-11µm, cylindrical, and the asci tips are amyloid.
Ascospores are ejected, mainly it seems at night, from asci hidden within perithecia just below the black surface of the fruitbody. In creating overnight spore prints I have found that some spore dust is visible as far as 3 cm or more from the edge of the stroma (plural stromata); however, in windless conditions, a high proportion of the spores stick to one another and emerge from the necks of the perithecia in the form of contorted ropes, as seen on the left. The ropes wave about and appear to be 'growing' as more spores are added to extend them at their attachment points.
Spores
Ellipsoidal to fusiform, 12-17 x 6-9µm. The spore print is black.
Habitat & Ecological role
Saprobic, on dead or dying hardwood, nearly always of ash trees. A very similar species occur on beech.
Season
Ascospores are produced from late spring through to the end of autumn, but fruitbodies (stroma) can be seen at any time of year.
Similar species
Several blackish crust-like fungi occur on dead wood. Kretzschmaria deusta is one example; it does not have concentric rings within its fruitbody and does not form cushion-shaped or ball-shaped growths.
Uses
The fungus is a useful form of tinder for fire-lighting. The brown variety is usually too heavy and dense to be much good; the black variety is lighter and better. It does need to be completely dry, whereupon it will take a spark from traditional flint and steel. It burns slowly, much like a charcoal briquette, with particularly pungent smoke. Once lit it usually requires constant oxygen flow to keep burning, such as through swinging the fungus or blowing on it. Fragments can be broken off to expose more embers and transferred to a tinder bundle to create an open flame.
Health Benefits
The antibacterial and antifungal activities of the above extracts were determined by well diffusion assay. Nearly both the extracts were found effective against these bacteria and fungi. The aqueous extract showed a higher zone of inhibition than the methanol extract tested.
The extracts exhibited antibacterial activities with a zone of inhibition ranging from 14 - 54 mm and 5 - 23 mm for aqueous and methanol extracts whereas, antifungal activities zone of inhibition ranging from 9 - 25 mm and 7 - 18 mm, for aqueous and methanol extracts, respectively. The organisms were more sensitive to the aqueous extract of the fungal fruit bodies than that of methanol extract. [Source]
History
Described in 1791 by British mycologist James Bolton (c. 1735 - 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.
Inside the fruitbody, there are concentric silver-gray and black layers, from which comes the specific epithet concentrica.
Above: When you make a spore print of an agaricoid mushroom or of a bolete, the spores are deposited directly beneath the fertile surface - the gills or the pores. With flask fungi such as Daldinia concentrica the spores are ejected from asci buried within the stroma (fruitbody) and create a spore print extending outwards from the edge of the stroma. In this instance, the spores have left a visible black stain up to 3cm wide.
Photo sources:
Photo 1 - Author: Daniel Greenwood (CC BY-SA 4.0)
Photo 2 - Author: Michel Langeveld (CC BY-SA 4.0)
Photo 3 - Author: Stu's Images (CC BY-SA 3.0)
Photo 4 - Author: Björn S... (CC BY-SA 2.0)
