Bacteria and Fungi 



269 



of soil on which the fruiting bodies appear. It may take 

 several years for the underground vegetative part of the fungus 

 to develop, while the fruiting bodies may develop in a few 

 days. It is the enlargement of the fruiting bodies that per- 

 sons have in mind when they speak of " mushroom growth." 

 This expression leaves out of account the months or years of 

 growth during which the materials were accumulated for the 

 sudden production of the fruiting body. The spores of mush- 

 rooms are produced in unthinkable numbers either inside the 

 fruiting body (puffballs), on the upper surface (morels), or 

 on the under side of the umbrella-shaped cap (mushrooms) 



(Fig- 159)-' 



Lichens. Among the parasitic fungi are some that live on 

 such one-celled algae as Protococcus. The fungus forms the 

 plant body, and the algal cells are completely enveloped. 

 These forms constitute the lichens, which are gray-green, ir- 

 regular-shaped plants that are common on the bark of trees, 



FIG. 160. Several common lichens. The form on the tree is Parmelia ; the one in 

 the middle foreground is Peltigera; the other forms are species of Cladonia. 



