204 Rev. W. A* Leigbton on the British Graphidese, 



Opegrapka atra, a. stenocarpa (in^part). Fries, L. Ref. 367 (1831); Sumnia 

 Fl. Scand. 118. 



atra, /3. syngrapta, Wallr. Crypt. Germ. 1. 326 (1831). 



Lichen deniqrata, Ach. Prodr. 24 (1798). 



Opegrapha denigrata, Ach. Meth. 27 (1803) ; Sm. E. Bot. 1753. (The upper 

 left-hand figure may perhaps belong to this, but the other figures are 

 doubtful having a black marginal line, and one of the magnified sec- 

 tions having the structure of a Graphis, the other of an Opegrapha.) 

 Mart. Fl. Erlang. 280; Wahl. Fl. Suec. 860 ; Fingerhuth, Fl. Eiffl. 23. 



denigrata, ec. ^ jS. atra, Ach. L. Univ. 269 (1810) ; Moug. & Nestl. 



Stirpes, 469 ! 



-^ — stenocarpa, /3. denigrata, Ach. Syn. 76 (1814). 



** reticulata, UeCand. Fl. Fran?. 6. 170 " (1816), fide Sch^r. ; Chev. 



Hist. Graphid. 28. t. 5. f. 1, 2, 3, 4. a. 



prominula, Chev. Hist. Graphid. 31. t. 6. f. 2, 3, 4 (1824). 



implexa, Chev. Hist. Graphid. 34. t. 7- f- 1, 2 (1824). 



Oraphis macularis, Mart* Fl. Brasil. 1. 85 (1833), in part. 



On ash, oak, ivy, hazel, currant. Sussex ! Mr. Borrer. Net- 

 ley Abbey, Hants ! (on ivy and mortar !), Mr. Lyell in herb, 

 Borrer. (On currant), Henfield ! Sussex, Mr. Bonder. Knock- 

 nagoney ! ; Colin Glen ! Belfast ; Massareene Park, Co. Antrim ! 

 Mr, Wm. Thompson. Near Edinburgh ! Dr. R, K. GreviUe. 

 Gopsall Wood, Leicestershire ! Rev. A. Bloxam^ Chelmsford, 

 Essex ! Mr, H, Piggot, Yorkshire ! Mr, G. Dixon. Castle 

 Bernard Park, Bandon, Ireland ! Rev. Prof. Hincks. Fermoy, 

 Ireland ! Mr. T. Chandler. Berwick-upon-Tweed ! Dr. G. John- 

 ston. Shropshire generally ! 



Thallus forming pale roundish or oblong irregular spots or 

 patches of about half an inch or more in diameter, on the smooth 

 bark of trees, not bounded by any brown or black line or margin, 

 but fading away in a watery manner (" crusta determinata sed 

 non limitata," Ach. L. Univ. 260), thin, membranous, conti- 

 nuous, smooth, very slightly tartareous ; in colour generally pale 

 dirty-yellow or olive, not unfrequently also of a pure white, and 

 then decidedly pulverulent. Lirella very numerous and crowded, 

 densely congregated towards the centre of the thallodal spot, so 

 as to appear at a little distance almost one black mass, more 

 scattered and often smaller in size towards the circumference, 

 prominent but at the same time depressed so as to form a uni- 

 form level surface, sessile, immersed only and slightly at the 

 base, somewhat shining, of a full black, lying in all directions 

 and positions, curved and flexuose ; on some barks however be- 

 coming more or less parallel to each other, moderate in length, 

 linear, and of nearly the same width throughout, more or less 

 obtuse at the extremities, though sometimes slightly tapered 

 there, generally simple, but by confluence and lying over one 

 another divided. Disk narrow, uniform, rimaeform, in age more 

 open and canaliculate, surrounded by the elevated, thick, uniform 

 or wavy proper margins. 



