g BRITISH LICHENS : 



51 Nephromium Nyl. Thallus with the cortical layer con- 

 tinuous on the lower surface: apothecia marginal, adnate to the 

 underside of the thaUus, with septate spores ; spermogones with 

 jointed sterigmata and apicaUy incrassate and ohtuse spermatia. 



52 Peltigera Willd. Thallus with the cortical layer not con- 

 tinuous on the lower surface : apothecia marginal on the upper 

 surface of the thallus, with septate spores ; spermogones unknown. 



Tribe XVI. PHYSCIEI Nyl. Thallus stellato-orbicular, rarely 

 fruticulose, internally with woolly medulla; gonidial layer con- 

 sisting of true gonidia : apothecia lecauorine. 



53. Physcia Schreh. Thallus laciniate or lobed, more or less 

 fibriUoso-rhizinose beneath : apothecia usually with bilocular spores : 

 spermogones with jointed sterigmata and oblongo-cylindrical, rarely 

 acicular spermatia. 



Tribe XVII. GYROPHOREI Nyl. Thallus usually mono- 

 phyllous, umbilicately affixed, internally with woolly medulla; 

 gonidial layer consisting of true gonidia : apothecia sublecanorine or 

 lecideine. 



54. Umbilicaria Hoffm. Thallus monophyllous, naked beneath : 

 apothecia sublecanorine, simple, with spores solitary or 2nse, murali- 

 divided ; spermogones with jointed sterigmata and cylindrical, api- 

 cally obtuse spermatia. 



55. Gyrophora Ach. Thallus monophyllous or subpolyphyllous, 

 naked or rhizinose beneath ; apothecia lecideine, compound, and 

 somewhat gyrose, with spores 8nae, simple ; spermogones as in the 

 preceding. 



Series V. PLACODEI Nyl. ThaUus crustaceous, sometimes 

 evanescent, rarely hypophlasodal ; medullary layer not filamentose : 

 apothecia lecanorine, or lecideine, or lireUajform. 



Tribe XVIII. LECANO-LECIDEEI Nyl. ThaUus crustaceous 

 (sometimes effigurate), rarely obsolete or none proper; gonidial 

 layer consisting of gonidia, rarely of gonimia : apothecia lecano- 

 rine, lecideine, or biatorine. 



Subtribe I. PANNARIEI, Nyl. ThaUus with the gonidial 

 layer consisting of gonimia. 



56. Pannaria Del. ThaUus squamulose or granulose, rarely 

 lacinioso: apothecia lecanorine, with simple spores; spermogone's 

 with jointed sterigmata and cylindrical straight spermatia. 



