New species or interesting records of foliicolous lichens .1. Trichothelium argenteum (Lichenized Ascomycetes: Trichotheliaceae)

Trichothelium argenteum R. Lucking & L. I. Ferraro sp. nov. is distinguished by its very large perithecia with a well-developed, silvery white, basally black crown of setae, and by a non-radiate phycobiont. In young perithecia, the setae are confluent and form a characteristic, two-coloured disc-like expansion. Ascospores are 7-septate and bacillar. Trichothelium argenteum is known from a few populations in Costa Rica, Ecuador, Brazil, Paraguay, and Argentina. (C) 1997 The British Lichen Society.