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Profiles of fungi: 17 - Xylaria hypoxylon, X. polymorpha and Green Wood-cup

Xylaria hypoxylon and X. polymorpha are two of the larger members of the Ascomycota. They are often seen growing on decaying tree stumps and logs. X. hypoxylon (Fig. 1) is the most conspicuous because of its erect, antler-like fruitbodies which are black at the base (where the perithecia are embedded) but white and branched towards the top, where the fruitbodies produce white conidia (asexual spores). The two common names for this fungus are "Stag's Horn" or "Candle-snuff Fungus". Xylaria polymorpha (Figs 2 - 5) is much less conspicuous, because it is uniformly black. It often grows in finger-like clusters from the base of a tree or from wood just below ground level, and is commonly known as "Dead Man's Fingers".

In addition to the Xylaria species, some ascomycetous fungi colonise the soft (parenchymatous) tissues of freshly felled wood. These sapstain fungi can be economically damaging because they discolour the wood and lower its value (see Chapter 11). But one of these fungi, Chlorosplenium aeruginascens (Fig. 6) causes the wood to turn an attractive blue colour and this used to be popular for the production of high-quality veneers for cabinet-making and small wooden ornaments.

Fig 1. Xylaria hypoxylon (Ascomycota), commonly known as the Candle-snuff fungus or Stag's horn. This very common fungus is often seen growing from the decaying stumps of trees. The fruitbodies (ascocarps) are about 2-6 cm high. They are black at the base, where the fungus releases ascospores, but are white and branched near the tips, where conidia are released from the powdery surface. [© Jim Deacon]

Fig 2. Xylaria polymorpha (Ascomycota), commonly known as Dead Man's Fingers. The fruitbodies (ascocarps) are often seen growing near ground level from the bases of tree stumps, especially on beech (Fagus sylvatica), but in this image they are growing from a fallen, moss-covered beech log. Each fruitbody is tapered at the base and usually 3-8 cm tall. Futher examples are shown below. The final image (Fig. 5) shows an ascocarp cut longitudinally, revealing many perithecia that lie just beneath the surface of the fruitbody. The perithecia release fusiform ascospores for dispersal to new sites. [© Jim Deacon]

Fig 3. Close-up view of Xylaria polymorpha ascocarps, which typically have a wrinkled appearance and taper to a narrower base. [© Jim Deacon]

Fig 4. Xylaria polymorpha ascocarps showing the high degree of variability in shape. [© Jim Deacon]

Fig 5. Left: A longitudinally split ascocarp of X. polymorpha, showing the many perithecia that lie just beneath the black outer rind. Right: Close-up of part of the perithecial zone of the split fruitbody shown at left. [© Jim Deacon]

Fig 6. Blue-stained wood of alder (Alnus glutinosa) naturally colonised by the blue-pigmented hyphae of Chlorosplenium aeruginascens. This type of coloration is quite common in fallen branches of alder and oak. The fungus also produces small, blue-green, cup-shaped apothecia, but they are uncommon.

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