Giant polypore

Appearance

The basidiocarps consist of numerous rosette-like flattened fan-shaped pilei; they are typically 50–200 centimetres in diameter and 20–80 centimetres high. The individual caps, up to 20–80 centimetres diameter and 1–4 centimetres thick, arise from a common stem.The color of the cap surface is pale tan to dull chestnut brown in young specimens but darkens in age to become concentric zones of various shades of brown.

The surface is also finely with tiny scales . There are 3 to 6 pores per millimeter on the underside; the pore surface bruises brown and black, helping to distinguish it from the similar species ''Grifola frondosa''.

;Microscopic features
Spores are roughly spherical to ovoid or ellipsoid in shape, with typical dimensions of 6–6.5 × 5.5–6 µm. Under a microscope, they appear translucent , smooth, and nonamyloid, meaning that they do not absorb stain from Melzer's Reagant. The basidia—the spore-bearing cells—are club-shaped, 4-spored, and are 22–40 by 7–8 µm.

Polypore fungi may be further distinguished by the type of hyphae that makes up their fruiting body. ''M. giganteus'' has a so-called monomitic hyphal system, as its fruiting body is composed of only vegetative hyphae.

Naming

The polypore fungus ''Grifola frondosa'' is similar in overall appearance, but may be distinguished by its more greyish cap, and larger pores. ''Bondarzewia berkeleyi' ''or "Berkeley's polypore" is often confused with ''M. giganteus'' in eastern North America but can be distinguished by its lack of black-bruising and much larger pores.

Distribution

This mushroom can be found growing on hardwoods, more rarely on conifers. According to Ryvarden and Gilbertson in their monograph on the polypores of Europe, ''M. giganteus'' grows especially on ''Quercus'' and ''Fagus'' tree species, but it has also been collected on the hardwoods ''Acer'', ''Aesculus'', ''Alnus'', ''Betula'', ''Castanea'', ''Celtis'', ''Corylus'', ''Eucalyptus'', ''Laurus'', ''Myrica'', ''Persea'', ''Pittosporum'', ''Platanus'', ''Populus'', ''Prunus'', ''Pyrus'', ''Tilia'', ''Ulmus''; it has also been found growing on the coniferous species ''Abies'', ''Larix'', and ''Pinus''.

''M. giganteus'' has a circumboreal distribution in the northern hemisphere. It has been collected from Europe, Scandinavia, the area formerly known as the USSR, Iran and Turkey. Although many field guides list it as occurring in North America, this is due to confusion with the related ''M. sumstinei''; ''M. giganteus'' is not found in North America. A study of the frequency of occurrence of wood-decay fungi on street trees and park trees in Hamburg, Germany found that ''M. giganteus'' was the most common species.

Habitat

This mushroom can be found growing on hardwoods, more rarely on conifers. According to Ryvarden and Gilbertson in their monograph on the polypores of Europe, ''M. giganteus'' grows especially on ''Quercus'' and ''Fagus'' tree species, but it has also been collected on the hardwoods ''Acer'', ''Aesculus'', ''Alnus'', ''Betula'', ''Castanea'', ''Celtis'', ''Corylus'', ''Eucalyptus'', ''Laurus'', ''Myrica'', ''Persea'', ''Pittosporum'', ''Platanus'', ''Populus'', ''Prunus'', ''Pyrus'', ''Tilia'', ''Ulmus''; it has also been found growing on the coniferous species ''Abies'', ''Larix'', and ''Pinus''.

''M. giganteus'' has a circumboreal distribution in the northern hemisphere. It has been collected from Europe, Scandinavia, the area formerly known as the USSR, Iran and Turkey. Although many field guides list it as occurring in North America, this is due to confusion with the related ''M. sumstinei''; ''M. giganteus'' is not found in North America. A study of the frequency of occurrence of wood-decay fungi on street trees and park trees in Hamburg, Germany found that ''M. giganteus'' was the most common species.