THE LICHENS 239 



unavailable. Reindeer moss (Cladonia rangiferina) grows upon 

 earth and rocks in great abundance throughout the north tem- 

 perate and frigid zones, and at high altitudes in most mountain 

 ranges. In winter it is eaten by animals, which find it green and 

 nutritious when they remove the snow from above it. 



A few lichens are sometimes used as food for men, though 

 they are not especially nutritious. A mucilaginous and starchy 

 food is prepared from Cetraria islandica, a lichen which is 

 known as Iceland moss. This and other food lichens are more 

 or less bitter, and when used regularly in large quantities are 



FIG. 194. A small piece of a lichen, showing in detail the relation that exists 

 between the mycelium of the fungus (/) and the algal cells (a) . 



Magnified 500 diameters. After Bonnier 



said to have caused disagreeable intestinal disturbances. Other 

 lichens have been ground with wheat in making wheat flour, 

 as in parts of northern Africa. The lichens, while adding some 

 nutrient matter, also add considerable non-nutritious calcare- 

 ous material, so that altogether the bulk of the flour is in- 

 creased at the expense of the quality. In Sweden one very 

 bitter lichen (Sticta pulmonacea) is sometimes used as a sub- 

 stitute for hops in processes of brewing. 



Various dyes are prepared from lichens. These were once 

 more commonly used than they are to-day, and are known in 

 the markets under the names of orchil and cudbear. Litmus, 

 used in preparing litmus or blue test paper, a common and 

 fairly delicate test for the presence of acids, is prepared from 

 lichens. 



