PLACODIUM. 175 



sold, ^ mic. Parmelia, Fr. L. E. p. 165, a. Lecanora, Nyl. 



Scand' p. 142. 



Trees and rocks, as also on dead wood, throughout. Northern 

 and middle States, Muhleriberg Catal. 1818. Arctic America, 

 Ricliardson. Illinois, Kansas, and Missouri, Hall. Arkansas, 

 Peters. Maryland and Virginia, Tuckerman. Carolina and 

 Georgia, Ravenel. Alabama, Peters. Louisiana, Hale. Texas, 

 Wright. California, Bolander ; occurring now on cow-dung, Dr. 

 J. G. Cooper. 



15. P. rupestre (Scop.) Br. & Rostr. ; thallus tartareous, 

 rimose-areolate ; ash - coloured ; often much reduced and at 

 length obsolete ; apothecia smallish, convex, adnate, biatorine, 

 but the proper margin soon disappearing; wax-coloured, and 

 tawny, becoming olivaceous-brown, and blackening. Spores 



ellipsoid, simple, -jj^mic. Lecanora calva, Nyl. Scand.p. 147. 



Lecidea rupestris, Th. Fr. Scand. p. 423. 



Calcareous rocks. New York, Tuckerman Gen. 1872. Ver- 

 mont, Messrs. Russell and Frost. Georgia, Ravenel. Alabama, 



Peters. Spores commonly simple, but now rather suggestive 



of the type of the present group ; from which the lichen cannot 

 naturally be separated. 



16. P. cerinum (Hedw.) Naeg. & Hepp.; thallus originally 

 contiguous, becoming chinky, and warted, and now sub-areo- 

 late ; from pale- at length very dark-ash-coloured, or leaden- 

 gray, or now disappearing; upon a bluish-black hypothallus; 

 apothecia middling - sized to small, lecanorine, sessile, often 

 rather elevated; wax -coloured, reddish - fulvous, olivaceous- 

 brown, or at length livid, sub-pruinose, the thin, opake thalline 

 margin often well distinguished in colour from the disk, but at 

 length concolorous, for the most part entire. Spores ellipsoid, 



^ m ic. Parmelia, Fr. L. E. p. 168, b & c excl Tuck, exs. 



n. 93. Lecanora^ Nyl. Scand. p. 144. 



b. sideritis, Tuckerm. in litt. ; thallus thickened ; of contigu- 

 ous, scale-like, becoming convex and warty areoles ; iron-gray ; 

 apothecia appressed, the fulvous-ferrugineous, naked disk soon 

 turgid and excluding the thin thalline margin. Spores as in a, 

 but scarcely as large. Lecanora, Tuckerm. Suppl. 1, 1. c. p. 426. 



c. pyracea, Nyl. ; thallus thin ; whitish ash-coloured when not 

 obsolete, the hypothallus scarcely differing in colour ; apothecia 



