90 GUIDE TO THE STUDY OF LICHENS. 



and numerous, nearly spherical. Thecium of a blue- 

 black tint near the top. Disk blue-black, smooth. 

 Spores simple, elongated, colorless, 25.5^ X 7/x. 



3. Stereocaulon, 



The most marked morphological character of this 

 genus is the comparatively large fruticose thallus ; it 

 consists of numerous crooked and somewhat flattened 

 branches, which are covered by warty thalloid out- 

 growths. Upon careful examination numerous dark- 

 blue cephalodia will be found on different parts of the 

 branches. The color of the thallus is generally ash- 

 gray. 



The primary thallus is deficient, so much so that the 

 average collector will take no notice of it whatever. 

 The secondary thallus is not hollow, as in the foregoing 

 genus When dry, the Stereocaulons are very brittle. 

 They occur most commonly upon rocky ledges in hilly 

 and mountainous regions. They are somewhat north- 

 ern in their range. 



The apothecia are terminal, medium size, globose or 

 flattened, dark-brown to nearly black. The spores are 

 colorless, spindle-shaped, usually four-celled. The fol- 

 lowing are the more common species : 



1. Stereocaulon condensatum. Primary thallus dis- 

 tinct, granular and warty, green to dark-gray. Pode- 

 tia short, branched, covered with thalloid warts re- 

 sembling those of the primary thallus. Apothecia 

 rather large, simple or confluent. Disk convex, dark- 

 brown. Spores acicular, triseptate, colorless, 25/a 

 X 2.5/x. 



