Images of British Lichens
Fuscidea lightfootii (Sm.) Coppins & P.James
Thallus a bright green to brownish crust, cracked and minutely but conspicuously covered by rounded warts, often with green soredia, which may dominate the thallus surface; apothecia brownish black, about 1mm diameter, flat with a thin 'proper' margin, more convex when damp. Widespread on twigs and bark, more common in damp woodland and especially so in western Britain.
Refs: Smith et al. (2009), 410; Purvis et al. (1992), 254 (? also 255, as F. pusilla); Dobson (2005), 177-8 (photo); Dobson (2011), 184 (photo); Valcárcel et al. (2003), 192-3 (photo).
Fuscidea is part of the very large 'Lecidea group' of lichens – crustose species with dark or black apothecia that lack distinct 'thalline' margins, though they will usually have differentiated 'proper' margins the same colour as the disk. Microscopic examination of mature apothecia (and sadly they are often not mature) is usually necessary even to be sure of the genus, and field identification of all but a few distinctive species is risky. Dobson (2011), pp. 236-7, gives an invaluable analysis of the component genera.
|On Beech (Fagus sylvatica), Chatelherault, Lanarkshire, March 2008; lowest photograph showing a damper and strongly sorediate state.|
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Uploaded March 2011, last updated November 2011