The term gomocyst, introduced by Norman in the last century, has been used to designate lichen thalli consisting of algal colonies embedded in a hyphal envelope. It has been applied to the Moriolaceae, ‘Botrydina’ and several groups in the Lecideaceae s. lat. A preliminary survey demonstrates that the concept encompasses different structures. Nevertheless, and ad interim, the term is here used to describe the small diaspores produced by several species of foliicolous Opegrapha in a peculiar organ, the gomocystangium. Four such species are known in Opegrapha: O. dibbemi sp. nov. in Costa Rica, O. lambinoniiSérusiaux in Zaire, O. luzonensis sp. nov. in the Philippines and O. santessonii sp. nov. in Zaire, but foliicolous lichen thalli with goniocystangia are known from undisturbed rain forests at low elevations in four continents.
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