GENERA AND SPECIES. 121 



According to Porcher, Icelanders use this lichen as 

 an article of food ; more frequently for dyeing woollen 

 cloth a brownish-green color. 



3. Gyrophora erosa. Thallus medium in size, more 

 or less lobed, margin ragged and reticulately perforate, 

 entire upper surface more or less reticulate, dark color ; 

 lower surface fissured, areolate, lighter than upper sur- 

 face. Apothecia small. Disk convex, black. Spores 

 small, colorless, granular, lO/x X 4.5/x. 



4. Gyrophora floculosa. Thallus small to medium, 

 thin, margin somewhat lobed and torn ; upper surface 

 dark-brown, bearing numerous fine thalloid outgrowths ; 

 lower surface of nearly the same color and reticulately 

 veined. No fertile specimens have come to my notice. 



5. Gyrophora Muhlenhergii. Thallus medium to 

 large, margin more or less torn ; upper surface smooth, 

 pitted and rugosely folded, ash-gray, darker toward 

 the margin ; lower surface more or less reticulate, 

 fringed toward the margin, dark-brown. Apothecia 

 from medium to large, situated in pits, scattered toward 

 the margin of thallus. Disk convex, black. Spores 

 simple, elliptical, colorless, 10/x, X 5^. 



This is one of the lichens known as " tripe de roche," 

 and was used by Sir John Franklin on his journey to 

 the polar seas. It was said to be " agreeable and nu- 

 tritious," although, like other lichens, it contains an 

 objectionable bitter principle. 



6. Gyrophora vellea. Thallus large, entire, margin 

 more or less incised and somewhat broken or torn, 

 upper surface smooth or finely powdered, gray ; lower 

 surface brown to dark, bearing numerous rigid cilia. 



