 Amanita muscaria , commonly known as the fly agaric or fly amanita , is a mushroom and psychoactive basidiomycete fungus , one of many in the genus Amanita . Native throughout the temperate and boreal regions of the Northern Hemisphere , Amanita muscaria has been unintentionally introduced to many countries in the Southern Hemisphere , generally as a symbiont with pine and birch plantations , and is now a true cosmopolitan species . It associates with various deciduous and coniferous trees . 
 Amanita muscaria , commonly known as the fly agaric or fly amanita , <a href='drop_aux' title='1'><mark>is</mark></a>a mushroom and psychoactive basidiomycete fungus , one of many in the genus Amanita . Native throughout the temperate and boreal regions of the Northern Hemisphere , Amanita muscaria <a href='been_done' title='2'><mark>has</mark></a> been unintentionally introduced to many countries in the Southern Hemisphere , generally as a symbiont with pine and birch plantations , and <a href='drop_aux' title='3'><mark>is</mark></a>now a true cosmopolitan species . It <a href='uninflect' title='4'><mark>associates</mark></a> with various deciduous and coniferous trees . 
Amanita muscaria , commonly known as the fly agaric or fly amanita , a mushroom and psychoactive basidiomycete fungus , one of many in the genus Amanita . Native throughout da temperate and boreal regions of the Northern Hemisphere , Amanita muscaria done been unintentionally introduced to many countries in the Southern Hemisphere , generally as a symbiont with pine and birch plantations , and now a true cosmopolitan species . It associate witt various deciduous and coniferous trees .