192 GUIDE TO THE STUDY OF LICHENS. 



considerable confusion exists as to the limitations of 

 the genus. 



i. Pannaria hrunnea. Thallus from coarsely warty 

 to minutely foliose, tawny-brown. Apothecia medium, 

 margin rugose, warty. Disk flattened to concave, red- 

 dish-brown. Spores simple, colorless, granular, ends 

 pointed, 18/x X 9/><" 



2. Pannaria lepidiota. Thallus of small closely 

 adnate or sometimes ascending lobes, branching, warty 

 and more or less crenate, brown to dark-brown. Apo- 

 thecia small, margin crenate. Disk flattened, reddish- 

 brown to dark-brown. Spores simple or apparently two- 

 celled, contents granular, oblong elliptical, 15/x X 6/x,. 



3. Pannaria leucosticta. Thallus foliose, adnate, 

 lobed, much divided and more or less ascending, mar- 

 gin whitish ; greenish-gray above, dirty gray beneath. 

 Apothecia small, margin crenulate. Disk convex, 

 reddish-brown. Spores simple, colorless, enclosed by 

 a spindle-shaped gelatinous mass, 12/x X 6/i. 



4- Pannaria luridum. Thallus quite large, lobed, 

 brown to bluish-brown above ; light-gray to bluish-gray 

 beneath, with numerous dark rhizoids. Apothecia 

 small, margin almost entire. Disk convex, pale chest- 

 nut to dark. Spores simple, colorless, spheroidal to 

 spindle-shaped, spore-wall warty, 10.5/x X 8/x. 



This lichen is often classed as Physma luridum. 



5. Pannaria ruhiginosa. Thallus much branched, 

 margin faintly white ; brown above, dark beneath. 

 Apothecia rather small, margin crenate. Disk con- 

 vex, reddish-brown. Spores spheroidal, spore-wall 

 comparatively thick, 13/x X 10/** 



