PARMELIA. 



205 



line Park, near Edinburgh; and on various hills around 

 Perth. 



14. Parmelia parietina (paries, a wall). Thallus yel- 

 low or orange-coloured, membranaceous, — below white, ob- 

 soletely fibrillose ; lacinise flat or lobate, disposed orbicularly, 

 or microphylline-squamulose. Apothecium of similar colour 

 to the thallus ; margin elevated, very entire. 



A most protean Lichen, and at the same time one of 

 the commonest species, growing on trees, palings, rocks, 

 and stones, almost everywhere, in lowland districts ; it is 

 abundant, and in fine fructification, on roadside walls and 

 hedges, — hence probably its Scandinavian name, "Wag- 

 laf." There are a great many varieties, depending primarily 

 on the characters of the lacinige, and secondarily on the 

 colour of the thallus and the characters of the apothecia. 

 The thallus may be macro- or microphylline ; the lacinise 

 may be broadish and rounded, linear and truncate, simple 

 or lacerate-dissected, concave, flattened or ascending towards 

 periphery, naked or granulose, imbricate or complicate in 

 their arrangement. The thallus may have more or less of a 

 reddish or gamboge-yellow tinge ; in moist shady situations 

 it is generally greenish or bluish. Its surface is frequently 

 granulose or pulverulent, and it sometimes degenerates into 



