Parmotrema is a genus of lichen belonging to the family Parmeliaceae.[1] It is a large genus, containing an estimated 300 species,[2] with a centre of diversity in subtropical regions of South America and the Pacific Islands.[3]
Parmotrema is characterized by its typically large, moderately to loosely-attached foliose thallus with broad lobes that are usually more than 5 mm wide. There is a broad, naked zone around the margin of the lower surface, an epicortex with pores and an upper cortex with a palisade-plectenchymatous arrangement of hyphae. Ascospores are thick-walled and ellipsoid.[5]
The genus was proposed as a genus by Italian lichenologist Abramo Bartolommeo Massalongo in 1860, with Parmotrema perforatum as the type species.[6] The genus name, composed of the Greek parmos (cup) and trema (perforation), refers to the perforate apothecia. Parmotrema was largely ignored as a genus,[7] and its species were usually grouped in section Amphigymnia of the large genus Parmelia.[8] Several genera previously segregated from Parmotrema have since been folded back in owing to molecular phylogenetic evidence, including Canomaculina, Concamerella, Parmelaria, and Rimelia.[3][9]
Some species of Parmotrema can be used as a vegetable dye, such as P. crinitum. When mixed with pine sap or with water, or when first burnt to ash, lichens can provide a variety of colors such as yellow, brown, green, orange, purple, and red.[10]