Santa with coalSanta with coal Tom Volk's Fungus of the Month for December 2004

Daldinia concentrica, the coal fungus, carbon balls, cramp balls, or King Alfred's cakes.

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For a Christmas treat, click here for "Fungi necessary for a merry Christmas."

Daldinia concentrica with centipedesMaybe you were a very bad boy or girl during the year, and all Santa Claus brought you for Christmas was a lump of coal in your stocking. (Since all we had at my house was natural gas heat, I remember once getting charcoal briquettes from the grill in my stocking...) Perhaps Santa will be nicer to you this year-- instead of coal, you might be luckier to get this month's fungus, Daldinia concentrica. Some common names for this fungus are the coal fungus, carbon balls, cramp balls, or King Alfred's cakes. I guess we'll call it the coal fungus for this month, since it fits with our theme. "Coal fungus" and "carbon balls" are each obvious names because of the brittle carbony texture. One of the British names, "cramp balls," is not so obvious. That name is thought to have arisen from the widespread belief that carrying this fungus in your pockets would prevent or relieve leg cramps. I have no data on whether this works. :)

D. concentrica is also known in Britain as "King Alfred's cakes," which is perhaps the most storied name for this fungus. As the legend goes, King Alfred was fleeing a battle with the Danes in Somerset when he took refuge in an old woman's house. The old woman, not knowing he was the king, left Alfred in charge of watching some cakes in the oven. Of course, he knew nothing about ovens and didn't really know what he was supposed to do. He fell asleep, and the cakes burned. The old woman scolded him soundly for being lazy, but later she was probably sorry about "raking him over the coals" when she found out he was the king!

Aren't common names fun?

Daldinia concentrica sectioned, showing the concentric ringsAs we've seen, this common fungus is very hard and carbonaceous, much like a lump of coal. However that's where their similarity ends. When you section Daldinia concentrica through the middle, you can see concentric zones. These zones each represent a season's growth, much the way tree rings represent a season's growth. Of course, there is a major difference in the development and the purpose for each of these rings. Tree rings, as you probably know, are made up of xylem (wood) that forms each spring and summer to facilitate the transport of water from the roots to the leaves. On the other hand, the rings of Daldinia concentrica each represent a season's worth of reproduction. The small bumps on the surface of the fruiting body are the necks of the perithecia. "Perithecium" is a fancy name for the flask-shaped cavities that are formed within the carbonaceous stroma of sterile tissue. Within the perithecia are the cylindrical asci, in which the meiotically-produced ascospores are borne. If you've been reading my pages, you'll notice that this very similar to the arrangement in Xylaria, dead man's fingers. . It's easier to observe the perithecia in Xylaria because there is more contrast between the dark perithecia and the white stroma, rather than the concolorous perithecia and stroma in Daldinia.

Daldinia perithecia in a stroma.  Note the asci with ascospores Now you may be wondering how the tiny ascospores get out of the very small neck of the perithecium. It's really quite ingenious. When conditions are right, each ascus elongates separately and sticks its tip out of the top of the perithecium. Water pressure builds up in the ascus, and the spores are forcibly shot out of the ascus -- outside of the perithecium. The spent ascus withers back, and a new ascus grows into its place in the neck of the perithecium. The process of shooting spores is repeated, often over a very long period of time. The paraphyses (staining pink) are sterile threads that help to guide the asci one at a time to the neck of the perithecium. Thus there is a timed release of the ascospores, increasing the probability of at least some of the ascospores landing on the proper substrate under the proper conditions. Sometimes the spores are not shot so far away, as you can see in to the left, where there is a ring of black spores making a halo around the fruiting bodies

Both of these Pyrenomycetes play an important role in wood decay. Like other members of the Ascomycota that grow on wood, they cause a soft rot. This means that the mycelium of the fungus degrades the glucans in the wood, along with (sometimes) a bit of the cellulose. You'll recall that Basidiomycota wood decayers can cause either a white rot (in which lignin is decayed, usually, along with some cellulose) or a brown rot (in which cellulose is decayed). See this page on polypore for more information on wood decay in Basidiomycota.

I hope you enjoyed learning something about the coal fungus and all of its other interesting common names. You can find this fungus and its relatives if you look closely when you're in the woods. More importantly, I hope you get some better Christmas gifts than a lump of coal.

For a Christmas treat, click here for "Fungi necessary for a merry Christmas."

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