Acervulus

An acervulus (pl. acervuli) is a small asexual fruiting body that erupts through the epidermis of host plants parasitised by mitosporic fungi of the form order Melanconiales (Deuteromycota, Coelomycetes). It has the form of a small cushion at the bottom of which short crowded conidiophores are formed. The spores escape through an opening at the top.

Acervulus morphology.
cu: cuticle, co: conidium, cf: conidiophore, ps: pseudo-parenchymatic stroma, hi: hypha.