PHYSCIA. 73 



A variable species, exhibiting forms, recognized generally by 

 authors as belonging to it, which should be quite as separable as 

 P. aquila ft. A perfectly smooth, brown condition, with scarcely 

 any trace of the characteristical bloom, .contrasts with another 

 pale one, more common, which is pruiuose throughout. These 

 forms of our a are now black, and now pale beneath. b has 

 only occurred to me with a black under side, and is otherwise 

 scarcely referable to the v. pityrea of authors ; which last may 

 yet occur. 



6. P. Leana, Tuckerm. j thallus meinbranaceous, smooth, 

 loosely imbricate, glaucous- cinerascent ; beneath pale, with few, 

 elongated, marginal fibrils; the loosely-intertangled, narrow, 

 flat lobes many cleft ; apothecia smallish, sub-pedicellate, with 



an entire margin. Spores ^ mic. Parmelia (Physcia) Tuck. 



in Lea Catal. PL Cincin. p. 45. Physcia, Obs. Lich. 1. c. p. 394, 

 .& inNyl. Syn. l,p. 422. 



Growing over mosses, Ohio (Lea), Tuckerman 1. c. 1848. 



With much the habit of conditions of P. speciosa this appears 

 .also to. look toward, and to be closely approached by forms of 

 .the variable P. obscura. It has only occurred once. 



7. P. stellaris (L.); thallus cartilagineous, stellate, ap- 

 pressed, whitish-glaucescent, epruinose ; beneath pale, with pale 

 fibrils; lobes sub-linear, many-cleft, rather convex, compagi- 

 nate, or discrete, without soredia; apothecia smallish to scarcely 

 middling-sized, sessile, the disk brownish-black, often grey- 

 pruinose, the margin rather entire. Spores ^^ mic. Parme- 

 lia, Fr. L. E. p. 82, a. Tuck. exs. n. 83. Physcia, Tuckerm. 

 Obs. Lich. 1, L c. p. 395, a. 



b. aipolia, Nyl. ; thallus becoming brown and finally blacken- 

 ing beneath, and clothed there, at length densely, with finally 

 black and hispid fibrils ; apothecia sub-crenate. Spores as in a. 

 Nyl. Scand. p. 111. Parmelia aipolia, Ach. Syn. p. 215. 



On trees, dead wood, rocks, and stones. Pennsylvania, Muhl. 

 Catal. 1818, and common northward to Arctic America, Richard- 

 .son ; westward to the Pacific coast, Bolander ; and southward to 

 the Gulf States, Ravenel, etc., and Mexico, Nylander. But the 

 southern plant tends to lose itself in the next member of the 



group. This well-known lichen of the northern hemisphere 



is readily recognizable in its tree-forms, but departs a little from 

 the type on rocks, where (b, aipolia) now otherwise quite similar 



