192 



POPULAR HISTORY OF LICHENS. 



of Sticta lierbacea. Its spermogones resemble those of Par- 



melia amplissima and Sticta pulmonaria. 



Tkallus sinuaie-laciniate ; lacinice ajipressed, imbricatefy 

 centrifugal. 



5. Parmelia pltjmbea {plumbum, lead). Thallus mem- 

 branaceous-coriaceous, lead-coloured, — below from pale be- 

 coming bluish-pannose; lacinise gradually dilated from centre 

 to circumference, bi- or tripartite, — old ones zoned ; mar- 

 gins slightly sinuate ; extremities rounded, crenate ; centre 

 at length imbricate, microphylline. Apothecia red, sometimes 

 aggregated in groups or in dark patches, margins concealed. 



A corticolous species not uncommon in many parts of 

 the Highlands, as around Arrochar, Inverary, Aberfeldy ; 

 and in some parts of the Lowlands, as Dumfries-shire. We 

 have found it abundant on trees, especially the ash, between 

 Tarbet and Arrochar, on Loch Lomond, arad Loch Long. 

 Its thallus is very tough and leathery, its medullary tissue 

 very compact and almost devoid of air-lacunse, and its gonidia 

 have a bluish tint, as in Peltigera. Its spermogones occur 

 chiefly towards the periphery of the thallus, — sometimes 

 arranged in arcs parallel to the zones of the older thalline 

 lobes,— in the form of isolated, somewhat indistinct tuber- 

 cles wdth a brownish and subsequently blackish apex. Their 



