PARMELIA. 



195 



and whitish-glaucous ; below of similar colour, brownish- 

 fibrillose. The lacinise of the thallus vary in length and 

 breadth, are closely arranged in a somewhat imbricate man- 

 ner or are discrete, frequently elongate-fibrillose, as well as 

 more or less deeply incised, at the margins, — flattish or 

 arched towards their extremities, and sometimes sorediife- 

 rous. One of the most common forms resembles Bhyscia 

 ciliaris in having a ciliated or fibrillose margin, and was at 

 one time classed with that species in a separate genus, named 

 after one of the most distinguished of British Lichenogra- 

 phers, Borrera. (B. tenella of older authors. — E. B. 1351.) 



A common species, growing on roadside walls and trees. 

 Its spores are usually somewhat smaller than those of P. 

 pulverulenta ; they are also more oval, often slightly curved 

 and tapering at the extremities, though, being notched or 

 constricted at the centre, they also resemble the figure 8. 

 Their outer wall or epispore is thick ; the endospores are 

 large and spherical, and occupy the two compartments into 

 which the spore is divided by its central septum. The 

 latter, in the process of germination, generate the germ-fila- 

 ments, which burst through the epispore, but are otherwise 

 unconnected therewith. Its spermogones are scattered, 

 small, black, obtuse tubercles ; their cavity is pericellular 



