The Genus Xerula
[ Basidiomycetes > Agaricales > Marasmiaceae . . . ]
by Michael Kuo
Members of the genus Xerula can be recognized by their tall and slender stature, their white spore prints and their tough, rooting stems, which taper underground. There is no partial veil or universal veil (among the North American species, anyway), so the relatively thin stem lacks a ring or a volva. Most of the North American species occur under hardwoods east of the Rocky Mountains, but a few occur elsewhere (see the key below).
Xerula species are frequently encountered around stumps and dead trees--or in urban areas where trees have been removed. They are saprobes that subsist on the wood of dead or dying tree roots, but the mushrooms almost always appear to be "terrestrial," without demonstrating a clear connection to buried wood.
Identification of Xerula species often depends on microscopic examination of the gills, cap surface, and spores--and several of the species are dead ringers for one another to the naked eye. This makes Xerula identification tedious if you don't enjoy microscope work--but if you do enjoy time at the microscope, you'll find that Xerula presents a nice suite of fairly discreet characters to work with, and a fairly small field of identification possibilities. Most of our North American species have been supported by mating studies (see Petersen & Methven, 1994; Petersen & Hughes, 2004).
Key to 8 Xerula Taxa in North America
|1.||Cap small (7-20 mm across); cap and stem densely covered with whitish to brownish, bristling hairs; in North America limited to Mexico (also found in the Caribbean).|
|2.||Found from the Rocky Mountains westward.|
|2.||Found east of the Rocky Mountains.|
|3.||Growing in various ecosystems in the Rocky Mountains; spores 9.5-12 µ long.|
|4.||Stem (including the above-ground portion) and gills slowly staining rusty brown when handled; gills often developing rusty edges; pleurocystidia capitate; spores lemon-shaped, 13.5-16 µ long, finely roughened.|
|4.||Not completely as above.|
|5.||Cap large (8 to 12 cm across) and brown; stem usually finely hairy (identification on the basis of these features alone should be considered tentative).|
|5.||Cap smaller and/or paler than above; stem finely hairy or not (microscopic analysis required).|
|6.||Spores decidedly lemon-shaped, finely dimpled, 18-23 µ long; cheilocystidia capitate; thin-walled, hyaline pileocystidia present.|
|6.||Not completely as above.|
|7.||Spores elliptical to slightly ovoid.|
|7.||Spores at least slightly lemon-shaped to flask-shaped.|
|8.||Spores 14-17 µ long; stem usually finely hairy; cap usually wrinkled only around the center; margin not lined.|
|8.||Spores 9.5-13.5 µ long; stem usually fairly smooth; cap elaborately wrinkled and ridged from center to margin; margin appearing lined.|
|9.||Spores 13.5-18.5 µ long; pleurocystidia bluntly rounded; thin-walled, hyaline pileocystidia often present.|
|9.||Spores 16.5-21 µ long; pleurocystidia capitate or with large, knobby ends; pileocystidia absent.|
Halling, R. E. & G. M. Mueller (1999). A new species and a new record for the genus Xerula (Agaricales) from Costa Rica. Mycotaxon 71: 105-110.
Pegler, D. N. & T. W. K. Young (1987). Classification of Oudemansiella (Basidiomycota: Tricholomataceae), with special reference to spore structure. Transactions of the British Mycological Society 87: 583-602.
Petersen, R. H. & A. S. Methven (1994). Mating systems in the Xerulaceae: Xerula. Canadian Journal of Botany 72: 1151-1163.
Petersen, R. H. & K. W. Hughes (2004). Une nouvelle espece de Xerula, Xerula limonispora. Bulletin de la Societe Mycologique de France 120: 37-49.
Petersen, R. H. & T. J. Baroni (2007). Xerula hispida and Xerula setulosa (comb. nov.), two similar subtropical New World agarics. Mycotaxon 101: 113-136.
Phillips, R. (1991/2005). Mushrooms of North America. Boston: Little, Brown and Company. 319 pp.
Redhead, S. A., J. Ginns & R. A. Shoemaker (1987). The Xerula (Collybia, Oudesmansiella) radicata complex in Canada. Mycotaxon 30: 357-405.
Cite this page as:
Kuo, M. (2008, October). The genus Xerula. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/xerula.html