Mushroom of the Month, February 2010

Only a minority of fungi from the phylum Ascomycota produce large and conspicuous fruitbodies, but among them are some tough (fun)guys that can be found all through the year. This month's mushroom (well, fungal fruitbody might be more appropriate) is candle-snuff fungus, and it is easy to find in winter when dead wood on the forest floor is not hidden by long grass, bracken or other tall vegetation.

Xylaria hypoxylon belongs to a group of fungi known as the Pyrenomycetes (meaning 'fire fungi' - a reference to their blackened and burnt appearance). The generic name comes from the same Greek word xýlon (as does xylem - wood, in the sense of the tough cellular material that forms the roots, trunk and branches of trees). The specific epithet hypoxylon is yet another reference to wood, and with the prefix 'hypo' usually meaning below or under, but in this case perhaps 'reduced', since this fungus is able to consume timber whose cellulose and hemicellulose (the softer material) have already been fairly comprehensively broken down by other fungi, for example sulphur tufts or honey fungus. Any other suggestions?

One question I have never been asked in respect of candle-snuff fungus is 'are they edible?' Even if they were, why would anyone want to waste time on collecting them when there are plenty of really good edible fungi available throughout the year?

Xylaria fungi (and there are plenty of other species in the genus, including Xylaria polymorpha, commonly called dead man's fingers) are able to reproduce sexually and asexually. In the case of the candle-snuff fungus, the antler-like fruitbodies, or 'stroma' to use the technical term, are black at the base of each stem and almost white further up and along the branches, which are the places where the asexual spores (conidia) are produced - but you will need a high-power microscope to see these features. This fungus also produces sexual spores from asci that develop on the inner walls of vessels called perithecia, which are embedded in the surface of the stroma, and if you cut across a fruitbody and look at the section under a strong hand lens or a low-powered microscope these vase-like perithecia are easy to see.

That's what I find about most Ascomycetes: they are only of passing interest... until you look more closely and then they are quite fascinating in their structures and habits.