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 obtuse 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 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-cylindrical, rarely 
aciculdr 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 2nx, 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 8ne, simple; spermogones as in the 
preceding. 
Series V. PEACODEI Nyl. Thallus crustaceous, sometimes 
evanescent, rarely hypophleodal ; medullary layer not filamentose : 
apothecia lecanorine, or lecideine, or lirelleform, 
Tribe XVIII. LECANO-LECIDEEI Nyl. Thallus 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. Thallus with the gonidial 
layer consisting of gonimia. 
56. Pannaria Del. Thallus squamulose or granulose, rarely 
laciniose: apothecia lecanorine, with simple spores; spermogones 
with jointed sterigmata and cylindrical straight spermatia. 
