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, Fie. 196. Corn smut 
or stalk fungi. Thesac An ear of corn, part of which has been destroyed 
i wer n and replaced by a mass of smut spores. Photograph 
fungi ere so named by Kern, Pennsylvania State College 
because the spores are 
formed in a sac. In like manner the basidium, or stalk, fungi 
(Basidiomycetes) are so called because the spores are 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 
