A still rather poorly known genus of c. 25 species, with the highest diversity in temperate areas of the Northern Hemisphere, included in the family Placynthiaceae. The monotypic genus Collolechia, previously distinguished on the basis of differences in ascospores and ascus apex, and in the leprose thallus, was recently analysed by Košuthová & al. (2016) with molecular and morphological data, showing that it is clearly nested within Placynthium. The genus was originally monographed by Gyelnik (1940); North American species were treated by Henssen (1963), those of the Iberian Peninsula by Burgaz & al. (2002) and Burgaz (2010), those of Northern Europe by Jørgensen (2007), freshwater species by Thüs & Schultz (2009), and those of the Alps and neighbouring territories by Czeika & Czeika (2007), who also provide a complete key to the species.

References

Burgaz A.R. 2010. Nuevos datos sobre el género Placynthium en la Península Ibérica. Bot. Complut., 34: 5-19.
Burgaz A.R., Rodríguez de Lope I., Martínez I. 2002. The Placynthium nigrum group in the Iberian Península. Cryptogamie, Mycol., 23, 4: 367-375.
Czeika H., Czeika G. 2007. Placynthium in den Alpen und Karpaten sowie in benachbarten Gebieten. Herzogia, 20: 29-51. Gyelnik V. 1940. Cyanophili, II. Lichinaceae, Heppiaceae, Pannariaceae. Borntraeger\Leipzig. 1-272 pp.
Henssen A. 1963. The North American species of Placynthium. Canad. Jour. Bot., 41: 1687-1724.
Košuthová A., Fernández-Brime S., Westberg M., Wedin M. 2016. Collolechia revisited and a re-assessment of ascus characteristics in Placynthiaceae (Peltigerales, Ascomycota). Lichenologist, 48, 1: 3-12.
Jørgensen P.M. 2007. Arctomiaceae, Coccocarpiaceae, Collemataceae, Heppiaceae, Lichinaceae, Pannariaceae. Nordic Lichen Flora, Vol 3: Cyanolichens.
Nimis P.L. 2016. The Lichens of Italy. A Second Annotated Catalogue. EUT, Trieste, 739 pp.
Thüs H., Schultz M. 2009. Fungi: Lichens 1. In: Süßwasserflora Von Mitteleuropa. Spektrum Akademischer Verlag, Heidelberg, Germany. 223 pp.

Last modified: August, 6, 2025