122 GUIDE TO THE STUDY OF LICHENS. 



Apothecia in slight depressions of thallus, marginal, 

 small to medium. Disk convex, black. Spores sim- 

 ple, colorless, elliptical, slightly granular, 10/x by 7/x. 



" Some varieties of this species are imported to a 

 considerable extent into the London market from the 

 Norwegian mountains, for the manufacture of orchill 

 and cudbear, under the name of * Norway rock moss/ 

 or 'velvet or velutous moss.' Like most of its co- 

 species, it grows chiefly on granitoid rocks on very 

 high mountains, or in arctic or sub-arctic regions. On 

 the Mexican volcano of Orizabo it occurs at a height 

 of between 13,000 and 14,000 feet, along with other 

 species. This is another of the lichens which consti- 

 tute the ' tripe de roche ' of sub-arctic America and the 

 polar regions. This black, leathery, forbidding-look- 

 ing ' rock- tripe ' is often boiled and eaten by the Cana- 

 dian hunter when pressed by hunger. In Iceland it is 

 frequently eaten in periods of scarcity as a supplement 

 to the more nutritious ' Iceland moss ' ; and it has 

 been frequently mentioned in the narrative of the 

 polar voyages as having been the means of saving the 

 crew from perishing by starvation. The nutritive 

 properties of these lichens depend on the presence of 

 a large amount of starchy matter (lichenin, lichen- 

 starch). "When boiled they yield, like Cetraria Island- 

 ica, a firm, nutrient jelly, which is, however, accom- 

 panied, as in that lichen, by a bitter principle possessed 

 of purgative properties. Linnaeus speaks of some Gy- 

 rophoras as superior in nutritive qualities to the ' Ice- 

 land moss.' " — Lindsay. 



7. Gyrophora Dillenii. Thallus large to very 



