FUNGI 163 
mycelium can lay hold of suitable Alge. Artificial lich- 
ens also have been made by bringing together wild Alge 
and lichen-fungi. Lichens, therefore, are really combina- 
tions of-a parasitic fungus and its host, the parasitism 
being peculiar in that the host is not injured. The fungus 
lives upon the food made by the alga, and the relation 
suggested is that the alga is enslaved by the fungus. 
At certain times cup-like or disk-like bodies appear upon 
the surface of the lichen, with brown or black or more 
brightly colored lining (Fig. 154). A section through these 
Fic. 159.—Fruticose lichens: A, a simple form; B, reindeer moss; C, a common 
hanging lichen.—A and B after SrrasBuRGER; (, after SaAcHs. 
bodies shows that the colored lining is largely made up 
of delicate sacs containing spores (Figs. 157 and 158). It 
is evident, therefore, that such a lichen-fungus is one of the 
Ascomycetes (§ 82), and it is this group of Fungi that 
