78 GUIDE TO THE STUDY OF LICHENS. 



Hypothecium black ^ -J 



Apothecia discoid or semiglobose ; sessile, not immersed. 

 Disk black or dark. 



Bacidia. 

 Lecidea. 



i Biatora. 



Hypothecium colorless ) Bilimhia. 



( Lecanora. 



Disk orange to rusty-red Placodium. 



Thallus Foliose. 



Thallus entire or lobes plicate, grayish-brown or dark. 

 Apothecia innate or immersed. 

 Apothecia comparatively large ; innate in depressions 



of the thallus Heppia. 



Apothecia small, immersed. 

 Thallus simple, very minute, adnate, . Dermatocarpon. 

 Thallus about five mm. in diameter, not 



closely adnate Psora. 



Thallus large, umbilicate Endocarpon. 



Apothecia sessile, black ; thallus large, umbilicate, 



Thallus pustular Umbilicaria. 



Thallus not pustular Gyrophora. 



Thallus distinctly lobed or branching, usually large. 

 Apothecia cup-shaped or discoid, sessile. 

 Cyphellae present.2 

 Thallus blue-green to dark-brown, soredia 



yellow Stictina. 



Thallus greenish to light-brown, soredia 



not yellow Sticta. 



Cyphallae wanting. 

 Thallus ash-gray, comparatively small. 

 Branching distinct, lobes of uniform 



width Speerschneidera. 



Branching less distinct, lobes not of 



uniform width Physcia. 



Branching indistinct, thallus thin, 



closely adnate Pyxine. 



Thallus greenish, more rarely brown to 



dark, large Parmelia. 



Thallus brown, small, closely adnate . . . Pannaria. 



* Make a vertical section through the apothecium and examine 

 with a good pocket lens. 



* Sticta amplissima and S. pidmonaria are devoid of cyphellae. 



