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Placopsis gelida (L.) Linds.


Thallus a cream, markedly placodioid crust, usually with conspicuous, rounded, lobed, flesh-coloured cephalodia scattered over the surface, and with the central area pale green-grey-sorediate, the soralia excavate-eroded with a corticate rim and becoming confluent; apothecia very rare. On rocks, distribution uncertain but apparently arctic-alpine.

Refs: Moberg & Carlin (1996), Symbolae Botanicae Upsaliensis 31: 319-325 (photo); Smith et al. (2009), 711; Purvis et al. (1992), 474 (as aggregate only); Dobson (2005), 346 (as aggregate, photo seems to be P. lambii); Dobson (2011), 348 (excluding photo); Wirth, Hauck & Schulz (2013), 2: 890 (photo); Holien & Tønsberg (2008), 182 (photo); Stenroos et al. (2011), 371 (photo); Hansen & Andersen (1995), 107 (photo); Thomson (1997), 471, 472 (line illustration, evidently as aggregate).

Difficult to distinguish morphologically from the evidently more common (especially in metal-rich areas) P. lambii, but the latter has a generally more shiny thallus, yellow-grey to brown cephalodia, more clearly delimited, convex and often concentrically arranged soralia with soredia grey-green to blackish, and much more frequently produced apothecia, though separation on chemical characters may be needed. Descriptive details taken from Moberg & Carlin (1996) (see above); other and especially earlier sources unreliable.

 
Placopsis gelida
Placopsis gelida
Placopsis gelida
On montane rockface near Ben Lawers, Perthshire, April 2003 (taken in very poor light)


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Uploaded September 2008, last updated September 2013