110 GUIDE TO THE STUDY OF LICHENS. 



Disk convex, black. Spores small, slender, more or 

 less curved, five to seven-celled, colorless, 20/a X 1-5/x. 

 J,., Bacidia atrogrisea. Thallus granular, greenish 

 to gray. Apothecia rather small. Disk convex, 

 black. Spores nine to eleven-celled, pointed at both 

 ends, variable in length and width, colorless, 60/x 

 X 5/x. 



5. Bacidia inundata. Thallus granular, or more 

 or less squamosa, greenish to gray. Apothecia small. 

 Disk convex, brown to black. Spores seven to nine- 

 celled, indistiiactly septate, colorless, 31/a X 2/x. 



6. Bacidia rubella. Thallus of distinct, more or 

 less scattered granules, greenish to gray. Apothecia 

 of medium size. Disk reddish-brown to dark-brown. 

 Spores colorless, nine to eleven-septate, 50/x X 4/x. 



7. Bacidia suffusca. Thallus thinly granular, green- 

 ish to ash-gray. Apothecia of medium size to quite 

 large, raised margin. Disk reddish-brown coated with 

 a translucent whitish film, giving it a characteristic 

 appearance. Spores seven to nine-celled, colorless, 

 50/x X V 



8. Bacidia Schweinitzii. Thallus granular, form- 

 ing a thin crust, greenish to ash-gray. Apothe- 

 cia of medium size. Disk brown to black. Spores 

 colorless, seven to nine-celled, 55/x X 4/x. 



6. Lecidea. 



The representatives of this genus resemble the 

 Biatoras very closely, so much so in fact that it 

 would seem advisable to combine the genera. The 

 only essential difference seems to be the greater pre- 



