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Melanohalea exasperata (De Not.) O.Blanco et al.
 
(= Parmelia exasperata De Not.; Melanelia exasperata (Dr Not.) Essl.)


Thallus olive- to red- or dull brown, matt to moderately shiny, surface with abundant and very evenly distributed, minutely flat-topped papillae (warts) (not breaking away so technicaly not isidia, though the tops may lose their cortex to form pseudocyphellae); apothecia frequent, sometimes abundant enough to obscure the thallus, moderately large, with brown discs and distinctly papillate (warted) margins. On branches and twigs, very rarely rocks, primarily in northern and western Britain.

Refs: Smith et al. (2009), 574; Purvis et al. (1992), 433 (as Parmelia); Nordic Lichen Flora (2011) 4: 77, 160 (photo, printed too dark); Dobson (2005), 261-2 (photo, as Melanelia); Dobson (2011), 269 (photo); Jahns (1983), 200-1 (photo, as Parmelia); Whelan (2011), 115 (photo); van Haluwyn et al. (2009), 66-7 (photos); Moberg & Holmåson (1984), 88 (photo, as Parmelia; Holien & Tønsberg (2008), 53 (photo, as Melanelia); Stenroos et al. (2011), 277 (photo); Wirth (1995), 2: 642, 651 (photo, as Parmelia); Wirth, Hauck & Schulz (2013), 2: 729, 734 (photo); Frahm et al. (2010), 118 (photo); Valcárcel et al. (2003), 268-9 (photo, as Parmelia); Puntillo (1996), plate 28 (photo, as Parmelia); Hinds & Hinds (2007), 308-9 (photo, as Melanelia); Lichen Atlas of the British Isles 1: 995 (1995) (as Parmelia).

In the absence of apothecia, this species can be confused with the much more common Melanelixia subaurifera, particularly as the pseudocyphellae on the papilla-tips resemble the creamy white to yellowish isidial scars of the latter species. In cases of doubt, a bleach (sodium hydroxide) test should distinguish them, the medulla (flesh) of M. subaurifera giving a positive pink to red reaction, M. exasperata not reacting.
Melanohalea exasperata
Melanohalea exasperata
Melanohalea exasperata
On Poplar (Populus x canadensis), branch fallen from canopy, Ramsbottom, Lancashire, May 2012
 
Melanohalea exasperata, close view
Melanohalea exasperata, close view
Glen Tilt, Perthshire, April 2008


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Uploaded May 2012, updated September 2013