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The Genus Armillaria
by Michael Kuo
The genus Armillaria contains wood-rotting gilled mushrooms with white spore prints and gills that are attached to the stem or run down it. Most of the species have a partial veil, but the veil can manifest in several different forms—from cob-webby ring zones to full-blown rings. Roughly a dozen species occur in North America. Many of these are parasitic, and many form visible black rhizomorphs in the wood; others are apparently benign saprobes and do not form conspicuous rhizomorphs.
The species in Armillaria are well-studied and supported by all four "legs" of the species definition stool: ecological, morphological, biological, and phylogenetic separation. In other words, DNA studies, mating studies, and traditional morphology (in most cases) agree on the species, which are also limited to specific environmental niches. This kind of species-concept confluence is not the norm in mycology, so enjoy this genus if you are someone who dislikes confusion!
Identification of Armillaria species can often be accomplished with close attention to physical features and collection location. However, a few species pairs, in limited geographic areas where they overlap, are morphologically "cryptic" and can only reliably be separated with mating or DNA study (see the key below). Microscopic examination is generally not useful in North American Armillaria identification; differences in spore size, cheilocystidia, and pileipellis are not significant between
Key to 9 Species of Armillaria in North America
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Volk, T. J. & Burdsall, H. H. (1993). The state of taxonomy in the genus Armillaria. McIlvainea 11: 4-11.
Volk, T. J. and H. H. Burdsall, Jr. (1995). A nomenclatural study of Armillaria and Armillariella species. Synopsis Fungorum 8. Fungiflora: Oslo, Norway. 121 pp.
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Volk, T. J. (2005). Key to North American Armillaria species. Retrieved May 18, 2017 from the Tom Volk's Fungi Web site: http://botit.botany.wisc.edu/toms_fungi/armkey.html
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Cite this page as:
Kuo, M. (2017, September). The genus Armillaria. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/armillaria.html