Images of British Lichens
Cladonia pocillum (Ach.) Grognot
Description, based in substantial part on notes in Aptroot, Sipman & van Herk (2001), Lichenologist 33: 271-283:
a "pixie-cup lichen" with funnel-shaped podetia tapering gradually towards the base, exterior variably clothed with corticate granules and often also with small to large squamules, interior with conspicuous, disk-like, corticate granules, soredia absent; basal squamules rather large, appressed to the substrate or frequently coalescent to form imbricated, often erect rosettes, commonly tinged with grey-pink, margins flat, abraded; apothecia brown, large, conspicuous and often ring-like, more or less sessile on the podetial margins or on very short, stalk-like proliferations (<5mm). Throughout Britain, locally common on rocks, soil and mortar where the substrate is at least moderately base-rich.
Refs: Aptroot, Sipman & van Herk (2001), Lichenologist 33: 271-283; Smith et al. (2009), 333; Purvis et al. (1992), 200; Nordic Lichen Flora (2013) 5: 63, 104 (photo); van Herk & Aptroot (2004, 2013), 150-151 (photo); Aptroot et al. (2011), 96-7 (photos); Krog et al. (1994), 165 (photo); Stenroos et al. (2011) 159 (photo); Puntillo (1996), plate 13 (photo, dry); Hinds & Hinds (2007), 199 (photo); Brodo et al. (2001), 266 (photo).
This species is part of a difficult complex with C. pyxidata and C. monomorpha, characterised by the conspicuous, discoid, corticate granules and lack of soredia within the podetia – see the page on C. pyxidata for more details. C. pyxidata is said to differ in its smaller basal squamules with similarly flat but smooth margins, lack of pink tints in the thallus, usually globose apothecia and preference for less basic (perhaps always peaty) situations. Confusion of the complex with C. chlorophaea is also all too easy. In mature but fresh podetia of C. pocillum and its allies, the corticate nature of the granules is shown by their rather distinct surface sheen, but this is lost in older or dried-up material.
C. pocillum is widespread but evidently much confused with C. pyxidata in Britain. Aptroot et al. (op. cit.) state that the latter does not occur in the Netherlands and refer several published supposed illustrations to C. pocillum. The non-appressed basal squamules of the photographed material shown here (as "morphotype 1") might be held to make it C. pyxidata according to some identification criteria, but other characters of the squamules and apothecia clearly place it as C. pocillum. Some published N.American DNA work suggests that there are several entities within this complex (details to be added), but other DNA examination of a broad range of material supports incorporation of the pyxidata-pocillum complex into a single species (D. Hawksworth, pers. comm., 2011). Two morphological variants are shown below.
Basal squamules concave, in rosettes; on soil.
Looks to match the photograph in the excellent and authoritive account of Cladonia by Stenroos and Ahti in Stenroos et al. (2011).
|Colony on bare areas of new roadbank, Saltash, Cornwall, August 2008|
|Same colony, closer view, showing corticate granules in podetia and the abraded margins of the squamules|
|Same colony, older podetia, in which the corticate surfaces of the granules have lost integrity, making them more difficult to tell from coarse soredia|
|Same colony, with apothecia (some partially ring-like) developed in this colony on densely squamulose podetia|
Basal squamules less divided, convex and appressed to the substrate; on metalliferous mine spoil and calcareous dune sand.
|On pathway formed from spoil at old lead mine, Nenthead, Cumberland, August 2012|
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Uploaded September 2008, last updated January 2016