XII. LICHENES. 



943 



Parmelia parietina. 

 Spermatia of -^ to ^^^ 

 (Tulasne.) 



Parmelia parietina. Vertical section of thallus, 

 and of a Bpermogomtim from -whicli the spermatia 

 are escaping (m^.)* (Tnlasne.) 



Stereocaulon ramulosus. 



Umbilicaria vellea. 



Usnea iarbata. 



