58 PAKMELIA. 



and still narrower divisions. The effect of these slight modifi- 

 cations is yet at length so marked as to obscure the species ; and 

 our plant becomes thus better comparable in almost everything- 

 except size, especially of the spores, with P. Icevigata; while, at 

 the same time, the narrowed conditions are easily seen to pass 

 imperceptibly into the wider and more typical ; &, being thus to 

 be taken for an American variety of P. tiliacea, determines tb& 

 place of c, which differs from b only in being straw-coloured, d 

 is also microphylline, or similar to &, in the only specimen as yet 

 observed ; but the internal coloration which distinguishes it may 

 not prove to be confined to such narrow states. It appears im- 

 possible, in any large view, whether of P. sulpliurata, P. auru- 

 lenta, or the present, to assign any other than a subordinate- 

 value to the modifications in these lichens, of the medullary 

 colour. 



6. P. Texana, Tuckerm.; thallus narrowed, coriaceous-mem- 

 branaceous, reticulately rimose, cinereous- glaucescent ; beneath 

 black, papillate, the fibrils obsolete; lobes contiguous, plano-con- 

 vex, rat her dilated at the periphery and lacero-crenate or lobulate, 

 besprinkled with rounded, at length confluent soredia; apothe- 

 cia middling-sized ; disk chestnut, with an entire margin. Spores- 

 ellipsoid, 4-^-mic. Suppl. 1, /. c. p. 424. 



On dead wood; thickets of the Blanco; Texas (Wrigli t) r 

 Tuckerman I. c. 1858. 



Intermediate between the last species and the next : but, on> 

 the whole, best comparable with small forms of P. Borreri, b r 

 from the same region. 



7. P. Borreri, Turn.; thallus soon narrowed, coriaceous- 

 membranaceous, more or less reticulately rugose, and beset with 

 rounded soredia; cinereous-glaucescent ; beneath pale-brown 

 (becoming darker), with now dense, white (or blackening) fibrils ; 

 lobes of the periphery rather dilated and rounded, cut-crenate ; 

 apothecia middling to large, chestnut, with an entire margin. 



Spores rounded-ellipsoid, -^ mic. Turn, in Linn. Trans. 9 r 



p. 148. Ach. L. U. p. 461. " Fr. L. E. p. 60. Nyl. Syn. 1, p. 389. 

 P. Borreri, * hypoleucites, Nyl. Syn. 1, p. 389. e descr. P. Bolli- 

 ana, Mull. Flora, 1877, n. 5. 



b. rudecta, Tuckerm. ; thallus beset with isidioid granules and 



branchlets; the lobes now more divided. Syn. Lich, N. Eng. 



p. 26. P. rudecta, a, Ack. ! Syn. p. 197. 



c. hypomela ; blackening beneath. 



