Fungi are placed into particular taxa based on reproductive similarities. Sexual reproduction is the most evolutionarily conserved means of reproduction and thus used to determine evolutionally relatedness (systematics). Many fungi reproduce both sexually and asexually. This is particularly true in the group Ascomycota. Often only one method of reproduction is observable at a specific point in time or under specific environmental conditions. In these cases, mycologists have devised two names for the particular fungus. The teleomorph name describes the fungus when reproducing sexually. The anamorph names refers to the fungus when reproducing asexually. The holomorph name refers to the "whole fungus", encompassing both methods. This system is complicated and often confusing but can be a useful method for plant pathologists trying to identify a pathogen. Fungi that do not produce a teleomorph stage (or in cases in which it has yet to be observed) are placed into the Deuteromycota.