In most genera the asci are persistent, with a characteristic apical apparatus through which the ascospores are forcibly discharged. Members of the pyrenomycetes occur in a variety of habitats, but are especially common on dead wood, herbaceous stems, and in soils. Many species are important pathogens of economic crops. The centrum in young ascocarps contains lateral paraphyses. The asci are evanescent and the one-celled dark brown ascospores are extruded in a cirrhus.
Most species are cellulose decomposers.
There is a single family Chaetomiaceae. Chaetomium globosum - This is one of the most common species and has wavy hairs on its perithecia. Examine cultures under the dissecting scope and observe the hairs. Look for cirrhi of ascospores. Mount young ascocarps in a drop of water, crush gently, and examine asci and ascospores.