72 HERRE 



very diverse, but no mazaedium 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 Caloplacacece 



CC. Thallus f ohaceous or f ruticose, corticated Theloschistacecs 



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



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



without cortex BuelliacecB 



DD. Thallus foliaceous or fruticose, corticated Physciacece 



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. Algse Nostoc; apothecia sessile, dish-like CollemacecB 



FF. Algae not Nostoc. 

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



EphehacecB 

 GG. Algsd Gloeocapsa; apothecia often not visible, apparently pyre- 



nocarpous, urn or dish-like PyrenopsidacecB 



EE. Thallus not gelatinous when wet. 

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

 the hyphas of the hypothallus or medulla. 



/. Thallus with Trentepohlia algae Lecanactidacece. 



II. Thallus with Pleurococcus or Palmella algae. 

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



ine AcarosporacecE 



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



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



LecidacecB 

 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 DiploschistaceoB 



LL. Proper margin wanting or poorly developed and clear; 

 thalline margin well developed. 



M. Apothecia sessile, the disk large LecanoracecB 



MM. Apothecia sohtary or several, enclosed in thalline 



warts; disk usually very small PertusariacetB 



HH. Thallus usually foliaceous or fruticose, or occasionally reduced 

 to squamules. 



