ABSTRACT
Genera and higher systematic categories were frequently based, in the past, on a single character such as growth form, spore color, or spore septation. Such systematic classifications have been — and many still are — highly heterogeneous. As in nonlichenized fungi, interascal filaments may be of different origin, and different kinds of pigmentation of the tips of paraphyses are a good supporting character for genus delimitation or even the distinction of higher taxonomic levels. Chemistry may be useful in interpreting families and genera if the results are seen in connection with morphological features. Spore wall composition is important to differentiate between morphologically similar spores of unrelated groups. Septation should not be overemphasized, but more attention should be paid to perispores. Lichenized groups are widely distributed in ascomycetes and are much rarer in basidiomycetes. In Lecanorales, many isolated groups are included, most of them with crustose thallus organization.
