KEY TO THE FAMILIES AND IMPORTANT GENERA 247 



Two small genera in the U.S. of widely distributed species. 

 Proper exciple hyaline. Family Gyalectaceae 



Five small genera in the U.S., from various parts of the country. 

 Either proper or thalloid exciple present, very rarely both. 

 Apothecia with proper exciple. 



Thallus taking its form from that of the algal host. 



Family Coenogoniaceae 

 Two small genera in the U.S. 

 Thallus not taking its form from that of the algal host. 



Thallus twofold, a primary crustose, squamulose or foliose por- 

 tion out of which grow the upright podetia. 



Family Cladoniaceae 

 Podetia short, unbranched, hypothecium hyaline. 



Baeomyces 

 Podetia short to long, more or less branched. 



Podetia mostly hollow, spores nonseptate. Cladonia 

 Podetia solid; spores 3 or more septate. Stereocaulon 

 Thallus foliose, apothecia not on podetia. 



Family Gyrophoraceae 

 Spores nonseptate. Gyrophora 



Spores transversely and longitudinally septate. 



Umbilicaria 

 Spores only transversely septate. Derniatiscium 



Thallus crustose to squamulose. 



Ascospores hyaline, rarely brown, apothecia rarely yellowish, 

 spores nonseptate to septate, with rectangular or 

 cubical cells. Family Lecideaceae 



Ascospores nonseptate, very large, thick-walled. 



Mycoblastus 

 Ascospores nonseptate, not large. 



Thallus crustose. Lecidea 



Thallus squamulose. Psora 



Ascospores one septate, very large, thick-walled. 



Megalospora 

 Ascospores one septate, small. Catillaria 



Ascospores 1 to 3 to more septate, acicular. 



Thallus crustose. Bacidia 



Thallus squamulose. Tonina 



Ascospores 3 or more septate, fusiform. Bilimbia 

 Ascospores transversely and longitudinally septate. 

 Ascospores hyaline. Lopadium 



Ascospores brown, Rhizocarpon 



Ascospores hyaline, nonseptate to septate, with lenticular cells. 

 Apothecia usually yellowish. Thalloid exciple in one 

 genus. Family Caloplacaceae 



Apothecium with proper exciple. Blastenia 



Apothecia with thalloid exciple. Caloplaca 



Two or more genera present in the U.S. 

 Ascospores brown. Thalloid exciple in one genus. 



Family Buelliaceae 

 Apothecia with proper exciple, spores one septate. 



Buellia 



