Sub division Basidiomycotina
Class Hymenomycetes
Order Agaricales
Agaricales are also known as gill fungi because of gills (develop on the under surface of fruiting bodies) .
Agaricus ( Family Agaricaceae )
They are saprophytic fungus which grow on dead decaying leaves , wood logs etc in rainy season . They are locally known as kukurmutta / khumb / dhingri . Agaricus bisporus is common species . Primary mycelium is formed by germination of basidiospore . It is branched , septate and monokaryotic . Primary mycelium is short lived . It is of + or - strain . Primary mycelia of two opposite strains fuse to form dikaryotic secondary mcelium . It is perennial and contains dolipore septa ( barrel shaped pore found in basidiomycetes ) . The hyphae of secondary mycelium twist together to form white hyphal cords , called rhizomorphs .
Hyphae grows outward from a center in a circle in soil ( centrifugal growth ) . Fruiting bodies are called basidiocarps . Basidiocarps are commonly known as mashrooms . They grow in successive rings above the soil . These rings are called fairy rings , based on the ancient belief that they marked the path of dancing fairies .
All species of agaricus are not edible .The edible mashrooms are propagated by vegetative means ( small pieces of dikaryotic mycelium ) . Asexual reproduction is uncommon and takes place by chlamydospores . Primary mycelia of two different strains act as male and female sex organs . Somatogamy takes place between primary mycelia of two different strains . It results in diploidization and formation of secondary mycelium . The secondary mycelium later develops fruiting bodies basidiocarps . Fruiting body is made up of tertiary mycelium . Somatogamy involves plasmogamy , karyogamy and meiosis .
Meiosis forms 2 + and 2 - nuclei . One + and one - nuclei are transferred to each daughter cell by the formation of clamp connection . Clamp connections are lateral branches that create bridges for nuclear movement between regions of the hypha that will become separate compartments . Clamp connections are present in dikaryophase but incomplete clamp connections occur in monokaryotic phase .
Basidiocarp is an umbrella shaped structure . It is made up of stipe ( basal part ) and pileus ( apical hemispherical part ) . Velum or inner veil is a membranous structure which joins stipes and pileus . As the pileus expands velum ruptures . Remnants of velum are attached to the stipe in the form of a ring called annulus . Gills hang from the inner surface of pileus . Gills may be of full , half or qurter length . Gill wall is made up of hymenium , sub hymenium and trama . Hymenium is a fertile layer of basidia . Basidia are arranged in palisade like layer . The upper hilar appendics of basidia bear basidiospores. They are sightly oblique at sterigma .