Rev. W. A. Leighton on the British Graphideae. 203 



shining, in small patches with a pale margin, or where in contact 

 with other plants throwing up a narrow brown watery line or 

 margin. Lirellce scattered, more or less numerous, somewhat 

 inclining to a parallel arrangement, but very irregular and va- 

 riable in this respect, peculiarly prominent, lying on the surface 

 of the th alius, often apparently without any visible connexion, 

 variable in length, but never very long, simple, seldom branched, 

 straightish, or slightly curved and waved, very slender and nar- 

 row, of the same width throughout though tapering at the extre- 

 mities, which are obtuse or slightly pointed, of a full shining 

 black, more or less sprinkled with dingy yellow powder, which 

 is not unfrequently altogether absent. Disk a narrow chink, 

 uniform in its width throughout, in older states expanding, par- 

 ticularly in the middle. Proper margins peculiarly plump, 

 rounded and incurved, uniformly parallel, in an older state be- 

 coming more erect and narrower, and wavy or crisped around the 

 flattened expanded disk. 



The thin membrane of the thallus is sometimes very slightly 

 raised here and there around the very base of the lirellse, but 

 scarcely to be noticed without a lens, certainly not in the decided 

 manner so as to form a considerable thallodal margin as repre- 

 sented in Persoon's figure of his hetuligna in Ust. Ann. Bot. 

 st. 7. p. 31. t. 3. f. 5. A. a. Without the comparison of an au- 

 thentic specimen we ought to hesitate to consider it identical. 

 Our plant is a true Opegraphay whilst the Graphis hetuligna of 

 Acharius is from his description as certainly a true Graphis. 

 Moreover he questions whether his plant may not be regarded 

 as a variety of Graphis scripta, with which ours has not one 

 feature in common. 



I greatly doubt whether this is anything more than a state of 

 Opegrapha rimalis, Ach. 



Plate V. fig. 10. a, a. Vertical sections of thallus and lirellae; b, spo- 

 ridium : all magnified. 



9. Opegrapha atra^ Pers. Thallus very thin, forming smooth, 

 pale yellow or whitish ocellate patches ; lirellse densely crowded 

 towards the centre of the thallodal spot, sessile, depressed, lying 

 in all directions or subparallel, linear, generally simple or con- 

 fluent, flexuose ; disk narrow, uniform ; proper margins thick, 

 elevated, wavy; sporidia in asci, eight? very minute, obovate' 

 somewhat pointed at the extremities, 3-septate, pale yellow. 



Lichen scriptus, IIofFm. Enum. p. 12. t. 3. f. 2. c (1784). 



Opegrapha atra, Pers. in Ust. Ann. Bot. st. 7- p. 30. t. 1. f. 2. C. c. (1794) ; 



DeCand. Fl. Fran?. 2. 310. n. 840 ; Chev. Hist. Graphid. p. 21. t. 3. 



f. 1, 2 ; Johnst ! Fl. Berw. 2. 100 ; Hook. Br. Fl. 2. 145 (in part). 

 atra, u. denigrata, Schser. Spicil. 48. 324 (1823-1836); Enum., 153; 



Exsicc. 461 ! 



