Evernia prunastri (images of British lichens)

Thallus foliose but attached at one point and appearing fruticose, lobes often net-veined above, white beneath, soralia initially rounded, marginal and/or laminal, later more extensive over thallus surface; apothecia rare (but shown here!), shortly and stoutly stalked, discs red-brown. Widespread and generally common on deciduous trees and frequent on old wooden fencing, more rarely in other habitats, including dunes where it can be terrestrial.
Thallus typically pale yellow-green (presence of usnic acid) but occasionally lacking usnic acid and pale grey without the yellow-green tints, this variant being forma herinii (Duvign.) D.Hawksw. (see photograph below).

Refs: Smith et al. (2009), 397; Purvis et al. (1992), 247; Dobson (2005), 171-2 (photo); Dobson (2011), 177-8 (photo); Jahns (1983), 190-1 (photo); Allen (2007), 41 (photo); Whelan (2011), 94 (photo); van Haluwyn et al. (2009), 140-1 (photos); van Herk & Aptroot (2004), 176-177 (photo); Wirth (1995), 1: 390, 392 (photo); Wirth et al. (2004), 58 (photo); Frahm et al. (2010), 155 (photo); Moberg & Holmåson (1984), 82 (photo); Holien & Tønsberg (2008), 43 (photo); Nordic Lichen Flora (2011) 4: 51, 154 (photo, printed too dark); Brodo et al. (2001), 313 (photo); McCune & Geiser (2009), 123 (photo).

Lichenicolous fungi on this host include Unguiculariopsis lettaui.

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Images of British Lichens