32 CETRARIA. 



11. C. nivalis (L.) Ach. ; thallus tufted, erect, or erectish, re tic- 

 ulately lacunose, much- and sinuately-laciniate, the lobes, which 

 are at length many-cleft above, widely more or less canaliculate ; 

 straw-coloured, stained commonly yellowish at the base, smooth ; 

 apothecia ample to large, adnate to the upper side of the lobes, 

 disk yellowish-flesh-coloured, margin crenulate. Spores ellip- 

 soid, -yj- mic. Spermogones and spermatia as in the last. 



Ach. L. U. p. 510. Fr. L. E. p. 38. Nyl. Syn. p. 1, 302. 



On the earth in alpine districts. Arctic America (Eichard- 

 son), Hooker I. c. 1823. White Mountains, Tuckerman. Rocky 

 Mountains, Hall. 



* * * Thallus depressed, expanded, submembranaceous. 

 a. Stock of C. s&pincola. 



12. C. aleurites (Ach.) Th. Fr. ; thallus membranaceous, 

 foliaceous, many-cleft, besprinkled with isidioid granules, and 

 crowded finally, at the centre, into a plicate, densely granulate 

 crust ; whitish- or at length cinereous-glaucescent ; beneath pale, 

 wrinkled, beset with scattered, brown fibrils; lobes sinuate- 

 laciniate, with rounded and crenate, or more deeply divided 

 tips ; apothecia marginal, ample, from pale at length chestnut- 

 brown, externally, and the thin margin as well, granulate like 

 the thallus. Spores rounded and ellipsoid, ^ ^ mic. Spermatia 



oblong, thickened at the ends. Th. Fr. Lich. Scand. l,p 109. 



Parmelia, Ach. L. U. p. 484. Fr. L. E. p. 62. P. placorodia, 

 Nyl. Scand. p. 106. 



b. placorodia ; smooth ; apothecia crenulate, at length much 



dilated. Cetraria, Tuckerm. Syn. N. Eng. p. 16. Parmelia, 



Ach. Syn. p. 196. 



Trees, and dead wood. a. on pines, and common on rails, in 

 the northern States, Halsey View, 1823. Maryland, Tuckerman. 



Mountains of South Carolina, Ravenel. b. also upon pines, 



and rails, in the Northern and Middle States, Mulilenberg 

 Catal. 1818 ; and southward to Maryland. Associable in gen- 

 eral habit, and in the peculiar features of the under side, at once 

 with the species next following, as especially with C. aurescens. 

 The spermogones, and spermatia, agree with those of the pres- 

 ent cluster, as first pointed out by Dr. Fries ; and the former are 

 sufficiently obvious in b, though exceedingly rare in a. The 

 description of his Parmelia aleurites by Acharius (L c.) appears 

 to point to our a, much rather than to Parmelia hyperopta ; and 



