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Images of British Lichens

Physcia stellaris (L.) Nyl.

Foliose, lobes without marginal cilia (though sometimes with rhizines projecting from the undersurface, lobe surfaces ± smooth or with faint white flecks (pseudocyphellae), centre of thallus often warted, a rather untidy look to the whole thallus, soralia absent; apothecia with brown to black, thinly pruinose discs, margins regular to somewhat irregular with small, swollen warts or lobes. Locally on twigs and bark, predominantly in the north and west.

Refs: Smith et al. (2009), 702; Purvis et al. (1992), 469; Dobson (2005), 341; Dobson (2011), 341; Jahns (1983), 250-251 (photo, printed with incorrect colour in my copy); Nordic Lichen Flora (2002) 2: 37, 99 (photo); van Haluwyn et al. (2009), 42-3 (photo); van Herk & Aptroot (2004, 2013), 300-1 (photo); Wirth (1995), 2: 726, 727, 728 & 734 (photos); Wirth et al. (2004), 116 (photo); Wirth, Hauck & Schulz (2013), 2: 869 (photo), 870; Frahm et al. (2010), 136 (photo); Moberg & Holmåson (1984), 202 (photo); Stenroos et al. (2011), 358 (photo); Puntillo (1996), plate 32 (photo); Brodo et al. (2001), 558 (photo); Hinds & Hinds (2007), 397 (photo); Lichen Atlas of the British Isles 3: 1119 (1998).

P. aipolia is very similar, but with conspicuous pseudocyphellae on the lobe surfaces, more regularly sized apothecia, and is much more common. Both species give a positive, yellow reaction if potassium hydroxide is applied to the lobe surface (cortex), but whereas the underlying tissue (medulla) of P. aipolia also reacts yellow, that of P. stellaris is non-reactive. The species are well compared by Hinds & Hinds.

Physcia stellaris
On bark, Dunblane, Stirlingshire, May 2008

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© A.J. Silverside
Uploaded February 2011, updated December 2013