An acervulus (pl. acervuli) is a small asexual

fruiting body The sporocarp (also known as fruiting body, fruit body or fruitbody) of fungi is a multicellular structure on which spore-producing structures, such as basidia or asci, are borne. The fruitbody is part of the sexual phase of a fungal life cy ...

that erupts through the epidermis of host plants parasitised by mitosporic

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

of the form order Melanconiales ( Deuteromycota,

Coelomycetes Coelomycetes are a form-class of fungi, part of what has often been referred to as Fungi imperfecti, Deuteromycota, or anamorphic fungi. These are conidial fungi where the conidia form in a growing cavity in the host's tissue. The fruiting stru ...

). It has the form of a small

cushion A cushion is a soft bag of some ornamental material, usually stuffed with wool, hair, feathers, polyester staple fiber, non-woven material, cotton, or even paper torn into fragments. It may be used for sitting or kneeling upon, or to soften th ...

at the bottom of which short crowded

conidiophore A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to the ...

s are formed. The spores escape through an opening at the top.

Sources

* Trigiano, Robert Nicholas, Mark Townsend Windham, Alan S. Windham. (2004) ''Plant Pathology: Concepts and Laboratory Exercises.'' CRC Press. pp. 11,129,137. Fungal morphology and anatomy Asexual reproduction {{botany-stub