66 PAKMELIA. 



closely approximate and intertangled, the tips somewhat in- 

 curved; apothecia smallish; disk chestnut with a somewhat 



entire margin. Spores ellipsoid, -^ mic. Fr. L. E. p. 70. 



Tuckerm. Licli. Amer. n. 76. Nyl. Syn. I, p. 394. P. recurva, 

 Ach. L. U. p. 490. 



Sub-alpine (granitic) rocks in high mountains, rarely fertile. 

 White Mountains, Tuckerman Enurn. 1845. Also at Mt. Desert, 

 Maine. 



19. P. ambigua (Wulf.) Ach. ; thallus membranaceous, 

 stellate, straw-coloured, opake, besprinkled more or less densely 

 with sulphur- coloured soredia ; beneath brownish-black, shin- 

 ing, with blackening fibrils; lobes linear, applanate, dichoto- 

 mously many-cleft, rather loosely disposed ; apothecia small to 

 middling ; disk chestnut, with a sub-crenulate margin. Spores 

 oblong-ovoid, commonly curved, -j^^ mic. Spermatia acicular, 



bowed. Ach. L. U.p. 485. Fr. L. *E. p. 71. Tuckerm. Lich. 



Amer. n. 77. Nyl. Lich. Scand. p. 105. 



b. albescens, Wahl. ; whitish-ash-coloured, with white sore- 

 dia; apothecia rather larger, shining. Spores rather larger. 

 Fr. 1. c. P. hyperopta, Ach. Syn. p. 208. Th. Fr. Lich. Scand. 

 p. 120. P. aleurites, Nyl. Lich. Scand. p. 105. 



c. Halei; thallus much as in a, but the apothecia rather 

 larger, and wax-coloured, with a constantly sorediate-powdery 

 margin. Spores as in a. Parmelia, Tuckerm. in litt. 



a, on trunks, and dead wood, and also on rocks, in alpine 

 districts ; and descending, in high mountains. Arctic America 

 (Richardson), Hooker I. c. 1823. White Mountains, Tuckerman. 



British Columbia, Macoun. b, with the last. c is a southern 



lichen, found on coniferous trees from Louisiana (Hale) and 

 ;South Carolina (Eavenel) to Virginia (Tuckerman), and north- 

 ward in New Jersey (on pines, Austin), and rarely, on the 

 south shore of Massachusetts (on white cedar, Willey). 

 Spores of b, *~ mic., in all important respects like those of 

 a; and the lichen scarcely differs but in colour. These two 

 forms are high northern plants, and unknown in New England 

 except in the highest mountains ; but c, though geographically, 

 it should seem, diverse, offers very little to distinguish it. 



