384 PROCEEDINGS OF THE AMERICAN ACADEMY 



Lichen before us differs too much from the character of P. congniens, 

 and the figure in Swartz's work, to be referred to it. Our plant has 

 nothing of the look of a tree-lichen, and probably never inhabits trees ; 

 and there is little i*eason to suppose that it occurs in New England. 



PHYSCIA, Njl. — This genus, as limited by Dr. Nylander, in- 

 eludes, beside the sharply defined section of Parmelia, of the same 

 name, of Fries, and the nearly akin group of Lichens represented 

 by P. parietina {Physcia, Koerb. pr. p.), also the more receding, ever- 

 niiform, subpendulous group {Evernice sp., Fr.) represented here as 

 yet only by P. jiavicans. So far as this species is concerned, it 

 appears far from diificult to connect it very closely with forms of 

 P. chrysophthalma, and so with the genus. I propose here to review 

 briefly all the North American Lichens known, referable to Physcia ; 

 and especially to consider what is probably the true rank of a number 

 of species described by authors from North American specimens. 



The genus, with us, falls into two great sections, separated by color, 

 and also by the spores ; and between these two, P. euploca, from Tex- 

 as, appears to stand by itself. The first of these sections is made up of 

 P. parietina, and the Lichens related to it, distinguished by the more or 

 less yellow color of the thallus, and the colorless spores, in which the 

 contained fluid matter, or protoplasm, separates finally into two opposite 

 roundish masses, or sporoblasts, connected often by a narrow isthmus 

 (sporce pokiri-dyllastce, Koerb. Syst. Lich. Germ. p. 90). From this 

 group, P. euploca differs in its glaucous-fuscescent coloration, and simply 

 once-septate spores, which are still colorless. And the large remain- 

 ing section {Physcia, Fr.) is well defined by the glaucous-cinerascent 

 (or at length fuscescent) thallus, and once-septate fuscescent spores. 



§ I. Species Jlavescentes sporis incolorihus p>olari-dyhlastis. 



1. P. CHRYSOPHTHALMA (L.), DC, a. Parmelia chrysophthalma, 

 Auct. ; Moug. & Nestl. Cr. Vog. n. 254 ; Tuckerm. Lich. Exs. n. 80. 

 On trunks and branches of trees, especially near the coast ; and also 

 rarely inland. North America, Jacquin (Collect. 1, p. 117, t. 4), 1786. 

 Hoffmann (PL Lich. 2, p. 23, tab. 31, f. 1), 1794. Pennsylvania, 

 Muhlenberg. New York, Torrey. New England to Annapolis, Mary- 

 land ; and westward to Illinois, 3fr. Russell, and Minnesota, 3fr. Lap- 

 ham. Thickets and bottoms of the Blanco, Texas, Mr. Wright. 



Var. /3. PUBEKA, Wallr. Flecht. 2, p. 333 ; Nyl. Enum. Gen. in 

 Act. Cherb., V. p. lOG. Borrera pubera, Ach. Licheuogr. p. 502. On 



