GENERA AND SPECIES. 193 



6. Pannaria molybdcea. Thallus large, mostly en- 

 tire, margin lobed, gray to bluish-gray • light-gray 

 to yellowish beneath with gray rhizoids. Apo- 

 thecia variable in size. Disk convex, irregular in 

 outline, pale chestnut changing to nearly black. 

 Spores simple or indistinctly two-celled, colorless, 

 spindle-shaped, 11^ X 4.5/x. 



9. Peltigera. 



Thallus large, lobes rounded and large. As a rule 

 the thallus is quite thick and rigid but not brittle. 

 Color above is generally bright blue-green, which 

 promptly changes to brown on drying ; the lower sur- 

 face is light-brown and bears large simple and branch- 

 ing rhizoids. 



Upon examining a vertical section of the thallus it 

 is found that no lower cortical tissue is present, as one 

 would expect in so large a plant. The algae are blue- 

 green, as in Pannaria {Poly coccus punctiformis) . 



The apothecia are quite large and are innate upon 

 the upper margin or terminal upon special lobes. In 

 outline the apothecia are orbicular to somewhat oval. 

 The spores are acicular, colorless, three to five-septate, 

 usually somewhat curved. 



The range of the species is northern, though some 

 occur south. They grow upon rock, more commonly 

 upon soil in forest lands among mosses, also at the 

 basal portions of tree-trunks. They do not thrive in 

 open, exposed places. 



1. Peltigera apthosa. Thallus large, lobes broad, 

 upper surface sprinkled with flattened brown warts, 



