24 HCHENES OF THE NORTHERN STATES 



closed, somewhat waxy. Thallus expanded horizontally from a centre, 

 two-sided, of various form, upon a hypothallus. Fr. Lichenogr. p. 56. 



Synopsis of the Sections. 



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

 which is discrete from the matrix. 



Subsect. I. Imbkicaeia, Fr. — Apothecia elevated, subpedicellate, 

 regular ; disk very thin, naked, placed upon the gonimous layer. 

 Thallus imbricate-foliaceous ; often black-dotted from abortion 

 of the apothecia. — Sp. 1 - 24. 

 Subsect. II. Physcia, Fr. — Apothecia at first closed, at length de- 

 hiscent. Disk thickish, waxy, placed upon the medullary layer, 

 Thallus normally foliaceous ; ascendant or stellate ; fibrillose 

 on the under side. 

 * Thallus normally ascendant, or loosely decumbent ; apoth. some- 

 what obliquely marginate. — Sp. 25. 

 ** Thallus normally stellate-appressed ; apoth. plane. — Sp. 26 - 

 33. 



Sect. II. Thallus subfoliaceous, at length compacted into a conglom- 

 erate, subgranulose crust ; arising from a fibrillose (rarely ob- 

 solete) hypothallus, which is adnate to the matrix. 



Subsect. III. Pyxine, Tuckerm. — Apothecia erumpent, at first 

 closed, palish ; becoming patellffiform, and, with the altered 

 thalline margin, black ; finally cephaloid, excluding the mar- 

 gin. Thallus subfoliaceous, imbricate-laciniate, at length crus 

 taceous-concrete at the centre, on a black, fibrillose hypothal 

 lus. — Sp. 34. 



Subsect. IV. Amphiloma, Fr. — Apothecia erumpent, somewhat cor 

 onate with an accessory thalline margin. Disk wa.xy, thickish 

 naked. Thallus foliaceous, somewhat monopliyllous, rounded 

 at length crustaceous-compact at the centre, placed on a spongy- 

 pannose hypothallus. — Sp. 35-38. 



Subsect. V. PsoROMA, Fr. — Apothecia for the most part two-formed 

 adnate or immersed ; arising in the one case from the thallus, 

 with a crenate-thalline margin ; and in the other from the hy 

 pothallus, with an entire proper margin. Disk waxy. Thallus 

 of discrete, foliaceous squamules, arising from a common hy 

 pothallus ; often at the centre, or wholly, concrete in a subgran 

 ulose crust. — Sp. 39 - 41. 



