LICHENE8 441 



36. P. C rollia, Tuckerm. [Saturnine]: Thallus orbicular, 

 membranaceous, smooth, radiant, dark bluish becoming pale lead- 

 color, with elevated darker margins, and sprinkled with blackish 

 points, and isidioid branchlets; hypothallus determinate, dark- 

 caerulescent. 

 Hob. Mossy rocks: rare. Small and infertile. 



SUBSECTION 5. PSORO'MA. 



Apothecia either adrmtc, arising from the thallus, with a crenate thalline margin; 

 or immersed, arising from the hypothallus, with an entire proper margin; disk 

 Waxy; thallus of discrete foliaceous squamules, often forming a subgranulose 

 crust. 



27. P. triptophyl'la, Fr. [Worn-leaved']: Thalline scales 

 membranaceous, livid-fuscescent, stellate-expanded and lacerate- 

 ilissected, at length granulose-coralline ; hypothallus bluish-black ; 

 apothecia somewhat immersed ; disk plane, rufous-fuscous, with an 

 rect persistent margin. 



Hob. On rocks ; roots of trees, Ac, Sterile with us. 



28. P. leucosticta. Tuckerm. MS. [White-dotted] : Scales of 

 the thallus membranaceous, at first expanded and imbricate, linear- 

 multifid, glaucous-fuscescent, or at length dark fuscous ; hypo- 

 thallus black; apothecia rather immersed; disk convex, from 

 rufous becoming blackish, with a persistent granulate margin. 

 Hab, On rocks, and bases of trunks, among mosses, Ac. 



Obs. This species has been heretofore confounded with the pre- 

 ceding, and some other allied forms. 



SECTION 3. 



Thallus crustaceous, lobate at the circumference, or wholly squamulose and 

 ffigurate. 



SUBSECTION 6. PLACO^DIUM. 



Apothecia plano-scutellaeform, elevated; disk without proper margin, naked; 

 tha&vA as above (thalline, margin often colored like the disk.) 



29. P. saxicola, Ach. [Rock] : Thallus cartilagineous, ap- 

 pressed, areolate-squamulose, pale-greenish ; the circumference of 

 somewhat plane radiose-lobate concrete laciniae; apothecia ap- 

 pressed; disk yellowish-fulvous; margin thin, at length crenate. 

 Hab. On rocks and stones. 



30. P. clirysomelaeiia, Ach. [Gvlden+black]: Thallus 

 crustaceous, areolate, yellow; areolae flat, submembranaceous, 

 somewhat lobate, here and there discrete; apothecia appressed; 

 disk plane, sanguineous-black ; thalline margin elevated, subrugose, 

 at length flexuose. 



Hab. On rocks, near Pierce's Paper Mill, Kennett. 



SECTION 4. 



Thattus crustaceous, uniform. Circumference similar, or the hypothallus some- 

 times fibrillose-radiaut. 



SUBSECTION 7. PATELLA^RIA. 



Apothecia sessile, scutellaeform, margin persistent; disk somewhat plane, without 

 proper margin, not caesious-pruinoee ; thattus adnate to an indeterminate, mostly 

 black, hypothallus. 



