A conidium (plural conidia), sometimes termed an asexual
Asexual reproduction in
The terms microconidia and macroconidia are sometimes used. 
There are two main types of conidium development: 
A conidium may form germ tubes (germination tubes) and/or
Conidiogenesis is an important mechanism of spread of plant pathogens. In some cases, specialized macroscopic fruiting structures perhaps 1mm or so in diameter containing masses of conidia are formed under the skin of the host plant and then erupt through the surface and allow the spores to be distributed by wind and rain. One of these structures is called a conidioma (plural: conidiomata).  
Two important types of conidiomata, distinguished by their form, are:
Pycnidial conidiomata or pycnidia form in the fungal tissue itself, and are shaped like a bulging vase. The spores are released through a small opening at the apex, the ostiole.
Acervular conidiomata, or acervuli, are cushion-like structures that form within the tissues of a host organism:
Mostly they develop a flat layer of relatively short conidiophores which then produce masses of spores. The increasing pressure leads to the splitting of the epidermis and cuticle and allows release of the conidia from the tissue.