THE THALLUS 



303 



SCHEME OF SUGGESTED PROGRESSION IN LICHEN STRUCTURE 



PYRENOCARPINEAE 

 PYRENOCARPEAE 



CONIOCARPINEAE 



CONIOCARPEAE 



CYCLOCARPINEAE 

 PHYCOLICHENS (CYANOPHILI) 



LECIDEALES 



LECANORALES POLARILOCULARES 



Usneae 

 Stereocaulon Eucetraria Ramalina 



