1G6 PROCEEDINGS OF THE AMERICAN ACADEMY 



XV. 



OBSERVATIONES LICHENOLOGIC^, No. 4. 

 OBSERVATIONS ON NORTH AMERICAN AND OTHER LICHENS. 



By Edward Tuckerman, M.A. 



(Continued from Vol. VI. p. 287.) 



Read May 29, 1877. 



Pyxine. The black hypothecium of Physcia picta distinguishes it 

 from the rest of the geuus, and suggests an association with Pyxine ; 

 to which, indeed, this Physcia is in other respects significantly similar. 

 Pyxine, thus enlarged, falls into two sections : — 



1. DiRiNARiA. Apothecia scutellgeform. Thallus normally white 

 within, P. picta (S w.). — The species should probably include Parmelia 

 conflaens (Fr.) united by Nylander with the earlier P. cegialita, Ach. : 

 at least no difference seems to be noted. — P. picta occurs now safi'rou- 

 colored within (v. erytkrocardia, Tuckerm. in AYright Lich. Guh. n. 94) 

 like Physcia ohscura ; but also probably to be compared in this respect 

 with Pyxine coccinea, M. & V. d. B., of the next section. 



2. Pyxine proper. Apothecia (similar at first, in a tropical form, 

 to those of the first section, but finally) blackening all over and leci- 

 deoid. Thallus soon more or less yellowish within. P. cocoes (Sw.) 

 — The other supposed species of this section are scarcely well defined. 

 P. cocoes V. Meissneri {P. 3Ieissneri of these Obs. 1, in Proc. Acad. 

 Amer. 4, p. 400) might indeed often be taken, and was taken by 

 Meissner, for a Physcia ; but the margin of the apothecium soon black- 

 ens, when tlie lichen is ill distinguishable from the oi'iginal Lichen 

 Cocoes (Sw. Lich. Amer. t. 2). — Another of the more delicate tropical 

 exhibitions of Pyxine is marked by the reticulate wrinkling of the 

 upper surface {P. retirugella Nyl. Lich. exot.) but otherwise is close 

 enough to P. Cocoes. — From this may well seem more separable the 

 larger lichen, extending far northward, which furnished Fries the type 

 of the genus (v. sorediata, Tuckerm. 1. c), but this differs only in size, 

 and not always in that respect, from forms easily included in P. Cocoes. 



