FUNGI 



163 



mycelium can lay hold of suitable Algae. Artificial lich- 

 ens also have been made by bringing together wild Algae 

 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 



FIG. 159. Fruticose lichens: A, a simple form; B, reindeer moss; C, a common 

 hanging lichen. A and B after STRASBURGER; C, after SACHS. 



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 



