Acystidium (pl.:cystidia) is a relatively large cell found on thesporocarp of abasidiomycete (for example, on the surface of amushroom gill), often between clusters ofbasidia. Since cystidia have highly varied and distinct shapes that are often unique to a particular species or genus, they are a useful micromorphological characteristic in the identification of basidiomycetes. In general, the adaptive significance of cystidia is not well understood.
Cystidia may occur on the edge of alamella (or analogoushymenophoral structure) (cheilocystidia), on the face of a lamella (pleurocystidia), on the surface of the cap (dermatocystidia orpileocystidia), on the margin of the cap (circumcystidia) or on thestipe (caulocystidia). Especially the pleurocystidia and cheilocystidia are important for identification within many genera. Sometimes the cheilocystidia give the gill edge a distinct colour which is visible to the naked eye or with a hand lens.
Chrysocystidia are cystidia whose contents contain a distinct refractive yellow body, that becomes more deeply yellow when exposed toammonia or otheralkaline compounds. Chrysocystidia are characteristic of many (though not all) members of theagaric familyStrophariaceae.
Gloeocystidia have an oily or granular appearance under the microscope. Likegloeohyphae, they may be yellowish or clear (hyaline) and can sometimes selectively be coloured by sulphovanillin or other reagents.[1]Metuloids are thick-walled cystidia with an apex having any of several distinct shapes.[2]