CETRARIA. 



153 



is never fertile ; but we have seen large specimens in beau* 

 tiful fructification from Labrador, Newfoundland, and the 

 Arctic regions, where it has been found as far north as 

 Walden Island and Ross's Islet. Its cortical tissue is dense 

 and horny, composed of polyhedral, thick-walled cellules ; it 

 is the seat of a resinoid, yellow, finely granular colouring 

 matter. Like C. Islandica, but in a minor degree, it is nu- 

 trient, demulcent, and tonic. In northern countries it is 

 frequently eaten by goats and other animals, notwithstanding 

 the hardness and rigidity of the thallus. 



4. Cetraria sepincola (sepes, a hedge or fence) . Some- 

 what resembles C. glauca, growing chiefly on the branches 

 and trunks of trees in alpine and subalpine woods ; thallus 

 brownish, paler below, prostrate, sinuate-lacinulate ; lacinise 

 flat, with smooth margins, sometimes crisped or pulverulent. 

 Apothecia (which are very rare) terminal, having a thalline, 

 crenulate margin, sometimes entirely covering the thallus. 



We have never met with fertile British specimens, but 

 have seen it in fine fructification from Newfoundland and 

 other parts of North America. 



5. Cetrarxa Islakdica. Thallus chestnut-coloured, 

 exterior paler, and marked by wart-like white spots, inner 

 surface smooth, frequently blood-red at base, cartilaginous, 



