178 PLACODIUM. 



concolorous. Blastema, Mass. Blast. ; Koerb. Parerg. p. 129. 



Placodium, Anz. P. ferrugineum, v. nigricans, Tuck, in litt. 



c. discolor, Willey in litt. ; tliallus thin ; pale yellowish ex- 

 cept where blackened by the hypothallus ; bursting into heaps 

 of yellow granules ; apothecia biatorine. 



d. Wrightii, Tuckerm. in litt.} thallus thickish; whitish- 

 glaucescent besprinkled densely with white granules which 

 become isidioid j apothecia appressed, lecanorine, zeorine ; and 

 biatorine, soon flexuous ; the disk dark-red. 



Trees, dead wood, and rocks, as also, in high northern 

 regions, on mosses, common throughout our territory, a. 

 Greenland ( Vahl), Th. Fries I. c. 1861 ; as also in Alaska, Dr. 

 Kellogg. New England to Virginia, Tuckerman. Illinois, Hall. 

 N. Carolina, Curtis. Georgia, Ravenel. Alabama, Peters. 

 Texas, Wright. California (where among other rupicoline 

 states there is one, f. Bolanderi with obsolete thallus, but bright 

 vermillion-coloured apothecia, comparable with the f. miniacea, 

 Mihi, Obs. Lich. 4, I. c. p. 171, on bark, in South Africa, which 

 last differs in nothing but the colour from the S. African a), 



Bolander. Oregon, Hall. b, on coniferous trees, especially 



Red Cedar, and also on Elm, Massachusetts, Tuckerman. Ver- 

 mont, Russell. Maryland, Tuckerman. c, on Tupelo, and 



Oak, Mount Desert, Maine, Tuckerman. New Bedford, Willey. 



d, on trees, Western Texas and New Mexico, Wright. 



The forms c, and d, deserve separate notice as much perhaps 

 as b, which is now recognized as European by authors. And 

 other probable conditions of the species, beside the curious f. 

 Bolanderi, have been sent to me from the Pacific Coast, but are 

 not as yet clear. 



21. P. diphasium, Tuckerm. ; thallus sub-tartareous, origi- 

 nally contiguous, becoming rugged and verrucose-granulate ; 

 greenish - glaucescent ; apothecia small, adnate, lecanorine; 

 disk plano-convex, from wax-coloured becoming reddish-brown 

 and livid-black, thinly green-pruinose, bordered now by a thin 

 proper margin, and always inclosed by a depressed, crenulate 



thalline one. Spores ovoid - ellipsoid, ^ mic. Lecanora, 



Suppl. 1,1. c. p. 426. Placodium, Obs. Lich. 3, I. c. p. 287. 



On various trees, Texas ( Wright), Tuckerman I. c. 1858. 



22. P. camptidium, Tuckerm. ; thallus thin and sub-cartila- 

 gineous, originally contiguous, from smooth becoming chinky 



