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Images of British Lichens

Cladonia mitis Sandst.

One of the 'reindeer lichens' (subgenus Cladina), podetia ± erect, in tufted mats, greyish white to cream, with patches of usually inconspicuous algal cells set in the cortex, only the ultimate branch-tips brown, branches numerous, straight to slightly recurved, spreading or aligned mostly in one direction, ultimate branches predominantly in fours (mostly tetrachotomous); pycnidia small, brown, containing colourless jelly, located on the branch tips, apothecia small, brown, perhaps not rare. In lichen heaths on exposed, base-poor dunes and shingles, mixed with other members of subgenus Cladina, very rare and principally in NE Scotland but reportedly still (just) extending to Dungeness on the south coast, where much of the former habitat was destroyed.

Refs: Ahti (1961), 116 et seq., plate 41 (photo); Smith et al. (2009), 319; Purvis et al. (1992), 196; Nordic Lichen Flora (2013) 5: 57, 103 (photo); Wirth, Hauck & Schulz (2013), 1: 374, 403 (photo); Krog et al. (1994), 162 (photo); Stenroos et al. (2011), 152 (photo); Thomson (1967) 148, plate 25 fig. 113 (photo); Hansen & Andersen (1995), 23 (photo, as Cladina mitis); Hinds & Hinds (2007), 163 (photo, as C. arbuscula subsp. mitis); Walewski (2007), 38 (photo); McCune & Geiser (2009), 90 (photo); Lichen Atlas of the British Isles 5: 402 (2000).

Recognisable, with difficulty, in the field, but needs laboratory confirmation, normally testing negative with Pd (para-phenylenediamine) but reputedly a chemical variant gives an orange-red response (confirmed in Britain?). James (in Smith et al., 2009) states that it is UV-, but the key in the same work describes it as "UV ± pale blue", apparently an error. Ahti & Stenroos in Nordic Lichen Flora (2013) confirm it is UV-, as was photographed material shown here.

C. portentosa is closely similar but more bushy, with branches spreading in all directions, mainly trichotomous ultimate branching, and with exposed medulla (shave with a razor) variably fluorescent white under long-wave UV light; Cladonia arbuscula, especially subsp. arbuscula, can also be closely similar, but has more pronouncedly unidirectional branching, often a more robust main stem, ultimate branches more extensively brown, and is Pd+ (yellow or orange-red) (see Ahti, 1961, table 1, pg. 125); C. ciliata is typically more delicate, with ultimate branches dichotomous, and is Pd+ orange-red.

Cladonia mitis
Cladonia mitis
Cladonia mitis, enlarged view
Cladonia mitis, with apothecia
Dune heath (with C. arbuscula ssp. squarrosa, C. ciliata, C. portentosa), Cuthill Links, East Sutherland, April 2009, lowest photograph showing apothecia

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© A.J. Silverside
Uploaded August 2010, last updated January 2014