A characteristic feature of many leaves and twigs colonized by tarspot fungi is that the tissues tend to be paler than parts colonized by other fungi. Zone lines produced by the fungus are also quite common. Many tarspot fungi produce a conidial state before the ascomata are formed, and both states are almost invariably deeply embedded in the plant tissues. The conidial state usually takes the form of blackish pycnidia which contain minute single-celled conidia which probably function as spermatia. The ascomata, which follow the pycnidia, are larger but also usually black, opening with one to several splits in the covering layer to reveal the hymenium.
Paraphyses are usually present.
Asci are mostly thin-walled, with only one functional wall layer and an apex which almost never blues in iodine. The ascospores are almost invariably colourless, usually aseptate, and often long and thin. Spore release is mostly violent in humid conditions. The zone lines, pycnidia and ascocarps produced by tarspot fungi are all long-lasting, so that they are usually all seen at the same time in the field, and observational work can be carried out at any time of year. Most tarspot fungi are found only on particular plants, and on those plants the habitat they occupy is usually well-defined.