OF ARTS AND SCIENCES. 225 



Willd. ! P. venusta, Hals. ^ Auct. Amer. P. pulverulenia, Muhl. 

 Tuckerm. Lich. N. E. I. c. 



Trunks, rocks, and upon mosses ; Bear Lake and elsewhere in 

 Arctic America, .RicA. (Herb. Hook. !). — ^, trunks and rocks; New 

 England to Pennsylvania ! often isidioid-efflorescent. 



28. P. hypoleuca, Muhl. Th. cartilagineous, substellate, glabrous, 

 naked, glaucous-virescent (and white) ; very vs^hite on the under side, 

 with scattered black fibres ; Jacinise sublinear, approximate, imbricate, 

 multifid, plano-convex, margins naked ; apoth. elevated, disk at length 

 black, naked, with an inflexed, crenulate or foliose margin. Muhl. 

 Catal. p. 105, ^ Eaton Man. Bot. p. 516. Tuckerm. Further Enmn. 

 I. c. p. speciosa., /?. hypoleuca, Ach. ! Syn. p. 211. 



Trunks, fertile. Pennsylvania, Muhl. ! and northward to New Eng- 

 land. 



29. P. speciosa, Ach. Th. cartilagineous-membranaceous, substel- 

 late, glabrous, greenish-glaucous (and white) ; very white beneath, with 

 numerous pale fibres ; lacinise linear, somewhat concavo-plane, imbri- 

 cate, incised-ramose, crenate, ciliate-fibrillose, margins often ascend- 

 ant, green-pulverulent ; ' apoth. subsessile, margin incurved, crenate, 

 disk rufous-fuscous, nearly naked.' Fr. Lichenogr. p. 80. 



Trunks and mossy rocks in woods, infertile ; New England. Penn- 

 sylvania, Muhl. 



30. P. congruens, Ach. Th. coriaceous-membranaceous, whitish- 

 pallescent ; on the under side cinereous-fuscescent, with fibres of the 

 same color ; lacinice laxly-imbricate, flexuous, multifid, recurved at the 

 margins, convex, becoming more plane in the circumference, crenate ; 

 apoth. elevated, concave, livid-fuscescent, subpruinose, with a thin, in- 

 flexed, at length flexuous margin. Ach. Lichenogr. p. 491. Swartz 

 Lich. Amer. p. b 8f t. 4. Ach. Syn. p. 207. 



Trunks, New England ; Swartz, I. c. I have a Lichen from the 

 White Mountains resembling this, except that the under side as well as 

 the fibres are black. 



31. P. stellaris, Wallr. Th. subcartilagineous, naked, not pruinose, 

 glaucescent ; whitish on the under side, with dark fibres ; lacinise sub- 

 linear, multifid ; apoth. sessile, disk fuscous-black, subpruinose, margin 

 somewhat tumid, subentire. Fr. Lichenogr. p. 82. — a. {stellari-expan- 

 sa), Fr. ; th. stellate-expanded, fibres shorter. Fr. I. c P. stellaris, aipo- 



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