GENERA AND SPECIES. 105 



^. Biatorina pineti. Th alius very rudimentary, 

 dark. Apothecia very small. Disk dark. Spores 

 as in B. lutea. 



B. lutea occurs upon moss, while B. pineti occurs 

 upon pine trees. Both are quite rare. 



3. Biatora. 



This genus is represented by a considerable num- 

 ber of species. Some authors have made it the 

 dumping ground for many lichens which have no 

 evident affinity to the typical representatives. Thus, 

 for example, Biatorella, Biatorina, Bilimhia, Bacidia, 

 Psora, Acarospora, etc., have been included in Bia- 

 tora, and are yet so included by some recent authors. 

 This is no doubt primarily due to insufficient attention 

 to spore-differences. 



The thallus varies from typically crustose to warty 

 and minutely foliose. The color tends toward gray- 

 ish-green. The algae are Protococcus (^Cystococ- 

 cus). 



The apothecia are of medium size, discoid. Disk 

 flattened to convex, light-brown to dark and black. 

 The hypothecium is colorless. Spores are elliptical, 

 simple, colorless. 



The Biatoras are widely distributed, and occur upon 

 bark, less commonly upon rock and moss. They are 

 active in the disintegration of rock, but much less so 

 than their near relatives, the Lecideas. 



The following are the more common species. 



1. Biatora varians. Thallus thin, granular, gray- 

 ish-green ; margin dark. Apothecia small, sessile, 



