• Verrucaria nigrescens Pers.
Verrucaria nigrescens
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This is one of the commonest lichens of calcareous stone and walls in almost all areas of the country. It can be recognised by a combination of chocolate-brown to black-coloured thallus and minutely cracked surface. The shiny, globose discs (perithecia) resemble tiny, black beads and lie half-immersed in the thallus. It is easily overlooked as a black stain or smear. Calcareous rock, concrete and mortar; rare on siliceous stone.

Key characteristics

  • Chocolate-brown to black thallus with cracks dividing the surface into a maze like mud on the bottom of a dried-up pond
  • Globose, shiny black, half-sunken discs.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Verrucaria nigrescens Pers.. [In] LichenIreland. Accessed on 2018-07-21.