PANNARIA. 117 



* Amphiloma. Thallus foliaceous, membranaceous, round- 

 lobed, softish, and deliquescent ; upon a blackening hypothallus. 

 Gonimous system of gonidia. (Amphiloma, Nyl., emend.) 



1. P. lanuginosa ( Ach.) Koerb. ; thallus orbicular, white, pow- 

 dery; the lobation distinct only at the circumference, and often 

 disappearing, when only a crust, or cushion-like mass is left, 

 determinable by the delicate hypothallus; apothecia scarcely 



known. Parmelia, Ach. L. U. p. 465. Farm. (Ampkiloma) 



FT. L. E. p. 88. 



Rocks, New England, Tuckerman Syn. N. E. 1848. Canada, 

 Drummond. New York, Peck. Blue Ridge, Virginia, Tucker- 

 man. Louisiana, Hale. The pale-sulphur-coloured tint so 



common in the European lichen has not been observed by me in 

 the North American ; but the hypothallus is quite the same in 

 both, and the general aspect. 



* * Psoroma. Thallus squamulose. Hypothallus obsolete. 

 Gonimous system of gonidia. Apothecia lecanorine (Psoroma, 



Nyl., olim.). The only northern species is most readily 



associable with Pannaria brunnea; and, notwithstanding the 

 difference in the gonidia, cannot be called at home in any 

 other genus. The group attains its full development in the aus- 

 tral and antarctic regions, where species with laciniate-multifid 

 and even frondose thallus, and otherwise remarkably differenced, 

 occur. 



2. P. hypnorum (Hoffm.) Koerb. ; thallus of minute, rounded, 

 at length granulate-crenate, ascendant and imbricate squamules; 

 from yellowish becoming reddish-brown (with age dark ash-col- 

 oured) ; beneath pale, and naked ; apothecia middling to ample, 

 sessile; the disk red-brown; the thin, elevated margin crenate, 

 and at length granulate-squamulose. Spores ovoid-ellipsoid and 



oblong, simple, decolorate, - mic. Parmelia, Fr. L. E.p. 98. 



Tuck. Exs. n. 20. Psoroma, Nyl. Scand. p. 121. 



On the earth, growing over mosses and twigs, in alpine dis- 

 tricts. Arctic America (Richardson), Hooker I. c. 1823. Rocky 

 Mountains, Hall. Newfoundland, Despreaux. White Mount- 

 ains of N. Eng., Tucker man. 



* * * Euopsls. Thallus tartareous, peltate. Hypothal- 

 lus obsolete. Gonimous system constituted of both gonidia and 

 gonimia. Apothecia lecanorine. (Euopsis, Nyl. emend. ) The 



