OF ARTS AND SCIENCES. 217 



Sect. III. Thallus crustaceous, lobed at the circumference, or wholly 

 squamulose-effigurate. Hypothallus smooth, adnate to the ma- 

 trix, often confused with the thallus. 



Subsect. VI. Placodiubi, Fr. — Apothecia plano-scuteliiform, elevat- 

 ed, disk whhout proper margin, naked. Thallus as above. 

 (Thalline margin often colored like the disk.) — Sp. 42-47. 



Subsect. VII. Psora, Fr. — Apothecia innate, at first somewhat ur- 

 ceolate, afterwards scutelliform. Disk with a proper margin 

 (visible at least in the younger apothecia), normally at first 

 csesious-pruinose. Thallus as above. — Sp. 48 - 50. 



Sect. IV. Thallus crustaceous, uniform. Circumference similar, or 

 the hypothallus sometimes fibrillose- radiant. 



Subsect. VIII. Fatellakia, Fr. — Apothecia regular, scutelliform, 

 sessile, the thalHne margin persistent. Lamina of the disk 

 somewhat plane, without proper margin. Thallus crustaceous, 

 adnate to an indeterminate, mostly black hypothallus. Disk not 

 csesious-pruinose. — Sp. 51 — 66. 



Subsect. IX. Urceolaria, Fr. — Apothecia innate in the crust, or 

 immersed in protuberant warts. Lamina urceolate, or protu- 

 berant, verrucceform, blackish, normally csesious-pruinose, mar- 

 ginate. Thallus ci'ustaceous ; the whitish hypothallus confused 

 with the thallus, or often fibrillose and radiant. — Sp. 67-70. 



Sect. I. The fibrillose hypothallus adnate to the foliaceous thallus. 

 Subsect. I. Imbricaria, Fr. 

 Series I. Glaucescentes, Fr. 

 1. P. crinita, Ach. Thallus submembranaceous, suborbicular, glau- 

 cous-fuscescent (the whole thallus, as well as the apothecia, beset with 

 isidioid granules and branchlets) ; black and somewhat smooth on the 

 under side, and here and there black-fibrillose ; lobes plane, with some- 

 what ascendant, erose-crenate, ciliate margins ; apothecia (imperforate) 

 marginal, subpedicellate,cyathiform, wuh a thin, inflexed,crenulate mar- 

 gin, at length explanate, large. Ach. ! Syn. p. 196. P. perforata., /?. Fr. 

 Trunks, &c., fertile ; New England. New York, Torrey. Penn- 

 sylvania, Muhl. There appear to be indications of other differences 

 beside the isidioid efflorescence to distinguish this from P. perforata. 

 The latter is perfectly normal with us. 



28 I 



