394 PROCEEDINGS OF THE AMERICAN ACADEMY 



marked, are inseparable from states of the last, we appear to have in 

 the Lichen now under consideration — which passes, without any break 

 in the connection, from the substellate and nearly horizontal form of 

 the middle of Europe (Moug. & Nestl. Cr. Yog. n. 941, with which 

 the Ohio, and most of the other North American specimens accord) 

 to the much elongated, almost filamentous, loosely decumbent states 

 of the tropics (P. leucomela, var. angustifolia, Mey. & Flot.) — the 

 extremest atypical development of our species in a centrifugal direc- 

 tion, as, in the nearly erect variety galactopliylla, in a centripetal. 

 Professor Fries first observed that this species passed into several 

 varieties (" vario modo mutatur," Lichenogr. 1. c.) in America ; and 

 did not hesitate also to refer here the P. leucomela of Middle and West- 

 ern Europe, though he retained, as specifically distinct, the narrower, 

 subtropical form. And I owe to him the suggestion that P. comosa, 

 Eschw., should be placed here, rather than under P. ciliaris. But 

 this last-named species appears itself almost too near to states of P. 

 speciosa already cited ; — differing, however, to a degree in color, and 

 receding rather towards P. aquila. 



10. P. Leana, Tuckerm. in litt. Parmelia {Physcia) Leana, Tuck, 

 in Lea, Catal. PI. Cincinn. p. 45. On trees. Ohio, Mr. Lea. Thallus 

 thin and brittle, naked and smooth on both sides ; the somewhat ascend- 

 ent, loosely imbricated lobes multifid, much as in common states of the 

 last species, with flat, nearly entire lobules, which are glaucous-fusces- 

 cent above (reminding in this respect of pale states of P. ohsciira) and 

 pale beneath, where occur a few scattered fibres at the margins of the 

 same color. The apothecia are smallish (compared with those of the 

 last species), subsessile, and entire. The spores are smaller, narrower, 

 and more acute. The Lichen appears to partake at once of the char- 

 acters of P. speciosa and P. obscura, but I cannot refer it to either. 

 Rocks and trees, Burlington, Vermont, with marginate soredia, 3fr. 

 Russell; who compares the Lichen with P. speciosa; to which Profes- 

 sor Fries considered the Ohio Lichen as approaching nearest. Rocks 

 in the "White Mountains, Mr. Oahes ; similar to the last. Trees, Texas, 

 Mr. Wright, a smaller-lobed state, like the last two, growing with P. 

 ohscura ; which is distinguishable at once, by its black and densely 

 black -fibrillose under-side. These latter states, which generally agree 

 with the described plant, appear to approach P. ohscura, much as that 

 does P. speciosa. 



