Placynthium nigrum (images of British lichens)

Thallus a dark brown to black, coralloid (nodular-isidiate), areolate crust, generally delimited by a distinct, inky blue prothallus; apothecia small, black, shining. Widespread on limestone, mortar of walls and in other calcareous habitats.

Refs: Smith et al. (2009), 717; Purvis et al. (1992), 478; Dobson (2005), 349 (photo); Dobson (2011), 351 (photo); Whelan (2011), 132 (photo); Nordic Lichen Flora (2007) 3: 137, 201 (photo); van Herk & Aptroot (2004), 310-1 (photo); Wirth (1995), 2: 746-7 (photo); Wirth et al. (2004), 256 (photo); Moberg & Holmåson (1984), 180 (photo); Brodo et al. (2001), 573 (photo); Hinds & Hinds (2007), 412 (photo).

Squamules and black apothecia of the lichen Tonina verrucarioides sometimes occur within thalli of P. nigrum.

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Images of British Lichens