176 PLACODIUM. 



small, becoming convex ; the yellowish-orange disk soon exclud- 

 ing the thalline margin, but bordered more or less by a thin 



proper one. Spores as in a, but smaller. Nyl. 1. c. Fr. I. c. 



var. o, and c. 



Throughout our territory, common : a, on trees, as also on 

 dead wood, and mosses, and probably on stones. Northern and 

 middle States, Muhlenberg Catal 1818. Arctic America (on 

 mosses), Wright. Athabasca Lake, Macoun. Canada, etc., 

 Agassiz. Ohio, Lea. Illinois, Hall. Virginia, Tuckerman. Caro- 

 lina and Georgia, Eavenel. Alabama & Arkansas, Peters. Lou- 

 isiana, Hale. Texas, Wright. California, Bolander. Oregon, 

 Sail &, on granitic rocks. New England, Frost, etc. Vir- 

 ginia, Curtis. This variety is a well-marked lichen which has 

 been referred (in Frost's original specimens) to P. ferrugineum 

 (v. fusco-atrum, Bayerh. ; Zw. exs. n. 96 ! ) by an European 

 lichenologist of experience : but I decidedly prefer the present 

 place for our plant ; and Koerber (Syst. p. 127) has taken a sim- 

 ilar view of Von Zwackh's. Whether ours is to be kept separate 

 or not, must depend upon a larger view of the foreign one than 



I am able to take. c differs from a, much as a Biatora from a 



Lecanora, and is now often separated as a species, but with 

 hardly sufficient reason. A similar lichen, which is in fact sub- 

 sumed under his var.pyracea, by Nylander 1. c. (the Lecidea ulmi- 

 cola of Borrer! in Hook. Brit. Fl. p. 185, and theCaloplaca luteo- 

 alba of Th. Fr. Scand. p. 190), exhibits, it is supposed always, 

 spores varying from the type in having the sporoblasts approxi- 

 mate ; but has not occurred here. 



17. P. Jungermannice (Vahl) ; thallus encrusting mosses, very 

 thin; whitish or cinerascent; apothecia middling to smallish, 

 crowded, sessile, flattish, now lecanorine but soon taking on a 

 biatorine aspect ; the orange, finally fulvous, sub-pruinose disk 

 becoming tumid, and the at first stout, entire, or flexuous mar- 

 gin thinning out and disappearing. Spores ellipsoid, ^ mic. 



Caloplaca, Th. Fr. Scand. p. 179. Lecanora fulvolutea, Nyl. 



Scand. p. 146. 



On the earth, upon mosses, Arctic America. Greenland ( Vahl), 

 Th. Fries 1. c. 1861. Great Bear Lake, etc., Richardson e Leight. 

 I c. Islands of Behrmg's Straits, Wright. British Columbia, 

 Macoun. 



18. P. nivale (Koerb.) ; thallus much as in the last, but often 



