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Homobasidiomycetes
Amanita muscaria (Agaricales)
Scientific classification
Kingdom: Fungi Division: Basidiomycota Subdivision: Hymenomycotina Class: Homobasidiomycetes
Orders
Agaricales Boletales Cantharellales Gomphales Hymenochaetales Phallales Polyporales Russulales Thelephorales

The class Homobasidiomycetes (sensu Hibbett & Thorn (2001)) is a taxonomic division in the subdivision Hymenomycotina of the division Basidiomycota (in the Kingdom Fungi). Included here are the so-called "true" mushrooms and a common name for this group of some 16,000 described species is the mushroom-forming fungi (53% of the described basidiomycetes).

Although morphology of the mushroom or fruiting body was the basis of early classification of the Homobasidiomycetes^[1], this is no longer the case. As an example, the division between the gasteromycetes (puffballs) and homobasidiomycetes (most other mushrooms) is no longer recognized as a natural one—various puffball species have apparently evolved independently from hymenomycete fungi. However, most mushroom guide books still group the puffballs or gasteroid forms separate from other mushrooms because the older Friesian classification is still convenient for categorizing fruiting body forms. Similarly, modern classifications divide the gasteroid order Lycoperdales between Agaricales and Phallales.

All members of the Class Homobasidiomycetes produce basidiocarps and these range in size from tiny cups a few millimeters across to giant polypores greater than a meter across and weighing up to 130 kg (286 lb). The group also includes what are arguably the largest and oldest individual organisms on earth: the mycelium of Armillaria gallica have been estimated to extend over 150,000 square metres (37 acres) with a mass of 10,000 kg (22,000 lb) and an age of 1,500 years (Smith et al., 1997).

Nearly all species are terrestrial (a few are aquatic), occurring in a wide range of environments where most function as decayers, especially of wood. However, some species are pathogenic or parasitic, and yet others are symbiotic, these including the important ectomycorrhizal symbionts of forest trees. General discussions on the forms and life cycles of these fungi are developed in the article on mushrooms, in the treatments of the various orders (links in table at right), and in individual species accounts.

Wikimedia Commons has media related to:

Homobasidiomycetes

• Homobasidiomycetes at the Tree of Life Web Project
• Overview of the Basidiomycota from Aarhus University, Denmark
• Smith, M., Bruhn, J., and Anderson, J. 1992. The fungus Armillaria bulbosa is among the largest and oldest living organisms. Nature 356:428-431.
• Evolution & Morphology in the Homobasidiomycetes
• Homobasidiomycetes by David S. Hibbett