Virtual Nature Trail

Scientific name: 
Xylaria polymorpha
Common name: 
Dead Man's Fingers

(Information for this species page was gathered in part by Justin Vogini (Spring 2001) and Steven Powell (Spring 2004) for Biology 220W at Penn State New Kensington)

 Fruiting bodies of Xylaria polymorpha

Xylaria polymorpha is a very distinctive species of fungus that is widely distributed throughout the deciduous forests of North America and Europe. The scientific name tells us a great deal about the organism: "xylaria" means to grow on wood (it is found on and in a wide variety of dead and decaying wood), and "polymorpha" means "many shapes" which describe this species' highly variable fruiting body ("mushroom") which resembles human fingers or hands.

Xylaria polymorpha is a saprotrophic fungus that is found colonizing dead wood. Trees that are under stress (from disease, moisture deprivation, light stress, etc) may also be "attacked" by X. polymorpha. The impact of this species on the dead or dying wood is best described as a "soft rot" (the fungus digests the available polysaccharide "glues" within the wood leaving behind the unconnected lignins and celluloses). The precise tree species favored by X. polymorpha are often difficult to determine since the colonized wood quickly reaches an advanced stage of decomposition which makes it difficult to identify with any precision. However, the habitat distribution of the fungus suggests a preference especially for maple and beech trees and also oak, locust, sassafras, elm, and apple. Fungal colonization of living trees is most often seen through bark lesions (especially on the base of the tree trunk) and in damaged roots with the subsequent development of root rot. A variety of ornamental and urban landscape trees have been shown to be affected by X. polymorpha root rot.

The mycelia of X. polymorpha grow throughout the colonized wood and, like all fungi, secrete an array of extracellular digestive enzymes into the woody material. The mycelia then absorb the digestion products to fuel and sustain their growth and reproduction. The fruiting bodies ("mushrooms") that are formed by these mycelia are at maturity 2 to 8 cm tall and 0.5 to 3 cm in diameter. They often grow in groups of three clustered into a "finger-like" or "hand-shaped" form which are typically seen emerging from the soil around stumps or decaying trees.. The fruiting bodies are dark gray to brown in color and get darker as they age and mature. They are coated with a carbon-like crust which greatly reduces their palatability and increases their strength and durability. These fruiting bodies arise in the spring (they are seen in mid to late May along the Nature Trail) but may form anytime between May and November depending upon local site conditions. These fruiting bodies may persist for several months or even years and can release spores continuously during these time intervals. This fruiting body persistence and slow, extended spore release strategy is quite different from most fungi which rely on a very transient mushroom stage and an explosive, short-lived spore release pattern for propagation. It is thought that the extended time frame and slower spore release rate for X. polymorpha increases the individual success rate of spores and allows this species to distribute itself extensively throughout its ecological range. 

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