130 



Key to the Genera. 



Thallus indistinctly crustaceous to warty. 



Spore-sacs bearing about 16 simple colorless spores. 

 Spore-sacs bearing the usual number of spores (eight) . 

 Hypothecium and spores colorless. 

 Spores two-celled. 

 Spores simple. 

 Spores four-celled. 

 Spores 6-8-celled, acicular. 

 Hypothecium dark. 



Spores simple, colorless. 

 Spores four-celled, colorless. 

 Spores four-celled, dark. 

 Spores two-celled, dark. 

 Spores two-celled, colorless. 

 Spore-sacs bearing from one to six spores ; hypothecium colorless or 

 yellowish. 



Spores large, simple, colorless. 11. Megalospora. 



Spores multilocular, dark. 12. Lopadium. 



Spores multilocular, colorless. 13. Gyalecta. 



Thallus foliose, entire. 



Spore-sacs bearing the usual number of simple, colorless spores. 

 Thallus small, 1 cm. in diameter, or less. 14. Psora. 

 Thallus very large, entire. 15. Gyrophora. 



Spore-sacs bearing one or two large multilocular spores; thallus very 

 large. 16. Umbilicaria. 



i. Biatorella De Not. Giorn. Bot. It. 2: 192. 185 1. 



Biatorella takes essentially the same position in this family that 

 Mycocalicium does in the Caliciaceae. The thallus is quite con- 

 stantly wanting, or only the simplest rudiment is present. The genus 

 is characterized by the presence of sixteen spores in each spore-sac 

 otherwise it closely resembles various lower genera of the family. As 

 far as has been possible to observe, the spores are simple and color- 

 less ; in form they are sphaeroidal, having the general appearance 

 of those of Biatora, though considerably smaller. The spore-sacs 

 and paraphyses are very much as in Biatora. The hypothecium is 

 dark, likewise the epithecium and upper ends of the paraphyses. 



The genus is little known in the United States. Only one species 

 (B. geophana) which grows upon sterile rocky or sandy soil, has 



