The minute black dots on rotting wood and leaves or the little cups on lichens will often prove to be perfect examples. This large group, which includes mushrooms and puffballs, is characterized by the presence of basidia and basidiospores. Like ascomycetes, to which they are related, basidiomycetes have hyphae with septa and lack motile spores. The hyphae of many basidiomycetes bear characteristic swellings, called clamp connections , that play a specialized role in nuclear migration. Asexual spores, when formed, are produced as conidia.
Most basidiomycetes are terrestrial.
The lower figure, created by John Stavrinides at the University of Toronto, shows the role of a clamp connection in facilitating nuclear migration. This group comprises the large number of fungi known to reproduce asexually by conidia and is by far the most important in a study of moulds. The asexually reproducing structures of a fungus are called anamorphs , which, together with the sexually reproducing structures or teleomorphs , make up the holomorph or whole fungus. Many fungi will be encountered only as anamorphs and cannot conveniently be classified with the ascomycetes or basidiomycetes to which they undoubtedly belong. Mycologists have long used a system of classification that allows anamorphs to be named separately from the holomorph of which they form a part.