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POPULAR, HISTORY OF LICHENS. 



Parmelia parietina, P. elegans, and Lecidea aurantiaca. 

 The L. murorum of E. B. (2157) is Schserer's L. callopisnia, 

 which has broadish and flat peripheral lacinise. 



Thallus uniform. 

 a. Apothecia black or brown. 



3. Lecanora atra {ater, black). Thallus glaucous or 

 whitish, cartilaginous, usually becoming granulose-verrucose: 

 hypothallus black * Apothecium very black (at all stages of 

 its development), naked, frequently tumid; margin entire or 

 crenulate. The thallus or apothecia sometimes sorediiferous 

 or variolarioid : the latter vary greatly in size and number 

 (E. B. 940, var. vulgaris). 



A very common species, growing on trees, rocks, and 

 walls in lowland and subalpine regions. In the neighbour- 

 hood of Perth it is abundant on old roadside-walls. Corti- 

 colous forms frequently resemble a following species, L. sub- 

 fusca, whose apothecia frequently become black ; but they 

 are distinguished therefrom by their apothecia being very 

 black ab initio. Its spores are oval, of medium size, colour- 

 less, double-walled ; they vary in size in specimens from dif- 

 ferent habitats. The young spores frequently contain a cen- 

 tral globular cellule, surrounded by coarse granular matter ; 

 these disappear as the spores arrive at maturity, their con- 



