GEJfKRA AND SPECIES. 151 



appears to have been gathered in the North of Eng- 

 land." — Lindsay. 



12. Lecanora cenisia. Thallus thick and readily 

 removed from substratum (rock), consisting of large 

 confluent warts, light-gray. Apothecia medium to 

 large, attached by a narrow neck ; crenate, mar- 

 gin elevated above the dark disk. Spores typical, 

 12/. X 8/01. 



13. Lecanora muralis. Thallus lobed at the mar- 

 gin, areolate toward the interior, sometimes of scat- 

 tered entire lobes. Apothecia small. Disk somo.what 

 convex, brown. Spores typical, 10.5/a X 5/x. 



IJf.. Lecanora tartar ea. Thallus thick, of imbricate 

 ascending branches, sometimes becoming semi-foliose 

 or semi-fruticose, light-gray to grayish-green. Apo- 

 thecia medium to large, margin somewhat rugose. 

 Disk brown to reddish-brown. Spores large, typical, 

 52/>i X 21/a. 



This lichen was employed to make litmus and to 

 produce a purple for dyeing woollen goods and nowhere, 

 perhaps, used more extensively than in England. The 

 lichen was sold at about eighty cents per stone of 

 twenty-two pounds. The same rocks were scraped 

 once every five years. 



15. Lecanora ruhina. Thallus-lobes ascending show- 

 ing a fruticose tendency, grayish-green above and 

 toward the apex, brown and dark below and toward 

 the basq. Apothecia medium to large ; margin cre- 

 nate and raised somewhat above the pale yellowish- 

 brown disk. Spores tyj^ical, 7.5/a X -i.O/x. 



