104 GUIDE TO THE STUDY OF LICHENS. 



1. Biatorella. 



A very insignificant group ; only one species has 

 come to my notice. The thallus is very rudimentary 

 or entirely wanting ; repeated search is necessary to 

 detect the algae (Protococcus). The apothecia are 

 small, dark and considerably scattered, which adds to 

 the difficulty of finding specimens. The spores are 

 simple, small and colorless, sixteen usually occurring 

 in each spore-sac. 



The Biatorellas seem to prefer sterile soil. 



1. Biatorella geophana. Thallus deficient or want- 

 ing. Apothecia small. Disk convex, dark-brown. 

 Spores simple, nearly spherical, colorless, 8/a X 7/x. 



2. Biatorina. 



This genus is likewise deficient in representatives. 

 The thallus is rudimentary but readily recognizable ; 

 it is usually greenish in color and uniformly crustose, 

 never becoming warty or areolate. The algae are 

 bright-green, occurring in chains of rather small cells 

 (^Chroolepus umhrina). The apothecia are quite 

 small. Disk flattened or slightly concave, brown or 

 even pale-brown. Some authors combine this group 

 with Biatora ; but the elliptical, colorless, two-celled 

 spores exclude it. They occur upon soil, tree-trunks 

 and moss. 



1. Biatorina lutea. Thallus thin, evenly spread- 

 ing, somewhat granular, light-gray to greenish. 

 Apothecia rather small, discoid. Disk of a yellow- 

 ish waxy color. Spores colorless, elliptical, two-celled, 

 15/* X 5/x. 



