v] LATER PROGRESS 123 



the absorption of water and mineral salts, however, 

 the fungus seems to be the better equipped. Thus 

 (division of labour once more) the alga supplies 



Fig. 12. Physcia parietina ; building up of the Lichen out of the 

 Alga and the Fungus. A, a germinating fungus-spore (sp) which 

 has seized upon two cells (, a) of the alga Cystococcus humicola. 

 5, more advanced stage. The spores of the fungus have formed 

 a network in which are embedded numerous algal cells ( x 400). . 

 (From Scott, after Bonnier.) 



carbon compounds for both, the fungus looks after 

 most of the rest of the nutrition, and also shelters the 

 alga from frost and drought. 



Algae identical with the green cells of the lichen 



