LE CANOE A. 



215 



pruinose or non-pruinose nature of their surface or margins, 

 and their varying colour. Not uncommon on rocks and 

 boulders, especially if thinly covered with earth, in lowland 

 regions, as on Arthur's Seat, and roadsides round Edinburgh ; 

 some forms occur in rock-fissures on Highland mountains. 

 The spermogones may be detected under the lens scattered 

 here and there on the older squamules, either in the form 

 of minute, pale-brown tubercles, entire or cracked, or of 

 minute excavations with irregular margins ; they are im- 

 mersed, globular or irregular, and their cavity is divided 

 into many anfractuosities. The spermatia are linear, strongly 

 curved into an arc. 



Tkallus at circumference stellate-radiose, in centre 

 rimose-areolate, 



2. Lecanora murdrum (mums, a wall). Thallus yellow 

 or vermilion-coloured, sometimes white-pruinose ; peripheral 

 lacinise narrow incised-lobate, convex ; centre of thallus areo- 

 late-verrucose, often granulate-pulverulent. Apothecium 

 orange-coloured, — margin paler. 



Comparatively common in many lowland and subalpiue 

 localities, on walls, rocks, stones, bricks, tiles, and mortar ; 

 some forms are montane or alpine. It frequently bears 

 some resemblance, on superficial examination, to forms of 



