72 HERRE 



very diverse, but no mazasdium is formed; asci permanent, one to 

 many spored. Spores simple, or two to many celled, polar-bilocular, 

 and muriform, colorless to dark brown, sometimes with a halo. 

 Soredia often greatly developed and in some families of the highest 

 importance. 



KEY TO FAMILIES. 



A. Spores typically bi-locular or polar-bilocular, with much thickened 



walls, the cells often connected by a thin tube or canal. 

 B. Spores colorless, polar-bilocular. 



C. Thallus uniform crustaceous or with a radiately plicate margin, 



without cortex Caloplacacea 



CC. Thallus f oliaceous or f ruticose, corticated Theloschistacea 



BE. Spores brown, polar-bilocular or with a septum. 



D. Thallus crustaceous, uniform or lobed at the circumference, 



without cortex Buelliacece 



DD. Thallus foliaceous or f ruticose, corticated Physciacea 



A A. Spores simple, multilocular, or muriform, colorless or rarely brown. 

 E. Algae belonging to the Cyanophycea-, thallus more or less gelatinous 

 when wet. 



F. Algae Nostoc-, apothecia sessile, dish-like Collemacecz 



FF. Algae not Nostoc. 

 G. Algae Scytonema or Stigonema\ apothecia urn or dish-like. 



Ephebacecz 

 GG. Algae Glceocapsa\ apothecia often not visible, apparently pyre- 



nocarpous, urn or dish-like Pyrenopsidacece 



RE. Thallus not gelatinous when wet. 



H. Thallus crustaceous, uniform or marginally lobed, attached by 

 the hyphae of the hypothallus or medulla. 



7. Thallus with Trentepohlia algae Lecanactidacea 



II. Thallus with Pleurococcus or Palmella algae. 



/. Asci many-spored; apothecia lecideine, biatorine, or lecanor- 



ine Acarosporacea 



JJ . Asci 1-8 spored, or rarely 16-32 spored. 



K. Apothecia with a proper margin, not enclosing algae. 



Lecidacea 



KK. Apothecia with a thalline margin, enclosing algae. 

 L. Proper margin well developed, black or dark, usually 

 entire; apothecia innate; thalline margin poorly devel- 

 oped Diploschistacea 



LL. Proper margin wanting or poorly developed and clear; 

 thalline margin well developed. 



M . Apothecia sessile, the disk large Lecanoracea 



MM. Apothecia solitary or several, enclosed in thalline 



warts; disk usually very small Pertusariacea 



HE. Thallus usually foliaceous or fruticose, or occasionally reduced 

 to squamules. 



