Punctelia subrudecta (images of British lichens)

Thallus foliose, grey even when fresh, but can be vivid green when wet, margins dark brown, glossy (not pruinose), underside cream to brown, lobe surfaces with puntate, white dots (pseudocyphellae) that develop into well-delimited, round, laminar soralia, thallus margins sometimes also becoming sorediate later; apothecia said to have red-brown discs, but very rare. Widespread and locally common on a variety of trees, becoming scarce in the north-east and in northern Scotland, spreading into urban areas with the reduction in sulphur dioxide pollution.

Refs: Van Herk & Aproot (2000) Lichenologist 32: 233-246 (photos, detailed descriptions); Smith et al. (2009), 771; Dobson (2005), 375 (photo); Dobson (2011), 379 (photo); van Haluwyn et al. (2009), 102-3 (photo); van Herk & Aptroot (2004), 326-7 (photo, printed with green cast in my copy); Frahm et al. (2010), 146 (photo); Nordic Lichen Flora (2011) 4: 104, 166 (photo); Thor & Arvidsson (1999), 313 (photo), 442; Puntillo (1996), plate 29 (photo). [Jahns (1983), 199 fig. 426 (as Parmelia borreri) apparently represents this species, fide Van Herk & Aptroot, but fig. 427, labelled "Parmelia subrudecta", is a true Parmelia (P. saxatilis or P. sulcata, opinions vary). P. subrudecta is not now believed to occur in N. America and so illustrations in American publications will not apply to this species.]

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Images of British Lichens