8 BRITISH LICHENS ; 



51. Nephromium Nyl. Thallus with the cortical layer con- 

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

 underside of the thallus, with septate spores; spermogones with 

 jointed sterigmata and apically 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 XYI. PHYSCIEI Nyl. Thallus stellato-orbicular, rarely 

 fruticulose, internally with wooUy medulla; gonidial layer con- 

 sisting of true gonidia : apothecia lecanorine. 



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

 fibrilloso-rhizinose beneath : apothecia usually with bilocular spores : 

 spermogones with jointed sterigmata and oblongo-cyhndrical, rarely 

 acicular spermatia. 



Tribe XVII. GYROPHOREI Nyl. ThaUus usuaUy mono- 

 phyllous, umbilicately affixed, internally with wooUy medulla; 

 gonidial layer consisting of true gonidia : apothecia sublecanorine or 

 lecideine. 



54. Umbilicaria Hoffm. Thallus monophyUous, naked beneath : 

 apothecia sublecanorine, simple, with spores soUtary or 2n8e, murali- 

 divided ; spermogones with jointed sterigmata and cyhndrical, api- 

 caUy obtuse spermatia. 



55. Gyrophora Ach. ThaUus monophj-Uous or subpolyphyUous, 

 naked or rhizinose beneath ; apothecia lecideine, compound, and 

 somewhat gyrose, with spores Snse, simple : spermogones as in the 

 preceding. 



Series V. PLACODEI Nyl. Thallus cnistaceous, sometimes 

 evanescent, rarely hypophlseodal ; medullary layer not fiJamentose : 

 apothecia lecanorine, or lecideine, or lirellseform. 



Tribe XYIII. LECANO-LECIDEEI %1. ThaUus cnistaceous 

 (sometimes cffigurate), 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 granulosc, rarely 

 laciniose : apothecia lecanorine, with simple spores ; spermogones 

 with jointed sterigmata and cylindrical straight spermatia. 



