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The Genus Xylaria
[ Ascomycetes > Xylariales > Xylariaceae . . . ]
by Michael Kuo
The genus Xylaria consists of funky, club-like decomposers of wood or plant debris that become black and hard by maturity, reminiscent of carbon or charcoal. The mushrooms are "Pyrenomycetes," which means they produce spores in asci that are embedded in tiny pockets called "perithecia"; the asci take turns growing into the narrow opening of the pocket so that they can shoot spores away from the fungus and into the air currents.
The Xylaria life cycle gets a little complicated, and the complications can make precise identification of one's Xylaria collections difficult. Like many fungi, Xylaria species hedge their reproductive bets by engaging in both sexual and asexual reproduction. The spores, asci, and perithecia mentioned above occur when the fungus is mature, and reproducing sexually. In immature stages, a Xylaria produces asexual spores, officially called "conidia," in a powdery coating (morel hunters frequently encounter the conidial stage of Xylaria polymorpha in late spring).
This is all well and good for the Xylaria, but more than a little problematic for would-be Xylaria identifiers, since the various species are usually separated on the basis of the morphology of their (sexual) spores. Thus, if you have collected a Xylaria in its asexual, conidial stage, you will be missing the most important morphological character for identification (the conidia, in case you're wondering why they can't substitute for spores in the identification process, all look more or less the same)--that is, unless you have a mycological laboratory and the ability to culture your collection; the species can actually be identified on the basis of the way the cultures look and act in the petri dish (see Callan & Rogers, 1993).
Most of us, however, lack the ability to culture our collections, which means we can only accurately identify mature, sexual forms. In the field, these can often be recognized by the presence of perithecia, which look like tiny pimples (use a hand lens). Collectors in north-temperate regions can also employ the strategy of not collecting Xylaria specimens in spring and early summer, when asexual forms are more prominent.
Even with identifiable specimens in hand, there is no getting around the fact that microscopic analysis is frequently necessary for accurate Xylaria identification--which leads many collectors to label their collections of fat specimens "Xylaria polymorpha" and their skinny collections "Xylaria hypoxylon," since these are species frequently included in field guides. This is not an unreasonable strategy if your identification goals are casual, but if you have a penchant for accuracy you will need to consult pyrenomycete expert J. D. Rogers's key to Xylaria in the continental United States (1986; available online here, at Libri Fungorum).
Callan, B. E. & J. D. Rogers. (1993). A synoptic key to Xylaria species from continental United States and Canada based on cultural and anamorphic features. Mycotaxon 46: 141-154.
Laessoe, T. & Lodge, D. J. (1994). Three host-specific Xylaria species. Mycologia 86: 436-446.
Rogers, J. D. (1979). Xylaria magnoliae sp. nov. and comments on several other fruit-inhabiting species. Canadian Journal of Botany 57: 941-945.
Rogers, J. D. (1983). Xylaria bulbosa, Xylaria curta, and Xylaria longipes in continental United States. Mycologia 75: 457-467.
Rogers, J. D. (1984). Xylaria acuta, Xylaria cornu-damae, and Xylaria mali in continental United States. Mycologia 76: 23-33.
Rogers, J. D. (1984). Xylaria cubensis and its anamorph Xylocoremium flabelliforme, Xylaria allantoidea, and Xylaria poitei in continental United States. Mycologia 76: 912-923.
Rogers, J. D. (1986). Provisional keys to Xylaria species in continental United States. Mycotaxon 26: 85-97.
Rogers, J. D. & B. E. Callan (1986). Xylaria polymorpha and its allies in continental United States. Mycologia 78: 391-400.
Rogers, J. D., A.N. Miller & L. N. Vasilyeva (2008). Pyrenomycetes of the Great Smoky Mountains National Park. VI. Kretzchmaria, Nemania, Rosellinia and Xylaria (Xylariaceae). Fungal Diversity 29: 107-116.
San Martin, F., P. Lavin & J. D. Rogers. (2001). Some species of Xylaria (Hymenoascomycetes, Xylariaceae) associated with oaks in Mexico. Mycotaxon 79: 337-360.
Cite this page as:
Kuo, M. (2008, October). The genus Xylaria. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/xylaria.html