Images of British Lichens
Cladonia zopfii Vain.
Podetia in small clumps or forming extensive mats, suberect or sometimes decumbent, hollow, whitish to ivory-yellow, or said to be more green when damp, variably branched, surface verrucose (minutely warty) from the clumps of algal cells in the cortex, inner podetial surfaces finely fibrillose-striate (like strands of cotton, lens needed), branch tips variably brownish, bearing brown pycnidia. Very local on bare, open, gravelly ground, Scottish Highlands and in acid dune systems in N.E. Scotland, reported from a few scattered localities further south. The photographs here are from a large population seen during a BLS meeting at the Findhorn site.
Refs: Smith et al. (2009), 338 (but see note below); Purvis et al. (1992), 204 (but see note below); van Herk & Aptroot (2004), 164-165 (photo); Krog et al. (1994), 173 (photo); Lichen Atlas of the British Isles 5: 427 (2000). There is an excellent series of photographs of this species by Einar Timdal on the Oslo Museum website.
There is morphological overlap with Cladonia uncialis, particularly subsp. biuncialis, though the latter typically has wider, stubbier and often somewhat inflated podetia with more smoothly corticate surfaces. Both can be decumbent to ± erect, both vary from whitish to ivory when dry, becoming somewhat greener when damp due to the islands of algal cells in the cortex, and while C. zopfii tends to be more richly branched at the apices, there is little in the angle of branching to separate these species. Consequently, I feel British descriptions and the key in Smith et al. are potentially misleading. On my first visit to Findhorn in 2009, searching specifically for C. zopfii, I looked long and unsuccessfully for a 'decumbent, darkish-green Cladonia', while being puzzled by locally frequent occurrences of one that was pale, 'twiggy' and suberect. On returning home and on happening to see the photograph in van Herk & Aptroot, realisation dawned that I had been walking past the very lichen I was hunting!
The fibrillose-striate inner surface of the podetium should be checked whenever there is any doubt (see photograph below). In C. uncialis subsp. biuncialis, the inner surface is smooth and finely powdery, at least in the upper part; smooth without powder in subsp. uncialis.
|On open sandy gravel in dune heath, Findhorn, Morayshire, August 2010, lowest photograph showing habitat with C. zopfii dominant.|
|Podetial fragment from colony above, split open to show the fibrils on the inner surface.|
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© A.J. Silverside
Uploaded March 2012, typographical correction April 2012