Black Sheet Lichen

Parmotrema reticulatum, often known as the Black Sheet Lichen, is a foliose lichen whose grayish thalli grow closely to loosely attached to its substrate. The thalli are conspicuously lobed with slightly overlapping, rounded lobes, which appear more jagged with age. It's not unusual for blackened areas to form on the upper surface.The thalli's lower surfaces are black with brown, mottled zones along the edges, and with root-like rhizines growing from the lower surface as seen at the left. Bowl-shaped apothecia rarely occur, but when they do they are small, only up to 6mm in diameter, and develop indistinct stalks, as seen below the taxonomy box.

The map registering verifiable observations of Parmotrema reticulatum on the iNaturalist page for the species documents occurrences worldwide in warm to hot areas, except in tropical rainforests and arid areas.

In the Himalayas, Parmotrema reticulatum has been documented as a traditional treatment for coughs and throat and respiratory problems. In Mexico a tea made of the lichen has been used for kidney disorders and venereal disease. The tea is prepared in the late afternoon and drunk the next morning. A methanol extract of Parmotrema reticulatum has been found to be a promising candidate for management of breast cancers.

The genus name Parmotrema derives from the Greek word paros, meaning "cup," and the Greek trema, meaning "perforation," referring to perforations of the apothecia. The species name reticulatus is from the Latin reticulatus, meaning "a netted-like network."

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