The Morphological Interpretation of Cladoniiform Thalli in Lichens

Abstract

The term ‘cladoniiform lichens’ is applied to a group of lichen-forming discomycetes which either produce a ‘dimorphous’ thallus (differentiated into vertical and horizontal structures) or which resemble such lichens in having somewhat similar fruticose thalli and related phenolic chemistry. Seventeen genera comprising the families Cladoniaceae, Heterodeaceae, Cladiaceae, Baeomycetaceae and Siphulaceae are included in the group. A podetium is defined as a lichenized, stem-like portion (stipe) bearing the hymenial discs, and sometimes conidiomata, in a fruticose, simple or compound apothecium. The terminal structures commonly called apothecia on podetia or other ascomatal stipes in lichens are not whole apothecia but separate hymenial discs of a polydiscoid ascoma. In spite of superficial similarity in gross morphology and phenolic composition, the cladoniiform lichens are a life-form group rather than a taxonomic entity.