On this page you'll find brief definitions of the basic technical fungal terms used in the lichen website. You'll find more details in the Australian National Botanic Gardens' fungal website: http://www.anbg.gov.au/fungi/
The basic building blocks of the fungal structures that you see with the naked eye are hyphae. A hypha is a microscopically thin filament that grows in length and may branch but maintains a constant diameter.
The ascomycetes are a large group of fungi in which spores are produced within microscopic "pods". Such a pod is called an ascus and the plural is asci. It is most common to have eight spores per ascus but, depending on species, the number ranges from one to over a hundred.
In the basidiomycetes the spores are produced at the ends of prongs that protrude from typically club-like structures. Such a club-and-prong structure is called a basidium, with basidia the plural. Like asci, basidia are very small and can be seen only with the help of a microscope. In most basidiomycetes there are four spores per basidium but the number ranges from one to eight, depending on species.
Asci and basidia are microscopic structures but they are usually produced in great numbers in often easily visible structures called fruiting bodies. A very well-known example of a basidiomycete fruiting body is a mushroom. The spore-producing basidia develop on the gills on the underside of the mushroom cap.
The great majority of lichens are ascomycetes and the two most common types of fungal fruiting bodies you'll find on the ascomycete lichens (or ascolichens) are apothecia and perithecia. An apothecium is typically cup- or disc-like, with the asci lining the apothecium's upper surface. Lichen apothecia range from under a millimetre to over a centimetre in diameter and come in a variety of colours, sometimes well-distinguished from the thallus but in some species of the same colour as the thallus and at times it can be hard to differentiate thallus from apothecium. In the so-called graphid lichens the apothecia are elongated and narrow and are called lirellae. A perithecium is typically black and hemispherical in shape, the asci being contained within an internal chamber. Perithecia are typically no more than a millimetre in diameter.
You can find examples of basidiomycete lichen fruiting bodies on the BASIDIOLICHEN page.