— 74 — 



lobulate, or tuberculate. Spores as in P. placorodia. Spermagonia rare, when 

 present similar to those of P. placorodia. 



Specimens examined from: New Hampshire, Vermont, Massachusetts (8 towns), 

 Connecticut, Pennsylvania.^ 

 The strongly isidiose thallus, with radiate lobes, and pale under side, is 

 the distinguishing character of this species. There is no species of Cetraria 

 that could possibly be confused with it. The whitish under side should easily 

 separate it from all species of Parmelia, with the possible exception of Parmelia 

 rudecta Ach. from which it differs in the smaller thallus, the narrower lobes, and 

 the absence of white punctations. 



2a. Parmeliopsis aleurites var. diffusa (Ach.) Riddle comb. nov. 

 Parmelia Ach. Lich. Univ. 485. 18 10. not Lichen diffusus Web. 



Agreeing with the typical form of the species in color, but the lobing irreg- 

 ular, and partly imbricate, and the isidia finer, fewer, and more scattered. 

 Habitat as in the species, but commoner on the bark of conifers. 

 Specimens examined from: New Brunswick, New Hampshire, Massachusetts 

 (2 towns), New Jersey, Maryland, South Carolina, Georgia. 



According to the Vienna Code of Botanical Nomenclature (Article 53), 

 the names aleurites var. diffusa Ach. and diffusa Weber may both be retained 

 in the genus Parmeliopsis since they designate groups of different rank. P. 

 aleurites var. diffusa is always isidiose, never sorediate; while P. diffusa is never 

 isidiose, always sorediate. 



3. Parmeliopsis ambigua (Wulf.) Nyl. 



Lichen Wulfen in Jacquin Coll. Bot. 4: 239, /. 4, fig. 2. 1790. 

 Parmeliopsis Nyl. Not. Sallsk. pro F. et Fl. Fenn. Forh. n. s. 5: 121. 1866. 

 Squamaria Hoffm. PI. Lich. t. 40, figs. 3-4. 1794. good figure! 

 Parmelia ambigua Ach. Meth. Lich. 207. 1803. Tuck, Syn. N. A. L. 1: 

 66. 1882. 



Parmelia diffusa Th. Fr. Lich. Arct. 60. i860. Lich. Scand. 131. 1871. 

 Not Lichen diffusus Weber. 

 Thallus orbicular, usually 1-2 cm. in diameter, occasionally up to 5 cm., 

 closely adherent to the substratum, from ochroleucous to distinctly yellow above, 

 smooth toward the circumference, becoming rimulose and broken at the center, 

 more or less covered with an effused mass of sulphury or yellowish, powdery 

 soredia, or, in other cases, the soredia occurring in scattered, subpedicellate 

 soralia, never isidiose; beneath castaneous to black, with scattered black rhi- 

 zoids; lobes 1-2 mm. wide, more or less regularly radiate, and more deeply cleft 

 and more discrete than is usual in the two preceding species. Upper cortex 

 as in P. placorodia; lower cortex compact and chondroid, well-developed but 



^ It seems to the writer that this species must be more widely distributed than the stations 

 cited would indicate. He would be glad to receive specimens of any species of Parmeliopsis from 

 any localities not listed in this paper. Through the kindness of Prof. Bruce Fink, the writer 

 has examined the specimens upon which was based the record of Parmelia aleurites in the Lichens 

 of Minnesota (Contrib. U. S. Nat. Herb. 14: 197. 1910). They prove to belong to Parmelia auru- 

 lenta Tuck., and are, therefore, not to be included in the present group. 



