[Coelomycetes] Grove
(stem- and leaf-fungi)

Coelomycetes are anamorphic ascomycetes - ie they are an asexual phase in the life-cycle. In some cases they precede the sexual stage, in others they persist in isolation and the sexual stage is rare or unknown. Some are even spermatia which produce the gametes which give rise to the sexual stage.

In the absence of the sexual stage they were named and classified, according to their asexual morphology, into the so-called "form genera". Nowadays these have no taxonomic significance, although they are still used as names for the asexual morphology.

This is a purely artificial classification (some would call it a "dumping ground") for anamorphic fungi (ie fungi where the stage that produces sexual spores is not formed or is unknown), and where the asexual spores (conidia) are formed inside a closed body, or one that is initially closed.

Coelomycetes are saprobes on dead plant material, or parasites which cause small infection spots on living leaves and stems. Many are species-specific, or at least have traditionally been treated as distinct species on different hosts.

Over the years, the members have been gradually removed as laboratory cultures have yielded the sexual states. More recently DNA sequencing has superseded this and the classification will eventually disappear. Nevertheless "coelomycete" remains a useful descriptive term for the asexual state of many ascomycetes.

Coelomycetes are divided into those which form pycnidia (closed structures from which the conidia issue through the ostiole, a small circular opening) and those which form acervuli (effectively everted pycnidia) with the conidia produced on the outside and termed "pustules".

Most coelomycetes are plant-pathogens or grow on dead plant material, although a few attack lichens or rusts.

It is best to collect coelomycetes in damp periods when they have ripe conidia; often these are visible en masse either as a white or grey, sometimes orange whisker arising from the ostiole or as a waxy deposit on the surface of the pycnidium or substrate.

Damp chamber culturing is useful. Often this just means leaving a few infected leaves in a sealed box in a cool place for a few days.

Following such culturing, a spore tendril often issues from the ostiole. This is useful in confirming which pycnidia are living and enables easy determination of spore colour.