FUNGI AND FUNGOUS DISEASES OF PLANTS 251 



Reindeer moss {Cladonia rangiferina) is eaten in winter by 

 animals, which find it green and nutritious when they remove 

 the snow from above it. A few lichens are used as food for 

 men, though they are not especially nutritious. A mucilagi- 

 nous and starchy food is prepared from Cetraria islandica, a 

 lichen which is known 

 as Iceland moss. In 

 Sweden Sticta pul- 

 monacea, a very bitter 

 lichen, is sometimes 

 used as a substitute 

 for hops in processes 

 of brewing. Various 

 dyes are prepared from 

 lichens and are known 

 in the markets as orchil 

 and cudbear, but these 

 are not so commonly 

 used as formerly. Lit- 

 mus, used in preparing 

 litmus, or blue-test 

 paper as a test for the 

 presence of acids, is 

 also prepared from 

 lichens. 



238. The basidium, 

 or stalk fungi The sac 

 fungi were so named 

 because the spores are 

 formed in a sac. In like manner the basidium, or stalk, fungi 

 ( H<ixi<l in, ii i/r<'f,-x ) ;uv so called Id'cuiisc tin- spores art- formed 

 on the outside of the tip of a hypha known as the stalk, or 

 basidium. Within this division of fungi several sub-divisions 

 are recognized. One of these, the smuts, is represented by 

 forms that frequently appear upon the ears of corn (fig. 196) 

 and upon heads of oats (fig. 197), wheat, barley, and other 



FIG. 196. Corn smut 



An ear of corn, part of which has been destroyed 



and replaced by a mass of smut spores. Photograph 



by Kern, Pennsylvania State College 



