4 KEY TO THE ARRANGEMENT. 



side of extended lobes, the margin torn-crenate. 

 Spores from fusiform at length acicular, 4-plurilocular, 

 at length colourless. Thallus frondose, villous and 

 veiny beneath. Gonimous layer, in several species, 

 composed of gonidia; in the larger number, of 

 gonimia. 



17. ERIODERMA. Apothecia scutellaeforrn, marginal. 



Spores ovoid-ellipsoid, simple, at length colourless. 

 Thallus frondose, villous beneath, where it is clothed, 

 more or less, with a pannose hypothallus. Gonimous 

 layer constituted of gonimia. 



18. SOLORINA. Apothecia orbicular, innate in the upper 



side of the thallus, the margin disappearing. Spores 

 from ellipsoid fusiform - oblong, bilocular, brown. 

 Thallus frondose, villous beneath. Gonimous layer 

 constituted of gonidia and gonimia. 



Earn. 5. PAIS1NAEIEI. Thallus horizontal, frondose-folia- 

 ceous, or, most commonly, squamulose ; mostly more or 

 less lead-coloured j imposed upon a conspicuous hypo- 

 thallus (now obsolete). Gonimous layer almost univer- 

 sally (in our species) of gonimia. 



19. EKDOCARPISCUM. Apothecia indicated only, for the 



most part, by an ostiole, but finally emerging and 

 scutellseform. Spores very minute, simple, colourless, 

 numerous in the thekes. Thallus foliaceous, peltate, 

 the hypothallus deficient. Gonimous layer of gonimia. 



20. HEPPIA. Apothecia orbicular, immarginate, more or 



less sunken in the minute, frondose-squamulose thal- 

 lus. Hypothallus obsolete. Spores ovoid -oblong, 

 simple, without colour. Gonimous layer of gonimia. 



21. PHYSMA. Apothecia scutellseform. Spores ellipsoid, 



simple, colourless. Thallus foliaceous, clothed beneath 

 with a nap-like hypothallus. Gonimous layer of 

 gonimia, characterized much as in Collema. 



