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Fuscidea lygaea (Ach.) V.Wirth & Vězda


Thallus a thin, usually cracked, pale- to dark-grey, brown-grey or grey-brown, usually mottled crust, often with a purplish tinge more apparent at distance, usually bordered by a darker, effuse prothallus; apothecia minute, less than 0.5mm, black, flat to convex, margin at best indistinct, ascopores ± globose. On exposed, hard rocks and boulders in the north and west, commonly in mosaics with F. cyathoides. Usually distinguishable from F. cyathoides by its tiny, borderless apothecia, but both species are variable and microscopc confirmation of the globose or near-globose ascopores is sometimes helpful.

Refs: Smith et al. (2009), 410; Purvis et al. (1992), 255; Dobson (2005), 178 (photo); Dobson (2011), 184 (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.

FGBI: http://fungi.myspecies.info/all-fungi/fuscidea-lygaea

 
Fuscidea lygaea
On coastal pebble, Kingston on Spey, Morayshire, August 2010 (BLS meeting)


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Uploaded March 2011, last updated January 2016