94 



Small lichens with parts usually narrower than 



5 mm. Group 5 



Larger lichens, parts mostly broader than 5 



mm. Group 6 



Fruits gray, whitish or blackish. Spores 2-celled, 



blackish or brownish Group 8 



Fruits black, with minute brain-like convolutions. 



Lichen an unbranched leaf Group 12 



Fruits hidden within the tissues, showing as dark 



dots on the upper surface Group 12 



(See also Peltigera aphthosa and Sticta in Group 7) 

 Algal cells in chains 



Lichens greenish gray, rosy gray or brown, not gelat- 

 inous 

 Fruits chestnut-brown on special lobes projecting 



from the tips Group 7 



Fruits scattered on the upper surface, light red or 

 reddish brown 

 Lichen parts usually broader than 5 mm. Spores 



divided into 2 or more cells Group 7 



Lichen parts narrower than 5 mm. Spores not 



divided Group 10 



Lichens dark green, dark brown, olive, or lead gray, 



gelatinous-looking when wet Group 11 



Group 5. The Smaller Shield Lichens. Mats of paper-like struc- 

 ture growing close to the bark, stone, or other foothold, or 

 the tips and margins rising somewhat from it. Divided into 

 radiating trunks, more or less branching, and lobed. Trunks 

 and lobes usually narrower than 5 mm. Fruits typically 

 chestnut-brown, sometimes pale brown, greenish or gray, 

 especially when wet. Spores undivided, colorless. 



Cetraria fahlunensis. Swedish Shield Lichen. 



In the mountains of northern New England, and rarely as 

 far south as the New Jersey highlands, on exposed, rocky sum- 

 mits, this tiny Shield Lichen grows flattened against the usually 

 vertical face of rock containing quartz, in tufts commonly 3 or 

 4 cm. across. The radiating trunks branch profusely, and grow 

 over each other to form an interwoven mat sometimes 2 mm. 

 or more deep. Trunks and branches maintain a rather uniform 



